A signal amplification of p DNA@Ag2S based photoelectrochemical competitive sensor for the sensitive detection of OTA in microfluidic devices

Abstract

In this work, a signal amplification competitive-type photoelectrochemical system comprised of bismuth sulfide/bismuth oxyiodide/zinc oxide (Bi2S3/BiOI/ZnO) nano-array as platform and Ag2S-modified aptamers probe DNA (p DNA@Ag2S) as competition content for rapid and sensitive detection of OTA in microfluidic devices. The BiOI nano-array was first growth on surfaces of ZnO by a simple electrodeposited method, which provided large specific surface area and high stability to solve distribution of sensing platform and loose of combination of sensing substrate. Then, the Bi2S3 could be in-situ growth by self-sacrificial part Bi3+ of BiOI to form heterojunction without destroying the structure of the nano-array. A strong photocurrent intensity was acquired by the Bi2S3/BiOI/ZnO modified onto indium tin oxide (ITO) electrode, due to its good matching cascade band-edge levels could improve efficient separation of photo-generated e-/h+ pairs. After immobilizing with the capture DNA (c DNA) and the sequential hybridization of p DNA@Ag2S, the photocurrent intensity reduced obviously because part photo-generated electron transformed to Ag2S rather than Bi2S3/BiOI/ZnO electrode. Subsequently, the photocurrent intensity increased evident when immobilized the target OTA, owing to the OTA could bind the p DNA@Ag2S to form the specific-complex that were released from the electrode surface. Under optimal conditions, the prepared PEC microfluidic sensor exhibited a linear concentration of OTA from 0.01 pg/mL to 200 ng/mL with a low detection limit of 0.0035 pg/mL (S/N = 3). Furthermore, it achieved high sensitivity, good specificity, and acceptable stability and further provided an efficient method for sensitive detection of other target mycotoxins in practical application.