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

Nature Nanotechnology volume 17, pages 301–309 (2022)Cite this article

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Abstract

Mapping the entire frequency bandwidth of brain electrophysiological signals is of paramount importance for understanding physiological and pathological states. The ability to record simultaneously DC-shifts, infraslow oscillations (<0.1 Hz), typical local field potentials (0.1–80 Hz) and higher frequencies (80–600 Hz) using the same recording site would particularly benefit preclinical epilepsy research and could provide clinical biomarkers for improved seizure onset zone delineation. However, commonly used metal microelectrode technology suffers from instabilities that hamper the high fidelity of DC-coupled recordings, which are needed to access signals of very low frequency. In this study we used flexible graphene depth neural probes (gDNPs), consisting of a linear array of graphene microtransistors, to concurrently record DC-shifts and high-frequency neuronal activity in awake rodents. We show here that gDNPs can reliably record and map with high spatial resolution seizures, pre-ictal DC-shifts and seizure-associated spreading depolarizations together with higher frequencies through the cortical laminae to the hippocampus in a mouse model of chemically induced seizures. Moreover, we demonstrate the functionality of chronically implanted devices over 10 weeks by recording with high fidelity spontaneous spike-wave discharges and associated infraslow oscillations in a rat model of absence epilepsy. Altogether, our work highlights the suitability of this technology for in vivo electrophysiology research, and in particular epilepsy research, by allowing stable and chronic DC-coupled recordings.

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Fig. 1: Flexible gDNP technology and characterization.
Fig. 2: Validation of in vivo full-bandwidth recording capabilities of gDNPs.
Fig. 3: Electrophysiological recording of characteristic epilepsy biomarkers.
Fig. 4: Chronic assessment of the stability, functionality and biocompatibility of gDNPs.

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Data availability

All relevant data obtained to evaluate the main findings of the paper are openly available in Zenodo at https://doi.org/10.5281/zenodo.5655535. All other raw data are available from the corresponding author upon reasonable request.

Code availability

Python v.3.7 packages (Matplotlib v.3.2.0 and Numpy v.1.17.4) and the following Python library were used for electric characterization of the gSGFET arrays: https://github.com/aguimera/PyGFET. A custom Simulink model was used for graphene microtransistor electrophysiological data acquisition; contact g.tec medical engineering for code access. Electrophysiological data were analysed using Python v.3.7 packages (Matplotlib v.3.2.0, Numpy v.1.17.4, Pandas v.0.25.3, seaborn v.0.9.0, Neo v.0.8.0 and Elephant) and the custom library PhyREC (https://github.com/aguimera/PhyREC/tree/PhyREC4). Custom scripts can be found at Zenodo (https://doi.org/10.5281/zenodo.5655535). Immunohistochemical data analysis was performed using Python v.3.7 script (https://github.com/kebarr/biocompatibility_study).

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Acknowledgements

This work has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 881603 (GrapheneCore3). ICN2 is supported by the Severo Ochoa Centres of Excellence programme, funded by the Spanish Research Agency (AEI, grant no. SEV-2017–0706), and by the CERCA Programme/Generalitat de Catalunya. A.B.C. is supported by the International PhD Programme La Caixa-Severo Ochoa (Programa Internacional de Becas ‘la Caixa’-Severo Ochoa). This work has made use of the Spanish ICTS Network MICRONANOFABS, partially supported by MICINN and the ICTS ‘NANBIOSIS’, more specifically by the Micro-NanoTechnology Unit of the CIBER in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN) at the IMB-CNM. We also acknowledge funding from the Generalitat de Catalunya (2017 SGR 1426), and the 2DTecBio project (FIS2017-85787-R) funded by the Ministerio de Ciencia, Innovación y Universidades of Spain, the Agencia Estatal de Investigación (AEI) and the Fondo Europeo de Desarrollo Regional (FEDER/UE). Part of this work was co-funded by the European Regional Development Funds (ERDF) allocated to the Programa operatiu FEDER de Catalunya 2014–2020, with the support of the Secretaria d’Universitats i Recerca of the Departament d’Empresa i Coneixement of the Generalitat de Catalunya for emerging technology clusters devoted to the valorization and transfer of research results (GraphCAT 001-P-001702). A.B.C. acknowledges that this work has been carried out within the framework of a PhD in Electrical and Telecommunication Engineering at the Universitat Autònoma de Barcelona. R.C.W. is funded by a Senior Research Fellowship awarded by the Worshipful Company of Pewterers. D.R. is a Biotechnology and Biological Sciences Research Council (BBSRC) LIDo sponsored PhD student. We thank M. Walker and L. Lemieux (UCL Queen Square Institute of Neurology) for their comments on the manuscript.

