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Alginate Microspheres for Protein Delivery in Tissue Engineering



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Three-dimensional polymeric scaffolds have been widely used in tissue engineering for protein delivery. Scaffolds fabricated with different biomaterials and structures display various functions in protein delivery. A microsphere based delivery system is one sophisticated method. In this research, the potentials of alginate microspheres as protein carriers were tested. Alginate microspheres were prepared by a water-in-oil emulsion external gelation technique and loaded with bovine serum albumin (BSA) or DyLight 800 dye-labeled rabbit immunoglobulin G (IgG). Chitosan coated protein-loaded alginate microspheres were also prepared. The effects of process parameters on microsphere size, size distribution, encapsulation efficiency, and in vitro protein release profiles were investigated. Scanning electron microscopic photos showed that high dispersing force and high calcium chloride concentration produce small and uniform alginate microspheres with spherical shape and smooth surface. The release profiles indicated that BSA release from large and heterogeneous alginate microspheres was rapid and had a large initial burst release, and IgG release from small and homogeneous microspheres was slower and had lower initial burst release. Chitosan coating caused slower protein release compared to uncoated alginate microspheres in all cases. Protein-loaded microspheres were incorporated into alginate cylindrical scaffolds by long-term moulding in tubing for BSA or by fast gelation extruded from tubing for IgG. The scaffolds contained dried BSA loaded microspheres prepared using either protein incorporation or incubation methods, or with wet IgG-loaded microspheres with different concentrations. The release studies of BSA indicated that dried microspheres provided fast release possibly. The IgG release from scaffolds illustrated that chitosan coated IgG microspheres had more prolonged release profiles, and fast gelation of scaffolds could potentially eliminate protein loss during long-term gelation. All release profiles of scaffolds demonstrated that the initial burst effect was diminished and the release was extended by using a delivery system in which microspheres were incorporated into larger scaffolds. These prepared alginate microspheres and microsphere-incorporated scaffolds have been proven to have abilities of carrying and releasing proteins. Their applications toward delivery of functional proteins at the target site in patients for therapeutic purposes should be considered.



Alginate microspheres, Uniform size, Chitosan coating, Protein release, Alginate scaffolds, Tissue engineering



Master of Science (M.Sc.)


Biomedical Engineering


Biomedical Engineering



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