Cu/Cu₂O-embedded carbon from Cu-MOF integrated with MWCNTs-COOH for sensitive levodopa detection in biological...

Reliable monitoring of levodopa (L-DOPA) is clinically crucial for optimizing Parkinson's disease therapy and minimizing side effects. Herein, a sensitive electrochemical sensor was constructed using a composite of Cu-MOF-derived Cu/Cu₂O-embedded carbon integrated with carboxylated multi-walled carbon nanotubes (C-Cu-MOF/MWCNTs-COOH). The key innovation of this work lies in designing a synergistic hetero-interface where carbonization yields Cu and Cu₂O species within a carbon framework, while the incorporated MWCNTs-COOH establish a conductive network that facilitates electron transfer. The enhanced electrochemical response arises from the synergistic interaction between the mixed-valence copper species and the carbon framework. Specifically, Cu⁺ serves as Lewis acid sites for L-DOPA enrichment while the carbon scaffold together with Cu⁰ promotes interfacial electron transfer. Kinetic analysis reveals an adsorption-controlled process involving two-electron and two-proton transfer. Under optimized conditions, the sensor delivers a broad linear response (0.01-15 μM) with a low detection limit of 0.007 μM, alongside satisfactory repeatability, reproducibility, and long-term stability (94.3% retention after 21 days). Notably, uric acid (UA), a major coexisting interferent in physiological fluids with overlapping oxidation potential, is well resolved from L-DOPA at the modified electrode, causing negligible interference in coexistent measurements. Practical applicability is further validated by recoveries of 94.8-105.2% in human serum and urine samples. These results demonstrate that C-Cu-MOF/MWCNTs-COOH is a highly effective sensing platform for L-DOPA, combining excellent sensitivity, selectivity, and practical utility for clinical monitoring.