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Significance Pain comprises a complex interaction between motor action and somatosensation that is dependent on dynamic interactions between the brain and spinal cord. This makes understanding pain particularly challenging as it involves rich interactions between many circuits (e.g., neural and vascular) and signaling cascades throughout the body. As such, experimentation on a single region may lead to an incomplete and potentially incorrect understanding of crucial underlying mechanisms. Aim We aimed to develop and validate tools to enable detailed and extended observation of neural and vascular activity in the brain and spinal cord. The first key set of innovations was targeted to developing novel imaging hardware that addresses the many challenges of multisite imaging. The second key set of innovations was targeted to enabling bioluminescent (BL) imaging, as this approach can address limitations of fluorescent microscopy including photobleaching, phototoxicity, and decreased resolution due to scattering of excitation signals. Approach We designed 3D-printed brain and spinal cord implants to enable effective surgical implantations and optical access with wearable miniscopes or an open window (e.g., for one- or two-photon microscopy or optogenetic stimulation). We also tested the viability for BL imaging and developed a novel modified miniscope optimized for these signals (BLmini). Results We describe “universal” implants for acute and chronic simultaneous brain–spinal cord imaging and optical stimulation. We further describe successful imaging of BL signals in both foci and a new miniscope, the “BLmini,” which has reduced weight, cost, and form-factor relative to standard wearable miniscopes. Conclusions The combination of 3D-printed implants, advanced imaging tools, and bioluminescence imaging techniques offers a coalition of methods for understanding spinal cord–brain interactions. Our work has the potential for use in future research into neuropathic pain and other sensory disorders and motor behavior. 

Abstract Objective.The recording instability of neural implants due to neuroinflammation at the device-tissue interface is a primary roadblock to broad adoption of brain-machine interfaces. While a multiphasic immune response, marked by glial scaring, oxidative stress (OS), and neurodegeneration, is well-characterized, the independent contributions of systemic and local ‘innate’ immune responses are not well-understood. We aimed to understand and mitigate the isolated the innate neuroinflammatory response to devices.Approach.Three-dimensional primary neural cultures provide a unique environment for studying the drivers of neuroinflammation by decoupling the innate and systemic immune systems, while conserving an endogenous extracellular matrix and structural and functional network complexity. We created a three-dimensionalin vitromodel of the device-tissue interface by seeding primary cortical cells around microwires. Live imaging of both dye and Adeno-Associated Virus (AAV) - mediated functional, structural, and lipid peroxidation fluorescence was employed to characterize the neuroinflammatory response.Main results.Live imaging of microtissues over time revealed independent innate neuroinflammation, marked by increased OS, decreased neuronal density, and increased functional connectivity. We demonstrated the use of this model for therapeutic screening by directly applying drugs to neural tissue, bypassing low bioavailability through thein vivoblood brain barrier. As there is growing interest in long-acting antioxidant therapies, we tested efficacy of ‘perpetual’ antioxidant ceria nanoparticles, which reduced OS, increased neuronal density, and protected functional connectivity.Significance.Our three-dimensionalin vitromodel of the device-tissue interface exhibited symptoms of OS-mediated innate neuroinflammation, indicating a significant local immune response to devices. The dysregulation of functional connectivity of microcircuits surround implants suggests the presence of an observer effect, in which the process of recording neural activity may fundamentally change the neural signal. Finally, the demonstration of antioxidant ceria nanoparticle treatment exhibited substantial promise as a neuroprotective and anti-inflammatory treatment strategy.