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Authors and Affiliations

  1. Catalan Institute of Nanoscience and Nanotechnology, CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Bellaterra, Spain

    Andrea Bonaccini Calia, Nathan Schäfer, Elisa Rodríguez-Lucas, Jose M. De la Cruz, Elena Del Corro, Damià Viana, Jessica Bousquet, Clement Hébert, Justin R. Sperling, Kostas Kostarelos & Jose A. Garrido

  2. Institut de Microelectrònica de Barcelona, IMB-CNM (CSIC), Bellaterra, Spain

    Eduard Masvidal-Codina, Xavi Illa, Elisabet Prats-Alfonso, Javier Martínez-Aguilar, Rosa Villa & Anton Guimerà-Brunet

  3. Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Madrid, Spain

    Eduard Masvidal-Codina, Xavi Illa, Elisabet Prats-Alfonso, Javier Martínez-Aguilar, Rosa Villa & Anton Guimerà-Brunet

  4. Department of Clinical and Experimental Epilepsy, Queen Square Institute of Neurology, University College London, London, UK

    Trevor M. Smith, Daman Rathore & Rob C. Wykes

  5. Nanomedicine Lab, National Graphene Institute and Faculty of Biology Medicine and Health, University of Manchester, Manchester, UK

    Matthew Drummond, Arnab Halder, Abbie Dodd, Katharine Barr, Sinead Savage, Kostas Kostarelos & Rob C. Wykes

  6. Departament de Fisica, Universitat Autonoma de Barcelona, Barcelona, Spain

    Jordina Fornell & Jordi Sort

  7. Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain

    Jordi Sort & Jose A. Garrido

  8. g.tec medical engineering, Guger Technologies, Schiedlberg, Austria

    Christoph Guger

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  1. Andrea Bonaccini Calia
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Contributions

A.B.C. carried out most of the fabrication and characterization of the gDNPs, contributed to the design and performance of the in vivo experiments, analysed the data and wrote the manuscript. E.M.-C. contributed to the design and planning of the in vivo experiments, to the data analysis and particularly to the DC-shift and SD analysis of the in vivo data. R.C.W. and T.M.S. performed the in vivo experiments. D.R. contributed to the in vivo experiments and DC-coupled recordings with the glass micropipette. N.S., E.R.-L., X.I. and J.M.D.l.C. contributed to the fabrication and characterization of the gDNPs. E.D.C., J.B. and C.H. contributed to the growth, transfer and characterization of the CVD graphene used in the gDNPs. E.P.-A., A.H. and E.R.-L. contributed to the optimization of the SF stiffening protocol of the gDNPs. J.M.-A. contributed to the fabrication of the custom electronic instrumentation and development of a Python-based user interface. D.V. contributed to the Python scripts and technical discussions. J.R.S. reviewed the manuscript. J.F. and J.S. contributed to the mechanical assessment of the SF and the SF back-coated gDNPs. M.D. performed all surgeries for the biocompatibility study. A.D. and K.B. contributed to the capture of histological images and image processing and analysis. S.S. and K.B. contributed to the preparation and review of the manuscript. A.G.-B. contributed to the design and fabrication of the custom electronic instrumentation, the development of a custom gSGFET Python library and analysis of the data. R.V., K.K., R.C.W., A.G.-B. and J.A.G. participated in the design of all experiments and thoroughly reviewed the manuscript. All authors read and reviewed the manuscript.

Corresponding authors

Correspondence to Rob C. Wykes, Anton Guimerà-Brunet or Jose A. Garrido.

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Competing interests

C.G. is the owner of g.tec medical engineering and Guger Technologies. J.A.G, K.K and A.G.-B declare financial interest in INBRAIN Neuroelectronics. All other authors have no competing interests.

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Peer review information Nature Nanotechnology thanks Matthew Nelson, Bozhi Tian and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Bonaccini Calia, A., Masvidal-Codina, E., Smith, T.M. et al. Full-bandwidth electrophysiology of seizures and epileptiform activity enabled by flexible graphene microtransistor depth neural probes. Nat. Nanotechnol. 17, 301–309 (2022). https://doi.org/10.1038/s41565-021-01041-9

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