Abstract

Advancing our fundamental understanding of brain (dys)function requires the development of novel nanotools capable of monitoring chemical signalling in complex biological systems.(1) Detecting small molecules in the brain is challenging due to low concentrations spanning orders of magnitude (picomolar to micromolar), limited mass and charge, and interference from high amounts of nonspecific molecules. Further, neurotransmitters co-exist with structurally similar metabolites across different brain regions. We tackle this challenge by integrating DNA -based recognition elements called aptamers, into nanopipettes with _{10 nm openings.(2) Aptamers are systematically designed oligonucleotide receptors that exhibit highly specific and selective recognition of targets. We employ aptamers designed to recognize small-molecule neurotransmitters such as serotonin and dopamine with high affinity and selectivity.(3) Upon reversible target binding, aptamers undergo a rearrangement of the negatively charged backbone, and these dynamic structural changes can be transduced as measurable changes in current through the nanopore. Nanoscale confinement of the sensor surface results in high sensitivity while simultaneously reducing nonspecific binding to the sensing area for long-term recordings, overcoming a critical bottleneck for clinical biosensors.(4) The nanoscale tip of the aptamer-modified nanopipettes approach the spatial resolution of synapses (}20-50 nm) where neurons communicate. Extensive characterizations of the target-specific aptamer conformational dynamics have led to a fundamental understanding of the mechanisms of our biosensing technologies. These findings lay the foundation for expanding this approach to conduct multiplexed detection of diverse neurochemicals at nanoscale resolution.