Investigation of the enhanced photoactivity of CdS/Bi2MoO6/MoSe2 and its application in antibody-free enzyme-assisted photoelectrochemical strategy for detection of N6-methyladenosine and FTO protein

N 6 -methyladenosine (m 6 A) is the most abundant and dynamic reversible modification of mRNA in eukaryotes discovered in the mid-1970s, which is widely involved in various physiological processes. Fat mass and obesity-associated protein (FTO protein) is not only a demethylase for m 6 A, but also a carcinogenic factor for many human cancers. Therefore, it is very important to build a simple and sensitive platform for simultaneous detection of m 6 A and FTO protein. To achieve this aim, a novel photoelectrochemical biosensor was constructed with the antibody-free detection strategy of DTT mediated –SH functionalization of m 6 A triggered by FTO protein catalyzed m 6 A oxidation . To achieve high detection sensitivity, CdS/Bi 2 MoO 6 /MoSe 2 system with matched energy gap was employed as photoactive material. To achieve high detection selectivity , the –CH 3 of m 6 A in the captured RNA sequence (m 6 A RNA) on the electrode surface was oxidized by FTO protein to form hydroxymethyl, followed with the covalent reaction of DTT with hydroxymethyl, making the labeling of m 6 A with –SH. Finally, a CdS nanoparticle was modified on the electrode through the specific covalent reaction between –SH and Cd, achieving the improvement of the photocurrent with the matched energy band . Under the optimal experimental conditions, the biosensor showed linear range from 0.001 to 50 nM and 0.0005–500 μg/L with the detection limit of 0.37 pM and 0.034 ng/L (S/N = 3) for m 6 A RNA and FTO protein, respectively. The applicability of the developed method was assessed by investigating the effect of entacapone on FTO protein activity.