Liposomal Polyion-Complexes based on Poly(allylamine) for Oral Peptide Delivery: Basic Investigations

The efficacy of polyion-complexes between charged liposomes and oppositely charged polymers for the oral delivery of therapeutic peptides and proteins has been reported previously. It was the aim of the current study, to investigate whether polyion-complexes between negatively charged liposomes and the cationic polymer poly(allylamine) (PALAM) can be formed. Furthermore, the protease inhibitory effect of PALAM, the drug-loading capacity of liposomal PALAM polyion-complexes as well as the toxicity of PALAM and liposomal PALAM polyion-complexes was evaluated. After mixing the negatively charged liposomes with a PALAM solution, the zeta-potential switched from a negative to a positive value, indicating the formation of the polyion-complexes. PALAM was capable of significantly inhibiting Trypsin, although this effect was not very pronounced. Drug-loading capacity using the hydrophilic marker fluorescein isothiocyanate-dextran (FD4) was determined to be 8.0 ± 1.5 %. Cytotoxicity tests using Caco-2 cells and MTS assay revealed that both, PALAM in solution as well as liposomal polyion-complexes displayed cell toxicity. Data gained within this study is believed to contribute to the development of PALAM based colloidal drug delivery systems.