Schematic of the constituents of the novel collagen-graphene composite, its interaction with neuronal cells, and fabrication into biodegradable circuits, 3D scaffolds, and biodegradable microneedles. Credit: Jack Maughan and Dr Pedro Gouveia.Traditional metal electrodes used for electrical stimulation-based medical therapies can cause scarring and other problems. As an alternative, researchers from Trinity College Dublin and the Royal College of Surgeons in Ireland (RCSI) have designed and fabricated a novel conductive biomaterial based on pristine graphene and collagen [Maughan et al., Applied Materials Today 29 (2022) 101629, https://doi.org/10.1016/j.apmt.2022.101629].
“We took graphene, a highly conductive, very strong material and combined it with collagen, the most abundant protein in the human body, to form a composite material for neural medical device applications… [that can] effectively deliver electrical stimulation at similar levels to native tissues,” explains Fergal J. O’Brien, Professor of Bioengineering & Regenerative Medicine at RCSI, who led the work.
Nerve cells, which are electrically sensitive, respond to conductive surfaces and to applied electrical stimulation. Stimulating neuron cells electrically can, therefore, encourage the repair and regrowth of neuronal tissue. While most metals are stiff and show poor biocompatibility, soft and flexible polymers – if imbued with charge-carrying conductive nanomaterials – offer a promising alternative. Type-I collagen occurs naturally and is compatible with neurons, supporting their growth. When combined with graphene, and its combination of conductivity, strength, and processability, a conductive nanobiocomposite with the physical properties necessary to interact with the neuronal interface and enhance neuronal response to electrical stimulation is produced. Graphene can be produced simply by sonicating graphite in the presence of the natural polymer gelatin. A loading of 60 wt% graphene produces a material with an effective combination of conductivity, biocompatibility, and mechanical properties closely resembling native tissue. The researchers explored the interaction of the nanocomposite with neurons from mice.
“Our conductive composite material [has a] beneficial effect on the growth and connections of electrically stimulated cells,” says O’Brien. “[It is] suitable for the delivery of electrical stimulation and [shows] versatility in usable processing techniques,” he adds.
The team produced a range of neuronal medical devices using the graphene/collagen nanobiocomposite ranging from a porous scaffold for spinal cord injury repair to 3D printed bioelectronic circuits for bio-safe electronics and microneedle arrays for stimulation devices.
“This versatility of application is difficult to attain in traditional materials, which are often optimized for very limited applications, and use complex and costly processing steps to achieve the desired devices,” points out O’Brien. “This [material] opens up applications in other areas such as deep brain stimulation and drug delivery to neural tissues.”