Engineering a Au-NPs/Nafion modified nanoporous diamond sensing interface for reliable voltammetric quantification of dopamine in human serum

Abstract

Electrode fouling is an inevitable phenomenon when encountering biological agents (e.g., dopamine, peptides, proteins), particularly working under continuous oxidation of fouling agents. Diamond is emerging as an ideal fouling-resistant sensing material due to favorable antifouling properties and biocompatibility, but the detection sensitivity and specificity narrow its biomedical applications. In this work, we engineered a Au-NPs/Nafion modified nanoporous diamond sensing interface (termed as NanoDiaSens) in which the target’s voltammetric response (i.e., dopamine) is dominant while interference agents (i.e., human serum, ascorbic acid) are eliminated, rendering reliable target quantification in human serum. The resulting nanopores and electrodeposited Au NPs have close size distribution of 43.1 ± 9.2 nm and 43.9 ± 12.7 nm respectively. The unique nanoporous diamond sensing surface provides anchored sites to stabilize electroactive gold nanoparticles preserving their long lifespan and high sensitivity, while surface-modified Nafion membrane effectively eliminates the voltammetric response of the interference agents and shifts the target’s potential window away from the interferent’s ones, achieving specific voltammetric quantification of the target. The NanoDiaSens also holds the highest heterogeneous kinetic constant of 6.7 × 10-3 cm s−1, indicating the significantly enhanced electrocatalytic properties. Leveraging NanoDiaSens, we realized high accuracy of > 90% recovery rate for dopamine’s voltammetric response currents over wide levels (from 3 to 100 μM) in human serum. NanoDiaSens preserves the reliable voltammetric signals within 2.1% signal attenuation up to one month and maintains 95% of the initial response current after six-month storage in the ambient environment. We expect NanoDiaSens holds the potentials for personalized dopamine monitoring for many months.