Effect of experimental parameters on the in vitro release kinetics of transforming growth factor β1 from coral particles

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Abstract
Coral bone graft substitutes have been supplemented in the past with growth factors to further enhance bone regeneration in defects. Little is known, however, on the dynamics of protein release from coral. Coral particles were studied for their ability to release transforming growth factor beta 1 (TGF‐β1) in vitro, under different adsorption conditions. Adsorption of TGF‐β1 (0.05 μg/mL) on coral particles (<80 μm or 300–450 μm) after 24 h of incubation was high, regardless of conditions. TGF‐β1 release kinetics in an artificial bone fluid followed a specific profile: an initial 1‐h protein burst, followed by a decreasing release during the next 24 h at which time the release increased again to reach a constant rate until the end of the 2‐week study. The protein release rate appeared mainly to depend upon the diffusion of TGF‐β1. TGF‐β1 release from coral particles was enhanced in the presence of bovine serum albumin (BSA) compared to the release in the presence of gelatin, and was dependent on the pH of adsorption. The highest total TGF‐β1 release was obtained when adsorption occurred with BSA at pH 7.4 (82 ± 3%), while the lowest release was observed when adsorption was done in the presence of gelatin at pH 11 (38 ± 1%). TGF‐β1 release was also found to vary with particle size, higher release being obtained with the smaller particles. These results suggest that coral particles could be used as a delivery system for growth factors, and that the release rate may be modulated through modification of the adsorption conditions and coral particle size. © 2001 Wiley Periodicals, Inc. J Biomed Mater Res 59: 403–410, 2002