Scientific Bibliography

Nanobiology and Cancer Nanotechnology
Nanotechnology Devices and Nanomaterials
Nanotechnology-Enabled Therapeutics Development and Delivery
Cancer Diagnostics and Biosensors
Nanotechnologies in Advanced Imaging
Environment, Health and Safety

Nanotechnologies in Advanced Imaging

2007  2006   2005   2004   2003   2002

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2007

Compact cysteine-coated CdSe(ZnCdS) quantum dots for in vivo applications.
Liu W, Choi HS, Zimmer JP, Tanaka E, Frangioni JV, Bawendi M.
J Am Chem Soc. 2007 Nov 28;129(47):14530-1.
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We have developed a versatile nanoparticle construct using a compact cysteine coating on a CdSe(ZnCdS) core(shell) nanocrystal (QD-Cys) that is biologically compatible, exceptionally compact, highly fluorescent, and easily functionalized. The small hydrodynamic diameter of QD-Cys ( approximately 6 nm) allows for renal clearance of these nanoparticles in rat models. Moreover, the ability to directly conjugate to QD-Cys opens up the possibility of functionalized nanocrystals for in vivo targeted imaging, in which small targeting molecules can be appended to QD-Cys, and unbound QDs can be rapidly cleared to achieve high signal/noise ratios and to reduce background toxicity.

InGaP@ZnS-Enriched Chitosan Nanoparticles: A Versatile Fluorescent Probe for Deep-Tissue Imaging.
Sandros MG, Behrendt M, Maysinger D, Tabrizian M.
Advanced Functional Materials. 2007;17(18):3724-30.
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InGaP QDs overcoated with several monolayers of ZnS are covalently bound to chitosan to address the challenges of developing highly biologically stable and fluorescent nanoparticle probes for deep-tissue imaging. Transmission electron microscopy images reveal that the average diameter of these luminescent nanoparticles is approximately 29 nm, and they contain multiple InGaP@ZnS QDs that have an average diameter between 4 and 5 nm. These new InGaP@ZnS-chitosan nanoparticles emit near the near IR region at 670 nm and are able to penetrate three times deeper into tissue (e.g., even through a mouse skull) while revealing a higher uptake efficiency into PC12 cells with a robust signal. Additionally, a cell viability assay demonstrates that these new fluorescent nanoparticles have good biocompatibility and stability with PC12 cells and neural cells. As a result, these near-IR-emitting nanoparticles can be used for real-time and deep-tissue examination of diverse specimens, such as lymphatic organs, kidneys, hearts, and brains, while leaving the tissue intact.

Folate-mediated tumor cell uptake of quantum dots entrapped in lipid nanoparticles.
Schroeder JE, Shweky I, Shmeeda H, Banin U, Gabizon A.
J Control Release. 2007 Dec 4;124(1-2):28-34.
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Quantum dots (QDs) are fluorescent semiconductor nanocrystals with superior optical properties compared to organic dyes currently undergoing rapid development for biological applications, particularly in fluorescence imaging. The folate receptor, overexpressed in a broad spectrum of malignant tumors, is an attractive target for selective delivery of imaging agents to tumor cells. This study examines nanoparticles containing QDs entrapped in a lipid shell, and post-loaded with a folate-lipid conjugate for targeting to mouse and human tumor cells expressing the folate receptor. Hydrophobic QDs were mixed with 1,2 dipalmitoyl-sn-glycero-3 phosphocholine and methoxy-polyethylene-glycol-distearoyl-phosphatidyl-ethanolamine (mPEG-DSPE) generating a nanoparticle referred to as lipodot, with a mean diameter size of approximately 100 nm. Folate-derivatized PEG-DSPE was post-loaded into the lipodots at 0.5% lipid molar concentration. Mouse J6456 lymphoma cells (J6456-FR) and human head and neck KB cancer cells (KB-FR), up-regulated for their folate receptors, were incubated with folate-targeted and non-targeted lipodots in vitro. Using fluorescence microscopy, it was found that only folate-targeted lipodots were taken up by tumor cells. Confocal depth scanning showed substantial internalization. Confirming the specificity of folate-targeted lipodots, binding and internalization were inhibited by free folate, and no uptake was found in a folate-receptor negative cell line. Selective binding and uptake of folate-targeted lipodots by J6456-FR cells was also observed in vivo after intra-peritoneal injection in mice bearing ascitic J6456-FR tumors based on FACS analysis and confocal imaging of harvested cells from the peritoneal cavity. Folate-targeted lipodots represent an attractive approach for tumor cell labeling both in vitro and in vivo.

Preparation and characterization of poly(lipid)-coated, fluorophore-doped silica nanoparticles for biolabeling and cellular imaging.
Senarath-Yapa MD, Phimphivong S, Coym JW, Wirth MJ, Aspinwall CA, Saavedra SS.
Langmuir. 2007 Dec 4;23(25):12624-33.
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The fabrication, characterization, and implementation of poly(lipid)-coated, highly luminescent silica nanoparticles as fluorescent probes for labeling of cultured cells are described. The core of the probe is a sol-gel-derived silica nanoparticle, 65-100 nm in diameter, in which up to several thousand dye molecules are encapsulated (Lian, W.; et al. Anal. Biochem. 2004, 334, 135-144). The core is coated with a membrane composed of bis-sorbylphosphatidylcholine, a synthetic polymerizable lipid that is chemically cross-linked to enhance the environmental and chemical stability of the membrane relative to a fluid lipid membrane. The poly(lipid) coating has two major functions: (i) to reduce nonspecific interactions, based on the inherently biocompatible properties of the phosphorylcholine headgroup, and (ii) to permit functionalization of the particle, by doping the coating with lipids bearing chemically reactive or bioactive headgroups. Both functions are demonstrated: (i) Nonspecific adsorption of dissolved proteins to bare silica nanoparticles and of bare nanoparticles to cultured cells is significantly reduced by application of the poly(lipid) coating. (ii) Functionalization of poly(lipid)-coated nanoparticles with a biotin-conjugated lipid creates a probe that can be used to target both dissolved protein receptors as well as receptors on the membranes of cultured cells. Measurements performed on single nanoparticles bound to planar supported lipid bilayers verify that the emission intensity of these probes is significantly greater than that of single protein molecules labeled with several fluorophores.

Temperature-responsive magnetite/PEO-PPO-PEO block copolymer nanoparticles for controlled drug targeting delivery.
Chen S, Li Y, Guo C, Wang J, Ma J, Liang X, Yang LR, Liu HZ.
Langmuir. 2007 Dec 4;23(25):12669-76.
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In this study, temperature-responsive magnetite/polymer nanoparticles were developed from iron oxide nanoparticles and poly(ethyleneimine)-modified poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymer. The particles were characterized by TEM, XRD, DLS, VSM, FTIR, and TGA. A typical product has an approximately 20 nm magnetite core and an approximately 40 nm hydrodynamic diameter with a narrow size distribution and is superparamagnetic with large saturation magnetization (51.34 emu/g) at room temperature. The most attractive feature of the nanoparticles is their temperature-responsive volume-transition property. DLS results indicated that their average hydrodynamic diameter underwent a sharp decrease from 45 to 25 nm while evaluating the temperature from 20 to 35 degrees C. The temperature-dependent evolution of the C-O stretching band in the FTIR spectra of the aqueous nanoparticles solution revealed that thermo-induced self-assembly of the immobilized block copolymers occurred on the magnetite solid surfaces, which is accompanied by a conformational change from a fully extended state to a highly coiled state of the copolymer. Consequently, the copolymer shell could act as a temperature-controlled "gate" for the transit of guest substance. The uptake and release of both hydrophobic and hydrophilic model drugs were well controlled by switching the transient opening and closing of the polymer shell at different temperatures. A sustained release of about 3 days was achieved in simulated human body conditions. In primary mouse experiments, drug-entrapped magnetic nanoparticles showed good biocompatibility and effective therapy for spinal cord damage. Such intelligent magnetic nanoparticles are attractive candidates for widespread biomedical applications, particularly in controlled drug-targeting delivery.

High cytotoxicity and resistant-cell reversal of novel paclitaxel loaded micelles by enhancing the molecular-target delivery of the drug
You J, Hu FQ, Du YZ, Yuan H, Ye BF.
Nanotechnology. 2007 Dec 12;18:495101.
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Many antitumor drugs, such as paclitaxel (PTX), are widely used in cancer chemotherapy. However, their clinical use is limited by systemic toxicity, rapid blood clearance, and the occurrence of resistance. To increase the therapeutic index of these drugs, the antitumor drug PTX was encapsulated in novel micelles with glycolipid-like structure, which were formed by stearate grafted chitosan oligosaccharide in aqueous medium. The micelles could load the poorly soluble antitumor drug (PTX) with high entrapment efficiency and drug loading. PTX release was retarded as a result of the encapsulation of the micelles. PTX loaded micelles present excellent internalization into tumor cells as well as resistant cells and subsequently reside in cytoplasm, which results in increased intracellular accumulation of PTX in its molecular-target site. Consequently, cytotoxicity of PTX loaded micelles was improved sharply and resistant cells were reversed. In conclusion, high cytotoxicity can be obtained and resistant cells can be reversed by enhancing PTX's molecular-target delivery and accumulation via the encapsulation of the micelles. The present micelles are a promising carrier candidate for effective therapy of antitumor drugs with the target molecule in cytoplasm.

Bimodal Paramagnetic and Fluorescent Liposomes for Cellular and Tumor Magnetic Resonance Imaging.
Kamaly N, Kalber T, Ahmad A, Oliver MH, So PW, Herlihy AH, Bell JD, Jorgensen MR, Miller AD.
Bioconjug Chem. 2008 Jan 16;19(1):118-129.
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A novel bimodal fluorescent and paramagnetic liposome is described for cellular labeling. In this study, we show the synthesis of a novel gadolinium lipid, Gd.DOTA.DSA, designed for liposomal cell labeling and tumor imaging. Liposome formulations consisting of this lipid were optimized in order to allow for maximum cellular entry, and the optimized formulation was used to label HeLa cells in vitro. The efficiency of this novel bimodal Gd-liposome formulation for cell labeling was demonstrated using both fluorescence microscopy and magnetic resonance imaging (MRI). The uptake of Gd-liposomes into cells induced a marked reduction in their MRI T 1 relaxation times. Fluorescence microscopy provided concomitant proof of uptake and revealed liposome internalization into the cell cytosol. The optimized formulation was also found to exhibit minimal cytotoxicity and was shown to have capacity for plasmid DNA (pDNA) transfection. A further second novel neutral bimodal Gd-liposome is described for the labeling of xenograft tumors in vivo utilizing the enhanced permeation and retention effect (EPR). Balb/c nude mice were inoculated with IGROV-1 cells, and the resulting tumor was imaged by MRI using these in vivo Gd-liposomes formulated with low charge and a poly(ethylene glycol) (PEG) calyx for long systemic circulation. These Gd-liposomes which were less than 100 nm in size were shown to accumulate in tumor tissue by MRI, and this was also verified by fluorescence microscopy of histology samples. Our in vivo tumor imaging results demonstrate the effectiveness of MRI to observe passive targeting of long-term circulating liposomes to tumors in real time, and allow for MRI directed therapy, wherein the delivery of therapeutic genes and drugs to tumor sites can be monitored while therapeutic effects on tumor mass and/or size may be simultaneously observed, quantitated, and correlated.

