Photoelectrochemical biosensor for 5-formylcytosine deoxyribonucleoside detection based on BiIO4-WS2/CuO ternary heterojunction

[Display omitted] •The photoelectrochemical photoactivity of BiIO4-WS2 was enhanced by CuO.•A Z-type heterojunction structure was constructed between BiIO4-WS2 and CuO.•A sensitive and selective photoelectrochemical biosensor was fabricated for 5fC detection.•The effects of SDZ and Hg2+ on 5fC expression in wheat seedlings were investigated. As an important epigenetic modification, 5-formylcytosine (5fC) plays a vital role in cell differentiation, genomic DNA structure and function regulation. Its low abundance in all suckler tissues and cells and high structural similarity with cytosine (C) and its derivatives, the sensitive and selective detection method for 5fC is required. In this work, a photoelectrochemical biosensor was constructed using BiIO4-WS2 composite as photosensitive material, the synergy of ternary heterojunction of BiIO4-WS2/CuO as signal amplification technology and 5-formylcytosine deoxyribonucleoside (5fdC) as target. Firstly, the ITO electrode modified by BiIO4-WS2 was aminated by (3- aminopropyl) triethoxysilane. 5fC was captured on the electrode surface with amidogen as recognition reagent, based on the amide bond formed between amidogen and aldehyde group. Then, 4-carboxyphenylboronic acid (4-CPBA) was linked by covalent reaction between boronic acid and O-diol of 5fdC. Finally, the signal amplification material of amino-functionalized CuO was deposited on the electrode surface through the formation of amide bond based on −COOH of 4-CPBA and –NH2 on CuO. In view of the constitution of a ternary heterojunction between CuO and BiIO4-WS2, the photoactivity of BiIO4-WS2 was greatly enhanced, which also increased the detection sensitivity with the wide examination area from 0.005 to 200 nM and low limit of detection was 0.38pM (3σ). Based on the specific covalent identification pattern, this method showed high selectivity for 5fC, even discriminating 5fC with C and 5hmC. The impacts of antibiotics and heavy metals on 5fdC content change in genomic DNA of wheat tissues were investigated, and thus the feasibility of this work was evaluated.