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Preparation and characterization of porous PDLLA/HA composite foams by supercritical carbon dioxide technology.

A composite poly(D,L)lactic acid (PDLLA)/hydroxyapatite (HA) biomaterial was prepared by in situ polymerization of D,L-lactide monomer and HA. Supercritical CO2 (SC CO2) technology was developed to prepare the biodegradable composite foams for use in tissue regeneration. In this technology, NaCl particles were used as porogen to produce an open-pore structure. Organic solvents were not used and high temperature was not necessary. The problem with pore interconnectivity was resolved. High-porosity composite foams (up to 90% +/- 2% porosity) were obtained with pore sizes ranging from 100 to 300 microm suitable for cell seeding. The microstructure and morphology of the composite foams could be controlled by saturation pressure, saturation time, and temperature as well as amount of NaCl particles. The compressive strength and water absorbability of the composite foams were also determined. With an increase in HA amount, the molecular weight of PDLLA/HA composite foams decreased, but the mechanical strength and hydrophilicity increased slightly.