Multifunctional magneto-polymeric nanohybrids for targeted detection and synergistic therapeutic effects on breast cancer.
Yang J, Lee CH, Ko HJ, Suh JS, Yoon HG, Lee K, Huh YM, Haam S.
Angew Chem Int Ed Engl. 2007;46(46):8836-9.
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No abstract available. (Citation link)

Oligonucleotide-coated metallic nanoparticles as a flexible platform for molecular imaging agents.
Nitin N, Javier DJ, Richards-Kortum R.
Bioconjug Chem. 2007 Nov-Dec;18(6):2090-6.
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Targeted metallic nanoparticles have shown promise as contrast agents for molecular imaging. To obtain molecular specificity, the nanoparticle surface must be appropriately functionalized with probe molecules that will bind to biomarkers of interest. The aim of this study was to develop and characterize a flexible approach to generate molecular imaging agents based on gold nanoparticles conjugated to a diverse range of probe molecules. We present two complementary oligonucleotide-based approaches to develop gold nanoparticle contrast agents which can be functionalized with a variety of biomolecules ranging from small molecules, to peptides, to antibodies. The size, biocompatibility, and protein concentration per nanoparticle are characterized for the two oligonucleotide-based approaches; the results are compared to contrast agents prepared using adsorption of proteins on gold nanoparticles by electrostatic interaction. Contrast agents prepared from oligonucleotide-functionalized nanoparticles are significantly smaller in size and more stable than contrast agents prepared by adsorption of proteins on gold nanoparticles. We demonstrate the flexibility of the oligonucleotide-based approach by preparing contrast agents conjugated to folate, EGF peptide, and anti-EGFR antibodies. Reflectance images of cancer cell lines labeled with functionalized contrast agents show significantly increased image contrast which is specific for the target biomarker. To demonstrate the modularity of this new bioconjugation approach, we use it to conjugate both fluorophore and anti-EGFR antibodies to metal nanoparticles, yielding a contrast agent which can be probed with multiple imaging modalities. This novel bioconjugation approach can be used to prepare contrast agents targeted with biomolecules that span a diverse range of sizes; at the same time, the bioconjugation method can be adapted to develop multimodal contrast agents for molecular imaging without changing the coating design or material.

Quantum dot-aptamer conjugates for synchronous cancer imaging, therapy, and sensing of drug delivery based on bi-fluorescence resonance energy transfer.
Bagalkot V, Zhang L, Levy-Nissenbaum E, Jon S, Kantoff PW, Langer R, Farokhzad OC.
Nano Lett. 2007 Oct;7(10):3065-70.
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We report a novel quantum dot (QD)-aptamer(Apt)-doxorubicin (Dox) conjugate [QD-Apt(Dox)] as a targeted cancer imaging, therapy, and sensing system. By functionalizing the surface of fluorescent QD with the A10 RNA aptamer, which recognizes the extracellular domain of the prostate specific membrane antigen (PSMA), we developed a targeted QD imaging system (QD-Apt) that is capable of differential uptake and imaging of prostate cancer cells that express the PSMA protein. The intercalation of Dox, a widely used antineoplastic anthracycline drug with fluorescent properties, in the double-stranded stem of the A10 aptamer results in a targeted QD-Apt(Dox) conjugate with reversible self-quenching properties based on a Bi-FRET mechanism. A donor-acceptor model fluorescence resonance energy transfer (FRET) between QD and Dox and a donor-quencher model FRET between Dox and aptamer result when Dox intercalated within the A10 aptamer. This simple multifunctional nanoparticle system can deliver Dox to the targeted prostate cancer cells and sense the delivery of Dox by activating the fluorescence of QD, which concurrently images the cancer cells. We demonstrate the specificity and sensitivity of this nanoparticle conjugate as a cancer imaging, therapy and sensing system in vitro.

Hybrid nanoparticles for magnetic resonance imaging of target-specific viral gene delivery.
Huh YM, Lee ES, Lee JH, Jun YW, Kim PH, Yun CO, Kim JH, Suh JS, Cheon J.
Advanced Materials. 2007;19(20):3109-12.
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No abstract available. (Citation link)

Conjugated polymer dots for multiphoton fluorescence imaging.
Wu C, Szymanski C, Cain Z, McNeill J.
J Am Chem Soc. 2007 Oct 31;129(43):12904-5.
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We report on the two-photon excited fluorescence of conjugated polymer dots (CPdots). As a new class of two-photon fluorescent probes, CPdots exhibit two-photon action cross sections as high as 2.0 × 105 GM, to our knowledge, the largest reported thus far for a nanoparticle. The cross section values are 3-4 orders of magnitude higher than those of conventional fluorescent dyes and an order of magnitude higher than those of inorganic quantum dots. Single particle fluorescence imaging was achieved using relatively low laser power.

Ultrasmall mixed ferrite colloids as multidimensional magnetic resonance imaging, cell labeling, and cell sorting agents.
Groman EV, Bouchard JC, Reinhardt CP, Vaccaro DE.
Bioconjug Chem. 2007 Nov-Dec;18(6):1763-71.
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One area that has been overlooked in the evolution of magnetic nanoparticle technology is the possibility of introducing informational atoms into the iron oxide core of the coated colloid. Introduction of suitable atoms into the iron oxide core offers an opportunity to produce a quantifiable probe, thereby adding one or more dimensions to the magnetic colloid's informational status. Lanthanide-doped iron oxide nanoparticles have been synthesized to introduce informational atoms through the formation of colloidal mixed ferrites. These colloids are designated ultrasmall mixed ferrite iron oxides (USMIOs). USMIOs containing 5 mol % europium exhibit superparamagnetic behavior with an induced magnetization of 56 emu/g Fe at 1.5 T, a powder X-ray diffraction pattern congruent with magnetite, and R1 and R2 relaxivity values of 15.4 (mM s) (-1) and 33.9 (mM s) (-1), respectively, in aqueous solution at 37 degrees C and 0.47 T. USMIO can be detected by five physical methods, combining the magnetic resonance imaging (MRI) qualities of iron with the sensitive and quantitative detection of lanthanide metals by neutron activation analysis (NA), time-resolved fluorescence (TRF), X-ray fluorescence, along with detection by electron microscopy (EM). In addition to quantitative detection using neutron activation analysis, the presence of lanthanides in the iron oxide matrix confers attractive optical properties for long-term multilabeling studies with europium and terbium. These USMIOs offer high photostability, a narrow emission band, and a broad absorption band combining the high sensitivity of time-resolved fluorescence with the high spatial resolution of MRI. USMIO nanoparticles are prepared through modifications of traditional magnetite-based iron oxide colloid synthetic methods. A 5 mol % substitution of ferric iron with trivalent europium yielded a colloid with nearly identical magnetic, physical, and chemical characteristics to its magnetite colloid parent.

Cancer cells assemble and align gold nanorods conjugated to antibodies to produce highly enhanced, sharp, and polarized surface Raman spectra: a potential cancer diagnostic marker.
Huang X, El-Sayed IH, Qian W, El-Sayed MA.
Nano Lett. 2007 Jun;7(6):1591-7.
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Human oral cancer cells are found to assemble and align gold nanorods conjugated to anti-epidermal growth factor receptor (anti-EGFR) antibodies. Immnoconjugated gold nanorods and nanospheres were shown previously to exhibit strong Rayleigh (Mie) scattering useful for imaging. In the present letter, molecules near the nanorods on the cancer cells are found to give a Raman spectrum that is greatly enhanced (due to the high surface plasmon field of the nanorod assembly in which their extended surface plasmon fields overlap), sharp (due to a homogeneous environment), and polarized (due to anisotropic alignments). These observed properties can be used as diagnostic signatures for cancer cells.

microPET-based biodistribution of quantum dots in living mice.
Schipper ML, Cheng Z, Lee SW, Bentolila LA, Iyer G, Rao J, Chen X, Wu AM, Weiss S, Gambhir SS.
J Nucl Med. 2007 Sep;48(9):1511-8.
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This study evaluates the quantitative biodistribution of commercially available CdSe quantum dots (QD) in mice. METHODS: (64)Cu-Labeled 800- or 525-nm emission wavelength QD (21- or 12-nm diameter), with or without 2,000 MW (molecular weight) polyethylene glycol (PEG), were injected intravenously into mice (5.55 MBq/25 pmol QD) and studied using well counting or by serial microPET and region-of-interest analysis. RESULTS: Both methods show rapid uptake by the liver (27.4-38.9 %ID/g) (%ID/g is percentage injected dose per gram tissue) and spleen (8.0-12.4 %ID/g). Size has no influence on biodistribution within the range tested here. Pegylated QD have slightly slower uptake into liver and spleen (6 vs. 2 min) and show additional low-level bone uptake (6.5-6.9 %ID/g). No evidence of clearance from these organs was observed. CONCLUSION: Rapid reticuloendothelial system clearance of QD will require modification of QD for optimal utility in imaging living subjects. Formal quantitative biodistribution/imaging studies will be helpful in studying many types of nanoparticles, including quantum dots.

