Enzyme-free amplified detection of cellular microRNA by light-harvesting fluorescent nanoparticle probes.

Detection of cellular microRNA biomarkers is an emerging powerful tool in cancer diagnostics. Currently, it requires multistep tedious protocols based on molecular amplification of the RNA target, e.g. RT-qPCR. Here, we developed a one-step enzyme-free method for microRNA detection in cellular extracts based on light-harvesting nanoparticle (nanoantenna) biosensors. They amplify the fluorescence signal by effective Förster resonance energy transfer (FRET) from ultrabright dye-loaded polymeric nanoparticle to a single acceptor and thus convert recognition of one microRNA copy (through nucleic acid strand displacement) into a response of >400 dyes. The developed nanoprobes of 17–19 nm diameter for four microRNAs (miR-21, let-7f, miR-222 and miR-30a) exhibit outstanding brightness (up to 3.8 × 107 M−1cm−1) and ratiometric sequence-specific response to microRNA with the limit of detection (LOD) down to 1.3 pM (21 amol), equivalent to 24 RT-qPCR cycles. They enable quantitative detection of the four microRNAs in RNA extracts from five cancerous cell lines (human breast cancer - T47D and MCF7, head and neck cancer - CAL33 and glioblastoma - LNZ308 and U373) and two non-cancerous ones (Hek293 and MCF10A), in agreement with RT-qPCR. The results confirmed that let-7f and especially miR-21 are systematically overexpressed in all studied cancerous cell lines. These nanoparticle biosensors are compatible with low-cost portable fluorometers and small detection volumes (11 amol LOD), opening a route to rapid point-of-care cancer diagnostics. • Fluorescent nanoprobes for microRNA detection in cell extracts are developed. • They amplify signal up to 130-fold by light-harvesting from ~400 FRET donor dyes. • They enable ratiometric analysis of microRNA with limit of detection down to 1.3 pM. • Biosensors for four microRNA are validated in 5 cancer and 2 healthy cell lines. • They are compatible with low-cost portable fluorometers and small detection volumes. [ABSTRACT FROM AUTHOR]