Polydopamine-gold composite-based electrochemical biosensor using dual-amplification strategy for detecting pancreatic cancer-associated microRNA.

Herein, we developed a dual-amplification-boosted, translational electrochemical biosensor for the detection of pancreatic cancer-associated microRNA, miR-196b. A biosensing event occurred when a hairpin target probe recognized miR-196b as a result of the opening of an electrode hairpin probe on a polydopmine-gold (PDA-Au) composite-modified screen-printed carbon electrode. The PDA-Au composite was synthesized in a alkaline condition where dopamine polymerized into polydopamine while gold(III) ion was in-situ reduced to gold nanoparticle, characterized by FT-IR, SEM, cyclic voltammetry and gel electrophoresis. The electrode modifier, PDA-Au, provided a functionalizable interface for the sensitization of electrode probes; besides, a suitable hydrophilic interface for an aqueous biosensing reaction, confirmed by water contact angle measurement and cyclic voltammetry. Validated by UV-VIS analysis and gel electrophoresis, the single polymerase created a dual amplification by target-recycling and generation of an catalytic DNAzyme product on the electrode probe-functionalized PDA-Au@SPCE. The isothermal, dual amplification was thereby translated into a TMB/HO-resulted electrochemical signal, acquired by scan wave voltammetry for quantifying target miR-196b. The novel electrochemical biosensor offered a detection limit of 0.26 pM, with a nice analytical reproducibility by CV (coefficient of variance) value of 8.5 ± 3.1%, and a recovery rate of 105 ± 4.1% obtained from a spiked, real human serum sample. The proposed biosensor showed great promise as a complementary tool for real sample detection in the clinic.