Photoelectrochemical biosensor for DNA formylation based on WS2 nanosheets@polydopamine and MoS2 nanosheets

Abstract

The photoresponse ability of MoS2 was excellently improved by polydopamine (PDA) coated WS2 composite (WS2@PDA) based on the matched energy band and solid electron donor property of PDA, which significantly blocked the recombination of photogenerated electron-hole pair. Taking the enhanced photoactivity performance of MoS2 and WS2@PDA compound, a simply and sensitively photoelectrochemical biosensor was developed for DNA formation detection, where DNA fragment with 5-formylcytosine (5fC-DNA) was employed as detection target. In the photoactive system, PDA was used as photoactive accelerant and 5fC recognized reagent. After immobilization of MoS2/WS2@PDA, the DNA fragment containing 5-formylcytosine was further captured through the formation of amide bond between the –NH2 of PDA and the –CHO of 5fC, causing the decreased photocurrent due to the electrostatic repulsion effect of negative DNA to photogenerated electron. The biosensor in this work presented wide linear range for 5fC-DNA detection from 0.005 to 200 nM with low detection limit of 3.7 pM (3σ). The developed method not only showed good detection selectivity, but also can discriminate cytosine, 5-methylcitosine and 5-hydroxymethylcytosine to increase its specificity. The applicability of this work was demonstrated by investigating the effect of environmental pollutants on 5fC expression in genomic DNA of maize and wheat seedling leaves respectively.