ABSTRACT
It was the aim of this study to design charge converting lipid nanoparticles (LNP) via a microfluidic mixing technique used for the preparation and coating of LNP. LNP consisting of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), cholesterol, N-(carbonyl-methoxypolyethyleneglycol-2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (MPEG-2000-DSPE), and various cationic surfactants were prepared at diverging flow rate ratios (FRR) via microfluidic mixing. Utilizing a second chip in the microfluidic set-up, LNP were coated with polyoxyethylene (9) nonylphenol monophosphate ester (PNPP). LNP were examined for their stability in different physiologically relevant media as well as for hemolytic and cytotoxic effects. Finally, phosphate release and charge conversion of PNPP-coated LNP were evaluated after incubation with alkaline phosphatase and on Caco2-cells. LNP produced at an FRR of 5:1 exhibited a size between 80 and 150 nm and a positive zeta potential. Coating with PNPP within the second chip led to LNP exhibiting a negative zeta potential. After incubation with 1 U/ml alkaline phosphatase for 4 h, zeta potential of the LNP containing 1,2-dioleoyloxy-3-trimethylammonium-propane chloride (DOTAP) as cationic component shifted from - 35 mV to approximately + 5 mV. LNP prepared with other cationic surfactants remained slightly negative after enzymatic phosphate cleavage. Manufacturing of LNP containing PNPP and DOTAP via connection of two chips in a microfluidic instrument proves to show efficient change in zeta potential from negative to positive after incubation with alkaline phosphatase.
ABSTRACT
In the present study, various surfactants were combined with insulin (INS), bovine serum albumin (BSA) and horseradish peroxidase (HRP) via hydrophobic ion pairing to increase lipophilicity and facilitate incorporation into self-emulsifying drug delivery systems (SEDDS). Lipophilicity of model proteins was successfully increased, achieving log Dn-butanol/water values up to 3.5 (INS), 3.2 (BSA) and 1.2 (HRP). Hereby, key factors responsible for complex formation were identified. In particular, surfactants with branched alkyl chains or chain lengths greater than C12 showed favorable properties for hydrophobic ion pairs (HIP). Furthermore, flexibility of the carbon chain resulted in higher lipophilicity and suitability of polar head groups of surfactants for HIP decreased in the rank order sulfonate > sulfosuccinate > phosphate = sulfate > carbonate > phosphonic acids = sulfobetaines. Stability studies of formed HIP complexes were performed in various gastrointestinal fluids and their solubility was determined in commonly used SEDDS excipients. Formed complexes were stable in simulated gastrointestinal fluids and could be incorporated into SEDDS formulations (C1: 10% caprylocaproyl polyoxyl-8 glycerides, 20% PEG-40 hydrogenated castor oil, 20% medium-chain triglycerides, 50% n-butanol; C2: 10% caprylocaproyl polyoxyl-8 glycerides, 20% PEG-40 hydrogenated castor oil, 20% medium-chain triglycerides, 40% n-butanol, 10% 1,2-butanediol), resulting in suitable payloads of up to 11.9 mg/ml for INS, 1.0 mg/ml for BSA and 1.6 mg/ml for HRP.