Biodegradable nanoparticles for targeted ultrasound imaging of breast cancer cells in vitro.
Liu J, Li J, Rosol TJ, Pan X, Voorhees JL.
Phys Med Biol. 2007 Aug 21;52(16):4739-47.
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Disease-specific enhanced imaging through a targeted agent promises to improve the specificity of medical ultrasound. Nanoparticles may provide unique advantages for targeted ultrasound imaging due to their novel physical and surface properties. In this study, we examined a nanoparticle agent developed from a biodegradable polymer, polylactic acid (PLA). The nanoparticles (mean diameter = 250 nm) were surface conjugated to an anti-Her2 antibody (i.e., Herceptin) for specific binding to breast cancer cells that overexpress Her2 receptors. We examined the targeting specificity and the resultant ultrasound enhancement in Her2-positive and negative cells. Flow cytometry and confocal imaging were used to assess the nanoparticle-cell binding. Her2-positive cells demonstrated substantial staining after incubation with nanoparticle/antibody conjugates, while minimal staining was found in Her2-negative cells, indicating receptor-specific binding of the conjugated PLA nanoparticles. In high-resolution ultrasound B-mode images, the average gray scale of the Her2-positive cells was consistently and significantly higher after nanoparticle treatment (133 +/- 4 in treated cells versus 109 +/- 4 in control, p < 0.001, n = 5), while no difference was detected in the cells that did not overexpress the receptors (117 +/- 3 in treated cells versus 118 +/- 5 in control). In conclusion, the feasibility of using targeted nanoparticles to enhance ultrasonic images was demonstrated in vitro. This may be a promising approach to target cancer biomarkers for site-specific ultrasound imaging.

Use of lanthanide-grafted inorganic nanoparticles as effective contrast agents for cellular uptake imaging.
Voisin P, Ribot EJ, Miraux S, Bouzier-Sore AK, Lahitte JF, Bouchaud V, Mornet S, Thiaudière E, Franconi JM, Raison L, Labrugère C, Delville MH.
Bioconjug Chem. 2007 Jul-Aug;18(4):1053-63.
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The improvement of commonly used Gd3+ -based MRI agents requires the design of new systems with optimized in vivo efficacy, pharmacokinetic properties, and specificity. To design these contrast agents, two parameters are usually considered: increasing the number of coordinated water molecules or increasing the rotational correlation time by increasing molecular weight and size. This has been achieved by noncovalent or covalent binding of low-molecular weight Gd3+ chelates to macromolecules or polymers. The grafting of these high-spin paramagnetic gadolinium chelates on metal oxide nanoparticles (SiO2, Al2O3) is proposed. This new synthetic strategy presents at least two main advantages: (1) a high T1-relaxivity for MRI with a 275% increase of the MRI signal and (2) the ability of nanoparticles to be internalized in cells. Results indicate that these new contrast agents lead to a huge reconcentration of Gd3+ paramagnetic species inside microglial cells. This reconcentration phenomenon gives rise to high signal-to-noise ratios on MR images of cells after particle internalization, from 1.4 to 3.75, using Al2O3 or SiO2 particles, respectively. The properties of these new particles will be further used to get new insight into gene therapy against glioma, using microglial cells as vehicles to simultaneously transport a suicide gene and contrast agents. Since microglia are chemoattracted to brain tumors, the presence of these new contrast agents inside the cells will lead to a better MRI determination of the in vivo location, shape, and borders of the tumors. These Gd3+-loaded microglia can therefore provide effective localization of tumors by MRI before applying any therapeutic treatment. The rate of carcinoma remission following a suicide gene strategy is also possible.

On-off regulation of 19F magnetic resonance signals based on pH-sensitive PEGylated nanogels for potential tumor-specific smart 19F MRI probes.
Oishi M, Sumitani S, Nagasaki Y.
Bioconjug Chem. 2007 Sep-Oct;18(5):1379-82.
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The pH-sensitive PEGylated nanogels constructed from tethered PEG chains and a polyamine gel core containing 19F compounds showed remarkable on-off regulation of 19F MR (magnetic resonance) signals in response to the extracellular pH (6.5) of the tumor environment, even in the presence of 90% fetal bovine serum, due to the increase in the molecular motion of the 19F compounds through the hydrophilic-hydrophobic (volume-phase) transition of the polyamine gel core. Eventually, an appreciably enhanced 19F MR signal at an extremely low 19F compound concentration (approximately 55 microM) was achieved, demonstrating the utility of these nanogels as solid tumor-specific smart 19F MRI probes.

Multifunctional nanoparticles for combining ultrasonic tumor imaging and targeted chemotherapy.
Rapoport N, Gao Z, Kennedy A.
J Natl Cancer Inst. 2007 Jul 18;99(14):1095-106.
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BACKGROUND: Drug delivery in polymeric micelles combined with tumor irradiation by ultrasound results in effective drug targeting, but this technique requires prior tumor imaging. A technology that combined ultrasound imaging with ultrasound-mediated nanoparticle-based targeted chemotherapy could therefore have important applications in cancer treatment. METHODS: Mixtures of drug-loaded polymeric micelles and perfluoropentane (PFP) nano/microbubbles stabilized by the same biodegradable block copolymer were prepared. Size distribution of nanoparticles was measured by dynamic light scattering. Cavitation activity (oscillation, growth, and collapse of microbubbles) under ultrasound was assessed based on the changes in micelle/microbubble volume ratios. The effect of the nano/microbubbles on the ultrasound-mediated cellular uptake of doxorubicin (Dox) in MDA MB231 breast tumors in vitro and in vivo (in mice bearing xenograft tumors) was determined by flow cytometry. Statistical tests were two-sided. RESULTS: Phase state and nanoparticle sizes were sensitive to the copolymer/perfluorocarbon volume ratio. At physiologic temperatures, nanodroplets converted into nano/microbubbles. Doxorubicin was localized in the microbubble walls formed by the block copolymer. Upon intravenous injection into mice, Dox-loaded micelles and nanobubbles extravasated selectively into the tumor interstitium, where the nanobubbles coalesced to produce microbubbles with a strong, durable ultrasound contrast. Doxorubicin was strongly retained in the microbubbles but released in response to therapeutic ultrasound. Microbubbles cavitated under the action of tumor-directed ultrasound, which enhanced intracellular Dox uptake by tumor cells in vitro to a statistically significant extent relative to that observed with unsonicated microbubbles (drug uptake ratio = 4.60; 95% confidence interval [CI] = 1.70 to 12.47; P = .017) and unsonicated micelles (drug uptake ratio = 7.97; 95% CI = 3.72 to 17.08; P = .0032) and resulted in tumor regression in the mouse model. CONCLUSIONS: Multifunctional nanoparticles that are tumor-targeted drug carriers, long-lasting ultrasound contrast agents, and enhancers of ultrasound-mediated drug delivery have been developed and deserve further exploration as cancer therapeutics.

Near-infrared resonant nanoshells for combined optical imaging and photothermal cancer therapy.
Gobin AM, Lee MH, Halas NJ, James WD, Drezek RA, West JL.
Nano Lett. 2007 Jul;7(7):1929-34.
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Metal nanoshells are core/shell nanoparticles that can be designed to either strongly absorb or scatter within the near-infrared (NIR) wavelength region ( approximately 650-950 nm). Nanoshells were designed that possess both absorption and scattering properties in the NIR to provide optical contrast for improved diagnostic imaging and, at higher light intensity, rapid heating for photothermal therapy. Using these in a mouse model, we have demonstrated dramatic contrast enhancement for optical coherence tomography (OCT) and effective photothermal ablation of tumors.

Radiopaque iodinated polymeric nanoparticles for X-ray imaging applications.
Galperin A, Margel D, Baniel J, Dank G, Biton H, Margel S.
Biomaterials. 2007 Oct;28(30):4461-8.
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Iodinated radiopaque polymeric nanoparticles of sizes ranging between 30 and 350 nm were formed by emulsion polymerization of the monomer 2-methacryloyloxyethyl(2,3,5-triiodobenzoate) in the presence of sodium dodecyl sulfate as surfactant and potassium persulfate as initiator. The influence of various polymerization parameters, e.g., monomer, initiator and surfactant concentrations on the molecular weight, polymerization yield, size and size distribution of the particles was elucidated. Characterization of these iodinated nanoparticles was accomplished by routine methods such as FTIR, 1H NMR, TEM, TGA, DSC, GPC and light scattering. These polymeric nanoparticles are composed of ca. 58% by weight iodine, and are therefore expected to possess significant radiopaque nature. In vitro radiopacity of the iodinated nanoparticles of 30.6+/-5.0 nm diameter, dispersed in water and in the dry state, was demonstrated with a CT scanner. In vivo CT-imaging performed in a dog model by intravenous administration of the uniform 30.6+/-5.0 nm diameter radiopaque nanoparticles dispersed in saline demonstrated significant enhanced visibility of lymph nodes, liver, kidney and spleen. These results indicate that these nanoparticles may be useful as new efficient contrast agents for X-ray imaging applications.

Self-Assembling Nanoparticles Image Tumor Cells.
Kim JS, Rieter WJ, Taylor KML, An H, Lin W, Lin W.
J. Am. Chem. Soc. 2007 July 25;129(29):8962-63.
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A layer-by-layer (LbL) polyelectrolyte deposition strategy is used to prepare multifunctional nanoparticles (MFNPs) with multimodal imaging capabilities. Alternating treatment of hybrid silica nanoparticles (NP0) containing a luminescent [Ru(bpy)3]Cl2 core and anionic monolayer coating of the Gd-(siloxylpropyl)diethylenetriamine tetraacetate (Gd-DTTA) complex with cationic Gd(III)-DOTA oligomer 1 and anionic poly(styrene sulfonate) (PSS) led to the deposition of multilayers of 1 and PSS via electrostatic interactions. This LbL deposition technique offers a superb strategy for the assembly of hybrid nanoparticles with imbedded luminophores and very high MR relaxivities. The PSS-terminated multilayered nanoparticles can be noncovalently functionalized with targeting peptides that carry positive charges under physiological conditions via electrostatic interactions to lead to cancer-specific MFNPs for optical and MR imaging of HT-29 human colon cancer cells. The generality of this approach should allow the design of imaging and/or therapeutic MFNPs that can specifically target a wide range of diseased cells.

