Selective SERS detection of dopamine in human urine using catechol oxidase-mimicking AgNPs@MOF-818

The integration of surface-enhanced Raman scattering (SERS) and nanozymes has proven to be a highly effective strategy in bioanalytical applications, owing to its superior capabilities in signal transduction and amplification. Nevertheless, clinical applications still face obstacles, particularly in achieving sufficient selectivity. In this work, we have presented a SERS strategy for the selective detection of dopamine in human urine with MOF-818 which exhibits selective catechol oxidase-like activities. AgNPs@MOF-818 catalyze the oxidation of o-phenylenediamine (OPD) to diaminobenzazine (DAP) molecules, when dopamine (DA) is present, the oxidation of OPD is inhibited while DA is catalyzed into o-quinones, thereby suppressing the SERS signal intensity. An indirect SERS detection strategy of dopamine with high sensitivity and selectivity was established. The catechol oxidase-like activity of MOF-818 provides ideal selectivity to dopamine, while the OPD-dopamine catalytic system induces significant changes in SERS intensity. The detection protocol was subsequently optimized to achieve high sensitivity for dopamine, yielding a linear response range of 0.1-30 μmol/L and a low limit of detection (LOD) of 0.04 μmol/L. The method was successfully applied to the quantitative analysis of dopamine in human urine samples, demonstrating excellent recovery rates and minimal relative error in comparison with results obtained by commercial dopamine ELISA kit. This strategy presents a cost-effective, efficient, and accurate approach for dopamine detection while delivering insights into the integration of selective multifunctional nanozymes with sensitive SERS technique.