Nano-Enabled Paper Detects Kidney Cancer Markers
Using common laboratory filter paper coated with antibody-labeled gold nanorods, a team of investigators at Washington University in St. Louis has developed a rapid and inexpensive method for detecting biomarkers of kidney cancer in urine. Srikanth Singamaneni and his collaborators published their findings in the journal Analytical Chemistry.
Kidney cancer, which accounts for three percent of all adult cancers, is a silent killer. It presents with few symptoms until it has spread throughout the body, at which point the disease is largely fatal. In the few instances where a kidney tumor is discovered at an early stage, usually during an abdominal scan for other reasons, surgical removal of the tumor is nearly 100 percent effective at curing this disease.
In 2010, two of Dr. Singamaneni’s colleagues at Washington University, Evan Kharasch and Jeremiah Morrissey, led a team that identified two candidate biomarkers for kidney cancer. These molecules, aquaporin-1 and adipophilin, are present in urine at elevated levels in patients with the most common forms of kidney cancer. In addition, the levels of these two proteins correlated with tumor size and fell by as much as 97 percent when tumors were removed surgically.
Urine-based tests have the potential to be used in routine screening efforts but only if they are inexpensive to perform. The technology now used clinically to detect specific proteins such as these two potential biomarkers, known as an enzyme-linked immunosorbent assay (ELISA), is both expensive and time-consuming, and requires a relatively high level of laboratory expertise to produce accurate results.
To solve this problem, Dr. Singamaneni and his colleagues created what they are calling bioplasmonic paper – filter paper impregnated with gold nanorods linked to antibodies that would bind to aquaporin-1. Gold nanorods respond to light by producing what is known as a localized surface plasmon resonance (LSPR), a specific type of light emission that involves waves of electrons moving across the surface of metal nanostructures. LSPR is very sensitive to molecular events that occur on or near the surface of the particles, including binding of biomolecules to attached antibodies.
Traditionally, LSPR detection devices are rigid, flat surfaces such as glass, but Dr. Singamaneni has shown that standard filter paper can also serve as an LSPR substrate. In fact, his team demonstrated that the sensitivity and limit of detection for their paper-based system is at least as good, if not better, than for conventional rigid substrates. In this case, the limit of detection matched that of the range of aquaporin-1 levels in patients with kidney cancer. Other advantages of using paper include its wicking properties, flexible surface for collection, compatibility with standard ink jet printing technology, low cost, and ease of disposal.
This work, which was supported in part by the National Cancer Institute, is detailed in a paper titled, “Bioplasmonic paper as a platform for detection of kidney cancer biomarkers.” An abstract of this paper is available at the journal's website.