Current research programmes in engineering the neural interface focus on multi-functional bio-mimetic materials. In particular, this research theme exploits the development of topographically and chemically functionalised conducting polymers, noble metals and metal oxides to enhance the formation of a stable neural interface and to modulate gliosis. Other interests in this research theme include the development of elastomeric nanocomposites with enhanced electrochemical and bioactive properties as next-generation biomaterials and components of medical devices.
Biomimetic polymer brushes as conducting coatings for neural probes
Neural tissue engineering has achieved great success as a way to treat central nervous system disorders. The implanted materials, however, have to provide chemical and physical properties analogous to the natural extracellular microenvironments. To meet these criteria, metal electrodes can be covered with biocompatible organic coatings to provide a biointerface with tailored properties. Conducting polymers are currently the most promising materials that can be used to serve as neural electrode coatings.
The aim of the project is to design a novel type of biomimetic coatings for neural electrodes based on conducting polymer brushes. It is expected that such structures will exhibit increased stability when compared with pristine polymer coatings, as well as will enhance the process of neural growth. The investigations will involve the optimization of synthesis procedures to obtain polymer brushes exhibiting high electrical conductivity and stability, simultaneously with good biological properties. Finally, polymer brush coatings will be used as carriers for selected neurotropic and anti-inflammatory factors.
Topographically Functionalised Polymeric Neural Interfaces
Although advances have been made in implantable electrode technologies, key improvements would be facilitated by making electrodes morphologically ‘neuron-like’. Biomimetic design is a paradigm of biomedical engineering and biomimetic morphology has been shown repeatedly by the Biggs lab to induce differential cell function. Concurrently, the Biggs laboratory has identified that nanoscale biomimetic features increase the electrode surface area and reduces electrical impedance, enhancing the signal recording quality. Furthermore, implantable electrode systems which mimic the physicochemical and mechanical properties of the extracellular matrix and that are also electrically conductive may provide solutions to the limitations inherent with neuroelectrode systems by acting as slow-release anti-inflammatory electrode approaches.
Laser Functionalised Neural Interfaces
Commercially available platinum Iridium (Pt/Ir) microelectrodes and planar Pt/Ir substrates were nanotopographically functionalised via femtosecond laser processing to generate surface rippling topography. Electrochemical analysis has shown that these microelectrodes, functionalised with lasered features, possess significantly reduced electrochemical impedance profiles relative to unmodified Pt/Ir electrodes and have an increased electrode electroactive surface area. In vitro microscopical analysis also show glial cells are more aligned along these rippled features relative to planar control. On further protein microarray array analysis, a downregulation of proteins involved in the activation of gliosis is demonstrated on rippled features compared to
control. Nanotopographical features such as these could promote chronic neuroelectrode functionality by reducing tissue encapsulation in situ and promoting organised interconnected neural network at the electrode interface.
Functionalised Neural Interfaces
As part of ongoing studies into the design of neural interfaces, the Biggs lab is also exploring “living electrode” technologies. Using a tissue engineering approach, scaffold loaded with neural cell population are integrated with traditional electrode materials, with a focus on mediating the interaction between a device and the host tissue and improving chronic device functionality. Using advanced photolithography techniques, the project aims to micro-engineer photocrosslinkable materials, creating scaffold architectures that will be capable of guiding encapsulated cells in the living electrode towards specific neural targets. This living electrode will be also capable of directly integrating specific cell populations with an implantable electrode, increasing device specificity and improving recording and stimulation capabilities. Living neural interfaces can also act as a repository for specific neural populations in degenerative diseases where native tissue has lost its function.