Biology subjects

Garrido, J. A.

Publications and source records attributed to Garrido, J. A..

9 recordsLinked to original sources

bioRxiv2026

Focal astrocyte Kir4.1 loss drives seizures, spreading depolarizations and postictal impairments

Astrocytic dysfunction is increasingly recognised as an important contributor to epileptogenesis and seizure dynamics. Kir4.1 potassium channels expressed in astrocytes play a critical role in activity-dependent extracellular potassium buffering, and their loss may impair network stability and promote pathological hyperexcitability. In epilepsy, seizures can be accompanied by spreading depolarizations (SDs), propagating waves of neuronal and glial depolarization. While seizure-associated SDs have been proposed to terminate seizures and limit seizure spread, they have also been implicated in postictal dysfunction and sudden unexpected death in epilepsy (SUDEP), and their significance in chronic epilepsy remains unclear. Here, we tested whether focal loss of astrocytic Kir4.1 in the adult hippocampus is sufficient to disrupt potassium buffering, generate spontaneous seizures, and promote seizure-associated SDs. Using astrocyte-targeted viral vector Cre recombinase in adult Kir4.1-floxed mice, we induced focal hippocampal reduction of Kir4.1 expression. This impaired activity-dependent potassium buffering, producing enhanced stimulation-evoked extracellular potassium accumulation and larger DC shifts in hippocampal slices. Chronic wireless EEG recordings demonstrated that focal astrocytic Kir4.1 loss was sufficient to induce spontaneous recurrent seizures and interictal epileptiform activity. To investigate seizure-associated SDs, we combined optogenetic stimulation with graphene-based micro-transistor recordings capable of stable full-bandwidth DC electrophysiology in awake head-fixed mice. Focal hippocampal loss of astrocytic Kir4.1 markedly increased susceptibility to evoked seizures accompanied by SDs. We used chronic wireless DC-coupled video-telemetry recordings to continuously monitor seizure and SD dynamics in freely moving mice. SDs occurred frequently during generalized seizures and were first detected in cortical channels. Seizures accompanied by SDs exhibited greater spectral power, longer duration, and prolonged postictal depression compared with seizures alone. Behaviourally, seizures accompanied by SDs were linked to postictal impairment characterised by behavioural arrest and abnormal motor behaviours. These findings highlight the utility of graphene micro-transistor arrays and chronic DC-coupled telemetry for resolving infraslow (<0.1 Hz) epileptic dynamics that are largely inaccessible using conventional electrophysiological approaches. Ground-truth DC-coupled recordings enabled identification of AC-band electrographic signatures that segregated seizures with SDs from seizures alone, raising the possibility that SD-associated seizures may be retrospectively inferred from conventional AC-coupled epilepsy datasets. We demonstrate that focal astrocytic Kir4.1 loss in the adult brain impairs potassium buffering and is sufficient to drive spontaneous seizures, supporting astrocytic potassium dysregulation as a determinant of seizure and spreading depolarization susceptibility in epilepsy. Furthermore, seizure-associated SDs are strongly linked to increased postictal impairments, supporting the concept that SDs are major determinants of pathological postictal states.

neuroscience↗

bioRxiv2026

Advances in Thin-Film Graphene Neurotechnology for Chronic Nerve Stimulation and Recording

Neurotechnology is being explored for restoring sensorimotor functions after paralysis or amputation, which requires peripheral nerve interfaces that are selective, bidirectional, and chronically stable. Reduced graphene oxide (rGO)-based microelectrodes offer low impedance and a high charge-injection limit; however, long-term in vivo performance has been limited by the durability of encapsulation. Here, we introduce a 10 {micro}m-thick transverse intrafascicular multichannel electrode (TIME) with a hybrid polyimide-Al2O3 encapsulation engineered to improve fabrication yield, electrode-to-electrode uniformity, and device stability. In vitro, devices maintained near-ideal capacitive behaviour after accelerated ageing (3 months in PBS at 57 {degrees}C) and sustained 109 biphasic stimulation pulses without detectable electrochemical degradation. In vivo, the arrays recorded compound nerve action potentials after one month and enabled selective activation of distinct peripheral nerve fibres with comparatively low current thresholds during four months of follow-up, remaining below the device maximum injectable current. Together, these results demonstrate that combining graphene microelectrodes with a thin hybrid encapsulation improves chronic reliability of intraneural thin-film interfaces and helps to close the gap between laboratory prototypes and clinically relevant neuroprosthetic systems.

bioengineering↗

bioRxiv2025

An artefact-resilient wide bandwidth bidirectional graphene neural interface

The ability to simultaneously record and modulate neural activity is critical for next-generation bidirectional neural interfaces aiming to enable adaptive neuromodulation therapies for neurological disorders. Active graphene transistor technologies are particularly promising for neural recordings, as they extend the ability to monitor brain activity at very low frequencies and support multiplexed operation for high-density neural interfaces. However, their limited charge injection capacity makes them unsuitable for stimulation. In this work, we present a bidirectional neural interface that combines nanoporous reduced graphene oxide (rGO) microelectrodes for high charge injection focal stimulation and graphene solution-gated field-effect transistors (gSGFETs) for brain activity monitoring, exploiting the advantages of both technologies in one single device. Using scalable cleanroom microfabrication techniques, we monolithically integrate these two graphene-based technologies into fully flexible probes. We evaluate the performance of the hybrid devices both in saline and in vivo, with a particular focus on transistor performance during stimulation. Our results demonstrate that the recording capability of this bidirectional neural interface, including the monitoring of infraslow and local field potential activity, is not compromised during stimulation. This work highlights the potential of this hybrid neural interface for both basic neurophysiological and clinical translation use.

