UC Riverside Undergraduate Research Journal

Biodegradable salicylic acid-based poly(anhydride-ester)s (SAPAE) have proven to be effective in many biomedical applications including controlling inflammation, promoting bone growth, and preventing biofilm formation due to the release of salicylic acid upon hydrolysis of the polymer anhydride and ester bonds. Microspheres of SAPAE polymer are one fabrication option available for the encapsulation and controlled release of hydrophobic small molecules. This project aims to evaluate and characterize the ability for SAPAE microspheres to encapsulate, protect, and deliver retinol, a small hydrophobic molecule which is highly used in dermatological and cosmetic products for anti-aging purposes. The SAPAE of interest is a copolymer of salicylic acid (SA), adipic acid, and a diphenylene acetic acid (PAA). Due to supply chain limitations, the polymers used to form microspheres were of two variations, low molecular weight and high molecular weight. Nonetheless, this allowed for comparison of microspheres characteristics including size, morphology, and retinol loading efficiency. Through scanning electron microscopy (SEM), it was confirmed that the unloaded and retinol-loaded microspheres had a spherical shape, and the sizes were similar between the low molecular weight and high molecular weight polymer versions. Residual methylene chloride solvent was successfully reduced in all samples which increases the viability for biological applications. Finally, ultraviolet-visible spectroscopy detected a maximum of 4% w/v loading of retinol in the microspheres.