Dendrimer-entrapped gold nanoparticles as a platform for cancer-cell targeting and imaging.
Shi X, Wang S, Meshinchi S, Van Antwerp ME, Bi X, Lee I, Baker JR Jr.
Small. 2007 Jul;3(7):1245-52.
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We present a general approach for the targeting and imaging of cancer cells using dendrimer-entrapped gold nanoparticles (Au DENPs). Au DENPs were found to be able to covalently link with targeting and imaging ligands for subsequent cancer-cell targeting and imaging. The Au DENPs linked with defined numbers of folic acid (FA) and fluorescein isothiocyanate (FI) molecules are water soluble, stable, and biocompatible. In vitro studies show that the FA- and FI-modified Au DENPs can specifically bind to KB cells (a human epithelial carcinoma cell line) that overexpress high-affinity folate receptors and they are internalized dominantly into lysosomes of target cells within 2 h. These findings demonstrate that Au DENPs may serve as a general platform for cancer imaging and therapeutics.

Nanoprobes with near-infrared persistent luminescence for in vivo imaging.
le Masne de Chermont Q, Chanéac C, Seguin J, Pellé F, Maîtrejean S, Jolivet JP, Gourier D, Bessodes M, Scherman D.
Proc Natl Acad Sci U S A. 2007 May 29;104(22):9266-71.
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Fluorescence is increasingly used for in vivo imaging and has provided remarkable results. Yet this technique presents several limitations, especially due to tissue autofluorescence under external illumination and weak tissue penetration of low wavelength excitation light. We have developed an alternative optical imaging technique by using persistent luminescent nanoparticles suitable for small animal imaging. These nanoparticles can be excited before injection, and their in vivo distribution can be followed in real-time for more than 1 h without the need for any external illumination source. Chemical modification of the nanoparticles' surface led to lung or liver targeting or to long-lasting blood circulation. Tumor mass could also be identified on a mouse model.

Quantum dots are phagocytized by macrophages and colocalize with experimental gliomas.
Jackson H, Muhammad O, Daneshvar H, Nelms J, Popescu A, Vogelbaum MA, Bruchez M, Toms SA.
Neurosurgery. 2007 Mar;60(3):524-9; discussion 529-30.
[ expand abstract ]

OBJECTIVE: The identification of neoplastic tissue within normal brain during biopsy and tumor resection remains a problem in the operative management of gliomas. A variety of nanoparticles are phagocytized by macrophages in vivo. This feature may allow optical nanoparticles, such as quantum dots, to colocalize with brain tumors and serve as an optical aid in the surgical resection or biopsy of brain tumors. METHODS: Male Fisher rats (Charles River Labs, Wilmington, MA) were implanted intracranially with C6 gliosarcoma cell lines to establish tumors. Two weeks after the implantation of tumors, 705-nm emission Qdot ITK Amino(PEG) Quantum Dots (Quantum Dot Corp., Hayward, CA) were injected via the tail vein at doses of 3 to 17 nmol. The animals were sacrificed 24 hours after the injection of quantum dots and their tissues were examined. RESULTS: Quantum dots are avidly phagocytized by macrophages and are taken up by the liver, spleen, and lymph nodes. A dose-response relationship was noted. At low doses, the majority of the quantum dots are sequestered in the liver, spleen, and lymph nodes. At higher doses, increasing quantities of quantum dots are noted within the experimental brain tumors. Macrophages and microglia colocalize with glioma cells, carrying the quantum dot and thereby optically outlining the tumor. Excitation with blue or ultraviolet wavelengths stimulates the quantum dots, which give off a deep red fluorescence detectable with charge-coupled device cameras, optical spectroscopy units, and in dark-field fluorescence microscopy. CONCLUSION: Quantum dots are optical nanoparticles that, when delivered in nanomole doses, are phagocytized by the macrophages and microglia that infiltrate experimental gliomas. The optical signal may be detected, allowing for improved identification and visualization of tumors, potentially augmenting brain tumor biopsy and resection.

In vivo imaging of siRNA delivery and silencing in tumors.
Medarova Z, Pham W, Farrar C, Petkova V, Moore A.
Nat Med. 2007 Mar;13(3):372-7.
[ expand abstract ]

With the increased potential of RNA interference (RNAi) as a therapeutic strategy, new noninvasive methods for detection of siRNA delivery and silencing are urgently needed. Here we describe the development of dual-purpose probes for in vivo transfer of siRNA and the simultaneous imaging of its accumulation in tumors by high-resolution magnetic resonance imaging (MRI) and near-infrared in vivo optical imaging (NIRF). These probes consisted of magnetic nanoparticles labeled with a near-infrared dye and covalently linked to siRNA molecules specific for model or therapeutic targets. Additionally, these nanoparticles were modified with a membrane translocation peptide for intracellular delivery. We show the feasibility of in vivo tracking of tumor uptake of these probes by MRI and optical imaging in two separate tumor models. We also used proof-of-principle optical imaging to corroborate the efficiency of the silencing process. These studies represent the first step toward the advancement of siRNA delivery and imaging strategies, essential for cancer therapeutic product development and optimization.

Hybrid gadolinium oxide nanoparticles: multimodal contrast agents for in vivo imaging.
Bridot JL, Faure AC, Laurent S, Rivière C, Billotey C, Hiba B, Janier M, Josserand V, Coll JL, Elst LV, Muller R, Roux S, Perriat P, Tillement O.
J Am Chem Soc. 2007 Apr 25;129(16):5076-84.
[ expand abstract ]

Luminescent hybrid nanoparticles with a paramagnetic Gd2O3 core were applied as contrast agents for both in vivo fluorescence and magnetic resonance imaging. These hybrid particles were obtained by encapsulating Gd2O3 cores within a polysiloxane shell which carries organic fluorophores and carboxylated PEG covalently tethered to the inorganic network. Longitudinal proton relaxivities of these particles are higher than the positive contrast agents like Gd-DOTA which are commonly used for clinical magnetic resonance imaging. Moreover these particles can be followed up by fluorescence imaging. This study revealed that these particles suited for dual modality imaging freely circulate in the blood vessels without undesirable accumulation in lungs and liver.

Simultaneous two-color spectral fluorescence lymphangiography with near infrared quantum dots to map two lymphatic flows from the breast and the upper extremity.
Hama Y, Koyama Y, Urano Y, Choyke PL, Kobayashi H.
Breast Cancer Res Treat. 2007 May;103(1):23-8.
[ expand abstract ]

Due to their small size and poor access, the lymphatic function has been difficult to study in vivo. Especially difficult is the mapping of lymphatic drainage from two basins into the same node. Quantum dots can be used to perform multicolor images with high fluorescent intensity and are of a nano-size size suitable for lymphatic imaging via direct interstitial injection. Here we show simultaneous two-color in vivo wavelength-resolved spectral fluorescence lymphangiography using two near infrared quantum dots with different emission spectra, which allow non-invasive and simultaneous visualization of two separate lymphatic flows draining the breast and the upper extremity and variations in the drainage patterns and the water sheds within the axillary node. Two-color spectral fluorescence lymphangiography can provide insight into mechanisms of drainage from different lymphatic basins that may lead to sentinel lymph nodes detection of the breast cancer as well as prevention of complications such as lymphedema of the arm.

Ligand conjugated low-density lipoprotein nanoparticles for enhanced optical cancer imaging in vivo.
Chen J, Corbin IR, Li H, Cao W, Glickson JD, Zheng G.
J. Am. Chem. Soc. 2007 May 9;129(18):5798-99.
[ expand abstract ]

LDL particles are high-capacity nanocarriers with precisely controlled size and are naturally biocompatible, biodegradable, and nonimmunogenic. However, their utilities as drug carriers are limited by the narrow purview of LDL receptor-positive tumors. Here, we synthsized a ligand-conjugated, NIR-labeled LDL that enables the first in vivo demonstration of rerouting LDL from LDL receptors to selected alternate receptors, thus drastically expanding the range of using LDL particles as nanocarriers for in vivo cancer imaging and treatment.

A paramagnetic nanoprobe to detect tumor cell death using magnetic resonance imaging.
Neves AA, Krishnan AS, Kettunen MI, Hu DE, Backer MM, Davletov B, Brindle KM.
Nano Lett. 2007 May;7(5):1419-23.
[ expand abstract ]

A 110 kDa (ca. 5 nm in diameter) bivalent paramagnetic nanoprobe for detecting cell death using magnetic resonance imaging (MRI) is described, in which two biotinylated C2A domains of the protein synaptotagmin-I were complexed with a single avidin molecule, which had been labeled with gadolinium chelates. This nanoprobe bound with high affinity and specificity to the phosphatidylserine exposed by dying cells and was demonstrated to allow MRI detection of apoptotic tumor cells in vitro.

Imaging of Vx-2 rabbit tumors with alpha(nu)beta3-integrin-targeted 111In nanoparticles.
Hu G, Lijowski M, Zhang H, Partlow KC, Caruthers SD, Kiefer G, Gulyas G, Athey P, Scott MJ, Wickline SA, Lanza GM.
Int J Cancer. 2007 May 1;120(9):1951-7.
[ expand abstract ]

Earlier tumor detection can improve 5-year survival of patients, particularly among those presenting with cancers less than 1 cm in diameter. alpha(nu)beta(3)-Targeted (111)In nanoparticles (NP) were developed and studied for detection of tumor angiogenesis. Studies were conducted in New Zealand white rabbits implanted 12 days earlier with Vx-2 tumor. alpha(nu)beta(3)-Targeted (111)In/NP bearing approximately 10 (111)In/NP vs. approximately 1 (111)In/NP nuclide payloads were compared to nontargeted radiolabeled control particles. In vivo competitive binding studies were used to assess ligand-targeting specificity. alpha(nu)beta(3)-Integrin-targeted NP with approximately 10 (111)In/NP provided better (p < 0.05) tumor-to-muscle ratio contrast (6.3 +/- 0.2) than approximately 1 (111)In/NP (5.1 +/- 0.1) or nontargeted particles with approximately 10 (111)In/NP (3.7 +/- 0.1) over the initial 2-hr postinjection. At 18 hr, mean tumor activity in rabbits receiving alpha(nu)beta(3)-integrin-targeted NP was 4-fold higher than the nontargeted control. Specificity of the NP for the tumor neovasculature was supported by in vivo competition studies and by fluorescence microscopy of alpha(nu)beta(3)-targeted fluorescent-labeled NP. Biodistribution studies revealed that the primary clearance organ in rabbits as a %ID/g tissue was the spleen. Circulatory half-life (t(1/2)beta) was estimated to be approximately 5 hr using a 2-compartment model. alpha(nu)beta(3)-Targeted (111)In perfluorocarbon NP may provide a clinically useful tool for sensitively detecting angiogenesis in nascent tumors, particularly in combination with secondary high-resolution imaging modalities, such as MRI.

