Transdermal photopolymerization of poly(ethylene oxide)-based injectable hydrogels for tissue-engineered cartilage

Transdermal photopolymerization, a minimally invasive method for implantati on, was used to subcutaneously place a mixture of polymer and isolated chon drocytes to regenerate cartilage tissue in vivo. Semi-interpenetrating netw orks of varying proportions of poly(ethylene oxide)dimethacrylate and poly( ethylene oxide) and primary, bovine articular chondrocytes were implanted i n athymic mice. Four mice (12 implants) were harvested at 2, 4, and 7 weeks . Chondrocytes survived implantation and photopolymerization and formed neo cartilage containing 1.5 to 2.9% wet weight collagen and 4 to 7% glycosamin oglycan Thirty-five percent of the total collagen was type II collagen. His tologic analysis exhibited tissue structure resembling neocartilage, and sa franin O staining demonstrated glycosaminoglycan distribution throughout th e hydrogels. This study demonstrates the potential use of transdermal photo polymerization for minimally invasive subcutaneous implantation of hydrogel s and chondrocytes for in vivo cartilage regeneration.