Characterization of an amino acid based biodegradable surfactant facilitating the incorporation of DNA into lipophilic delivery systems.

Lysine based cationic surfactants are well-tolerated tools for hydrophobic ion pairing (HIP) with DNA and its incorporation into lipophilic delivery systems. Di-Boc-lysine was esterified with 1-hexadecanol and the Boc-residues were cleaved off resulting in hexadecyl lysinate (HL). Subsequently, its Log POctanol/water and the critical micelle concentration (CMC) were determined. Degradability was evaluated utilizing trypsin and pancreas lipase as well as Caco-2 cells. Afterwards, the viability of Caco-2 cells upon incubation with HL was investigated. Finally, HL was ion-paired with plasmid DNA (pDNA, 6159 bp) and the obtained complex was incorporated into self-emulsifying drug delivery systems (SEDDS) for transfection studies on HEK-293 cells. HL was synthesized with a yield of 53% and subsequent characterization revealed a Log PWater/Octanol of 0.05 and a CMC of 2.7 mM. Enzymatic degradation studies showed rapid degradation of HL by isolated enzymes and Caco-2 cells and cell viability experiments revealed no toxic effect of HL even in a concentration of 250 µg·ml-1 within 24 h. HIP with pDNA was the most efficient in a molar ratio of 6159:1 (HL:pDNA) equalling a charge ratio of 1:1. Formed complexes could be incorporated into SEDDS facilitating successful transfection of HEK-293 cells.