Synthesis and Analysis of Anionic Hydrogel Scaffolds for Endothelial Cell Tissue Engineering

Acidic hydrogels are cross-linked polymer networks that contain neutral and negatively charged monomers. The degree of negative charge on these soft materials plays a critical role in their biomedical applications. In particular, their use as a scaffold for cardiovascular applications depends on their charged and swollen states. The amount of negative charge, however, is a complicated function of the fabrication conditions, monomeric dissociation constants, ionic strengths and pH of the surround bath solution. This study, therefore, considered four representative acidic hydrogels and their physical properties and interactions with endothelial cells. The acidic monomers methacrylic acid (MAAc) and sulfoethylmethacrylate (SEMA) were polymerized with the neutral monomer 2-hydroxyethylmethacrylate (HEMA) or polyethylene glycol dimethacrylate (PEG) to produce acidic hydrogels with a range of charges and physical properties. The acidic monomers MAAc and SEMA represent weak and strong acidic monomer, respectively. Swelling measurements showed a dependence on both the degree of charge and the properties of the neutral monomer. Diffusion potentials measured were found to be in consistent with the theoretical predictions. Endothelial cells were inoculated on these acidic hydrogels and an algorithm using MATLAB was developed for calculating the cell covered area. Highly charged hydrogels showed greater affinity for cell adhesion while hydrogels with low charge densities showed little or no affinity for cell adhesion.