(549e) Low-Fouling Sulfobetaine-Based Hydrogels with Improved Mechanical Properties

Hydrophilic crosslinked polymer networks, or hydrogels, are commonly studied systems for many biological applications ranging from corneal implants to drug delivery and wound dressings. The key attributes of hydrogels that make them particularly well-suited to biological applications are their high water content, biological stability, optical transparency, permeability to metabolites, and sufficient crosslinking to prevent dissolution. Poly(2-hydroxyethyl methacrylate) (pHEMA) has emerged as the leading hydrogel candidate for most biological applications, especially implants and tissue engineering scaffolds, due to its chemical stability and mechanical integrity. In order to expand the scope of hydrogels' impact in the biomedical arena, several challenges must be addressed, primarily improving mechanical properties and lowering friction, without reducing its beneficial properties. Currently, water content and permeability come at the expense of mechanical strength, and hydration due to hydrogen bonding comes at the expense of low friction.

Poly(sulfobetain methacrylate) (pSBMA) has been shown to be highly resistant to fouling from both protein and bacteria due to the high hydration around the zwitterionic side-chains. This high hydration renders chemically crosslinked pSBMA hydrogels superswelling, with water content as high as 90%, and low-fouling, with approximately one-third of the protein adsorption of pHEMA hydrogels. This high water content, however, greatly decreases the mechanical strength of pSBMA hydrogels relative to pHEMA. A chemical-physical (interpenetrating network, or IPN) SBMA hydrogel doubled the compression strength of pSBMA hydrogels, and the first part of this work will focus on our efforts to further improved mechanical strength by molecularly engineering the SBMA monomer to create zwitterionic, nonfouling hydrogels with incorporated stiffening moieties in the side-chains or backbone.

Recent findings in our group have shown that the ordering of water molecules around zwitterionic materials, such as hydrogels, serves to create low-friction tribological properties of these materials. The second part of this work will describe the results of molecular dynamic simulations of the friction of zwitterionic hydrogels, with the goal of developing these hydrogels for in vivo joint repairs, lubricants, and implants.