Robust Type-specific Hemisynapses Induced by Artificial Dendrites

Distinct Exocytosis Behavior at Synaptic Membrane Protein-Protein Coupled Cell-Electrode Interfaces Revealed by Single-Cell Amperometry

Neural interfacing technologies, combined with biospecific targeting and neuroelectrochemical analysis, provide a powerful platform for advancing the understanding of neural communication at the single-cell level. A key factor in this integration is the role of protein-mediated cell adhesion at the cell-electrode interface, which can influence cellular processes such as exocytosis. However, the specific impact of this interaction remains largely unexplored. In this study, a biospecific electrode platform functionalized with genetically engineered neuroligin-2 (eNLG2) is developed and its effect on exocytosis in PC12 cells is investigated. The findings reveal that eNLG2-modified electrodes significantly slowed exocytosis kinetics and increased the amount of neurotransmitters released per event compared to non-protein-modified and laminin-modified electrodes. These results suggest that synaptic membrane proteins, such as neuroligin and neurexin, modulate vesicle fusion dynamics likely by influencing membrane properties and intracellular signaling. This study highlights the potential of combining biospecific neural interfacing technologies with neuroelectrochemical approaches to gain comprehensive insights into exocytosis and neural communication.

On-Site Formation of Functional Dopaminergic Presynaptic Terminals on Neuroligin-2-Modified Gold-Coated Microspheres

Advancements in neural interface technologies have enabled the direct connection of neurons and electronics, facilitating chemical communication between neural systems and external devices. One promising approach is a synaptogenesis-involving method, which offers an opportunity for synaptic signaling between these systems. Janus synapses, one type of synaptic interface utilizing synaptic cell adhesion molecules for interface construction, possess unique features that enable the determination of location, direction of signal flow, and types of neurotransmitters involved, promoting directional and multifaceted communication. This study presents the first successful establishment of a Janus synapse between dopaminergic (DA) neurons and abiotic substrates by using a neuroligin-2 (NLG2)-mediated synapse-inducing method. NLG2 immobilized on gold-coated microspheres can induce synaptogenesis upon contact with spatially isolated DA axons. The induced DA Janus synapses exhibit stable synaptic activities comparable to that of native synapses over time, suggesting their suitability for application in neural interfaces. By calling for DA presynaptic organizations, the NLG2-immobilized abiotic substrate is a promising tool for the on-site detection of synaptic dopamine release.

Robust Induced Presynapse on Artificial Substrates as a Neural Interfacing Method

Over the recent years, the development of neural interface systems has stuck to using electrical cues to stimulate neurons and read out neural signals, although neurons relay signals via chemical release and recognition at synapses. In addition, conventional neural interfaces are vulnerable to cell migration and glial encapsulation due to the absence of connection anchoring the neuron into the device unlike synapses, which are firmly sustained by protein bonding. To close this discrepancy, we conducted an intensive investigation into the induced synapse interface by employing engineered synaptic proteins from a neural interface perspective. The strong potential of induced synaptic differentiation as an emerging neural interfacing technique is demonstrated by exploring its structural features, chemical release kinetics, robustness, and scalability to the brain tissue. We show that the exocytosis kinetics of induced synapses is similar to that of endogenous synapses. Moreover, induced synapses show remarkable stability, despite cell migration and growth. The synapse-inducing technique has broad applications to cultured hippocampal and cortex tissues and suggests a promising method to integrate neural circuits with digital elements.

Multiplexed and spatiotemporal measurements of glutamate secreted by neurons and bacteria

By applying an in vivo biotinylation platform, glutamate-sensing protein can be easily immobilized on streptavidin-functionalized magnetic microbeads, which expands the detection modality for the spatiotemporal measurements of glutamate secreted by adherent neuronal cells and suspension microbial cells using fluorescence microscopy and microplate photometers.