Aptamer-based photoelectrochemical biosensor for antibiotic detection using ferrocene modified DNA as both aptamer and electron donor

Graphite-like carbon nitride (g-C 3 N 4 ) nanosheet is a new type of photoactive semiconducting material with promising application in photoelectrochemical (PEC) biosensor. In the present work, a simple and selective PEC biosensor was fabricated using g-C 3 N 4 nanosheets as photoactive material coupled with capture-release strategy. DNA aptamer labeled with ferrocene (DNA-Fc) was served as both recognition reagent of antibiotic chloramphenicol and electron donor of PEC biosensor. Based on the decreased affinity of aptamer to g-C 3 N 4 nanosheets causing by the formation of aptamer-chloramphenicol complex, DNA-Fc could be released from g-C 3 N 4 nanosheets modified ITO surface, resulting a decreased PEC response. The developed method showed a wide linear range from 1 pM to 100 nM and a low detection limit of 0.22 pM (3σ). The fabricated PEC biosensor also illustrated good detection specificity and can be applied to detect chloramphenicol residue in water samples with recoveries ranging from 94.5% to 107.3%.