Applications of Polarization Microscope in Determining the Physical Status of API in the Wet-Spinning Drug-Loaded Fibers

The API (Active Pharmaceutical Ingredients) physical status and distributions in the drug-loaded fibers have a manifest influence on the drug-loaded capabilities and drug-released controlled properties. In the present study, an easy and useful method was developed for determining the drug physical status and distributions in the wet spinning API-loaded fibers. The fibers prepared from co-dissolved wet spinning methods were observed under orthogonal polarized light. The results demonstrated that the API in the fibers lost its original needle crystal shape, double refraction features and natural polychrome, but transferred to tiny white circular particles and evenly distributed on the fibers' surface. The results from scanning electron microscope and X-ray diffraction analysis were basically concurred with those observations, illustrating the availability of polarization microscope observations. Polarization microscopy is a simple and useful method for the development of novel drug-loaded fibers.