Encapsulation of chondrocytes in injectable alkali-treated collagen gels prepared using poly(ethylene glycol)-based 4-armed star polymer.

An in situ gel system was developed to encapsulate chondrocytes under physiological conditions using an alkali-treated collagen (AlCol) and pentaerythritol poly(ethylene glycol) ether tetrasuccinimidyl glutarate (4S-PEG) as a crosslinker. AlCol gels were obtained at crosslinker concentrations from 0.1 to 3.0 mM. Chondrocytes were encapsulated and dispersed homogeneously in AlCol gels. Results of MTT staining showed that cells survived after encapsulation in AlCol gels. Biochemical analysis demonstrated that DNA content in AlCol gels was constant after 3 weeks. Glycosaminoglycan content and mRNA expression of type II collagen and aggrecan increased with culture time. These results suggest that this in situ gel system is useful for regenerating cartilage in vitro and for minimally invasive therapy for cartilage defects.