(116v) Characterization of Real-Time Drug Release from Engineered Biomedical Coatings

The current development of drug-releasing biomedical coatings has yielded wide application in the medical industry. Controlled drug release from biomedical coatings is of specific interest to engineers designing internal medical devices. However, the release mechanisms and the design parameters affecting them are poorly understood. Composite coatings of polyisobutylene-polystyrene polymer with 10% (wt/wt) dexamethasone or rapamycin, both anti-inflammatory drugs, were generated on a stainless steel substrate using the ElectroNanospray(TM) process. These coatings were then analyzed using atomic force microscopy (AFM) and confocal Raman spectroscopy imaging. The drug sequestration in the polymer and release into solution over time was observed. Raman imaging showed that the drug was aggregated in larger micron-sized domains, and that release was primarily due to the decay of these larger features. AFM showed these drug domains eluting through spherical formations on the surface; these domains increased in number within the first 6 hours and decayed by 24 hours. These results demonstrate the power of these complimentary techniques for characterizing drug release from thin films. It is hoped that subsequent characterization will lead to a better understanding of the mechanism(s) of drug release. This understanding should allow for coatings to be engineered matching release profiles to biologic needs.