No abstract

Neuroelectronic devices are critical for the diagnosis and treatment of neuropsychiatric conditions, and are hypothesized to have many more applications. A wide variety of materials and approaches have been utilized to create innovative neuroelectronic device components, from the tissue interface and acquisition electronics to interconnects and encapsulation. Although traditional materials have a strong track record of stability and safety within a narrow range of use, many of their properties are suboptimal for chronic implantation in body tissue. Material advances harnessed to form all the components required for fully integrated neuroelectronic devices hold promise for improving the long‐term efficacy and biocompatibility of these devices within physiological environments. Here, it is aimed to provide a comprehensive overview of materials and devices used in translational neuroelectronics, from acquisition and stimulation interfaces to methods for power delivery and real time processing of neural signals.

Bioelectronic devices should optimally merge a soft, biocompatible tissue interface with capacity for local, advanced signal processing. Here, we introduce an organic mixed-conducting particulate composite material (MCP) that can form functional electronic components by varying particle size and density. We created MCP-based high-performance anisotropic films, independently addressable transistors, resistors, and diodes that are pattern free, scalable, and biocompatible. MCP enabled facile and effective electronic bonding between soft and rigid electronics, permitting recording of neurophysiological data at the resolution of individual neurons from freely moving rodents and from the surface of the human brain through a small opening in the skull. We also noninvasively acquired high–spatiotemporal resolution electrophysiological signals by directly interfacing MCP with human skin. MCP provides a single-material solution to facilitate development of bioelectronic devices that can safely acquire, transmit, and process complex biological signals.

Recording from the human brain at the spatiotemporal resolution of action potentials provides critical insight into mechanisms of higher cognitive functions and neuropsychiatric disease that is challenging to derive from animal models. Here, organic materials and conformable electronics are employed to create an integrated neural interface device compatible with minimally invasive neurosurgical procedures and geared toward chronic implantation on the surface of the human brain. Data generated with these devices enable identification and characterization of individual, spatially distribute human cortical neurons in the absence of any tissue penetration (n = 229 single units). Putative single‐units are effectively clustered, and found to possess features characteristic of pyramidal cells and interneurons, as well as identifiable microcircuit interactions. Human neurons exhibit consistent phase modulation by oscillatory activity and a variety of population coupling responses. The parameters are furthermore established to optimize the yield and quality of single‐unit activity from the cortical surface, enhancing the ability to investigate human neural network mechanisms without breaching the tissue interface and increasing the information that can be safely derived from neurophysiological monitoring.

Chitosan (CS) is a biocompatible, inexpensive organic polymer that is increasingly used in neural tissue applications. However, its intrinsic fluorescence has not yet been leveraged to facilitate localization of neural interface devices, a key procedure to ensure accurate analysis of neurophysiological signals. A process is developed to enable control of mechanical and chemical properties of CS‐based composites, generating freestanding films that are stable in aqueous environments and exhibit concentration‐dependent fluorescence intensity. The shape and location of CS‐coated probes are reliably visualized in vitro and in vivo using fluorescence microscopy. Furthermore, CS neural probe marking is fully compatible with classical immunohistochemical and histological techniques, enabling localization of high spatiotemporal resolution surface electrocorticography arrays in adult rats and mouse pups. CS composites have the potential to simplify and streamline experimental procedures required to efficiently acquire, localize, and interpret neurophysiological data.