Quantum Rod Bioconjugates as Targeted Probes for Confocal and Two-Photon Fluorescence Imaging of Cancer Cells.
Yong KT, Qian J, Roy I, Lee HH, Bergey EJ, Tramposch KM, He S, Swihart MT, Maitra A, Prasad PN.
Nano Lett. 2007 Feb 9; [Epub ahead of print].
[ expand abstract ]

Live cell imaging using CdSe/CdS/ZnS quantum rods (QRs) as targeted optical probes is reported. The QRs, synthesized in organic media using a binary surfactant mixture, were dispersed in aqueous media using mercaptoundecanoic acid (MUA) and lysine. Transferrin (Tf) was linked to the QRs to produce QR-Tf bioconjugates that were used for targeted in vitro delivery to a human cancer cell line. Confocal and two-photon imaging were used to confirm receptor-mediated uptake of QR-Tf conjugates into the HeLa cells, which overexpress the transferrin receptor (TfR). Uptake was not observed with QRs that lacked Tf functionalization or with cells that were presaturated with free Tf and then treated with Tf-functionalized QRs.

Spatial dose distributions in solid tumors from (186)Re transported by liposomes using HS radiochromic media.
Medina LA, Goins B, Rodriguez-Villafuerte M, Bao A, Martinez-Davalos A, Awasthi V, Galvan OO, Santoyo C, Phillips WT, Brandan ME.
Eur J Nucl Med Mol Imaging. 2007 Feb 8; [Epub ahead of print].
[ expand abstract ]

PURPOSE: A procedure for the measurement of spatial dose rate distribution of beta particles emitted by (186)Re-liposomes in tumoral tissue, using HS GafChromic films, is presented. METHODS: HNSCC xenografts were intratumorally injected with 3.7 or 11.1 MBq of (186)Re-liposomes, and planar gamma camera images were acquired to determine the liposome retention in the tumor. After imaging, rats were sacrificed and tumors were excised and processed in slices; HS film sections were placed between slices and the tumor lobe was reassembled. Tumors and films were kept in the dark at 4 degrees C for 18 h. After irradiation, films were removed and response was read using a transmission scanner. Films were analyzed to determine two-dimensional spatial dose rate distributions and cumulative dose volume histograms. Dose rate distributions were quantified using a (60)Co calibration curve, the (186)Re physical half-life, and a perturbation factor that takes into account the effect of the film protective layer. RESULTS: Dose rate distributions are highly heterogeneous with maximal dose rates about 0.4 Gy h(-1) in tumors injected with 3.7 MBq and 1.3 Gy h(-1) in tumors injected with 11.1 MBq. Dose volume histograms showed dose distributed in more than 95% and 80% of the tumor when injected with the lower and the higher activity, respectively. CONCLUSION: The described procedures and techniques have shown the potential and utility of HS GafChromic film for determination of dose rate distributions in solid tumors injected intratumorally with (186)Re-liposomes. The film's structure and the liposomes' biodistribution must be taken into account to obtain quantitative dose measurements.

19F magnetic resonance imaging for stem/progenitor cell tracking with multiple unique perfluorocarbon nanobeacons.
Partlow KC, Chen J, Brant JA, Neubauer AM, Meyerrose TE, Creer MH, Nolta JA, Caruthers SD, Lanza GM, Wickline SA.
FASEB J. 2007 Feb 6; [Epub ahead of print].
[ expand abstract ]

MRI has been employed to elucidate the migratory behavior of stem/progenitor cells noninvasively in vivo with traditional proton ((1)H) imaging of iron oxide nanoparticle-labeled cells. Alternatively, we demonstrate that fluorine ((19)F) MRI of cells labeled with different types of liquid perfluorocarbon (PFC) nanoparticles produces unique and sensitive cell markers distinct from any tissue background signal. To define the utility for cell tracking, mononuclear cells harvested from human umbilical cord blood were grown under proendothelial conditions and labeled with nanoparticles composed of two distinct PFC cores (perfluorooctylbromide and perfluoro-15-crown-5 ether). The sensitivity for detecting and imaging labeled cells was defined on 11.7T (research) and 1.5T (clinical) scanners. Stem/progenitor cells (CD34(+)CD133(+)CD31(+)) readily internalized PFC nanoparticles without aid of adjunctive labeling techniques, and cells remained functional in vivo. PFC-labeled cells exhibited distinct (19)F signals and were readily detected after both local and intravenous injection. PFC nanoparticles provide an unequivocal and unique signature for stem/progenitor cells, enable spatial cell localization with (19)F MRI, and permit quantification and detection of multiple fluorine signatures via (19)F MR spectroscopy. This method should facilitate longitudinal investigation of cellular events in vivo for multiple cell types simultaneously.

Fluorescence Analysis with Quantum Dot Probes for Hepatoma Under One- and Two-Photon Excitation.
Yu X, Chen L, Deng Y, Li K, Wang Q, Li Y, Xiao S, Zhou L, Luo X, Liu J, Pang D.
J Fluoresc. 2007 Feb 6; [Epub ahead of print].
[ expand abstract ]

A new class of fluorescent probe produced by conjugating semiconductor quantum dots (QDs) with protein molecule is proposed as an alternative to conventional organic labels. However the fluorescence characteristics of the QD bioconjugates are not clear while they are excitied with one- or two-photon laser pulse. We synthesized specific immunofluorescent probes by linking QDs to alpha fetoprotein (AFP) antibody for specific binding alpha-fetoprotein -an important marker for hepatocellular carcinoma cell lines, and archived specific fluorescence detection with the QDs-Anti-AFP in nude mice. Then, we have analyzed the fluorescence characteristics of QDs-Anti-AFP and original QDs both under one- and two-photon excitations. The results demonstrated that QDs-Anti-AFP's fluorescent spectral and lifetime haven't varied much from that of original QDs. Moreover, QDs-Anti-AFP have exhibited higher fluorescence efficiency than QDs under two-photon examination.

Moving in the right direction-Nanoimaging in cancer cell motility and metastasis.
Soon L, Braet F, Condeelis J.
Microsc Res Tech. 2007 Feb 5; [Epub ahead of print].
[ expand abstract ]

Although genetic and protein manipulations have been the cornerstone for the study and understanding of biological processes for many decades, complimentary nanoscale observations have only more recently been achieved in the live-imaging mode. It is at the nano measurement level that events such as protein-protein interactions, enzymatic conversions, and single-molecule stochastic behavior take place. Therefore, nanoscale observations allow us to reinterpret knowledge from large-scale or bulk techniques and gain new insight into molecular events that has cellular, tissue, and organismal phenotypic manifestations. This review identifies pertinent questions relating to the sensing and directional component of cancer cell chemotaxis and discusses the platforms that provide insight into the molecular events related to cell motility. The study of cell motility at the molecular imaging level often necessitates the use of devices such as microinjection, microfluidics, in vivo/intravital and in vitro chemotaxis assays, as well as fluorescence methods like uncaging and FRET. The micro- and nanofabricated devices that facilitate these techniques and their incorporation to specialized microscopes such as the multiphoton, AFM, and TIR-FM, for high-resolution imaging comprise the nanoplatforms used to explore the mechanisms of carcinogenesis. In real-time observations, within a milieu of physiological protein concentrations, true states of dynamic and kinetic fluxes can be monitored.

Imaging of Vx-2 rabbit tumors with alpha(nu)beta(3)-integrin-targeted (111)In nanoparticles.
Hu G, Lijowski M, Zhang H, Partlow KC, Caruthers SD, Kiefer G, Gulyas G, Athey P, Scott MJ, Wickline SA, Lanza GM.
Int J Cancer. 2007 Feb 2; [Epub ahead of print].
[ expand abstract ]

Earlier tumor detection can improve 5-year survival of patients, particularly among those presenting with cancers less than 1 cm in diameter. alpha(nu)beta(3)-Targeted (111)In nanoparticles (NP) were developed and studied for detection of tumor angiogenesis. Studies were conducted in New Zealand white rabbits implanted 12 days earlier with Vx-2 tumor. alpha(nu)beta(3)-Targeted (111)In/NP bearing approximately approximately 10 (111)In/NP vs. approximately approximately 1 (111)In/NP nuclide payloads were compared to nontargeted radiolabeled control particles. In vivo competitive binding studies were used to assess ligand-targeting specificity. alpha(nu)beta(3)-Integrin-targeted NP with approximately approximately 10 (111)In/NP provided better (p < 0.05) tumor-to-muscle ratio contrast (6.3 +/- 0.2) than approximately approximately 1 (111)In/NP (5.1 +/- 0.1) or nontargeted particles with approximately approximately 10 (111)In/NP (3.7 +/- 0.1) over the initial 2-hr postinjection. At 18 hr, mean tumor activity in rabbits receiving alpha(nu)beta(3)-integrin-targeted NP was 4-fold higher than the nontargeted control. Specificity of the NP for the tumor neovasculature was supported by in vivo competition studies and by fluorescence microscopy of alpha(nu)beta(3)-targeted fluorescent-labeled NP. Biodistribution studies revealed that the primary clearance organ in rabbits as a %ID/g tissue was the spleen. Circulatory half-life (t(1/) (2) (beta)) was estimated to be approximately approximately 5 hr using a 2-compartment model. alpha(nu)beta(3)-Targeted (111)In perfluorocarbon NP may provide a clinically useful tool for sensitively detecting angiogenesis in nascent tumors, particularly in combination with secondary high-resolution imaging modalities, such as MRI.

