Abstract
The objective of this study was designed to extend the application of poly(ϵ‐caprolactone) (PCL) in delivery of macromolecular proteins. The strategy applied here is to create a porous structure in PCL films in order to control the diffusion rate of protein. Various amounts of both high‐molecular‐weight and low‐molecular‐weight poly(ethylene glycol) (PEG) were used as pore‐forming agents. The porous films were prepared by a solvent‐casting‐leaching method. The thicknesses of the prepared films were controlled to be in the range of 75.3 ± 0.6 ∼ 81.7 ± 0.6 μm. The pore fraction of films was determined to be 27.7 ± 1.0% ∼ 52.5 ± 0.8% for PEG~10000~ and 26.6 ± 1.8% ∼ 48.8 ± 1.4% for PEG~4000~. The pore fraction initially increased with increasing amounts of PEG, independent of the molecular weight of PEG. In the permeation study, lysozyme was used as a model diffuser. The permeation rate of protein increased as the pore fraction of films increased, especially when 30 ∼ 40% of PEG was added initially, and this phenomenon was more prominent when low‐molecular‐weight PEG was used. This result was probably due to the highly porous structure creating interconnected channels in the films, further enhancing protein diffusion. In addition, the size of micropores formed by PEG~4000~ was observed to be larger than by PEG~10000~, which also accounted for faster permeation rate of lysozyme through PCL‐PEG~4000~ porous films. © 2002 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 63: 220–225, 2002; DOI 10.1002/jbm.10120