Dual enzyme-mimicking bimetallic MOF for selective SERS detection of L-DOPA in human serum based on cascade catalytic reaction.

Surface-enhanced Raman scattering (SERS) in conjunction with nanozymes has emerged as a powerful technique for bioanalysis due to their signal conversion and amplification effect. However, clinical applications continue to encounter challenges such as inadequate selectivity. Herein, we proposed a novel approach for the selective SERS detection of L-DOPA in human serum with dual enzyme-mimicking MOF-919(Fe-Cu). This material exhibits both catechol oxidase-like and peroxidase-like activities, enabling it to catalyze catecholic compounds to o-quinones and subsequently oxidize 3,3',5,5'-tetramethylbenzidine (TMB) molecules into SERS-active ox-TMB. Ultrasonic-assisted synthesis ensures uniform and dense loading of AgNPs within MOF-919(Fe-Cu), thereby enhancing SERS activity. A sensitive and selective method for SERS detection of L-DOPA was developed. The catechol oxidase-like activity of MOF-919(Fe-Cu) provides ideal selectivity and anti-interference to L-DOPA, while the cascade catalytic system transforms weak SERS signals of L-DOPA into amplified SERS signals of ox-TMB. The mechanism of dual enzyme-mimicking activity was further discussed. The detection process was optimized to achieve high sensitivity towards L-DOPA with a linear range 0.5-100 μmol/L and low limit of detection (LOD) of 0.16 μmol/L. Furthermore, it has been applied in serum sample of Parkinson's patients, demonstrating excellent recovery and low relative error compared to HPLC-UV. This approach offers an economical, efficient and accurate strategy for the detection of L-DOPA and provides valuable insights for the integration of selective multifunctional nanozyme and sensitive SERS detection method.