Design of self-emulsifying oral delivery systems for semaglutide: reverse micelles versus hydrophobic ion pairs

It was the aim of this study to evaluate the potential of reverse micelles (RM) and hydrophobic ion pairs (HIP) for incorporation of semaglutide into self-emulsifying oral drug delivery systems. Reverse micelles loaded with semaglutide were formed with a cationic (ethyl lauroyl arginate, ELA) and an anionic surfactant (docusate, DOC), whereas HIP were formed between semaglutide and ELA. Maximum solubility of the peptide and the rate of dissolution was evaluated in various lipophilic phases (glycerol monocaprylocaprate:caprylic acid 1:4 (m/m), glycerol monolinoleate:caprylic acid 1:4 (m/m) and glycerol monocaprylocaprate:glycerol monolinoleate 1:4 (m/m)). Self-emulsifying drug delivery systems (SEDDS) loaded with RM and HIP were characterized regarding size distribution, zeta potential, cytocompatibility and Caco-2 permeability. Droplet sizes between 50 and 300 nm with polydispersity index (PDI) around 0.3 and zeta potentials between - 45 mV (RM_DOC) and 36 mV (RM_ELA) were obtained. RM provided an almost 2-fold higher lipophilicity of semaglutide than HIP resulting in a 4.2-fold higher payload of SEDDS compared to HIP. SEDDS containing RM or HIP showed high cytocompatibilities with a cell survival above 75% for concentrations up to 0.1% on Caco-2 cells and acceptable hemolytic activity. Permeation studies across Caco-2 monolayer revealed an at least 2-fold increase in permeability of semaglutide for the developed formulations.