A novel photoelectrochemical strategy based on quenching effect of CdS quantum dots on PTB7 as photoelectroactive material for methylated DNA detection

Herein, a novel photoelectrochemical (PEC) strategy was proposed for ultrasensitive DNA methylation assay based on poly [[4,8-bis[(2-ethylhexyl)oxy] benzo [1,2-b:4,5-b′]dithiophene-2,6-diyl] [3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl]] (PTB7) as photoactive material and the CdS quantum dot (QD) as its efficient quencher. Firstly, the CdS QD-labeled signal probe (CdS@SP) and anti-IgG antibody were immobilized on the gold nanoparticle to forming the bio-complex (anti-IgG-AuNP-S0-CdS@SP) as signal quencher. As designed, the target methylated DNA could hybridize with the capture DNA immobilized on the PTB7 modified electrode and immunoreact with anti-5-methylcytosine antibody, when there was a high PEC signal. And then, the prepared signal quencher, anti-IgG-AuNP-S0-CdS@SP, could be recognized based on the special immunoreaction and a decreased PEC signal could be obtained due to the efficient quenching effect of CdS@SP on PTB7, which was related with the concentration of methylated DNA. As expected, the developed PEC biosensor performed linear correlation with the concentrations of methylated DNA in range from 50 aM to 500 pM. The success in the establishment of the sensitive PEC strategy based on PTB7 with significantly high photoelectric conversion efficiency, providing an avenue for DNA methylation detection for cancer diagnosis.