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Polymer thin films are generally employed as coatings on implants to prevent protein adsorption. Polymer chain mobility and surface softness have been found to contribute to the protein resistance, but also bring film instability in a liquid protein medium. We investigated the protein resistance ability of three low-T g polymers, including hydrophobic polymers polyisoprene (PI), poly( n -butyl methacrylate) (PnBMA) and hydrophilic polyethylene oxide (PEO), by overcoming the instability issue with crosslinking. We found that the T g s of PI and PEO can be increased to around 0 °C after crosslinking. The remained strong chain mobility of both films can still resist protein adsorption regardless the hydrophobicity, yet greatly increases the film stability under an aqueous circumstance. The PnBMA film increased its T g to around room temperature after crosslinking, which deteriorated the protein-resistance ability having the surface covered by BSA molecules. Our results support that the chain mobility of a polymer film plays an important role in resisting protein adsorption due to the increased entropy associated with more mobile polymer chains. By tune the degree of crosslinking, the stability of polymer in aqueous environment can be increased while the protein resistant ability can be remained. Our results provide a new strategy to design polymer materials for effective antifouling. [ABSTRACT FROM AUTHOR]

Poly(trimethylene carbonate) (PTMC) with molecular weights greater than 100 kg/mol is known to degrade readily in vivo while PTMC of less than 70 kg/mol is resistant to degradation. The reason for the molecular weight dependent degradation rate of PTMC is unclear, and may be due to differences in macrophage behavior or enzyme adsorption or activity. Macrophage number and production of reactive oxygen species (ROS) and esterase were measured when cultured on 60 and 100 kg/mol PTMC. Cholesterol esterase and lipase were adsorbed to 60 and 100 kg/mol PTMC and mass and viscoelastic properties of the adsorbed enzyme layers were measured. No significant differences were observed in macrophage number or production of degradative species. Significant differences were measured in mass, shear modulus and viscosity of the adsorbed cholesterol esterase layer, suggesting that the cholesterol esterase is adsorbing in a different conformation on the 60 and 100 kg/mol PTMC. Despite similar bulk moduli, the surface modulus of 60 kg/mol PTMC was significantly lower than 100 kg/mol. It is proposed that the difference in surface stiffness and polymer chain flexibility affect the arrangement of water bound to and freed from the polymer chains during adsorption, thus affecting enzymatic adsorption, conformation, and activity. [ABSTRACT FROM AUTHOR]

Abstract: Cells are known to respond differently when grown on materials of varying stiffness. However, the mechanism by which a cell senses substrate stiffness is unknown. Lower crosslink density elastomers formed from acrylated star-poly(d,l lactide-co-ϵ-caprolactone) have previously been shown to support higher smooth muscle cell proliferation in in vitro culture. This difference in growth was hypothesized to be due to differences in protein adsorption that resulted from differences in polymer chain mobility at the surface. Therefore, layer mass and viscoelastic properties were measured for HSA, IgG, fibronectin, vitronectin, and serum supplemented media adsorbed to elastomers of two crosslink densities. Significantly more fibronectin adsorbed to the lower crosslink density surface while significantly more IgG adsorbed to the higher crosslink density surface. Furthermore, differences in fibronectin and IgG layer shear moduli were observed, suggesting that there was a difference in the conformation of the adsorbed protein. ATR-FTIR analysis showed that the lower crosslink density elastomer absorbed more surface water. The increased amount of water may cause greater entropic gains upon protein adsorption to the lower crosslink density surface, which increases total protein adsorption from serum and may cause differences in protein conformation and thus cell behavior. [Copyright &y& Elsevier]