Biology subjects

Illa, X.

Publications and source records attributed to Illa, X..

3 recordsLinked to original sources

bioRxiv2022

Graphene-based thin film microelectrode technology for in vivo high resolution neural recording and stimulation

Neuroprosthetic technology aims to restore nervous system functionality in cases of severe damage or degeneration by recording and stimulating the electrical activity of the neural tissue. One of the key factors determining the quality of the neuroprostheses is the electrode material used to establish electrical communication with the neural tissue, which is subject to strict electrical, electrochemical, and mechanical specifications as well as biological and microfabrication compatibility requirements. This work presents a nanoporous graphene-based thin film technology and its engineering to form flexible neural implants. Bench measurements show that the developed microelectrodes offer low impedance and high charge injection capacity throughout millions of pulses. In vivo electrode performance was assessed in rodents both from brain surface and intracortically showing high-fidelity recording performance, while stimulation performance was assessed with an intrafascicular implant that demonstrated low current thresholds and high selectivity for activating subsets of axons within the sciatic nerve. Furthermore, the tissue biocompatibility of the devices was validated by chronic epicortical and intraneural implantation. Overall, this works describes a novel graphene-based thin film microelectrode technology and demonstrates its potential for high-precision neural interfacing in both recording and stimulation applications.

bioengineering↗

bioRxiv2022

Epithelial monolayer development and tight junction assembly on nanopillar arrays

Nanostructured materials provide an outstanding opportunity to both stimulate and measure cellular processes. In the context of tight junctions, it was previously reported that transient application of a nanotopographic surface over the apical brush border membrane of epithelial monolayers triggers redistribution of ZO-1, claudins, and F-actin that increases paracellular macromolecular flux. In excitable tissues, nanomaterials have been used to apply and measure electrical signals, such action potentials. As a first step towards translating these technologies for use in analysis of epithelial function, we sought to culture monolayers composed of transporting epithelia over nanopillar arrays without perturbing cellular structure or function. Madin-Darby Canine kidney I (MDCK I) cells were cultured on collagen-coated silicon chips with [~]1 m diameter nanopillar arrays. Fluorescence and scanning electron microscopy were used to assess the impact of height on nanopillar-epithelial interactions. Monolayers formed over and were largely unaffected by short nanopillars. These nanopillars were located beneath basal epithelial surfaces and were not preferentially located within lateral intercellular spaces or beneath ZO-1-containing junctions. In contrast, tall nanopillars that exceeded cell height disrupted MDCK I monolayer growth. Cells interacted with, encircled, and extended cytoplasm over the top of tall nanopillars, and dense ZO-1 and F-actin accumulations occasionally surrounded apical membranes adjacent to nanopillars. Finally, when grown over arrays composed of nanopillars 1 - 2 m shorter than cells, MDCK I frequently grew between nanopillars. As a result, nanopillars were more commonly present within lateral intercellular spaces beneath junctions. Apical complex structure was intact, as assessed by fluorescence microscopy of ZO-1, occludin, claudin-2, F-actin, and E-cadherin. Apical microvilli were also unaffected. We therefore show that conditions can be defined to allow growth of mature, correctly assembled epithelial monolayers with nanopillars localized to lateral intercellular spaces. This sets the stage for application of nanotechnologies for perturbation and analysis of epithelial biology.

cell biology↗

bioRxiv2021

Full bandwidth electrophysiology of seizures and epileptiform activity enabled by flexible graphene micro-transistor depth neural probes

Mapping the entire frequency bandwidth of neuronal oscillations in the brain is of paramount importance for understanding physiological and pathological states. The ability to record simultaneously infraslow activity (<0.1 Hz) and higher frequencies (0.1-600 Hz) using the same recording electrode would particularly benefit epilepsy research. However, commonly used metal microelectrode technology is not well suited for recording infraslow activity. Here we use flexible graphene depth neural probes (gDNP), consisting of a linear array of graphene microtransistors, to concurrently record infraslow and high frequency neuronal activity in awake rodents. We show that gDNPs can reliably record and map with high spatial resolution seizures, post-ictal spreading depolarisation, and high frequency epileptic activity through cortical laminae to the CA1 layer of the hippocampus in a mouse model of chemically-induced seizures. We demonstrate functionality of chronically implanted devices over 10 weeks by recording with high fidelity spontaneous spike-wave discharges and associated infraslow activity in a rat model of absence epilepsy. Altogether, our work highlights the suitability of this technology for in vivo electrophysiology research, in particular, to examine the contributions of infraslow activity to seizure initiation and termination.

neuroscience↗