Block copolymer arrangement and composition effects on protein conformation using atomic force microscope-based antigen-antibody adhesion

The conformational changes of fibronectin (FN) deposited on various block copolymers where one block is composed of poly(methyl methacrylate) (PMMA) and the other block is either poly(acrylic acid) (PAA) or poly(2-hydroxyethyl methacrylate) (PHEMA) were investigated using a functionalized atomic force microscope (AFM) tip. The tip was modified with an antibody sensitive to the exposure of the arginine-glycine-aspartic acid (RGD) groups in FN. By studying the adhesive interactions between the antibody and the proteins adsorbed on the block copolymer surface and phase imaging, it was found that the triblock copolymers PAA-b-PMMA-b-PAA and PMMA-b-PHEMA-b-PMMA, which both have large domain sizes, are conducive to the exposure of the FN RGD groups on the surface. On the basis of these results, it is concluded that the surface chemistry as well as the nanomorphology dictated by the block copolymer arrangement could both tune protein conformation and orientation and optimize cell adhesion to the biomaterial surface.

Fracture toughness of modified dental resin systems

This study compared the relative fracture toughness of a Bis-GMA//TEGDMA (50:50 wt%)-based resin system modified by 5, 10, and 15 wt% of a methacrylate-terminated poly(butadiene-acrylonitrile-acrylic acid) terpolymer toughening agent. After storage in distilled water at 37 +/- 2 degrees C for 7 days, plane strain fracture toughness (KIC) was determined on an Instron testing machine at a 0.5-mm min-1 displacement rate. The glass transition temperature (Tg) in degrees C was determined after 7 days (dry and wet) storage by thermomechanical analysis. The results of this study showed significantly improved fracture toughness and lowered water sorption with the modified resin systems which was indicated by higher wet glass transition temperatures.

Influence of hyperbranched multi-methacrylates for dental neat resins on proliferation of human gingival fibroblasts

We have previously shown that hyperbranched multi-methacrylate (H-MMA)-modified dental resins have VLC activities, lower polymerization shrinkage, and improved mechanical properties, compared to the 2,2-bis[4-(2-hydroxy-3-methacryloyolxypropoxy)phenyl]propane/triethyleneglycol dimethacrylate (BisGMA/TEGDMA) neat resin. The results are due to the unique molecular structure and high molecular weight of H-MMA intermediates. The purpose of this study was to evaluate the biocompatibility of H-MMA-modified dental neat resins. The cell proliferation of three human gingival fibroblast strains on either H-MMA, BisGMA/TEGDMA, or a polystyrene disk was examined. Following 10 days of cell proliferation, there was no statistical difference in cell number between H-MMA-modified and unmodified resin disks. H-MMA-modified resins had less free monomer leaching than the unmodified resin but showed similar properties in water sorption and contact angle values. All these results suggest that the biocompatibility of H-MMA-modified dental neat resins is as good as that of commercially used BisGMA/TEGDMA resin and H-MMA has potential applications in dental composites.