Enhanced photoactivity of perovskite Bi4NbO8Cl/PTC-NH2 heterojunction and its application for photoelectrochemical sensing of DNA hydroxymethylation

A novel photoelectrochemical (PEC) biosensor was constructed for DNA hydroxymethylation detection based on Bi4NbO8Cl/PTC-NH2 heterojunction and Fe-MIL-88NH2, where Bi4NbO8Cl/PTC-NH2 was employed as photoactive material and Fe-MIL-88NH2 was adopted as artificial hydrogen peroxide mimic enzyme. Based on the structure of hydroxymethylated cytosine in DNA sequence, 5-hydroxymethyl-2'-deoxycytidine (5hmdC) was employed as detected target molecule for the first time using PEC technique. After Bi4NbO8Cl/PTC-NH2 heterojunction was modified on the substrate electrode, thioglycolic acid (TGA) was captured by forming amide bond, where the sulfhydryl group (-SH) of TGA was employed as the specific recognition of 5hmdC. Under M. HhaI catalysis, the -CH2OH of 5hmdC reacted selectively with the -SH. Finally, Fe-MIL-88NH2 was modified on the electrode based on the crosslinker of 4-formylphenylboronic acid (FPBA), where FPBA possessed two active groups of formyl and boronic acid group, reacting with glycosyl of 5hmdC and amino of Fe-MIL-88NH2. Under the catalysis effect of Fe-MIL-88NH2, the insoluble substance was produced on the surface of electrodes, resulting in distinct lessening of PEC response. Under optimal conditions, the photocurrent shows a linear relationship with the logarithm value of 5hmdC concentration from 0.01-100 nM with a low detection limit of 6.48 pM. More importantly, this method can be applied to investigate the influence of exogenous phytohormone on 5hmdC content in the genomic DNA of rice seedling roots and leaves.