Direct determination of small RNAs using a biotinylated polythiophene impedimetric genosensor

A direct determination of small RNAs is described using a functional-polymer modified genosensor. The analytical strategy adopted involves deposition by electropolymerization of biotinylated polythiophene films on the surface of miniaturized, disposable, gold screen-printed electrodes, followed by the layer-by-layer deposition of streptavidin, and then biotynilated capture probes. A small RNA (miR-221) target was determined via the impedimetric measurement of the hybridization event in a label-free and PCR-free approach. Under optimized conditions, the limit of detection (LOD) was 0.7 pM miR-221 (15% RSD). The genosensor was applied for determination of miR-221 in total RNA extracted from human lung and breast cancer cell lines, discriminating between the cancer-positive and -negative cells, without any amplification step, in less than 2 h.