Amidosulfobetaines Promote Solubilization and Removal of Lipophilic Antigens from Bovine Pericardial Extracellular Matrix Scaffolds for Use in Heart Valve Prostheses

Despite a staggering 100,000 heart valve replacements performed in the United States per year, current glutaraldehyde‐fixed xenogeneic bioprosthetic replacements are far from ideal. Although glutaraldehyde‐fixation effectively masks tissue antigenicity in the short term, chronic graft‐specific immune responses still commonly occur, limiting valve life expectancy. Additionally, glutaraldehyde‐fixation crosslinks extracellular matrix proteins preventing remodeling and growth in juvenile patients. A heart valve bioprosthesis formed from an unfixed xenogeneic ECM scaffold, in which antigenic burden has been eliminated or significantly reduced, has potential to overcome deficiencies of current heart valve replacements and improve patient outcomes. Based on protein chemistry principles of sequential, differential solubilization, we hypothesized that amidosulfobetaines would improve lipophilic antigen solubilization and subsequent removal from bovine pericardium following antigen removal (BP‐AR). Antigen removal (AR) was achieved by subjecting native BP samples to hydrophilic AR (48 h), followed by lipophilic AR (hydrophilic solution plus ASB‐14 or ASB‐16 at 0, 1, 2, 5, 8 and 0.1, 2, 3, 4, 5% respectively) (48 h), nuclease digestion (24 h) and washout (48 h). Residual protein was extracted from minced BP‐AR samples using 0.1% sodium dodecyl sulfate (SDS) (hydrophile extract) followed by 1% SDS (lipophile extract). Hydrophile and lipophile extracts ( n = 6 per group) were assessed for residual antigenicity using 1‐DE western blots assessed for IgG positivity using anti‐BP immune serum. Uniaxial tensile testing was performed on BP‐AR scaffolds to determine Young's modulus and Ultimate Tensile Strength. No significant change in scaffold residual hydrophile antigenicity was found between groups, with an average reduction in hydrophile antigenicity of 93.59% compared to untreated control tissue. Both ASB‐14 and ASB‐16 demonstrated statistically significant concentration dependent decreases in residual lipophile antigenicity of BP‐AR, which plateaued at 5% for ASB‐14 and 3% for ASB‐16 (79% and 92% lipophilic antigen removal respectively) ( p < 0.0001). Compared to native BP, there were no significant changes in Young's modulus and Ultimate Tensile Strength between BP‐AR scaffolds generated in the presence of ASB‐14 at 5% or ASB‐16 at 3% ( p < 0.6198) This study demonstrates that increasing amidosulfobetaine concentration increases removal of lipophilic antigens from candidate xenogeneic heart valve biomaterial. The extent to which the achieved reduction in biomaterial antigenicity equates to avoidance of in vivo recipient graft‐specific adaptive immune responses remains to be determined. Additionally, future studies are necessary to quantify ECM protein composition and histology of the resultant xenogeneic BP‐AR scaffolds. However, BP‐AR scaffolds generated using 5% ASB‐14 or 3% ASB‐16 represent promising xenogeneic heart valve prosthesis biomaterials. Support or Funding Information National Institutes of Health (NIH) R01HL115205