A photoelectrochemical biosensor based on fullerene with methylene blue as a sensitizer for ultrasensitive DNA detection.

In this protocol, a photoelectrochemical (PEC) biosensor based on methylene blue (MB) sensitized fullerene (C60) was designed for ultrasensitive DNA detection. First, C60 nanoparticles (C60 NPs) as photoactive material was modified on the electrode surface to obtain an initial photocurrent signal. Additionally, the nicking endonuclease (Nb.BvCI enzyme)-assisted signal amplification strategy was implemented to transform limited target to plenty of products, which hybridized with DNA2 to form plentiful DNA duplex for immobilizing numerous MB as the sensitizer, thus accomplishing the effective sensitization toward C60 NPs and achieving an enhanced photocurrent for quantitatively detecting target DNA. This established PEC strategy realized the target DNA detection with the detection limit down to 3.3 fM, which paved a new avenue for DNA determination and exhibited huge application potential for other biomarkers in clinical analysis and disease diagnosis.