Photoinitiated crosslinked degradable copolymer networks for tissue engineering applications

Diethylene glycol was used to initiate the ring opening polymerization of D,L-lactide and epsilon -caprolactone, as well as combinations of the two monomers. Esterification of the oligomer end groups with methacryloyl chloride led to divinyl terminated macromers that were reacted via photoinitiated polymerizations to produce crosslinked networks. The lactic and/or caproic acid repeat units can be hydrolyzed under physiological conditions, leading to degradable networks that may be useful for tissue engineering applications. Specifically, methacryloyl terminated poly(lactic acid-co-caproic acid) diethylene glycol based oligomers were prepared and characterized by 1H NMR. The number of ester linkages was kept constant while the ratio of lactic:caproic acid segments was varied. These macromers were then photopolymerized at 450 nm using a visible light initiating system to produce crosslinked degradable networks. The kinetics of the polymerizations were followed by DSC, and the dynamic mechanical behavior was monitored as a function of temperature to obtain the T(g) for each network composition. 1mm thick disks were subjected to hydrolytic degradation in an aqueous phosphate buffer solution at a pH=7.4 and 37 degrees C. The changes in the compressive modulus, as well as the % mass loss as a function of time, were recorded. Cellular compatibility was determined by seeding primary rat calverial osteoblast cells onto the disks and characterizing the cell morphology using scanning electron microscopy.