Project Summary All neurons are remarkably different and existing approaches do not allow de novo visualization of specific living cells in intact brains, without laborious tasks of making transgenic animals. The project will address this grand challenge: our interdisciplinary team will develop and validate novel nanoscopic probes, to rapidly (<30 min) label specific neurons within highly heterogeneous cell populations. For these applications, in vitro neuronal selection Neuro-SELEX (systematic evolution of ligands by exponential enrichment) will be used to generate libraries of nucleic acid-based probes. These aptamer-based tools will also serve as “pull-out” molecular constructs to identify cell-specific membrane proteins associated with unique neuronal identity and wiring. As a result, this research will provide a broad spectrum of advanced nanotools to decipher the organization of neural circuits at the level of single cells and their compartments. Our preliminary data indicate that the Neuro-SELEX can produce multipurpose toolkits to uniquely map specific neurons or axons without a priori knowledge about their molecular diversity in the intact nervous system. These results, together with our published data, provide the scientific premise for three proof-of-the-concept aims. Arguably, Aplysia is a very powerful experimental model for such technology development. First, to selectively label identified neurons and glial cells, hybrid fluorescent aptamers will be generated using chemical evolution for neuron-specific selection. We will develop a high-throughput cost-efficient system to manufacture molecular probes at a large scale, targeting each key, functionally identified, neuron within a simple-memory forming circuit. Second, we will design fluorescent probes (e.g., modified nucleic acids with fluorophores) for multiplex labeling of several neuronal cell types in vivo. This bar-coding would allow simultaneous visualization of pre- and postsynaptic partners within the same circuit in real time. Furthermore, these probes will be chemically modified to self-deliver molecular constructs into hundreds of target cells without the needs of direct injection, electroporation or making transgenic animals. Third, in proteomic experiments, we will utilize these probes as specific binding tags or ligands to capture and identify membrane proteins specific for each neuronal type of the model circuit including possible synaptic components and receptors. These versatile nanoprobes, with high selectivity and high-throughput fabrication capabilities, will be resourceful to test causality relationships between cellular genomes and complex neuronal phenotypes. Technologies and infrastructure should be applicable to virtually all animal cell types and organs. In perspective, novel fluorescent markers and molecular reporters can be used in early diagnostics and therapy for a broad spectrum of neurological and cell-specific disorders as well as in personalized m...