Application of coherent anti‐stokes Raman scattering microscopy to image the changes in a paclitaxel–poly(styrene‐b‐isobutylene‐b‐styrene) matrix pre‐ and post‐drug elution

Mapping the drug distribution in a polymeric film and following the subsequent changes that result during and after drug release is important to better understand the mechanism of drug release. This understanding leads to more efficiently designed tailor-made release profiles for drug-containing biomedical devices. Coherent anti-Stokes Raman scattering (CARS) microscopy was used for in situ imaging of local drug distribution in polymeric films, taking advantage of the three-dimensional (3D) resolution, high speed, high sensitivity, and noninvasiveness of the technology. Additionally, the morphological changes of poly(styrene-b-isobutylene-b-styrene) (SIBS) films during paclitaxel release were characterized by scanning electron microscopy, and drug release was quantitatively determined by high performance liquid chromatography. The time-dependent changes in the 3D distribution of paclitaxel in the polymer film were visualized using CARS microscopy. CARS images showed that the paclitaxel was uniformly distributed throughout the SIBS matrix. Changes in the paclitaxel distribution during release were monitored using depth intensity profiles and showed that, upon exposure of the paclitaxel-loaded film to a release medium, the quantitative CARS intensity of paclitaxel decreased. These results indicate that paclitaxel was dissolved and depleted from the SIBS film during in vitro drug elution, supporting the use of CARS microscopy as an effective nondestructive technique for chemical imaging of paclitaxel elution dynamics in polymer films.