Mechanism and Structural Factors of Lipid and Surfactant in the Formation of Self-Emulsified Nanoemulsion.

The study aims to elucidate the mechanism and the role of the molecular structure of surfactants and lipids in the formation of oil-in-water (o/w) self-emulsified nanoemulsions (SENs). The hypothesis is that the overall change of Gibb's free energy (ΔGf) during the mixing of the lipid and surfactant, the formation of the interface between the lipid nanodroplets and water, and the dispersion of the lipid nanodroplets into the water are the determinants of the formation of SEN, which are the result of the intermolecular interactions between the excipients involved. Various lipids and surfactants of different structures were studied for the possible formation of SEN. The results demonstrate that the formation of SEN requires (1) enough hydrophobic attractions between the surfactant molecule and the lipid molecule, which can break up the lipid-lipid and surfactant-surfactant intermolecular binding forces and (2) the surfactant to be able to associate with enough water molecules which can effectively cover the lipid droplets' surface to prevent coalescence.

Impact of digestion on the transport of dextran-loaded self-emulsified nanoemulsion through MDCK epithelial cell monolayer and rat intestines.

Many of the lipids and surfactants used to prepare the self-emulsified nanoemulsion (SEN) are subjected to the gastro-intestinal enzymatic digestion, which may affect the absorption of the loaded drug. The present study was to investigate the impact of such digestion on the transport of hydrophilic macromolecules (10-kDa dextran as the model compound) loaded in SEN through the MDCK cell monolayer and ex-vivo rat intestines. FITC-labeled dextran (FD) was loaded inside the inner oil phase of SEN by the formation of FD-phospholipid solid dispersion (FDPS). After digestion, the droplet size increased from 31.06 ± 2.10 nm to 494.6 ± 22.1 nm, and the FD content in the external aqueous phase increased from 41.6 ± 4.2% to 61.1 ± 4.4%. Compared to the FD solution, SEN without digestion enhanced the transport of FD through MDCK cell monolayer 4.1 times and through rat intestines 3.0-7.4 times. However, the digestion reduced the transport of FD 3.5 times through MDCK cell monolayer and 1.3-2.0 times through rat intestines, compared to that without digestion. This reduction was due to the destruction of lipid nano-droplets and release of FD to the external aqueous phase of SEN. This finding should be considered when SEN is used as a delivery system for hydrophilic macromolecules.

Transport of lipid nano-droplets through MDCK epithelial cell monolayer.

This study aims to investigate the transport of lipid nano-droplets through MDCK epithelial cell monolayer. Nanoemulsions of self-nano-emulsifying drug delivery systems (SNEDDS) labeled with radioactive C18 triglyceride were developed. The effect of droplet size and lipid composition on the transport was investigated. The results showed that the lipid nano-droplet transport through MDCK cell monolayer was as high as 2.5%. The transport of lipid nano-droplets was higher for nanoemulsions of medium chain glycerides than the long chain glycerides. The transport was reduced by more than half when the average lipid nano-droplet size increased from 38nm to 261nm. The droplet size measurement verified the existence of lipid nano-droplets in the receiver chamber only when the nanoemulsions were added to the donor chamber but not when the surfactant or saline solution was added. Cryo-TEM images confirmed the presence of lipid nano-droplets in both donor and receiver chamber at the end of transport study. In conclusion, lipid nano-droplets can be transported through the cell monolayer. This finding may help to further explore the oral and other non-invasive delivery of macromolecules loaded inside SNEDDS.

Separation of external aqueous phase from o/w nanoemulsions.

The aim of this study is to develop a simple, reliable, timesaving and cost-effective method for separation of the external aqueous phase from o/w nanoemulsions. The method is based on centrifugation through a hydrophilic membrane. Five o/w nanoemulsions (droplet size of 20-200nm) with radio-labeled C18 triglyceride were prepared. These nanoemulsions were placed in tubes with cellulose membranes (10-50K molecular weight cut-off) and centrifuged at 250-3000g for 5-15min. The filtrates were analyzed for the presence of lipid droplets and radioactivity. The applicability of this method was tested on FITC-dextran-loaded nanoemulsion (FITC-dextran was expected to be in the lipid droplets) and a blank nanoemulsion mixed with FITC-dextran (FITC-dextran was expected to be in the external aqueous phase). The results show that no droplets were detected in the filtrate. The radioactivity in the filtrate was in the range of 0.3-2.9%. The volume of the filtrate increased with increase in the membrane pore size, centrifugal force and time, and decrease in droplet size. There was 41.6±4.2% and 98.4±0.8% FITC-dextran in the aqueous phase of the FITC-dextran-loaded nanoemulsion and the blank nanoemulsion mixed with FITC-dextran, respectively. In conclusion, centrifugation with hydrophilic membrane is an efficient and convenient method for the separation of the external aqueous phase from o/w nanoemulsions with droplet sizes in the range of 20-200nm.

Oral delivery of glucagon like peptide-1 by a recombinant Lactococcus lactis.

PURPOSE: To develop a live oral delivery system of Glucagon like peptide-1 (GLP-1), for the treatment of Type-2 Diabetes. METHODS: LL-pUBGLP-1, a recombinant Lactococcus lactis (L. lactis)) transformed with a plasmid vector encoding GLP-1 cDNA was constructed and was used as a delivery system. Secretion of rGLP-1 from LL-pUBGLP-1 was characterized by ELISA. The bioactivity of the rGLP-1 was examined for its insulinotropic activity on HIT-T15 cells. Transport of rGLP-1 across MDCK cell monolayer when delivered by LL-pUBGLP-1 was studied. The therapeutic effect of LL-pUBGLP-1 after oral administration was investigated in ZDF rats. RESULTS: DNA sequencing and ELISA confirmed the successful construction of the LL-pUBGLP-1 and secretion of the active form of rGLP-1. In vitro insulinotropic studies demonstrated that LL-pUBGLP-1 could significantly (p < 0.05) stimulate HIT-T15 cells to secrete insulin as compared to the controls. When delivered by LL-pUBGLP-1, the GLP-1 transport rate across the MDCK cell monolayer was increased by eight times (p < 0.01) as compared to the free solution form. Oral administration of LL-pUBGLP-1 in ZDF rats resulted in a significant decrease (10-20%, p < 0.05) in blood glucose levels during 2-11 h post dosing and a significant increase in insulin AUC0-11h (2.5 times, p < 0.01) as compared to the free solution. CONCLUSION: The present study demonstrates that L. lactis when genetically modified with a recombinant plasmid can be used for the oral delivery of GLP-1.