Biodegradable nanocomposite hydrogel structures with enhanced mechanical properties prepared by photo-crosslinking solutions of poly(trimethylene carbonate)-poly(ethylene glycol)-poly(trimethylene carbonate) macromonomers and nanoclay particles.
Soft hydrogels with elasticity modulus values lower than 100kPa that are tough and biodegradable are of great interest in medicine and in tissue engineering applications. We have developed a series of soft hydrogel structures from different methacrylate-functionalized triblock copolymers of poly(ethylene glycol) (PEG) with poly(trimethylene carbonate) (PTMC) by photo-crosslinking aqueous solutions of the macromonomers in 2.5 and 5wt.% colloidal dispersions of clay nanoparticles (Laponite XLG). The length of the PTMC blocks of the macromonomers and the clay content determined the physicomechanical properties of the obtained hydrogels. While an increase in the PTMC block length in the macromonomers from 0.2 to 5kg/mol resulted in a decrease in the gel content, the addition of 5wt.% Laponite nanoclay to the crosslinking solution lead to very high gel contents of the hydrogels of more than 95%. The effect of PTMC block length on the mechanical properties of the hydrogels was not as pronounced, and soft gels with a compressive modulus of less than 15kPa and toughness values of 25kJm(-3) were obtained. However, the addition of 5wt.% Laponite nanoclay to the formulations considerably increased the compressive modulus and resilience of the hydrogels; swollen nanocomposite networks with compressive modulus and toughness values of up to 67kPa and 200kJm(-3), respectively, could then be obtained. The prepared hydrogels were shown to be enzymatically degradable by cholesterol esterase and by the action of macrophages. With an increase in PTMC block length in the hydrogels, the rates of mass loss increased, while the incorporated Laponite nanoclay suppressed degradation. Nanocomposite hydrogel structures with a designed gyroid pore network architecture were prepared by stereolithography. Furthermore, in the swollen state the porous gyroid structures were mechanically stable and the pore network remained fully open and interconnected.