Paper BI-TuP7
Determining the Surface Release Kinetics of KGF Protein from a Biodegradable Polymer Film

Tuesday, October 16, 2007, 6:00 pm, Room 4C

Biodegradable polymers are of interest in developing strategies to control protein drug delivery. The protein that was used in this study is Keratinocyte Growth Factor (KGF) which is a protein involved in the re-epithelialization process. The protein is stabilized in the biodegradable polymer matrix during formulation and over the course of polymer degradation with the use of an ionic surfactant Aerosol-OT (AOT) which will encapsulate the protein in an aqueous environment. The release kinetics of the protein from the surface of the polymer matrix requires precise timing which is a crucial factor in the efficacy of this drug delivery system. Determining the release kinetics was accomplished by a two fold method. The first step was to measure the accumulation of the surfactant and protein at the surface of the polymer film. X-ray Photoelectron Spectroscopy (XPS) was used to measure the surface concentration of the surfactant and polymer using the unique elemental composition of these compounds. The surfactant has been identified from the polymer matrix using the sulfur region while protein identification utilizes the nitrogen signal. Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) was used in the same capacity to identify the molecular ion peak of the surfactant and polymer and use this to determine surface concentration. The surfactant molecular ion peak was observed in the positive and negative mode at m/z 467 and 422, respectively. These peaks were determined to be [AOT + Na+]+ and [AOT-Na+]-. These methods are used to identify the surfactant and protein from the polymer matrix and are used to measure the rate of surface accumulation. The second step was to compare this accumulation rate with the release rate of the protein into an aqueous solution during the degradation of the biodegradable film. This rate is compared to fluorescence spectroscopy measurements that were done using the autofluorescence of the protein that has been released into an aqueous solution. This study was done to determine the release kinetics of an unmodified biodegradable system containing only a polymer, surfactant, and protein. One method that is currently being used to tune the release rate of the polymer is micro-patterning. The pattern will determine the rate at which the polymer degrades and the rate at which protein is released.