Novel bioresorbabale composite fiber structures loaded with proteins for tissue regeneration applications: microstructure and protein release.

Novel bioresorbable core/shell composite fiber structures loaded with proteins were developed and studied. These unique polymeric structures are designed to combine good mechanical properties with a desired controlled protein-release profile, to serve as scaffolds for tissue regeneration applications. Core/shell fiber structures were formed by "coating" poly(L-lactic acid) fibers with protein-containing poly(DL-lactic-co-glycolic acid) porous structures. Shell preparation (coating) was performed by the freeze-drying of water in oil emulsions. The present study focused on the effect of the emulsion's formulation on the porous shell structure and on the resulting cumulative protein release from the composite fibers for 90 days. Horseradish peroxidase (HRP) was used as the protein source. The release profiles usually exhibited an initial burst effect, accompanied by a decrease in release rate with time, as is typical for diffusion-controlled systems. The HRP content and the emulsion's organic:aqueous phase ratio exhibited significant effects on both the shell microstructure and the HRP release profile from the composite fibers, whereas the polymer content of the emulsion's organic phase only affected these fiber characteristics in certain cases. Proper selection of the emulsion's parameters can yield core/shell fiber structures with the desired protein release behavior and other useful physical properties.