Growing clinical demands for electrical stimulation-based therapies for central nervous system applications requires the development of conductive biomaterials balancing conductivity, biocompatibility, and mechanical performance. Traditional conductive materials often induce scarring, due to their stiffness and poor biocompatibility, hindering their clinical translation and efficacy. To address these issues, we report the development of a pristine graphene-based (pG) composite material consisting of type I collagen and 60 wt% pG, yielding conductivities (~1 S/m) necessary for efficient electrical stimulation, and with versatile processability.
Materials and Methods
Pristine graphene and collagen films (60 wt%, CpG) (CpG60%) were synthesised. Different neurons (SHSY-5Y, NSC-34, iPSC-derived) and glial cells were seeded on the composites, and the metabolic activity, DNA content, cell morphology and release of inflammatory cytokines were assessed. Electrical stimulation was applied to mouse primary cortical neurons to enhance neurite outgrowth and viability. Finally, to demonstrate the versatility of CpG composites for a number of applications, the CpG was fabricated into porous 3D scaffolds, microneedle arrays, and bioelectronics circuits, using freeze drying, dry casting, and 3D printing approaches respectively.
Of all composites tested (N=4), CpG60% exhibited physiologically relevant conductivities (~1 S/m), and robust mechanical properties (~17.8 MPa). Four neuronal and glial cell types exhibited robust growth when grown on composite films with no change in inflammatory markers IL-6, IL-10, or IL-1β, and good biocompatibility. Induced pluripotent stem cell-derived neurons exhibited typical cellular morphology after 15 days growth on the films. The achieved conductivity enabled the efficient delivery of electrical stimulation to mouse primary cortical neurons on the composite (200mV/mm, 12Hz, 4h/day, 5 days), and enhanced neurite outgrowth, cellular viability and morphology compared to collagen controls. Finally, the diverse potential applications of the composite were demonstrated using a range of neural-interfacing structures, including porous scaffolds with aligned pores visible under SEM, microneedle arrays, and 3D-printed working LED circuits for bioelectronics.
These results show that (CpG60%) composites form a versatile neurotrophic platform that balances the requirements for physiologically relevant conductivity, robust mechanical properties, and excellent biocompatibility. The mechanical properties of the composite give it an advantage over stiffer traditional electrode materials, which can cause scarring due to extreme mechanical mismatch. The CpG60% composite supported robust neuronal and glial cell growth, with an absence of neuro-inflammatory responses. In addition, CpG60% efficiently delivered electrical stimulation to neurons, which when coupled with these conductive materials enhanced neurite outgrowth, viability, and cellular morphology. Finally, the versatile processing capabilities of the CpG composites using various fabrication techniques demonstrate its potential as platform for fabrication of next-generation neuronal medical devices.
 Gouveia, P.J., Maughan, J., Gutierrez Gonzalez, J., Leahy, L., Woods, I., O’Connor, C., McGuire, T., Garcia, J., O’ Shea, D., McComish, S.F., Kennedy, O.D., Caldwell, M.A., Dervan, A., Coleman, J.N., O’Brien, F.J., Collagen/Pristine Graphene as an Electroconductive Interface Material for Neuronal Medical Device Applications, Materials Today, 2022, Under Review.
 Ryan et al. Electroconductive Biohybrid Collagen/Pristine Graphene Composite Biomaterials with Enhanced Biological Activity, Advanced Materials 30(15)(2018)(1706442).
Science Foundation Ireland AMBER Centre, IRFU Charitable Trust, and the Anatomical Society"