Synthesis and characterization of photopolymerized multifunctional hydrogels: Water-soluble poly(vinyl alcohol) and chondroitin sulfate macromers for chondrocyte encapsulation

To design a carrier for chondrocytes that emulates the critical aspects of native cartilage tissue, hydrogels were formulated from a synthetic component based on poly(vinyl alcohol) (PVA) and from a natural component, negatively charged chondroitin sulfate (ChSA, a main component of proteoglycans). The synthesis of photoreactive and crosslinkable macromers based on PVA and ChSA is described in detail. A range of macroscopic hydrogel properties was obtained by varying the macromer molecular weight, concentration, and functionality prior to photoinitiated polymerization. Depending on the formulation, the PVA homopolymer gels had compressive moduli (K) ranging from 5 to 1680 kPa with equilibrium mass swelling ratios (q) of 2.4 to 15. Similar variations in pure ChSA gels produced networks with K's from 10 to 2600 kPa and q's from 5.9 to 27.5. Copolymer networks containing both ChSA and PVA had increased mechanics and increased swelling as compared to the homopolymer gels. An additional benefit to incorporating ChSA was the creation of enzymatically degradable gels. By use of chondroitinase ABC, the degradation kinetics of various homo- and copolymer networks were investigated. Finally, preliminary histological results indicate that these copolymer gels can support chondrogenesis of photoencapsulated cells.