Zwitterionic tissue expanders reduce infection and fibrosis for enhanced biocompatibility

Current osmotic tissue expanders suffer from protein adsorption, bacterial colonization, and excessive fibrotic encapsulation that compromise device performance. In this study, we synthesized zwitterionic hydrogels using methyl methacrylate, n-vinyl pyrrolidone, and varying percentages (5-50%) of [2-(Methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA) to simultaneously enhance swelling capacity while reducing biological fouling. In vitro characterization demonstrated that SBMA incorporation significantly increased swelling potential while maintaining the mechanical integrity required for effective tissue expansion. Zwitterionic hydrogels exhibited superior resistance to lysozyme, fibrinogen, and bovine serum albumin (BSA) adsorption compared to ionized controls. Bacterial attachment studies revealed reduced Staphylococcus aureus attachment on zwitterionic surfaces, particularly in lysozyme-containing environments that mimic physiological conditions. Subcutaneous implantation in Sprague Dawley rats for 14 days showed that hydrogels with 5-30% SBMA formed significantly thinner fibrous capsules compared to ionized controls, with the 30% SBMA formulation producing the most uniform and loose capsular matrix. These results demonstrate that zwitterionic hydrogels represent a significant advancement in osmotic tissue expansion technology, addressing key limitations of current devices through bulk incorporation of zwitterionic monomers, potentially improving clinical outcomes and reducing the need for revision surgeries. STATEMENT OF SIGNIFICANCE: Tissue expanders are medical devices used to stretch skin and soft tissues for reconstructive surgery, but current osmotic expanders fail due to protein buildup, bacterial infections, and excessive scar tissue formation. We developed new hydrogel materials incorporating zwitterionic compounds, i.e., molecules with balanced positive and negative charges, that resist biological fouling while maintaining effective tissue expansion properties. Our zwitterionic hydrogels demonstrated superior resistance to protein adsorption and bacterial attachment compared to conventional materials. Most importantly, when implanted in rats, these hydrogels formed significantly thinner, less dense scar tissue capsules, particularly the 30% zwitterionic formulation. This breakthrough addresses major clinical limitations of current tissue expanders and could reduce surgical complications and the need for revision procedures, ultimately improving patient outcomes in reconstructive surgery.