Controlling mineralized tissue formation and distribution by osteoblasts photoencapsulated in PEG hydrogels

Encapsulation of osteoblasts in PEG hydrogels is attractive as a cell delivery vehicle to treat damaged or diseased bone due to the biocompatibility of the polymer carrier and its tailorable chemistry and degradation. Adhesive peptides (i.e., RGD) were tethered to the network and promoted both the attachment of osteoblasts and the production of mineralized tissue by osteoblasts photoencapsulated in the modified hydrogels. Degradable units (i.e., lactic or caproic acid) were added to the networks and used to control the spatial distribution of extracellular matrix in the hydrogels. Specifically, by using hydrogels with degradable units of varying hydrophobicity, and consequently, hydrolysis rates, a range of degradation properties was attained. After 12 weeks of in vivo implantation, collagen was distributed evenly through a copolymer network composed of both lactic and caproic acid (50:50), whereas collagen was limited to the pericellular region when only caproic acid was used as the degradable linker.