Rapid Sub-attomole MicroRNA Detection on a Portable Microfluidic Chip

Microfluidic devices are an attractive choice for meeting the requirements of point-of-care microRNA detection. A method using a microfluidic device can drastically shorten the incubation time because the device conveys sample molecules right straight to the surface-immobilized probe DNAs by hydrodynamic force. In this review, we present an overview of a new method for rapid and sensitive microRNA detection from a small sample volume using a power-free microfluidic device driven by degassed poly-dimethylsiloxane (PDMS). Two key technologies for this detection method are summarized. One of the methods relies on the coaxial stacking effect of nucleic acids during sandwich hybridization. This effect is also efficient for stabilizing sandwich hybridization consisting of small DNA and microRNA. The other is the laminar flow-assisted dendritic amplification, which increases the fluorescent signal by supplying two amplification reagents from laminar streams to surface-bound molecules. Utilizing both technologies, microRNA detection is possible with a 0.5 pM detection limit from a 0.5 mu L sample corresponding to 0.25 attomoles, with a detection time of 20 min. Since microRNAs are associated with various human diseases, future studies of these technologies might contribute to improved healthcare and may have both industrial and societal impacts.