Liposomal Formulations of Serratiopeptidase: In Vitro Studies Using PAMPA and Caco-2 Models

The feasibility of using liposomes as a potential oral delivery system for the systemic delivery of other peptides and protein-based pharmaceuticals has been studied. Serratiopeptidase, a proteolytic enzyme, was used as a model drug. Liposomes were prepared by a thin film hydration method using various lipids, namely, soya lecithin, DMPC and DMPE. It was further investigated whether the liposomal formulations of serratiopeptidase altered the permeability/absorption of the drug using PAMPA, a non-cell-based assay, and Caco-2 assay, a cell monolayer system, mimicking in vivo GI epithelium cells. The entrapment efficiency of the formulations was found to be 62%, 84% and 86% for the liposomes of soya lecithin, DMPC and DMPE respectively. The effectiveness of the liposomal formulations against the pure drug in terms of permeability/absorption was compared. The effective permeability (log P_e) values from PAMPA study varied from −7.47 to −6.5 cm/s whereas for the serratiopeptidase it was −7.72 cm/s. The apparent permeability values calculated from Caco-2 assay varied from 1.25 × 10⁻⁶ to 1.61 × 10⁻⁶ cm/s whereas for the serratiopeptidase it was 1.25 × 10⁻⁶ cm/s. The flux was found to be 3.88–4.96 µg/cm²/h for the formulations when compared to 3.208 µg/cm²/h for serratiopeptidase. The results obtained indicated that in comparison with the pure drug, incorporation of drug into liposomes improved the permeability. Thus it could be concluded that the liposomal formulations would improve the oral absorption of serratiopeptidase.