Equilibrium and non-equilibrium charge-dependent quantification of endothelial cell hydrogel scaffolds

Using equilibrium swelling and non-equilibrium membrane potential measurements, this study assesses the charge density in two representative series of polyelectrolyte hydrogels and examines the morphological and proliferative responses of endothelial cells as a function of the prepared charge offset. The neutral monomers 2-hydroxyethylmethacrylate (HEMA) and poly(ethylene glycol) dimethacrylate (n = 1,000) (PEGDMA) were copolymerized with either the acidic monomer 2-sulfoethyl methacrylate (SEMA) or the basic monomer methacryloxy ethyltrimethylammonium chloride (MAETAC) to make membranes with pregelation charge offset concentrations varying from 0 to +/-200 mM. A thermodynamic analysis of swelling and membrane potential measurements quantified the hydrogel charge density state following equilibration at different ion strengths. Porcine pulmonary artery endothelial cells were seeded on samples of each HEMA and PEGDMA copolymer and the amount of cell coverage was measured over a 4-day period. Cellular attachment and proliferation increased with increasing proportions of charged monomers and showed a threshold pattern of attachment and growth on the positively charged HEMA-MAETAC copolymer hydrogels with increasing proportions of initially prepared charge. The series of PEGDMA copolymer hydrogels remained relatively resistant to cellular attachment and proliferation over the range of prepared charges considered in this study.