Irregular expressions of a panel of regulatory microRNAs (miRNA) in blood and other physiological fluids may allow early screening of many kinds of cancer. However, the current technologies for identifying and quantifying small numbers of these short (22 bases) molecules in physiological samples require expensive instrumentation and extensive personnel. These technical obstacles will prevent use of future cancer-screening tests in doctor/dental clinics or even at home, where they can be personalized and used frequently for maximum effectiveness. Chang's group has developed a simple technology that can identify and quantify from 100 to 1 million copies of each miRNA within 15 minutes---and with low-cost instrumentation. They apply an electric field through a nano pipette, constructed by melting and pulling an ordinary laboratory capillary, to assemble a small (micron-sized) gold nano particle crystal at the tip of the nano pipette. The gold nano particles are covered with "smart" molecular probes that can capture specific miRNA targets and emit light after capturing them. The intensity of this molecular beacon is proportional to the intensity of the external illumination. The trick in this new technology is to use the external voltage to tune the spacing of the nano particle assembly so that it can resonantly trap and intensify the external illumination from a cheap light source to remove the need for expensive lasers and optical detectors. The extreme sensitivity the technology offers also suggests that PCR amplification or other personnel-extensive operations are unnecessary and a single turn-key device can be designed for quantifying (profiling) a panel of different free-floating miRNA targets in physiological samples or in cells and exosomes within the samples. Chang's group is currently working on such integrated biochips and the complementary turn-key instrument that can profile a large panel of miRNAs from raw samples.
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