Colorimetric detection of l-Dopa via anti-etching of Au nanorods catalyzed by an MIL-88A (Fe)-TMB system†

Abstract

L-Dopa (L-3,4-dihydroxyphenylalanine) is a key precursor of dopamine and is extensively used in the treatment of Parkinson's disease. Accurate and efficient monitoring of L-Dopa levels is essential for optimizing therapeutic efficacy. In this study, we developed a novel and sensitive colorimetric sensor for L-Dopa detection based on the inhibition of gold nanorod (AuNR) etching by TMB²⁺. The sensor utilizes the antioxidant properties of L-Dopa, which inhibit the oxidation of AuNRs induced by the oxidized product of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H₂O₂. The MIL-88A (Fe) metal–organic framework (MOF) catalyzes the formation of TMB²⁺, which subsequently oxidizes Au⁰ to Au⁺, converting AuNRs into spherical AuNPs and causing a distinct blue shift in the plasmonic peak. However, in the presence of L-Dopa, the oxidation of TMB is suppressed, thereby preserving the shape and optical properties of AuNRs. This colorimetric method is simple, rapid, and cost-effective, and shows great promise for non-invasive L-Dopa monitoring in clinical and diagnostic applications.