Synergistic UCNP/CRISPR-Cas12a enhanced near-infrared photoelectrochemical biosensor for quantitative Kanamycin detection.

Antibiotic residues in food pose significant health risks, and sensitive on-site detection remains challenging in complex matrices. We report a near-infrared photoelectrochemical (NIR-PEC) biosensor with CRISPR-Cas12a signal amplification for sensitive detection of kanamycin in food. A ZnO/CdS heterojunction photoanode boosts visible-light charge separation, producing a photocurrent of 4.6 mA-96 % higher than ZnO alone. Upconversion nanoparticles (NaYF4:Yb3+, Er3+) convert 980 nm light into 542 nm emission to drive the heterojunction under NIR illumination. In the presence of kanamycin, activator DNA is displaced from an aptamer, triggering Cas12a to cleave ssDNA probes on the electrode and reduce photocurrent. The sensor shows a linear response from 10 to 1000 nM, a detection limit of 0.284 nM and less than 2.8 % cross-reactivity with related compounds. Average recovery in spiked milk samples averages 97 % (RSD = 2.2 %). This platform offers high specificity and sensitivity for antibiotic residue analysis in complex food matrices.