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

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 BiIO 4 -WS 2 composite as photosensitive material, the synergy of ternary heterojunction of BiIO 4 -WS 2 /CuO as signal amplification technology and 5-formylcytosine deoxyribonucleoside (5fdC) as target. Firstly, the ITO electrode modified by BiIO 4 -WS 2 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 –NH 2 on CuO. In view of the constitution of a ternary heterojunction between CuO and BiIO 4 -WS 2 , the photoactivity of BiIO 4 -WS 2 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.