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We have developed a versatile delivery platform comprising a novel composite of two biomaterials with proven track records: apatite and poly(lactic-co-glycolic acid) (PLGA). These composites have been tested in the delivery of a model protein, bovine serum albumin (BSA), as well as a growth factor, bone morphogenetic protein-2 (BMP-2), which is a potent inducer of bone formation. The controlled release strategy is based on the use of a polymer with acidic degradation products to control the dissolution of a basic inorganic component, resulting in protein release. The release profile can be modified systematically by changing variables that affect polymer degradation and/or apatite dissolution, such as polymer molecular weight, polymer composition, apatite loading, and apatite particle size. We have found that an increase in polymer molecular weight and polymer hydrophobicity led to slower polymer degradation, and in turn, slower apatite dissolution and protein release. Protein release was enhanced by reducing apatite particle size and by lowering the apatite content in the composites. We anticipate that this delivery platform can be extended to the controlled release of other therapeutic proteins and chemicals. |
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