Graphene-based Cell Culture Substrates for the Investigation of the Impact of Electrical Stimulation on Pluripotent Stem Cell Differentiatione

Abstract

Endogenous bioelectic signalling is highly involved in embryonic development as well as in cellular morphogenesis, proliferation, migration and patterning in tissue repair. Coincidentally, these are also the natural behaviours that researchers are most interested in replicating for use in tissue engineering and regenerative medicine applications. Based on these processes, this thesis hypothesised that electrical stimulation could be used as an instructive cue for directing embryonic stem cell (ESC) differentiation. ESCs have the capability to form any cell type in the adult body and thus are of enormous interest to those developing regenerative therapies. The ability to direct their behaviour using electrical stimulation could become an invaluable tool to help ESCs achieve their considerable potential uses in clinical practice. In order to test this hypothesis, a conductive cell culture substrate with a high degree of capacitive charge injection was required. This approach would enable electrical charge to be delivered evenly across samples without the release of faradaic species and associated pH changes that have been shxown to affect stem cell differentiation. Owing to their biocompatibility, conductivity and chemical stability, graphene materials made ideal candidates for this application. A high porosity steam-treated reduced graphene oxide (SrGO) material with very high levels of capacitive charge injection was developed and fully characterised. The material has been found to be highly conducive to cell growth with proliferation and neurite outgrowth of neuronal cell lines even exceeding tissue culture polystyrene. This material is now being further developed for use in stimulating and recording bioelectronics implants. In order to test the ability of electrical stimuli to direct ESC differentiation, cells were cultured on the SrGO surface and charge-balanced sinusoidal potential waveforms were applied at different frequencies and durations. The expression of marker proteins for pluripotency and differentiation were then assessed by flow cytometry and compared to non-stimulated controls. Electrical stimulation was found to increase the differentiation of mESCs, with the cells responding most strongly to low frequency stimulation. It appears that the frequency of electrical stimulation may also affect the differentiation pathway of the cells, with an upregulation of mesodermal differentiation. This thesis has demonstrated the utility of electrical stimulation in directing stem cell behaviour. With further development, it is hoped that this technology may go on to become a cornerstone of stem cell culture.

Date of Award	1 Aug 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Kostas Kostarelos (Supervisor) & Cyrill Bussy (Supervisor)