Porous scaffolds with the structure of an interpenetrating polymer network made by gelatin methacrylated nanoparticle-stabilized high internal phase emulsion polymerization targeted for tissue engineering

The interlacing of biopolymers and synthetic polymers is a promising strategy to fabricate hydrogel-based tissue scaffolds to biomimic a natural extracellular matrix for cell growth. Herein, open-cellular macroporous 3D scaffolds with a semi-interpenetrating network were fabricated through high internal phase emulsion templating. The scaffolds are prepared by (I) the curing of PEG diacrylate (PEGDAC) and gelatin methacrylate (GelMA) in the continuous aquatic phase of a coconut oil-in-water emulsion stabilized by GelMA nanoparticles, and (II) the removal of the internal phase. The effect of the main contributing parameters such as pH, GelMA content, and GelMA/PEGDAC weight ratio on the emulsion features was investigated systematically. Due to the isoelectric point of GelMA at around pH 6, the GelMA particle (aggregation) size decreased at both sides of pH from 1000 to 100–140 nm because of the increased number of positive and negative charges on GelMA. These GelMA nanoparticles were able to produce stable emulsions with narrowly distributed small emulsion droplets. Moreover, the stability and emulsion droplet size were enhanced and increased, respectively, with GelMA content increasing and GelMA/PEGDAC weight ratio decreasing. These trends lie in the prevented coalescence phenomenon caused by the improved viscosity and likely partially formed network by GelMA chains in the continuous phase. Hence, the following formulation was selected for scaffold preparation: φ(oil) = 74%, pH = 12, GeMA = 4 wt%, and GelMA/PEGDAC = 10/8. Then, PCL in different contents was infiltrated into the scaffold to balance hydrophilicity and hydrophobicity. The cell culture assay proved that the scaffold with a pore size of 60–180 μm and containing 51.2 wt% GelMA, 10.3 wt% PEG, and PCL 27.2 wt% provided a suitable microenvironment for mouse fibroblast cell (L929) adhesion, growth, and spreading. These results show that this strategy suggests promising culture for tissue engineering applications.