In vivo tumor targeting and radionuclide imaging with self-assembled nanoparticles: mechanisms, key factors, and their implications.
Cho YW, Park SA, Han TH, Son DH, Park JS, Oh SJ, Moon DH, Cho KJ, Ahn CH, Byun Y, Kim IS, Kwon IC, Kim SY.
Biomaterials. 2007 Feb;28(6):1236-47.
[ expand abstract ]

The development of more selective delivery systems for cancer diagnosis and chemotherapy is one of the most important goals of current anticancer research. The purpose of this study is to evaluate various self-assembled nanoparticles as candidates to shuttle radionuclide and/or drugs into tumors and to investigate the mechanisms underlying the tumor targeting with self-assembled nanoparticles. By combining different hydrophobic moieties and hydrophilic polymer backbones, various self-assembled nanoparticles were prepared, and their in vivo distributions in tumor-bearing mice were studied by radionuclide imaging. One type of nanoparticles (fluorescein isothiocyanate-conjugated glycol chitosan (FGC) nanoparticles) exhibited highly selective tumoral localization. Scintigraphic images obtained 1 day after the intravenous injection of FGC nanoparticles clearly delineated the tumor against adjacent tissues. The mechanisms underlying the tumor targeting with self-assembled nanoparticles were investigated in terms of the physicochemical properties of nanoparticles and tumor microenvironments. FGC nanoparticles were preferentially localized in perivascular regions, implying their extravasation to tumors through the hyperpermeable tumor vasculature. The magnitude and pattern of tumoral distribution of self-assembled nanoparticles were influenced by several key factors--(i) in vivo colloidal stability: nanoparticles should maintain their intact nanostructures in vivo for a long period of time, (ii) particle size, (iii) intracellular uptake of nanoparticle: fast cellular uptake greatly facilitates the tumor targeting, (iv) tumor angiogenesis: pathological angiogenesis permits access of nanoparticles to tumors. We believe that this work can provide insight for the engineering of nanoparticles and be extended to cancer therapy and diagnosis, so as to deliver multiple therapeutic agents and imaging probes at high local concentrations.

MR lymphangiography using dendrimer-based contrast agents: A comparison at 1.5T and 3.0T.
Hama Y, Bernardo M, Regino CA, Koyama Y, Brechbiel MW, Krishna MC, Choyke PL, Kobayashi H.
Magn Reson Med. 2007 Feb;57(2):431-6.
[ expand abstract ]

Most macromolecular contrast agents (CAs) show lower r(1) and higher r(2) relaxivities at 3.0T than at 1.5T. MR lymphangiography in mice using a macromolecular G6 dendrimer-based CA was serially performed and compared at both 1.5T and 3.0T. The r(1) and r(2) relaxivities of the G6 CA were 25 and 78/s/mM at 1.5T and 17 and 82/s/mM at 3.0T, respectively. The lymph node (LN)-to-fat ratios (LN signal intensity (SI)/fat SI) of T(1)-weighted 3D-fast spoiled gradient-echo (3D-FSPGR) were 3.2 +/- 0.4 (mean +/- standard deviation (SD)) at 1.5T and 2.7 +/- 0.3 at 3.0T (P = 0.021), and the LN-to-fat ratios of T(2)/T(1)-weighted 3D-fast imaging employing steady-state acquisition with phase cycling (3D-FIESTA-C) were 1.8 +/- 0.2 at 1.5T and 1.2 +/- 0.4 at 3.0T (P = 0.003). Although 3D-FSPGR successfully delineated the LNs at both 1.5T and 3.0T, 3D-FIESTA-C at 3.0T failed to visualize the LNs. Magn Reson Med 57:431-436, 2007.

Surface modification of magnetite nanoparticles using lactobionic acid and their interaction with hepatocytes.
Kamruzzaman Selim KM, Ha YS, Kim SJ, Chang Y, Kim TJ, Ho Lee G, Kang IK.
Biomaterials. 2007 Feb;28(4):710-6.
[ expand abstract ]

In the current study, superparamagnetic magnetite nanoparticles were surface-modified with lactobionic acid (LA) to improve their intracellular uptake and ability to target hepatocytes. Maltotrionic acid (MA)-modified nanoparticles were also synthesized as a control. Cell culture experiment showed that LA-modified nanoparticles were internalized into hepatocytes and atomic absorption spectrometer (AAS) measurement indicated that the uptake amount of LA-modified magnetite into hepatocytes was higher than that of unmodified and MA-modified nanoparticles. LA-modified nanoparticle solution was injected in rabbit and the magnetic resonance (MR) images obtained showed that LA-coated nanoparticles were selectively accumulated onto the hepatocytes. This result demonstrates that the LA-modified magnetite nanoparticles have a great potential to be used as contrast agent for liver diagnosis.

Sentinel Lymph Node Imaging Using Quantum Dots in Mouse Tumor Models.
Ballou B, Ernst LA, Andreko S, Harper T, Fitzpatrick JA, Waggoner AS, Bruchez MP.
Bioconjug Chem. 2007 Jan 31; [Epub ahead of print].
[ expand abstract ]

We demonstrate that quantum dots injected into two model tumors rapidly migrate to sentinel lymph nodes. PEG-coated quantum dots having terminal carboxyl, amino, or methoxyl groups all migrated from the tumor to surrounding lymph nodes similarly. Passage from the tumor through lymphatics to adjacent nodes could be visualized dynamically through the skin; at least two nodes could usually be defined. Imaging during necropsy confirmed confinement of the quantum dots to the lymphatic system and demonstrated easy tagging of sentinel lymph nodes for pathology. Examination of the sentinel nodes identified by quantum dot localization showed that at least some contained metastatic tumor foci.

Nanoshell Magnetic Resonance Imaging Contrast Agents.
Su CH, Sheu HS, Lin CY, Huang CC, Lo YW, Pu YC, Weng JC, Shieh DB, Chen JH, Yeh CS.
J Am Chem Soc. 2007 Jan 31; [Epub ahead of print].
[ expand abstract ]

Nanocontrast agents have great potential in magnetic resonance (MR) molecular imaging applications for clinical diagnosis. We synthesized Au3Cu1 (gold and copper) nanoshells that showed a promising MR contrast effect. For in vitro MR images, the large proton r1 relaxivities brightened T1-weighted images. As for the proton-dephasing effect in T2, Au3Cu1 lightened MR images at the low concentration of 0.125 mg mL-1 (3.84 x 10-7 mM), and then the signal continuously decreased as the concentration increased. For in vivo MR imaging, Au3Cu1 nanocontrast agents enhanced the contrast of blood vessels and suggested their potential use in MR angiography as blood-pool agents. We propose that (1) the cooperativity originating from the form of the nanoparticles and (2) the large surface area coordinated to water from their porous hollow morphology are important for efficient relaxivity. In a cytotoxicity and animal survival assay, Au3Cu1 nanocontrast agents showed a dose-dependent toxic effect: the viability rate of experimental mice reached 83% at a dose of 20 mg kg-1 and as much as 100% at 2 mg kg-1.

Gum Arabic as a Phytochemical Construct for the Stabilization of Gold Nanoparticles: In Vivo Pharmacokinetics and X-ray-Contrast-Imaging Studies.
Kattumuri V, Katti K, Bhaskaran S, Boote EJ, Casteel SW, Fent GM, Robertson DJ, Chandrasekhar M, Kannan R, Katti KV.
Small. 2007 Jan 29;3(2):333-341 [Epub ahead of print].
[ expand abstract ]

Gold nanoparticles (AuNPs) have exceptional stability against oxidation and therefore will play a significant role in the advancement of clinically useful diagnostic and therapeutic nanomedicines. Despite the huge potential for a new generation of AuNP-based nanomedicinal products, nontoxic AuNP constructs and formulations that can be readily administered site-specifically through the intravenous mode, for diagnostic imaging by computed tomography (CT) or for therapy via various modalities, are still rare. Herein, we report results encompassing: 1) the synthesis and stabilization of AuNPs within the nontoxic phytochemical gum-arabic matrix (GA-AuNPs); 2) detailed in vitro analysis and in vivo pharmacokinetics studies of GA-AuNPs in pigs to gain insight into the organ-specific localization of this new generation of AuNP vector, and 3) X-ray CT contrast measurements of GA-AuNP vectors for potential utility in molecular imaging. Our results demonstrate that naturally occurring GA can be used as a nontoxic phytochemical construct in the production of readily administrable biocompatible AuNPs for diagnostic and therapeutic applications in nanomedicine.

Optical and Magnetic Resonance Imaging of Cell Death and Platelet Activation Using Annexin A5-Functionalized Quantum Dots.
Prinzen L, Miserus RJ, Dirksen A, Hackeng TM, Deckers N, Bitsch NJ, Megens RT, Douma K, Heemskerk JW, Kooi ME, Frederik PM, Slaaf DW, Zandvoort MA, Reutelingsperger CP.
Nano Lett. 2007 Jan 10;7(1):93-100.
[ expand abstract ]

A quantum-dot-based nanoparticle is presented, allowing visualization of cell death and activated platelets with fluorescence imaging and MRI. The particle exhibits intense fluorescence and a large MR relaxivity (r1) of 3000-4500 mM-1 s-1 per nanoparticle due to a newly designed construct increasing the gadolinium-DTPA load. The nanoparticle is suitable for both anatomic and subcellular imaging of structures in the vessel wall and is a promising bimodal contrast agent for future in vivo imaging studies.

Magnetic resonance imaging of temperature-sensitive liposome release: drug dose painting and antitumor effects.
Ponce AM, Viglianti BL, Yu D, Yarmolenko PS, Michelich CR, Woo J, Bally MB, Dewhirst MW.
J Natl Cancer Inst. 2007 Jan 3;99(1):53-63.
[ expand abstract ]

BACKGROUND: In preclinical studies, lysolipid-based temperature-sensitive liposomes (LTSLs) containing chemotherapy drugs administered in combination with local hyperthermia have been found to increase tumor drug concentrations and improve antitumor efficacy of the drugs. We used a novel magnetic resonance imaging (MRI) method to measure the temporal and spatial patterns of drug delivery in a rat fibrosarcoma model during treatment with LTSLs containing doxorubicin and an MRI contrast agent (manganese) (Dox/Mn-LTSLs) administered at different times with respect to hyperthermia. METHODS: Rats bearing 10- to 12-mm fibrosarcomas (n = 6-7 per group) were treated with Dox/Mn-LTSLs (at a dose of 5 mg doxorubicin/kg body weight) before and/or during 60 minutes of local tumor hyperthermia administered via a catheter inserted at the center of the tumor. Drug distribution was monitored continuously via MRI. Magnetic resonance changes were used to calculate intratumoral doxorubicin concentrations throughout treatment. Tumors were monitored until they reached five times their volume on the day of treatment or 60 days. Doxorubicin concentrations and times for tumors to reach five times their volume on the day of treatment were analyzed using the Kruskal-Wallis test and the Kaplan-Meier product-limit method, respectively. All statistical tests were two-sided. RESULTS: Administration of Dox/Mn-LTSLs before, during, and both before and during hyperthermia yielded central, peripheral, and uniform drug distributions, respectively. Doxorubicin accumulated more quickly and reached higher concentrations in the tumor when Dox/Mn-LTSLs were administered during hyperthermia than when administered before hyperthermia (rate: 9.8 versus 1.8 microg/min, difference = 8.0 microg/min, 95% confidence interval [CI] = 6.8 to 12.8 microg/min, P = .003; concentration: 15.1 versus 8.0 ng/mg, difference = 7.1 ng/mg, 95% CI = 3.6 to 10.6 ng/mg, P = .028). LTSL administered during hyperthermia also yielded the greatest antitumor effect, with a median time for tumors to reach five times their volume on the day of treatment of 34 days (95% CI = 30 days to infinity) compared with 18.5 days (95% CI = 16 to 23 days) for LTSL before hyperthermia and 22.5 days (95% CI = 15 to 25 days) for LTSL before and during hyperthermia. CONCLUSIONS: In this rat fibrosarcoma model, LTSLs were most effective when delivered during hyperthermia, which resulted in a peripheral drug distribution.

