(700e) DNA Functionalized, Fluorescent Nanomaterials for the Specific, Ratiometric Detection of Dopamine for In Vivo Sensing

Monitoring changes in neurotransmitter concentration is essential for understanding brain function, making the development of new biosensors critical for advances in the neurological imaging of neurotransmitters. Nanomaterials with distinct optical, chemical and material properties show promise for developing such sensitive and specific sensors for temporal and spatial study of biological activity.

First, we evaluate the use of DNA-stabilized fluorescent silver nanoclusters (AgNCs), few-atom fluorescent clusters stabilized using single-stranded DNA, as optical sensors for specifically and sensitively probing neurotransmitter concentration. We identify two particular DNA-AgNC sensors that have broad fluorescence peaks with large Stokeâ??s shift that respond to exogenous addition of neurotransmitter dopamine. We find that dopamine can specifically quench the fluorescence of one sensor (ex580nm/em650nm) and induces a chromatic shift (-40nm) with a limit of detection of 50 nM. Additionally, when combined with another DNA strand prior to synthesis, dopamine enhances the fluorescence of the resulting AgNCs (ex535nm/em615nm) with a limit of detection of 1 µM. These responses are specific to dopamine and are screened alongside a library of neurotransmitters, interferents and chemical homologues.

Second, we show that AgNC dopamine sensors are readily attached to DNA-dispersed single-walled carbon nanotubes (SWCNTs) through non-covalent coupling, and can be observed via unchanged fluorescence emission. The SWCNT scaffold provides structural stability to more easily perform single-molecule microscopy for analyzing AgNC population variance, as well as colocalizing the fluorescence of the sensors with the intrinsic nIR fluorescence of the nanotubes for ratiometric sensing. The implementation of sensors for in vivo work inevitably hinge on invariance of the sensor to anything other than the analyte, for which a colocalized ratiometric signal can be exploited. We extrapolate our results in vitro to evaluate their potential for use in vivo to correlate external stimuli to neurotransmission within the brain.