One of the major goals of neuroscience is to unravel how the brain functions in its entirety and how it generates behavior. The biggest challenge in solving this puzzle is represented by the sheer complexity of nervous systems and the interactions between individual neurons.
This revolutionizing research is expected to lead to new medical treatments and many new answers on how the brain functions. The flexibility in designing semiconductor NPs with exquisite control of sizes, compositions, bandgaps, excited state (exciton) wavefunction and lifetime, makes their development into biomedical reagents highly attractive.
We propose to develop targetable voltage sensing nanoparticles (vsNPs) in the shape of nanorods (vsNRs) that self-insert into the cell membrane and optically record, non-invasively, action potentials (APs) at the single-particle and nanoscale level, at multiple sites, in a large field-of-view.
Once the recognition molecule binds to a target (a specific membrane protein), the vsNR self- inserts into the cell membrane in close proximity to that target. With single-molecule sensitivity, vsNRs could allow nanoscale recording of pre- and post-synaptic membrane potentials during release of- and signaling by- neurotransmitters, record sub-threshold events or monitor individual ion channel activity, simultaneously at many sites, over a large field-of-view, and potentially at a resolution exceeding the diffraction limit.
We and others have recently demonstrated both theoretically and experimentally that engineered NRs could display large QCSE even at room temperature and on the single particle level, and therefore could act as efficient nanoscale vsNRs by displaying changes in fluorescence quantum yield, fluorescence lifetime and/or peak emission wavelength in response to local field perturbation. Moreover, we have tested the feasibility of a functionalization approach for stable membrane insertion of vsNRs into HEK293T cell membranes and demonstrated feasibility of voltage sensing by vsNRs. Our experimental and theoretical studies suggest that vsNRs could afford simultaneous monitoring of the spiking output of a large number of cells.
Here we seek to optimize all aspects of vsNPs synthesis, functionalization, delivery, targeting and detection in order to provide neuroscientists and physiologists a viable and user-friendly technology for the study of AP signals in the brain and in healthy or diseased heart and muscle tissues. Our aims are: (i) development of synthetic routes for heterostructure nanoparticles to produce ultrasensitive vsNPs and characterization of their performance by advanced spectroscopy; (ii) development of functionalization methods based on ligand exchange with transmembrane (amphiphilic) peptides by self-assembly and optimization of vsNPs insertion into the membrane; (iii) development of optical vsNPS recording methodologies and benchmarking of vsNPs performance; (iv) demonstration of vsNPs utility in model neuronal systems and exploration of their use in studying synapses and the molecular dynamics involved in neuronal integration of excitatory and inhibitory inputs.
