Abstract
Direct electrical recording and stimulation of neural activity using micro-fabricated silicon and metal micro-wire probes have contributed extensively to basic neuroscience and therapeutic applications; however, the dimensional and mechanical mismatch of these probes with the brain tissue limits their stability in chronic implants and decreases the neuron-device contact. Here, we demonstrate the realization of a three-dimensional macroporous nanoelectronic brain probe that combines ultra-flexibility and subcellular feature sizes to overcome these limitations. Built-in strains controlling the local geometry of the macroporous devices are designed to optimize the neuron/probe interface and to promote integration with the brain tissue while introducing minimal mechanical perturbation. The ultra-flexible probes were implanted frozen into rodent brains and used to record multiplexed local field potentials and single-unit action potentials from the somatosensory cortex. Significantly, histology analysis revealed filling-in of neural tissue through the macroporous network and attractive neuron-probe interactions, consistent with long-term biocompatibility of the device.
Highlights
Direct electrical recording and stimulation of neural activity using microfabricated silicon and metal micro-wire probes have contributed extensively to basic neuroscience and therapeutic applications; the dimensional and mechanical mismatch of these probes with the brain tissue limits their stability in chronic implants and decreases the neuron-device contact
We have shown that 3D macroporous electronic device arrays can function as a scaffold for and allow for 3D interpenetration of cultured neuron cell networks without an adverse effect on cell viability[31], and such networks can be injected by syringe through needles into materials, including brain tissue[32]
Taking the above facts into consideration, we define an ideal implantable neural probe as (i) possessing a stiffness similar to brain tissue to minimize/eliminate mechanically-induced scarring, (ii) a high-degree of porosity and cellular/subcellular feature sizes to allow for interpenetration and integration of neurons and neural projections with the electronics, (iii) a means for implantation of the resulting extremely flexible structure, and (iv) facile I/O to allow for multiplexed recording
Summary
Direct electrical recording and stimulation of neural activity using microfabricated silicon and metal micro-wire probes have contributed extensively to basic neuroscience and therapeutic applications; the dimensional and mechanical mismatch of these probes with the brain tissue limits their stability in chronic implants and decreases the neuron-device contact. Images recorded post-insertion (Supplementary Fig. S6a) highlight the high flexibility of our macroporous probe outside the brain, which allows for positioning without moving the implanted portion within the tissue.
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