Core−Shell ZIF-67@CoFePBA Nanozyme with Dual Functions in PEC Signal Modulation and Fenton-like Colorimetric Catalysis for Cyfra21-1 Immunoassay

Abstract A novel dual-mode immunosensing platform integrating photoelectrochemical (PEC) and colorimetric detection was developed for the early and reliable determination of the non-small cell lung cancer biomarker cytokeratin 19 fragment (Cyfra21-1). An ordered ReS2/In2S3 type-II heterojunction array was constructed, which not only enlarged the effective electroactive surface area but also introduced an interfacial built-in electric field. As a result, the separation and directional transport of photogenerated charge carriers were significantly promoted, leading to markedly enhanced photoelectric conversion efficiency. In addition, ZIF-67@CoFePBA nanozymes with peroxidase-like activity were employed as dual-function signal probes. Under the PEC detection mode, the photocurrent signal was significantly suppressed during the immunorecognition process, as the steric hindrance effect induced by ZIF-67@CoFePBA nanozymes inhibited the effective migration of photogenerated charge carriers, thereby enabling the quantitative determination of Cyfra21-1. Good linear analytical performance was achieved over a concentration range from 100 fg/mL to 50 ng/mL, with a detection limit of 66.5 fg/mL. Meanwhile, under the colorimetric detection mode, the ZIF-67@CoFePBA nanozymes catalyzed the 3,3′,5,5′-tetramethylbenzidine (TMB)/H2O2 reaction to generate a visually distinguishable colorimetric signal. A good linear response was obtained in the concentration range of 0.5−25 ng/mL, with a detection limit of 0.14 ng/mL. The dual-signal output endowed the platform with an intrinsic self-validation capability through cross-verification of two independent yet correlated signal channels, thereby effectively minimizing false responses induced by environmental interference. This provides a promising analytical strategy for lung cancer biomarker detection.