Photoelectrochemical immunosensor for microRNA detection based on gold nanoparticles-functionalized g-C3N4 and anti-DNA:RNA antibody

Herein, a sensitive and selective photoelectrochemical (PEC) immunoassay is developed for microRNA, where the graphite-like C3N4 (g-C3N4) is used as photoactive material and anti-DNA:RNA antibody is used as target microRNA recognition unit. With the doping of gold nanoparticles (AuNPs), the photoactivity of g-C3N4 is greatly improved. The capture probe for microRNA is assembled on the AuNP5-g-C3N4 modified ITO surface through the Au-S bond. After hybridizing with target microRNA, the DNA:RNA hybrids can be recognized by anti-DNA:RNA antibody and this antibody can be further captured on the electrode surface. Through the specific interaction between antibody and alkaline phosphatase labeled IgG (ALP-IgG), ALP-IgG can be captured, which can catalyze the hydrolysis of ascorbic acid-2-phosphate (AAP) to produce ascorbic acid as electron donor. As a result, a strong photocurrent is obtained and the expression level of microRNA can be detected based the change of photocurrent. The fabricated biosensor presents good detection sensitivity with the linear range of 5-3000 fM and the detection limit of 2.26 fM. The developed biosensor also shows accepted detection selectivity with identifying even single-base mismatched microRNA. The applicability of the biosensor is further evaluated by assaying the expression level change of microRNA in rice leaves with and without phytohormone incubation. This work is not only providing a new detection platform for microRNA assay, but also affording some information on the role of microRNA in phytohormone signaling. (C) 2015 Elsevier B.V. All rights reserved.