Development of Quantum dot-based enzyme biosensor for the detection of dopamine in urine.

Dopamine (DA), a neurotransmitter released by the hypothalamus, plays a significant role in maintaining mental well-being. Abnormal DA level leads to neurological disorders such as depression and schizophrenia. Consequently, DA is commonly monitored in urine using various analytical methods as a non‑invasive approach for assessing its physiological status. The available methods for DA detection are laborious and time-consuming. To circumvent this issue, we developed a Quantum dot-based enzyme biosensor for the rapid, sensitive detection of DA. Fluorescence quenching of QDs was in proportion with the DA concentration and was found to be linear with an R = 0.99, with p < 0.05. The biosensor used to detect DA in urine samples in the range of 1.2 µM-8 µM, with R² = 0.97 and p < 0.05, and a limit of detection (LOD) of 1.2 µM in a urine sample (1:100). Spiking and recovery analysis in urine showed 94-98% recovery with p < 0.05. The developed method showed specificity towards detecting DA in the presence of common interfering factors such as uric acid and ascorbic acid. The results show that dopamine-specific quenching is consistent and concentration-dependent, effectively distinguishing the target from background components in complex samples. This approach provides a promising platform for reliable DA monitoring in clinical diagnostics.