A mathematical model for release of biologics from porous hollow fibers

The application of porous hollow fibers has recently been extended to the controlled release of biologics such as protein growth factors and lipid angiogenesis promoters. Release of these materials tends to occur more rapidly than would be predicted by conventional diffusion-based models of controlled release. Analysis of other modalities of transport as well as structural analysis of the controlled release system itself was performed to provide insight into the observed controlled release behavior from such systems. Specifically, it was discovered that osmotic-driven processes play a significant role in controlled release of proteins including vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). It was also found that the fiber pore microstructure and (more importantly) macrostructure influences release behavior. Model-guided design was implemented to adjust the physical properties of the fiber wall, leading to a release system that is better able to sustain the delivery of VEGF. This model may be used to more easily achieve a desired complex release behavior when used in combination with external regulation of the reservoir. (C) 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A:, 2012.