How Neuromorphic Microstructures Control In Vitro Neuronal Outgrowth

In tissue engineering and bioelectronics, neuromorphic materials represent a new class of materials that mimic neuronal architectures and features to better replicate the physiological environment of native neuronal tissue. Biomimetic micro- and nanostructures can provide physical support and guidance for neurons, aiming to engineer chip-based platforms capable of monitoring and stimulating neuronal networks. Two major challenges remain: controlling the morphology of neuromorphic materials and understanding how these materials affect neural network development during different outgrowth phases.<br/>Here, we present ad hoc biomimetic microstructure arrays fabricated via two-photon polymerization to resemble various morphologies and spatial arrangements of neuronal dendritic spines, with fixed material. We identified three geometries: thin shapes that initiate contacts with presynaptic terminals, crucial in early spinogenesis; mushroom shapes resulting from the dynamic reshaping of neuronal circuits during synaptic development; and stubby forms. The experimental approach involved primary cortical neurons. Our work demonstrated mechanical interactions at focal adhesion sites, which oversee the continuous remodeling and adjustment of cells on the material's surface and generate localized traction forces. Neurons utilize these forces for directed movement through contact guidance and for membrane invagination during engulfment, leading to precise localization of transmembrane proteins, including integrins, and specific cytoskeletal arrangements.<br/>The integration of non-conductive polymers in neural recording devices is pivotal for advancing the field of bioelectronic interfaces. Our recent research underscores the profound impact these materials have on the mechanical rearrangement and the overall recording quality.<br/>Microelectrodes, when combined with non-conductive polymers, significantly influence the directionality and remodeling of neural networks. This effect is particularly noticeable during the growth cone phase, where the transition from pausing to a resting state is critical. Our findings indicate that different pitch configurations of microelectrodes can alter the growth cone rate, emphasizing the importance of precise design in neural recording systems.<br/>One of the key discoveries of our research is the role of biomimetic topographical cues. These cues rapidly affect membrane adhesion proteins, thereby enhancing the efficiency of neural recordings. Through advanced techniques like 3D reconstruction integrated into an electrical equivalent model, we've demonstrated that these topographical cues can significantly improve membrane interactions and overall signal integrity.<br/>Looking ahead, the insights gained from our study hold promise for future applications in controlling signal dissipation. By leveraging the unique properties of non-conductive polymers and the strategic design of microelectrodes, it is possible to enhance the recording capabilities of devices used with electrogenic cells. This can lead to more accurate and reliable data collection, ultimately benefiting various fields such as neuroscience, bioengineering, and medical diagnostics.<br/>We characterized the cell response considering neuronal-material interface processes such as adhesion, endocytosis, polarity, and network development. These new platforms pave the way for improved biomaterial-neuronal coupling aimed at neuroengineering and monitoring/stimulation.<br/>In summary, the utilization of non-conductive polymers in recording technologies not only improves mechanical rearrangement but also enhances the overall efficiency and accuracy of neural recordings. Our research highlights the importance of material choice and design in developing advanced bioelectronic interfaces, paving the way for future innovations in the field.