A Dual-Readout Near-Infrared Fluorescent Fiber Probe for High Spatiotemporal Resolution Neurotransmitter Mapping

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Abstract
Neuromodulators such as dopamine (DA) operate through volume transmission in the brain, creating spatially distributed fields that shape circuit excitability. However, conventional sensing modalities, including voltammetry and fiber photometry, inherently collapse these multidimensional dynamics into one-dimensional, single-point signals, thereby obscuring spatial heterogeneity and propagation behavior. Here, we introduce the Neural Remote Imaging Fiber Interface (NeuRIFI), a dual-readout near-infrared (NIR) sensing platform that bridges localized neurochemical detection and field-level spatial interpretation. By functionalizing implantable optical fibers with DNA-functionalized SWCNT nanosensors, this platform leverages NIR fluorescence emission within the tissue-transparent optical window to enable synchronous fiber-guided photometry and remote NIR imaging without genetic labeling. In this configuration, the photometric channel provides a spatially anchored validation reference, while the remote imaging channel preserves the spatial information on neurochemical signals. We validated the interface across tissue phantoms and ex vivo mouse brains, demonstrating reliable deep-brain signal acquisition at a 3 mm depth. Furthermore, by computing frame-to-frame intensity derivatives, we resolved transient DA flux at a temporal resolution of 20 ms, a spatial resolution of ∼1.5 μm per pixel, and a concentration sensitivity of 90 nM, enabling high spatiotemporal resolution mapping of neurochemical transport across the sensing surface. Collectively, this dual-readout architecture provides a framework linking point-validated sensing to remotely observable spatial structures, offering spatial accessibility for studying complex neurochemical landscapes in deep-brain structures and extending neurochemical field mapping toward in vivo settings.

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