The development of novel hydrogel composites for use in bone tissue engineering

Objectives Hydrogels are gaining interest as biomaterials in bone tissue engineering (BTE). However, hydrogels must be mechanically stable, receptive to mineralisation, non-cytotoxic and support adhesion and growth of bone forming cells. Ease of sterilisation and antibacterial activity are also desirable. This study evaluated the extent to which three hydrogels fulfilled these criteria: 1.Electron irradiated Gelatin hydrogels supplemented with Alkaline Phosphatase (ALP) 2.Whey Protein Isolate (WPI) hydrogels supplemented with Phloroglucinol (PG) 3.WPI hydrogels supplemented with Carbon Nanotubes (CNTs) Methods Gelatin hydrogels were crosslinked using electron beam irradiation and subject to ALP-mediated mineralisation. Mineralisation was evaluated by spectroscopic and microscopical techniques. Mechanical properties were examined via compressive testing. Cytocompatibility was assessed using osteoblast-like MG-63 cells. Similarly, 40% WPI solution was supplemented with CNTs or PG prior to simultaneous hydrogel fabrication and sterilisation by autoclaving. Antibacterial properties of WPI-CNT hydrogels were assessed using Staphylococcus aureus. Cell viability was assessed against Human Foetal Osteoblast (hFOB; WPI-CNT only) and MG-63 cells. Surface topography and molecular structures were evaluated microscopically and spectroscopically. The effect of CNT/PG supplementation on mechanical properties was also evaluated. Results Calcium phosphate (CaP) deposits were successfully formed in gelatin-ALP hydrogels, which coincided with an elevated compressive modulus. Importantly, electron beam-crosslinked hydrogels, both mineralized and unmineralized, supported MG-63 cell adhesion and proliferation. Both CNTs and PG were successfully incorporated into WPI hydrogels. CNTs interacted with WPI and increased stiffness, but not compressive strength, of hydrogel composites. PG concentration had little impact on hydrogel mechanical properties. Importantly, WPI-CNT hydrogels exhibited antibacterial activity and supported growth of MG-63 cells. However, MG-63 viability appeared to reduce with increasing PG concentration. Conclusions The successful supplementation of hydrogels with additives to confer desirable properties, coupled with the practicality of simultaneous fabrication and sterilisation, demonstrates their applicability in BTE and future research in this space