Abstract by Zhuoxuan Li

Peptide and protein-based drugs by oral administration often exhibit poor bioavailability due to extensive degradation by enzymes in the gastrointestinal tract as well as limited permeability across mucus membranes. Parenteral dosage forms intended for subcutaneous (s.c.) injection have been a common strategy for peptide and protein-based drug delivery, however, are confronting the challenges in the design of peptide and protein injectables and suitable in vitro characterization methods. In situ forming implants (ISFIs) constitute an attractive platform among injectable depot formulations. Upon s.c. injection of ISFIs, solvent diffuses into the surrounding tissue along with drug release while water at the injection site enters into the formulation by diffusion. The complex processes associated with implant formation, drug release and tissue response is not fully understood. Unfortunately, the conventional in vitro approaches for evaluation of parenteral formulations typically measuring drug concentration in the release medium are unable to monitor the complex processes. UV-Vis imaging capable of generating temporally and spatially resolved images based on absorbance values of analytes at different wavelengths might be helpful. The characterization of ISFIs was conducted using hydrogels as release media coupled with UV-Vis imaging. The overall aim of the current Ph.D. project was to develop suitable in vitro methods based on UV-Vis imaging for characterization of the performance of in situ forming drug delivery systems intended for s.c. administration.