Artificially engineered magnetic nanoparticles for ultra-sensitive molecular imaging.
Lee JH, Huh YM, Jun YW, Seo JW, Jang JT, Song HT, Kim S, Cho EJ, Yoon HG, Suh JS, Cheon J.
Nat Med. 2007 Jan;13(1):95-9.
[ expand abstract ]

Successful development of ultra-sensitive molecular imaging nanoprobes for the detection of targeted biological objects is a challenging task. Although magnetic nanoprobes have the potential to perform such a role, the results from probes that are currently available have been far from optimal. Here we used artificial engineering approaches to develop innovative magnetic nanoprobes, through a process that involved the systematic evaluation of the magnetic spin, size and type of spinel metal ferrites. These magnetism-engineered iron oxide (MEIO) nanoprobes, when conjugated with antibodies, showed enhanced magnetic resonance imaging (MRI) sensitivity for the detection of cancer markers compared with probes currently available. Also, we successfully visualized small tumors implanted in a mouse. Such high-performance, nanotechnology-based molecular probes could enhance the ability to visualize other biological events critical to diagnostics and therapeutics.

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2006

Targeting of cancer cells with ferrimagnetic ferritin cage nanoparticles.
Uchida M, Flenniken ML, Allen M, Willits DA, Crowley BE, Brumfield S, Willis AF, Jackiw L, Jutila M, Young MJ, Douglas T.
J Am Chem Soc. 2006 Dec 27;128(51):16626-33.
[ expand abstract ]

Protein cage architectures such as virus capsids and ferritins are versatile nanoscale platforms amenable to both genetic and chemical modification. Incorporation of multiple functionalities within these nanometer-sized protein architectures demonstrate their potential to serve as functional nanomaterials with applications in medical imaging and therapy. In the present study, we synthesized an iron oxide (magnetite) nanoparticle within the interior cavity of a genetically engineered human H-chain ferritin (HFn). A cell-specific targeting peptide, RGD-4C which binds alphavbeta3 integrins upregulated on tumor vasculature, was genetically incorporated on the exterior surface of HFn. Both magnetite-containing and fluorescently labeled RGD4C-Fn cages bound C32 melanoma cells in vitro. Together these results demonstrate the capability of a genetically modified protein cage architecture to serve as a multifunctional nanoscale container for simultaneous iron oxide loading and cell-specific targeting.

Accumulation of liposome with Sialyl Lewis X to inflammation and tumor region: Application to in vivo bio-imaging.
Hirai M, Minematsu H, Kondo N, Oie K, Igarashi K, Yamazaki N.
Biochem Biophys Res Commun. 2006 Dec 19; [Epub ahead of print].
[ expand abstract ]

We prepared the liposome binding Sialyl Lewis X (SLX) on the surface in order to specifically and efficiently deliver substances (fluorescent materials, chemical substances, proteins, genes, etc.) to inflammation or tumor regions. The liposome with SLX (SLX-Lipo-Cy5.5), in which fluorescent substance Cy5.5 was included, was administered intravenously to arthritis or Ehrlich Ascites Tumor (EAT) bearing mouse, and the accumulation of liposome was observed using two types of in vivo fluorescent imaging equipment. The result was that the accumulation of SLX-Lipo-Cy5.5 to inflammation or tumor regions was significantly higher than the control liposome without sugar chain (Lipo-Cy5.5) at 24 and 48h after administration. In addition, it was confirmed that this accumulation showed a shift of liposome from blood vessels to the surrounding tissues. Thus, it was proven that this liposome is useful not only as an in vivo bio-imaging reagent but also as a drug delivery system (DDS).

Dual-Mode Nanoparticle Probes for High-Performance Magnetic Resonance and Fluorescence Imaging of Neuroblastoma.
Lee JH, Jun YW, Yeon SI, Shin JS, Cheon J.
Angew Chem Int Ed Engl. 2006 Dec 11;45(48):8160-8162.
[ expand abstract ]

No abstract available

Recent advances in iron oxide nanocrystal technology for medical imaging.
Corot C, Robert P, Idee JM, Port M.
Adv Drug Deliv Rev. 2006 Dec 1;58(14):1471-504.
[ expand abstract ]

Superparamagnetic iron oxide particles (SPIO and USPIO) have a variety of applications in molecular and cellular imaging. Most of the recent research has concerned cellular imaging with imaging of in vivo macrophage activity. According to the iron oxide nanoparticle composition and size which influence their biodistribution, several clinical applications are possible: detection liver metastases, metastatic lymph nodes, inflammatory and/or degenerative diseases. USPIO are investigated as blood pool agents with T1 weighted sequence for angiography, tumour permeability and tumour blood volume or steady-state cerebral blood volume and vessel size index measurements using T2() weighted sequences. Stem cell migration and immune cell trafficking, as well as targeted iron oxide nanoparticles for molecular imaging studies, are at the stage of proof of concept, mainly in animal models.

Cervical lymph node metastases: MR imaging of gadofluorine M and monocrystalline iron oxide nanoparticle-47 in a rabbit model of head and neck cancer.
Choi SH, Han MH, Moon WK, Son KR, Won JK, Kim JH, Kwon BJ, Na DG, Weinmann HJ, Chang KH.
Radiology. 2006 Dec;241(3):753-62.
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PURPOSE: To prospectively compare the accuracy of gadofluorine M with that of monocrystalline iron oxide nanoparticle (MION)-47 for the depiction of cervical lymph node metastases at magnetic resonance (MR) imaging in a rabbit model of head and neck cancer by using histologic analysis as the reference standard. MATERIALS AND METHODS: Experiments were approved by the animal care committee. VX2 carcinomas were implanted in both ears of 11 rabbits 4 weeks before MR imaging. T2-weighted, T2*-weighted, and T1-weighted MR images were acquired, and sequential T1-weighted MR imaging was performed immediately and 30 minutes after administration of gadofluorine M (0.05 mmol gadolinium per kilogram body weight). T2-weighted and T2*-weighted MR imaging were performed 24 hours after administration of MION-47 (2.6 mg iron per kilogram body weight). Gadofluorine M- and MION-47-enhanced MR imaging were performed separately and independently by two radiologists who had no knowledge of histopathologic results, and the presence of metastases in lymph nodes was evaluated. A receiver operating characteristic analysis was conducted to compare the diagnostic value of gadofluorine M- and MION-47-enhanced MR imaging. RESULTS: Metastases were confirmed in 20 of 77 lymph nodes at histopathologic analysis. The area under the curve was significantly greater for gadofluorine M-enhanced MR imaging (0.997 and 0.981 for readers 1 and 2, respectively) than for MION-47-enhanced MR imaging (0.889 and 0.846 for readers 1 and 2, respectively). For gadofluorine M-enhanced MR imaging, sensitivity was 100% for both readers and specificity was 89.5% for reader 1 and 87.7% for reader 2. For MION-47-enhanced MR imaging, sensitivity was 80.0% for both readers and specificity was 75.4% for reader 1 and 71.9% for reader 2. CONCLUSION: Gadofluorine M-enhanced MR imaging has higher accuracy for depicting lymph node metastases than does MION-47-enhanced MR imaging.

Comparison of lymphotropic nanoparticle-enhanced MRI sequences in patients with various primary cancers.
Saksena M, Harisinghani M, Hahn P, Kim J, Saokar A, King B, Weissleder R.
AJR Am J Roentgenol. 2006 Dec;187(6):W582-8.
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OBJECTIVE: This study was performed to empirically evaluate T2-weighted fast spin-echo, moderately T2*-weighted gradient-refocused echo (GRE), and heavily T2*-weighted GRE sequences to determine which sequence is the most effective for nodal characterization on lymphotropic nanoparticle-enhanced MRI (LNMRI). MATERIALS AND METHODS: The study included 65 patients who had proven primary cancer and were scheduled for either surgical lymph node dissection or imaging-guided lymph node biopsy. All patients underwent LNMRI using T2-weighted fast spin-echo, moderately T2*-weighted GRE, and heavily T2*-weighted GRE sequences. Unequivocal correlation of histopathology and MRI could be made in 140 nodes and only these were included in the analysis. Two blinded reviewers performed qualitative analysis of the nodes. Alternative free-response receiver operating characteristic (ROC) curves with a continuous rating scale were plotted for each sequence for both reviewers and the diagnostic accuracy of fast spin-echo T2-weighted and GRE T2*-weighted images were compared by calculating the area under the curve (A(Z)). A two-tailed Student's t test was performed to test the significance (p < 0.05) of the differences between the ROC curves derived from the three sequences. RESULTS: Irrespective of reviewer experience, T2*-weighted sequences showed better nodal characterization when compared with T2-weighted sequences. For both reviewers, there was a statistically significant difference between the A(Z) for T2- and the two T2*-weighted sequences (p < 0.05). Neither reviewer showed a statistically significant difference between the two T2*-weighted sequences. CONCLUSION: GRE T2*-weighted sequences are superior for nodal characterization on LNMRI to fast spin-echo T2-weighted sequences. Imaging protocols for LNMRI should include fast spin-echo T2-weighted imaging for anatomic localization, but characterization of nodes should be based on their appearance on contrast-enhanced T2*-weighted images. The T2*-weighted images acquired with dual TE values, one of which is intermediate and the other longer, improve nodal characterization.

