A Study of 3D Graphene-based Scaffolds for Advanced Neural Engineering

Abstract

The field of tissue engineering aims to create functional tissues/organs using scaffold biomaterials and cell sources to treat a multitude of diseases. To guide the regeneration process, the development of biomaterials with desirable characteristics, described as scaffold, is required. It is believed that 3D scaffolds can effectively reflect the realistic characteristic of living tissues, in contrast to 2D culture systems. Graphene, a 2D carbon allotrope, brings several advantages in neural tissue engineering owing to its unique properties including high surface area, suitable biocompatibility, mechanical properties and excellent electrical conductivity. In this study, 3D graphene-based composite scaffolds, consisting of Graphene Oxide (GO) and Sodium Alginate (Na-ALG), were fabricated as functional neural scaffolds. The fabrication method, physical and chemical characterizations of synthesized scaffolds are extensively studied and analysed to match neural tissue engineering requirements. Besides, electrically conductive scaffolds are developed based on the in-situ bioreduction of GO/Na-ALG aerogels which makes scaffolds more favourable for engineering of electroactive tissues. GO/Na-ALG scaffolds showed great improvement in hydrophilicity, electrochemical properties and mechanical integrity. Furtheremore, in vitro biodegradation study reveals that the proposed composite scaffolds have a controlled biodegradation rate. The prepared scaffold with interconnected porous structure and suitable mechanical properties is an appropriate platform for 3D stem cell culture. As a result, human dental pulp stem cells (hDPSCs) are combined with the fabricated graphene-based scaffolds to support cellular responses. The biological effects of prepared graphene-based 3D scaffolds on dental pulp stem cells (DPSCs) in terms of proliferation, cell viability, and cytotoxicity were investigated. The Alamar Blue (AB) assay shows that DPSCs viability cultured onto Na-ALG and GO/Na-ALG scaffolds was higher than that of 2D controls confirming the desirable initial cell adhesion to the scaffolds’ surface followed by cell spreading through pores. Besides, the LDH release measurements show that DPSCs toxicity on the GO/Na-ALG and RGO/Na-ALG scaffolds was comparable to that obtained on the 2D surface in the absence of the biomaterial. The cellular viability and activity are improved on scaffolds coated with PLL, being superior to combined PLL+LAM coating. The incorporation of graphene into the composite scaffold supported higher DPSCs viability and function, suggesting that the selected biomaterials are biocompatible with DPSCs which is ascribed to unique surface chemistry, good mechanical properties, high surface area, and excellent physicochemical properties of graphene-based nanomaterials. The cytotoxicity of GO/Na-ALG and RGO/Na-ALG scaffolds indicates that DPSCs can be seeded in serum-free media without cytotoxic effects. This is critical for human translation as cellular transplants are typically serum-free. The findings from the current study suggest that proposed composite 3D graphene-based scaffolds had a favourable effect on the biological responses of DPSCs. The knowledge and contributions made in the current work can be exploited for further studies on electrical stimulation and in vivo investigation of the engineered scaffolds for neural regeneration.