image: Figure 1 shows the new power-free RNA detection microchip. Left: Fabricated microchip. Right: Microchannel design. view more
Credit: RIKEN
A new power-free microfluidic chip developed by researchers at the RIKEN Advanced Science Institute (ASI) enables detection of microRNA from extremely small sample volume in only 20 minutes. By drastically reducing the time and quantity of sample required for detection, the chip lays the groundwork for early-stage point-of-care diagnosis of diseases such as cancer and Alzheimer's.
MicroRNAs (miRNAs) are small, non-coding RNA molecules that regulate gene expression in a wide range of biological processes including development, cell proliferation, differentiation and cell death (apoptosis). Concentration of certain miRNA in body fluids increases with the progression of diseases such as cancer and Alzheimer's, generating hope that these short RNA may hold the key to faster, more accurate diagnosis. Currently available techniques for sensitive miRNA detection, however, require days to reach a diagnosis and involve equipment operated only by trained personnel, making them impractical for use in many situations.
The research team set out to overcome these obstacles by developing a device that enables fast, easy-to-use point-of-care (POC) diagnosis from only a very small sample. In earlier research, the team developed a device in the form of a microchip which uses polydimethylsiloxane (PDMS), a silicone compound known for its air absorption properties, to pull reagents into a capture probe for analysis. This pumping technique simplified design by eliminating the need for external power sources, but the device required a quantity of sample too large for practical applications.
The new device also uses PDMS as an air pump, but drastically improves the method's sensitivity through a signal amplification method called laminar flow-assisted dendritic amplification (LFDA). First, DNA fragments which bond to specific miRNA sequences are fixed to a glass surface along with the miRNA sample to be analyzed, and then sandwiched under a layer of PDMS with channels in it (Figure 1). Emptied of air in a vacuum, the PDMS layer induces a pump effect which pulls amplification reagents, inserted at the channel inlets, into the channels and into contact with the miRNA, creating fluorescence-labeled dendritic structures that grow over time and can be quickly detected.
The sensitivity of this technique drastically reduces the sample quantity required for diagnosis to only 0.25 attomoles (10-18 mole), a thousand-fold improvement over the team's earlier model. Together with its detection time of only 20 minutes, these properties make the self-powered device ideal for use in resource-poor environments, promising portable point-of-care diagnosis for millions in developing countries and around the world.
Reference:
Hideyuki Arata, Hiroshi Komatsu, Kazuo Hosokawa, and Mizuo Maeda "Rapid and Sensitive MicroRNA Detection with Laminar Flow-Assisted Dendritic Amplification on Power-Free Microfluidic Chip". PLOS ONE, 2012, doi:10.1371/journal.pone.0048329
About RIKEN
RIKEN is Japan's flagship research institute devoted to basic and applied research. Over 2500 papers by RIKEN researchers are published every year in reputable scientific and technical journals, covering topics ranging across a broad spectrum of disciplines including physics, chemistry, biology, medical science and engineering. RIKEN's advanced research environment and strong emphasis on interdisciplinary collaboration has earned itself an unparalleled reputation for scientific excellence in Japan and around the world.
About the RIKEN Advanced Science Institute
The RIKEN Advanced Science Institute (ASI) is an interdisciplinary research institute devoted to fostering creative, curiosity-driven basic research and sowing the seeds for innovative new projects. With more than 700 full-time researchers, the ASI acts as RIKEN's research core, supporting inter-institutional and international collaboration and integrating diverse scientific fields including physics, chemistry, engineering, biology and medical science.
Reach us on Twitter: @rikenresearch
Journal
PLoS ONE