Abstract
Oxytocin is a neuropeptide involved in regulating social and emotional behavior. Current techniques for oxytocin imaging are generally limited in spatial and temporal resolution, real-time imaging capacity, selectivity for oxytocin over vasopressin, and application in young and non-model organisms. To address these issues, we developed a method to evolve purely synthetic molecular recognition for oxytocin on the surface of near-infrared fluorescent single-walled carbon nanotubes (SWCNT) using single-stranded DNA (ssDNA). The best-performing nanosensor nIROT-SELEC reversibly undergoes up to a 172% fluorescence increase in response to oxytocin with micromolar dissociation, nanomolar limit of detection, and and high selectivity over oxytocin analogs, receptor agonists and antagonists, and co-released neurochemicals. We next demonstrated the versatility of nIROT-SELEC by performing live imaging of synaptic evoked oxytocin released in acute brain slices of mice and prairie voles. Our method for high throughput evolution of neuropeptide nanosensors holds promise to enable synaptic scale visualization of neuropeptide signaling in the brain cross different species and developmental stages, to advance the study of neurochemical signaling for its role in both health and disease.