MicroRNA’s (miRNA), short bits of RNA that help out with all sorts of processes in the body, have been identified in the past few years as great markers for various cancers and other diseases. Although useful for diagnostics, detecting target miRNA molecules requires expensive equipment and lots of waiting time before results come in.
Researchers at Japan’s RIKEN Advanced Science Institute have designed a microfluidic sensor capable of fast detection of microRNA from a small liquid sample. The device, which doesn’t require a power source, provides results within twenty minutes and can be manufactured at little cost. The technology promises to deliver cheap miRNA detection to advanced countries and introduce it to the developing world as well.
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.
RIKEN press release: New portable device enables RNA detection from ultra-small sample in only 20 minutes
Study in PLoS ONE: Rapid and Sensitive MicroRNA Detection with Laminar Flow-Assisted Dendritic Amplification on Power-Free Microfluidic Chip