Quantification of tRNA fragments by electrochemical direct detection in small volume biofluid samples

Elevated levels of transfer RNA (tRNA) fragments were recently identified in plasma samples from people with epilepsy in advance of a seizure, indicting a potential novel class of circulating biomarker. Current methods for detection and quantitation of tRNA fragments (tRFs) include northern blotting, RNA sequencing or custom Taqman-based PCR assays. The development of a simple, at home or clinic-based test, would benefit from a simple and reliable method to detect the tRFs using small volumes of biofluids. Here we describe an electrochemical direct detection method based on electrocatalytic platinum nanoparticles to detect 3 specific tRFs: 5'AlaTGC, 5'GlyGCC, and 5'GluCTC. Using synthetic tRF mimics we showed this system was linear over 9 orders of magnitude with sub-attomolar limits of detection. Specificity was tested using naturally occurring mismatched tRF mimics. Finally, we quantified tRF levels in patient plasma and showed that our detection system recapitulates results obtained by qPCR. We have designed a tRF detection system with high sensitivity and specificity capable of quantifying tRFs in low volumes of plasma using benchtop apparatus. This is an important step in the development of a point-of-care device for quantifying tRFs in whole blood.