PCR-Free, Multiplexed Expression Profiling of microRNAs Using Silicon Photonic Microring Resonators.

We describe an approach for multiplexed microRNA analysis using silicon photonic microring resonators to detect cDNA reverse transcription products via a subsequent enzymatic signal enhancement strategy. Key to this method is a modified stem loop primer that facilitates downstream signal amplification via enzymatic turnover and improves the sensor signal 20-fold when compared to traditional stem loop primers. This approach facilitates targeted microRNA quantification in only 2.5 h and without requiring target amplification via the polymerase chain reaction (PCR). Primers for 7 miRNA targets were orthogonally designed to avoid cross-hybridization between capture probes. This approach was applied to the detection of total RNA from human tissues and found to display differential expression profiles consistent with literature precedent. This development holds promise as an alternative to single-plex RT-qPCR methods and more expensive RNA-seq by offering a cost-effective method to analyze targeted miRNA panels in emerging diagnostic applications.