Photoelectrochemical Biosensor for 5‐Formylcytosine Based on WS2/Bi/Bi2O2CO3 Nanocomposite and Rolling Circle Amplification

Comprehensive Summary As a key epigenetic modification, 5‐formylcytosine (5fC) controls many important cell functions, such as gene expression and cell differentiation. However, 5fC exists in mammalian tissues and cells with low content, and its structure is highly similar to 5‐methylcytosine (5mC), 5‐hydroxymethylcytosine (5hmC) and 5‐carboxycytosine (5caC), which requires the detection method for detecting 5fC with high sensitivity and specificity. In this experiment, WS 2 /Bi/Bi 2 O 2 CO 3 was used as the photoactive material, 5fC antibody was used as the target molecule recognition reagent, and rolling amplification (RCA) was employed as the signal amplification strategy to construct a novel photoelectrochemical biosensor for detecting 5‐formylcytosine deoxynucleotide (5fdCTP). Firstly, WS 2 /Bi/Bi 2 O 2 CO 3 nanocomposite was prepared and characterized, and then modified on the ITO electrode. Then, polyacrylic acid (PAA) was immobilized by electrostatic adsorption, which was employed as the antibody capture reagent based on the covalent reaction of –COOH on PAA with –NH 2 on Ab. Subsequently, 5fdCTP was recognized through immunoreaction, triggering the subsequent rolling circle amplification reaction with the aid of the crosslinker of Zr 4+ . Finally, positive methylene blue (MB) was adsorbed by negative ssDNA, resulting in an increased photoelectric conversion efficiency of WS 2 /Bi/Bi 2 O 2 CO 3 and improved detection sensitivity. The linear range of the PEC biosensor for detecting 5fdCTP was 0.05—100 nmol/L, and the minimum detection concentration was 12.4 pmol/L (S/N = 3). The applicability of this method has been evaluated by studying the influence of Cd 2+ and antibiotic concentration on the 5fC content in the genomic DNA of maize seedlings.