New bioactive, degradable composite microspheres as tissue engineering substrates

Novel bioactive, degradable polymer/glass/ ceramic composite microspheres w ere developed using a solid-in-oil-in-water (s/o/w) emulsion solvent remova l method. Modified bioactive glass (MBG) powders were encapsulated into the polylactic acid (PLA) matrix. Scanning electron microscopy and energ-dispe rsive X-ray analyses revealed that the MBG powders were mostly embedded in the polymer matrix, and submicron-size pores were present at the surface. i mmersion in simulated physiological fluid (SPF) was used to evaluate the su rface reactivity of the microspheres. The polymeric surface was fully trans formed into carbonated calcium hydroxyapatite (c-HA) after 3 weeks of immer sion. In contrast, PLA microspheres showed no evidence of any calcium phosp hate deposition. ion concentration analyses revealed a decrease in Ca and P concentrations and an increase in Si concentration in the SPF immersed wit h composite microspheres during the 3-week period. The Ca and P uptake rate s decreased after 2 days of incubation. This coincided with the decrease of the Si release rate. These data lend support to the suggestion that the Si released from the MBG powders present in the polymer matrix is involved in the formation of the Ca-P layer. Our results support the concept that thes e new bioactive, degradable composite microspheres may serve as microcarrie rs for synthesis of bone and other tissues in vitro and in vivo. (C) 2000 J ohn Wiley & Sons, Inc.