Zwitterionic Hydrogels: an in Vivo Implantation Study

Zwitterionic hydrogels, including poly(sulfobetaine methacrylate) (polySBMA) and poly(carboxybetaine methacrylate) (polyCBMA), and co-polymeric hydrogels of CBMA and 2-hydroxyethyl methacrylate (HEMA) (poly(CBMA-co-HEMA)) were prepared. Their in vitro and in vivo properties were evaluated and compared with those of polyHEMA hydrogels. Bovine aortic endothelial cells (BAECs) were incubated with zwitterionic and polyHEMA hydrogels to evaluate their bioadhesion properties. Both polySBMA and polyCBMA hydrogels were found to be non-cytotoxic and their endotoxin levels were found to be acceptable for in vivo implantation. Results from in vivo subcutaneous implantation showed reduced cell attachment to the surfaces of polySBMA and poly(CBMA-co-HEMA) hydrogels after one-week implantation as compared with polyHEMA hydrogels. After a 4-week implantation, capsules with higher vascularities surrounding the two zwitterionic hydrogels were found. However, polyHEMA, polySBMA and poly(CBMA-co-HEMA) hydrogels showed similar capsule thicknesses and similar numbers of attached foreign body giant cells (FBGCs). In this work, zwitterionic hydrogels demonstrate healing and integration comparable to polyHEMA hydrogels, but with improved vascularity. These zwitterionic hydrogels are promising alternatives to polyHEMA hydrogels as implantable materials.