(650g) Characterizing the Physical Properties of Polyampholyte Hydrogels with Different Ethylene Glycol Cross-Linkers

When bone tissue is damaged to the level of a critical sized defect, it is unable to naturally regenerate and repair itself. This has led to the pursuit of polymeric tissue engineering scaffolds to induce wound regeneration across these defects, but the materials used often lead to infection, scarring, and immune rejection. Nonfouling polymers have been proposed as an approach for eliminating these biomaterial-induced concerns. Polyampholyte hydrogels are one class of nonfouling polymers currently being looked at for tissue engineering and drug delivery applications. This family of materials are composed of an equimolar mixture of positively and negatively charged monomer subunits and they have been demonstrated to present not only nonfouling properties, but also tunable bioactive molecule delivery and mechanical properties. In this study we investigate the influence of the cross-linker species on the nonfouling properties, mechanical strength, and degradation behavior of polyampholytes composed of a 1:1 molar ratio of [2-(acryloyloxy)ethyl] trimethylammonium chloride (TMA, positively charged) and 2-carboxyethyl acrylate (CAA, negatively charged) monomers. Specifically, we evaluated the influence that the number of ethylene glycol repeat units has on the overall material performance by synthesizing and evaluating hydrogels containing di-, tri-, and tetra-ethylene glycol dimethacrylate cross-linker species. The degradation studies were conducted for over 100 days in Sorenson’s buffer with pH values of 4.5, 7.4, and 9.0 by tracking the swelling behavior and weight change over time. The mechanical properties were evaluated using compression testing to failure. The retention of the nonfouling and protein conjugation capabilities were demonstrated using fluorescently labeled bovine serum albumin (FITC-BSA). The results demonstrate the tunability of both the degradation behavior and mechanical properties through the cross-linker selection, without impacting the key nonfouling and biomolecule delivery capabilities. Therefore it is concluded that polyampholyte hydrogels represent a promising platform for bone tissue engineering.