Targeted PARACEST nanoparticle contrast agent for the detection of fibrin.
Winter PM, Cai K, Chen J, Adair CR, Kiefer GE, Athey PS, Gaffney PJ, Buff CE, Robertson JD, Caruthers SD, Wickline SA, Lanza GM.
Magn Reson Med. 2006 Dec;56(6):1384-8.
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A lipid-encapsulated perfluorocarbon nanoparticle molecular imaging contrast agent that utilizes a paramagnetic chemical exchange saturation transfer (PARACEST) chelate is presented. PARACEST agents are ideally suited for molecular imaging applications because one can switch the contrast on and off at will simply by adjusting the pulse sequence parameters. This obviates the need for pre- and postinjection images to define contrast agent binding. Spectroscopy (4.7T) of PARACEST nanoparticles revealed a bound water peak at 52 ppm, in agreement with results from the water-soluble chelate. Imaging of control nanoparticles showed no appreciable contrast, while PARACEST nanoparticles produced >10% signal enhancement. PARACEST nanoparticles were targeted to clots via antifibrin antibodies and produced a contrast-to-noise ratio (CNR) of 10 at the clot surface.

Emerging concepts in molecular MRI.
Sosnovik DE, Weissleder R.
Curr Opin Biotechnol. 2006 Nov 23; [Epub ahead of print].
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Molecular magnetic resonance imaging (MRI) offers the potential to image some events at the cellular and subcellular level and many significant advances have recently been witnessed in this field. The introduction of targeted MR contrast agents has enabled the imaging of sparsely expressed biological targets in vivo. Furthermore, high-throughput screens of nanoparticle libraries have identified nanoparticles that act as novel contrast agents and which can be targeted with enhanced diagnostic specificity and range. Another class of magnetic nanoparticles have also been designed to image dynamic events; these act as 'switches' and could be used in vitro, and potentially in vivo, as biosensors. Other specialized MR probes have been developed to image enzyme activity in vivo. Lastly, the use of chemical exchange and off-resonance techniques have been developed, adding another dimension to the broad capabilities of molecular MRI and offering the potential of multispectral imaging. These and other advances in molecular MRI offer great promise for the future and have significant potential for clinical translation.

Vascular targeted nanoparticles for imaging and treatment of brain tumors.
Reddy GR, Bhojani MS, McConville P, Moody J, Moffat BA, Hall DE, Kim G, Koo YE, Woolliscroft MJ, Sugai JV, Johnson TD, Philbert MA, Kopelman R, Rehemtulla A, Ross BD.
Clin Cancer Res. 2006 Nov 15;12(22):6677-86.
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PURPOSE: Development of new therapeutic drug delivery systems is an area of significant research interest. The ability to directly target a therapeutic agent to a tumor site would minimize systemic drug exposure, thus providing the potential for increasing the therapeutic index. EXPERIMENTAL DESIGN: Photodynamic therapy (PDT) involves the uptake of a sensitizer by the cancer cells followed by photoirradiation to activate the sensitizer. PDT using Photofrin has certain disadvantages that include prolonged cutaneous photosensitization. Delivery of nanoparticles encapsulated with photodynamic agent specifically to a tumor site could potentially overcome the drawbacks of systemic therapy. In this study, we have developed a multifunctional polymeric nanoparticle consisting of a surface-localized tumor vasculature targeting F3 peptide and encapsulated PDT and imaging agents. RESULTS: The nanoparticles specifically bound to the surface of MDA-435 cells in vitro and were internalized conferring photosensitivity to the cells. Significant magnetic resonance imaging contrast enhancement was achieved in i.c. rat 9L gliomas following i.v. nanoparticle administration. Serial magnetic resonance imaging was used for determination of pharmacokinetics and distribution of nanoparticles within the tumor. Treatment of glioma-bearing rats with targeted nanoparticles followed by PDT showed a significant improvement in survival rate when compared with animals who received PDT after administration of nontargeted nanoparticles or systemic Photofrin. CONCLUSIONS: This study reveals the versatility and efficacy of the multifunctional nanoparticle for the targeted detection and treatment of cancer.

Real-time Imaging and Quantification of Brain Delivery of Liposomes.
Krauze MT, Forsayeth J, Park JW, Bankiewicz KS.
Pharm Res. 2006 Nov;23(11):2493-504.
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The surgical delivery of therapeutic agents into the parenchyma of the brain is problematic because it has been virtually impossible to know with any certainty where infused material is going, and how much to infuse. We have started to use liposomes loaded with Gadoteridol (GDL) as a tracer that allows us to follow infusions in real-time on magnetic resonance imaging (MRI). MRI allows precise tracking and measurement of liposomes loaded with markers and therapeutics. This review provides an overview of real-time delivery of liposomes to the central nervous system (CNS), and discusses the technical aspects of delivery, liposomes as colloidal systems of delivery, real-time distribution of liposomes in CNS, and quantification of liposome distribution. Our data suggests that real-time monitoring of liposomal drug infusion is likely to improve outcomes of clinical trials where convection-enhanced delivery (CED) is being used to target drugs to specific brain structures through limitation of systemic toxicity and reduction of side effects. This review is a summary of work done by our group over the past four years.

One-Pot Synthesis of PEGylated Ultrasmall Iron-Oxide Nanoparticles and Their in Vivo Evaluation as Magnetic Resonance Imaging Contrast Agents.
Lutz JF, Stiller S, Hoth A, Kaufner L, Pison U, Cartier R.
Biomacromolecules. 2006 Nov;7(11):3132-8.
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A well-defined copolymer poly(oligo(ethylene glycol) methacrylate-co-methacrylic acid) P(OEGMA-co-MAA) was studied as a novel water-soluble biocompatible coating for superparamagnetic iron oxide nanoparticles. This copolymer was prepared via a two-step procedure: a well-defined precursor poly(oligo(ethylene glycol) methacrylate-co-tert-butyl methacrylate), P(OEGMA-co-tBMA) (M(n) = 17300 g mol(-1); M(w)/M(n) = 1.22), was first synthesized by atom-transfer radical polymerization in the presence of the catalyst system copper(I) chloride/2,2'-bipyridyl and subsequently selectively hydrolyzed in acidic conditions. The resulting P(OEGMA-co-MAA) was directly utilized as a polymeric stabilizer in the nanoparticle synthesis. Four batches of ultrasmall PEGylated magnetite nanoparticles (i.e., with an average diameter below 30 nm) were prepared via aqueous coprecipitation of iron salts in the presence of variable amounts of P(OEGMA-co-MAA). The diameter of the nanoparticles could be easily tuned in the range 10-25 nm by varying the initial copolymer concentration. Moreover, the formed PEGylated ferrofluids exhibited a long-term colloidal stability in physiological buffer and could therefore be studied in vivo by magnetic resonance (MR) imaging. Intravenous injection into rats showed no detectable signal in the liver within the first 2 h. Maximum liver accumulation was found after 6 h, suggesting a prolongated circulation of the nanoparticles in the bloodstream as compared to conventional MR imaging contrast agents.

Cervical Lymph Node Metastases: MR Imaging of Gadofluorine M and Monocrystalline Iron Oxide Nanoparticle-47 in a Rabbit Model of Head and Neck Cancer.
Choi SH, Han MH, Moon WK, Son KR, Won JK, Kim JH, Kwon BJ, Na DG, Weinmann HJ, Chang KH.
Radiology. 2006 Oct 10; [Epub ahead of print] .
[ expand abstract ]

Purpose: To prospectively compare the accuracy of gadofluorine M with that of monocrystalline iron oxide nanoparticle (MION)-47 for the depiction of cervical lymph node metastases at magnetic resonance (MR) imaging in a rabbit model of head and neck cancer by using histologic analysis as the reference standard. Materials and Methods: Experiments were approved by the animal care committee. VX2 carcinomas were implanted in both ears of 11 rabbits 4 weeks before MR imaging. T2-weighted, T2*-weighted, and T1-weighted MR images were acquired, and sequential T1-weighted MR imaging was performed immediately and 30 minutes after administration of gadofluorine M (0.05 mmol gadolinium per kilogram body weight). T2-weighted and T2*-weighted MR imaging were performed 24 hours after administration of MION-47 (2.6 mg iron per kilogram body weight). Gadofluorine M- and MION-47-enhanced MR imaging were performed separately and independently by two radiologists who had no knowledge of histopathologic results, and the presence of metastases in lymph nodes was evaluated. A receiver operating characteristic analysis was conducted to compare the diagnostic value of gadofluorine M- and MION-47-enhanced MR imaging. Results: Metastases were confirmed in 20 of 77 lymph nodes at histopathologic analysis. The area under the curve was significantly greater for gadofluorine M-enhanced MR imaging (0.997 and 0.981 for readers 1 and 2, respectively) than for MION-47-enhanced MR imaging (0.889 and 0.846 for readers 1 and 2, respectively). For gadofluorine M-enhanced MR imaging, sensitivity was 100% for both readers and specificity was 89.5% for reader 1 and 87.7% for reader 2. For MION-47-enhanced MR imaging, sensitivity was 80.0% for both readers and specificity was 75.4% for reader 1 and 71.9% for reader 2. Conclusion: Gadofluorine M-enhanced MR imaging has higher accuracy for depicting lymph node metastases than does MION-47-enhanced MR imaging.

Calcium-sensitive MRI contrast agents based on superparamagnetic iron oxide nanoparticles and calmodulin.
Atanasijevic T, Shusteff M, Fam P, Jasanoff A.
Proc Natl Acad Sci U S A. 2006 Oct 3;103(40):14707-12.
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We describe a family of calcium indicators for magnetic resonance imaging (MRI), formed by combining a powerful iron oxide nanoparticle-based contrast mechanism with the versatile calcium-sensing protein calmodulin and its targets. Calcium-dependent protein-protein interactions drive particle clustering and produce up to 5-fold changes in T2 relaxivity, an indication of the sensors' potency. A variant based on conjugates of wild-type calmodulin and the peptide M13 reports concentration changes near 1 muM Ca(2+), suitable for detection of elevated intracellular calcium levels. The midpoint and cooperativity of the response can be tuned by mutating the protein domains that actuate the sensor. Robust MRI signal changes are achieved even at nanomolar particle concentrations (<1 muM in calmodulin) that are unlikely to buffer calcium levels. When combined with technologies for cellular delivery of nanoparticulate agents, these sensors and their derivatives may be useful for functional molecular imaging of biological signaling networks in live, opaque specimens.

Noninvasive vascular cell adhesion molecule-1 imaging identifies inflammatory activation of cells in atherosclerosis.
Nahrendorf M, Jaffer FA, Kelly KA, Sosnovik DE, Aikawa E, Libby P, Weissleder R.