A SERS and colorimetric dual-mode biosensor based on stimulus-responsive DNA/MOF-bound bimetallic nanozyme for the ultrasensitive detection of chloramphenicol in food.

A dual-mode detection platform utilizing colorimetric and Raman was developed based on the exponential amplification reaction (EXPAR) strategy and a "core-satellite" structure constructed by bimetallic nanozymes to detect chloramphenicol (CAP). Initially, DNA-gated metal-organic frameworks (MOFs) incorporating cascaded amplification were used to be nanocarriers for the colorimetric and Raman reporter molecules (3,3',5,5'-tetramethylbiphenyl; TMB). Subsequently, assembled DNA served as gatekeepers to create a stimulus-responsive DNA-gated MOF (TMB@DNA/MOF). Upon the introduction of the target, the efficient and isothermal EXPAR was initiated, producing numerous amplicons that facilitated the unlocking of pores and subsequent release of TMB. This process amplified the release signal, enhancing the selectivity and sensitivity of the biosensor. Moreover, through base complementary pairing, TMB@DNA/MOF and magnetic bimetallic nanozymes FeO@MOF-gold nanostars (GNS) formed a stable "core-satellite" structure. The addition of HO led to the oxidation of released TMB to oxTMB, resulting in a color change and generation of Raman signals. The biosensor exhibited excellent detection performance for CAP, with a colorimetric detection range of 1.00 × 10 ~ 2.50 × 10 M and a detection limit of 2.07 × 10 M, while the SERS detection range was 1.00 × 10 ~ 1.00 × 10 M with a detection limit of 9.74 × 10 M. Overall, this biosensor provided an effective method for detecting antibiotics in complex samples.