Physico-chemical properties of hydrophilic and amphiphilic crosslinked systems that influence biological responses

The effect of physical, chemical, and biological cues on the behavior of smooth muscle cells (SMCs) and attachment of marine organisms was investigated. Both hydrophilic and amphiphilic crosslinked polymer networks with varying chemical and mechanical properties were used to direct biological responses. Poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels were fabricated with tunable mechanical properties by varying the di-functional monomer concentration in the feed composition. Amphiphilic hydrogels composed of 2-hydroxyethyl methacrylate (HEMA), 1,3-bis(3-methacryloxypropyl)tetrakis(trimethylsiloxy)disiloxane (MPTSDS), and tris(trimethylsiloxy)-3-methacryloxypropylsilane (TRIS) were copolymerized using ultraviolet (UV) light and a photo-initiator. Hydrogels prepared with varying concentration of di-functional monomer, MPTSDS, exhibited an order of magnitude difference in elastic moduli. Not only were the bulk material properties influenced by the crosslinking agent concentration in the feed composition, but the surface properties (i.e., contact angle and hysteresis) were influenced as well.;Modulus (E) has been reported to be positively correlated with the settlement of marine organisms. However, this was not the case for the amphiphilic gels tested against biomolecules and marine organisms. Stiffer gels inhibited fouling of proteins and marine organism, Ulva linza, to a greater extent than the softer gels. Furthermore, the network structure, in regards to the molecular weight between crosslinks Mc, was found to have a greater influence on fouling. A strong correlation was observed between protein adsorption and Mc of the amphiphilic crosslinked networks compared to just the modulus and surface energy (ϒ) alone. A higher correlation was also obtained between Mc and Ulva sporeling biomass than between sporeling biomass and elastic modulus E, exhibiting R² value of 0.98 and 0.38, respectively. The percent removal of sporeling biomass growth was shown to be positively correlated with the (E ϒ) 1/2, which is a contrast to what has previously been reported. Again, there was a higher correlation between Mc and percent removal of sporeling biomass than between (E ϒ)1/2 and percent removal of sporelings (R² value of 0.83 and 0.57, respectively). The differences in biofouling ability is most likely due to differences in mesh size between hydrogel compositions. Biomolecule accumulation and absorption was made easier by the larger mesh size in hydrogels with lower crosslinking concentration in the feed composition.;The influence of chemical and physical properties on mammalian cells was also investigated. Amphiphilic crosslinked networks were fabricated with tunable mechanical properties and their ability to modulate smooth muscle cell (SMC) phenotype was studied by assessing cell proliferation. Bioactive molecules, Arg-Gly-Asp-Ser (RGDS), were incorporated into the crosslinked matrix to promote adhesion and facilitate cell growth. The elastic modulus of the substrate and the concentration of RGDS were shown to positively correlate with the attachment and proliferation of SMCs; indicating that the physic-chemical network properties play a large role in behavior of unicellular organisms.