Highly mucus permeating and zeta potential changing self-emulsifying drug delivery systems: A potent gene delivery model for causal treatment of cystic fibrosis.

Aim: It was the aim of the study to develop self-emulsifying drug delivery systems (SEDDS) with the ability to change their zeta potential towards higher values at the adsorption membrane and in this way facilitate the release of the DNA-cetrimonium complex and enhance transfection.

Methods: Plasmid DNA was complexed via hydrophobic ion pairing utilizing various surfactants and the complex was incorporated into SEDDS achieving a payload of 1% (m/v). Log P of the complex was determined. SEDDS were characterized regarding droplet size, zeta potential, stability and toxicity. Alkaline phosphatase presented in the sputum of cystic fibrosis patients was quantified using 4-nitrophenyl phosphate disodium salt and 5-bromo-4-chloro-1H-indol-3-yl phosphate dipotassium salt as substrates. SEDDS containing 0.4% (m/v) 1,2-dipalmitoyl-sn-glycero-3-phosphate monosodium salt were characterized regarding their zeta potential changing properties utilizing isolated alkaline phosphatase and cystic fibrosis sputum. The mucus permeating properties of SEDDS were evaluated via Transwell method using cystic fibrosis sputum. Finally, the transfection efficiency of incorporated plasmid DNA was investigated.

Results: Cetrimonium bromide showed the highest precipitation efficiency of 99.5 ± 2.72% for the complexation of pDNA. SEDDS containing propylene glycol, Capmul PG-8, Captex 300, Captex 355, Captex 8000, Cremophor EL, Cremophor RH-40 and Brij O10 showed stable emulsions with a droplet size between 20 and 100 nm and zeta potential <-3 mV over 4 h. SEDDS demonstrated highly protective effect against enzymatic degradation and moderate cell viability on freshly obtained pulmonary tissue. The pDNA-cetrimonium complex incorporated into SEDDS revealed a log P of about 2. A concentration of 0.879 ± 0.103 U/g alkaline phosphatase was found in the sputum of cystic fibrosis patients. SEDDS containing 1,2-dipalmitoyl-sn-glycero-3-phosphate monosodium salt showed a high potential of changing the zeta potential by applying isolated alkaline phosphatase as well as cystic fibrosis sputum along with high mucus permeating properties. Formulation C demonstrated the highest transfection efficiency with a 7.2-fold increased fluorescence intensity compared to naked pDNA.

Conclusion: The novel developed zeta potential changing SEDDS are opening versatile opportunities for the treatment of cystic fibrosis caused by gene mutation.