neuroscience↗

bioRxiv2025

Graphene Micro-transistor Arrays Reveal Perfusion-Dependent Electrophysiological and Haemodynamic Signatures of Cortical Spreading Depolarizations in Ischaemic Stroke

Cortical spreading depolarizations (CSDs) are large-scale disruptions of neuronal homeostasis that contribute to secondary injury in ischaemic stroke. In healthy cortex, CSDs induce vasodilation to meet metabolic demand, whereas in ischaemic tissue, they can provoke vasoconstriction and sustained hypoperfusion, exacerbating damage. We present a multimodal neurotechnology platform integrating flexible, transparent graphene solution-gated field-effect transistor (gSGFET) arrays with laser speckle contrast imaging (LSCI), enabling simultaneous DC-coupled electrophysiological recordings and cerebral blood flow imaging with high spatiotemporal fidelity. gSGFETs enable stable, distortion-free recording of infraslow potentials essential for resolving CSD waveforms in vivo. In two murine stroke models, we show that CSD waveform duration and morphology scale with local perfusion, delineating electrophysiological subtypes predictive of tissue viability and haemodynamic response. In metabolically compromised cortex, CSDs exhibit double peaks or negative ultraslow components that result in vasoconstriction, contrasting with narrow, monophasic waveforms eliciting vasodilation in healthy regions. Systemic ketamine shortens CSD duration and converts vasoconstriction to vasodilation in perfusion-deficit tissue, revealing a mechanism for its neuroprotective action. This platform enables high-fidelity investigation of brain-blood flow interactions in vivo.

neuroscience↗

bioRxiv2024

Large-scale infra-slow dynamics of extracellular potentials linked to synchronous states revealed by graphene neural probes

Infra-slow (<0.5 Hz) brain dynamics reflect homeostatic and neuromodulatory processes that modulate neuronal excitability and shape faster oscillations across brain regions. Infra-slow brain activity is typically inferred from magnetic or optical imaging, but these methods are limited in temporal resolution and compatibility with unconstrained behavior. Infra-slow local field potentials (isLFPs) could provide a direct measure of infra-slow network dynamics, but have remained poorly characterized due to the absence of scalable, DC-coupled recording methods. Here, we introduce DC-coupled electrophysiological imaging based on arrays of up to 512 multiplexed graphene transistors enabling stable, high-density recordings across cortical regions and cortical layers in freely moving rats. We developed an analytical framework for the analysis of wide-band LFP, revealing that synchronous oscillatory states of variable duration and spatial scale are consistently linked to topographically and translaminarly structured DC potential shifts. We propose a physiological model linking these DC shifts to sustained gradients of extracellular K+ concentration, providing a mechanistic connection between neuronal synchrony and isLFP dynamics. By integrating DC-coupled sensing, multiplexed scalability, and depth-surface co-registration, this work establishes a new modality for imaging-like electrophysiology in freely moving animals and a framework for interpreting infra-slow dynamics.

neuroscience↗

bioRxiv2024

Flexible graphene-based neurotechnology for high-precision deep brain mapping and neuromodulation in Parkinsonian rats

Deep brain stimulation (DBS) is a neuroelectronic therapy for the treatment of a broad range of neurological disorders, including Parkinsons disease. Current DBS technologies face important limitations that impact their efficacy, such as large electrode size, invasiveness, and lack of adaptive therapy based on biomarker monitoring. The use of novel electrode materials is expected to contribute to overcome these limitations. In a previous study, we reported that nanoporous reduced graphene oxide (rGO) is a promising electrode material due to its high charge injection capacity and low impedance. Here, we investigate the potential benefits of using the rGO technology in DBS. To this end, we implant a flexible high-density array of rGO microelectrodes in the subthalamic nucleus (STN) of healthy and hemi-parkinsonian rats to investigate specific electrophysiological Parkinsonian biomarkers and to assess the effect of microscale stimulation. We demonstrate that these microelectrodes record action potentials with high signal-to-noise ratios (SNR > 6), allowing the precise localization of deep brain structures like the STN, and the tracking of multiunit-based biomarkers such as STN bursts. The bidirectional capability to deliver high-density focal stimulation and to record high-fidelity signals unlocks the visualization of the local neuromodulation of the multiunit biomarker. These findings demonstrate the potential of bidirectional high-resolution neural interfaces to investigate the mechanisms around DBS in preclinical models and suggest new avenues for the use of adaptive closed-loop operation based on electrophysiological biomarkers monitoring.

bioengineering↗

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↗

bioRxiv2021

A novel hybrid protein promotes Aβ clearance and reduces inflammatory response through MerTK

Alzheimers disease (AD) is the worlds leading cause of dementia and the most common neurodegenerative disorder. Its major pathological features are amyloid beta (A{beta}) plaques, tau tangles, and neuroinflammation that eventually leads to massive death of nerve cells. Even with the multifactorial aspect of AD, the most accepted theory is that A{beta} is the driving force of AD pathogenesis. We engineered a novel hybrid protein that facilitates the phagocytosis of A{beta} and redirect its clearance to the noninflammatory Mer tyrosine kinase (MerTK) pathway. The novel hybrid protein facilitates robust uptake and clearance of A{beta} in BV2 microglia through MerTK receptor with reduced production of inflammatory factors and oxidative products. In APP/PS1 transgenic AD mouse model, intraperitoneal administration of the hybrid protein for two months results in significant reduction of A{beta} burden in the brain and protection of nerve cells from dying. Taken together, our results suggest that the novel hybrid may have the potential for AD treatment by targeting both A{beta} clearance and reduction of inflammation.

molecular 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↗