A Fossilization-Inspired Photoelectrochemical Sensing Platform: DNA-Induced In Situ CaCO3 Crystal Growth Modulates The Photoelectrochemical Response of Gold Electrodes for Ultrasensitive Aflatoxin B1 Detection

Although photoelectrochemical (PEC) sensing offers low background and high sensitivity, most PEC platforms rely on semiconductor materials and immobilized recognition probes, which complicate electrode fabrication and reduce operational simplicity. Herein, we report a fossilization-inspired photoelectrochemical sensing platform (FIPSP) for ultrasensitive detection of aflatoxin B1 (AFB1) based on DNA-induced in situ CaCO 3 crystal growth on a gold electrode (AuE). We found that nucleic acids could induce interfacial biomineralization of calcite-like CaCO 3 crystals on AuE, and the resulting mineralized layer effectively modulated the intrinsic anodic PEC response of AuE. In this design, a bead-immobilized initiator DNA was first hybridized with an AFB1 aptamer. Upon target recognition, the aptamer dissociated from the bead-immobilized initiator DNA, allowing the initiator to trigger a hybridization chain reaction (HCR) between two hairpin DNA probes. After alkaline treatment, the HCR products were disassembled into DNA strands, which were then released and adsorbed onto AuE to induce in situ CaCO 3 crystal growth. The mineralized layer hindered interfacial charge transfer and ascorbic acid diffusion, thereby suppressing the photocurrent and enabling detection of AFB1. Under optimized conditions, the developed FIPSP exhibited a linear range from 1 ag mL –1 to 10 pg mL –1 and a detection limit of 0.61 ag mL –1 , together with excellent selectivity and reproducibility. It also showed satisfactory performance in soybean oil and maize samples. This work establishes a simplified PEC electrode construction strategy that requires neither semiconductor photoactive material synthesis nor probe immobilization on the electrode surface, providing a promising platform for ultrasensitive AFB1 analysis.