Selective and robust dopamine detection is enabled by aptamer-SWCNT optical sensors in physiological media

Monitoring dopamine in complex biological environments is essential for understanding neurological disorders and disease diagnosis, though it presents a unique chemical challenge. In this work, we rationally designed several single-walled carbon nanotube (SWCNT)-based near-infrared fluorescent sensors for dopamine using ssDNA aptamers as selective molecular recognition elements. The performance of three dopamine-selective aptamer-SWCNT hybrids and sensitive but non-selective (GT)₁₀-SWCNT constructs were evaluated and compared for their magnitude of response, sensitivity, and selectivity to dopamine. We performed these studies in buffer, in complex media with noradrenaline and serotonin, and in synthetic cerebrospinal fluid. We evaluated sensor constructs alone, with heat + divalent cation addition, and with four different molecular passivation agents. Ultimately, sensors passivated with bovine serum albumin (BSA) demonstrated strong selectivity for dopamine relative to noradrenaline, serotonin, and ascorbic acid, with a greater magnitude of response compared to (GT)₁₀-SWCNT. Concentration-response curves in PBS, in a serotonin and noradrenaline solution, and artificial cerebrospinal fluid (aCSF) revealed dynamic ranges between 30 and 200 nM, and we found that the response occurs within five minutes. Together, these results demonstrate that dopamine aptamer-SWCNT sensors enable more selective and robust optical detection in complex biological environments.