Tailored cell attachment and cytotoxicity in PEG-based polysaccharide-derivatized hydrogels

Hydrogels have been given significant attention as biomaterials in tissue engineering and drug delivery, due to their capacity to mimic various functions of the macromolecular-based components found in the extracellular matrix (ECM). The ECM not only displays important adhesion ligands to anchorage-dependent cells, but also regulates cell behavior through physical, biochemical, and mechanical properties. The specific hydrogel networks have been developed to mimic aspects of the composition, assembly, and function of the ECM, including PEG-based polysaccharide-derivatized hydrogels that assemble based on non-covalent interactions between low molecular weight heparin (LMWH) bound to a four-arm star poly (ethylene glycol) (PEG) and heparin binding peptides (HBP) also bound to PEG.; The goal of this work is to tailor cell attachment and cytotoxicity in PEG-based polysaccharide-derivatized hydrogels through studying cellular behavior since cellular response on the hydrogels is a critical factor for the applications of artificial scaffolds. Firstly we examined the effect of the dilute peptide---PEG-heparin interacting protein (HIP) in the growth medium on cell growth. The results show that cells on the surface of TC plate remain viability ≥ 95% of control after 24 hours of incubation, at the PEG-HIP concentration ≤ 0.006 mg/mL; cell viability declines to 45% of control with the PEG-HIP concentration increasing to 0.096 mg/mL. In the study of the cytotoxicity of PEG-HIP incorporated within PEG-based hydrogels, the results indicate that (1) the PEG-acrylate/PEG-HIP hydrogel experience no cytotoxicity to cells, and (2) cells are viable on the surface of the PEG-LMWH/PEG-HIP hydrogels for up to 48 hours but these hydrogels are not able to support cell adhesion. Secondly, to improve cell adhesion, we modified PEG-acrylate hydrogel as a model network with ligands, including collagen, fibronectin, and vitronectin. Cell attachment response are controlled and optimized through tuning ligand density within PEG-acrylate hydrogels, for both fibroblasts and endothelial cells. As a result, projected cell area exhibited an optimal value at a specific ligand density, i.e., 189.0 molecules/mum2 for collagen, 267.6 molecules/mum 2 for fibronectin, 223.7 molecules/mum2 for vitronectin, with different cell types showing different cell attachment to the same ligand. For instance, NIH3T3 fibroblasts have the greatest cell attachment response to the addition of fibronectin whereas human dermal microvascular endothelial cells (HDMVECs) attach preferentially to vitronectin. In addition, the gel elasticity was investigated and did not significantly affect cell adhesion in the lower range of 400 Pa to 2000 Pa.; These findings implicate that PEG-based polysaccharide-derivatized hydrogels, as successful scaffolds, have potential to mimic the natural environment of a living cell since they not only exhibit non-cytotoxicity, but also support cell adhesion, which has established a solid foundation for the further work including the study cell behavior on the remodeling and degradation of these materials.