Aims
Different stiffness preferences of CNS cell types affect neuronal regeneration after injury. In this work, we aimed to determine the optimal printing GelMA hydrogel parameters for a 3D in vitro SCI model, thorough investigations into biocompatibility with astrocyte cells, and investigations into the mechanical properties of the hydrogel environment.
Methods
Different GeLMA hydrogel solid fractions (polymer concentration) of 5%, 10%, and 15% (w/v) were prepared by mixing GeLMA powder and LAP photoinitiator. GeLMA bioprinting was performed using a BIO X 3D Bioprinter and hydrogels were rapidly crosslinked by UV light irradiation to maintain the bioprinted desired structure. The stiffness of hydrogel samples was assessed using Brillouin microscopy as a non-destructive, label- and contact-free method. ATP-lite and live/dead assays were performed to analyse C6 rat glioma cell line viability in hydrogels over time.
Results
Bioprinting parameters were optimised to print the desired dimensions and geometry of GeLMA structures at different concentrations of 5%, 10%, and 15% (w/v) GeLMA. The results demonstrated the 10% (w/v) solid fraction of GeLMA achieved better printability at the optimised printing temperature and pressure of 27° C and 20 KPa, respectively. Here we attempted to investigate the mechanical properties of hydrogels at various concentrations. In Brillouin microscopy measurement, a positive correlation between the Brillouin frequency shift/linewidth and the hydrogel solid fraction was observed. Furthermore, the 3D bioprinted cell-laden GeLMA hydrogels at various concentrations were also studied to probe the effect of C6 cells on the mechanical properties of the hydrogel networks. The results demonstrated that stiffness of 10 % (w/v) GeLMA hydrogels was decreased by incubating cells in the hydrogel matrix. In terms of biocompatibility, the bioprinted hydrogel at 10% (w/v) concentration supported higher cell viability after seven days compared to 5% and 15% (w/v) GeLMA concentrations.
Conclusions
In summary, the results suggest that using GeLMA hydrogels with tunable physical and mechanical properties is possible for our purpose. The results indicated high viability and proliferation for the C6 glial cells in 10% (w/v) GeLMA hydrogel scaffolds.