With sufficient concentrations of a target, the "most sensitive microRNA detector yet" can analyze a drop of blood for cancer-specific biomarkers called microRNAs in just 20 minutes, say scientists at Japan's Riken Advanced Science Institute (Wako).1
The self-powered microfluidic chip aims to provide a quick, inexpensive, point-of-care means of detecting microRNAs that are sometimes present in blood long before symptoms become evident. It uses an internal pressure gradient to pump a sample through microchannels; thus, it requires no external power supply.
The Riken researchers' invention improves upon earlier versions of the chip that were able to detect microRNA only at concentrations far above those required for early-stage cancer detection. The original chip worked by immobilizing target microRNA on probe DNA in the main microchannel, where each bound site produced a fluorescent signal. In the new chips, the researchers added a fluorescence amplification process that involves passing two amplification reagents over the immobilized microRNA. The reagents—a fluorescent tag and a branched linker—bind to the microRNA to form dendritic structures that amplify the fluorescence signal by up to 1,000 times.
The team hopes next to simplify the device by eliminating the need for a fluorescence microscope. Doing so will involve replacing the fluorescent tags with another type of marker-perhaps gold particles, which would enable naked-eye detection.
1. H. Arata, H. Komatsu, K. Hosokawa, and M. Maeda, PLoS ONE, 7, 11, e48329 (2012).