MicroRNA Biosensing with Two-Dimensional Surface Plasmon Resonance Imaging.

Two-dimensional surface plasmon resonance (2D-SPR) imaging, which provides a real-time, sensitive, and high-throughput analysis of surface events in a two dimensional manner, is a valuable tool for studying biomolecular interactions and biochemical reactions without using any tag labels. The sensing principle of 2D-SPR includes angular, wavelength, and phase interrogation. In this chapter, the 2D-SPR imaging technique is applied for sensing a target microRNA by its corresponding oligonucleotide probes, with sequence complementarity, immobilized on the gold SPR sensing surface. However, the low SPR signal due to intrinsic properties such as low molecular weight and quantity (pico-nanomolar) of the microRNA in clinical samples limits the direct detection of microRNA. Therefore, we developed a biosensing technique known as MARS (MicroRNA-RNase-SPR) assay, which utilizes RNase H to digest the microRNA probes enzymatically for fast signal amplification, i.e., in order to increase both the SPR signal and readout speed without the need for pre-amplification of target cDNA by polymerase chain reaction (PCR). Practically, we targeted microRNA hsa-miR-29a-3p, whose signature correlates to influenza infection, for rapid screening of influenza A (H1N1) patients from throat swab samples.