Effects of excipients on the interactions of self-emulsifying drug delivery systems with human blood plasma and plasma membranes.

Due to its versatility in formulation and manufacturing, self-emulsifying drug delivery systems (SEDDS) can be used to design parenteral formulations. Therefore, it is necessary to understand the effects of excipients on the behavior of SEDDS formulations upon parenteral administration, particularly their interactions with blood plasma and cell membranes. In this study, we prepared three neutrally charged SEDDS formulations composed of medium-chain triglycerides as the oil phase, polyoxyl-35 castor oil (EL35) and polyethylene glycol (15)-hydroxystearate (HS15) as the nonionic surfactants, medium-chain mono- and diglycerides as the co-surfactant, and propylene glycol as the co-solvent. The cationic surfactant, didodecyldimethylammonium bromide (DDA), and the anionic surfactant, sodium deoxycholate (DEO), were added to the neutral SEDDS preconcentrates to obtain cationic and anionic SEDDS, respectively. SEDDS were incubated with human blood plasma and recovered by size exclusion chromatography. Data showed that SEDDS emulsion droplets can bind plasma protein to different extents depending on their surface charge and surfactant used. At pH 7.4, the least protein binding was observed with anionic SEDDS. Positive charges increased protein binding. SEDDS stabilized by HS15 can adsorb more plasma protein and induce more plasma membrane disruption activity than SEDDS stabilized by EL35. These effects were more pronounced with the HS15 + DDA combination. The addition of DDA and DEO to SEDDS increased plasma membrane disruption (PMD) activities, and DDA (1% w/w) was more active than DEO (2% w/w). PMD activities of SEDDS were concentration-dependent and vanished at appropriate dilution ratios.

Mucolytic self-emulsifying drug delivery systems (SEDDS) containing a hydrophobic ion-pair of proteinase.

AIM: The aim of this study was to form hydrophobic ion-pairs of proteinase with cationic surfactants and to incorporate them into self-emulsifying drug delivery systems (SEDDS) to improve their mucus permeating properties. METHODS: Proteinase was ion-paired with benzalkonium chloride (BAK), hexadecylpyridinium chloride (HDP), alkyltrimethylammonium bromide (ATA) and hexadecyltrimethylammonium bromide (HDT) at pH 8.5-9.0, and subsequently incorporated into SEDDS consisting of Cremophor EL, propylene glycol, and Capmul 808-G (40/20/40). Mucus permeation of SEDDS containing proteinase complexes was evaluated via rotating tube technique and cell-free Transwell® insert system. Additionally, enzymatic activity of proteinase complexes as well as their potential cytotoxicity was evaluated. RESULTS: Among all tested hydrophobic ion-pairs, proteinase/BAK showed highest potential. Mucus diffusion of SEDDS containing proteinase/BAK complex yielded in 2.3-fold and 2.5-fold higher mucus permeability with respect to blank SEDDS at Transwell® insert system and rotating tube technique, respectively. Furthermore, proteinase/BAK complex maintained the highest enzymatic activity of 50.5 ± 5.6% compared to free proteinase. At a SEDDS concentration as low as 0.006% cell viability was just 80%. The addition of proteinase complexes to SEDDS increased cytotoxicity on Caco-2 cells in a concentration-dependent manner. CONCLUSION: SEDDS loaded with proteinase/BAK complexes are promising nanocarriers because of enhanced mucus permeating properties.

Hydrophobic ion pairing of a GLP-1 analogue for incorporating into lipid nanocarriers designed for oral delivery.

The lipophilic character of peptides can be tremendously improved by hydrophobic ion pairing (HIP) with counterions to be efficiently incorporated into lipid-based nanocarriers (NCs). Herein, HIPs of exenatide with the cationic surfactant tetraheptylammonium bromide (THA) and the anionic surfactant sodium docusate (DOC) were formed to increase its lipophilicity. These HIPs were incorporated into lipid based NCs comprising 41% Capmul MCM, 15% Captex 355, 40% Cremophor RH and 4% propylene glycol. Exenatide-THA NCs showed a log Dlipophilic phase (LPh)/release medium (RM) of 2.29 and 1.92, whereas the log DLPh/RM of exenatide-DOC was 1.2 and -0.9 in simulated intestinal fluid and Hanks' balanced salts buffer (HBSS), respectively. No significant hemolytic activity was induced at a concentration of 0.25% (m/v) of both blank and loaded NCs. Exenatide-THA NCs and exenatide-DOC NCs showed a 10-fold and 3-fold enhancement in intestinal apparent membrane permeability compared to free exenatide, respectively. Furthermore, orally administered exenatide-THA and exenatide-DOC NCs in healthy rats resulted in a relative bioavailability of 27.96 ± 5.24% and 16.29 ± 6.63%, respectively, confirming the comparatively higher potential of the cationic surfactant over the anionic surfactant. Findings of this work highlight the potential of the type of counterion used for HIP as key to successful design of lipid-based NCs for oral exenatide delivery.

The Effect of Counterions in Hydrophobic Ion Pairs on Oral Bioavailability of Exenatide.

The aim of this study was to evaluate the potential of n-octadecyl sulfate (SOS) as a counterion for hydrophobic ion pairing (HIP) with exenatide-a potent glucagon-like peptide-1 (GLP-1) analogue in the treatment of diabetes mellitus-to improve its oral bioavailability. Exenatide was ion-paired with SOS and docusate (DOC) serving as the gold standard followed by the incorporation in a self-emulsifying drug delivery system (SEDDS) comprising Capmul MCM EP, Captex 355, Kolliphor RH40, and propylene glycol at a mass ratio of 41:15:40:4. The hydrophobicity of exenatide-SOS and exenatide-DOC was characterized by determining the butanol-water partition coefficient (log Pbutanol/water). Droplet size and zeta potential of the ion pair-loaded SEDDS were characterized followed by intestinal membrane permeability determination on freshly excised rat intestines compared to exenatide solution. Furthermore, the oral bioavailability of exenatide-SOS- and exenatide-DOC-loaded SEDDS was also evaluated in vivo in healthy male Sprague-Dawley rats. Hydrophobic ion pairing increased the log Pbutanol/water of exenatide from -1.9 to 2.0 for exenatide-SOS and to 1.2 for exenatide-DOC. SEDDSs loaded with 0.26% (m/m) exenatide-SOS and 0.17% (m/m) exenatide-DOC had mean droplet size less than 30 nm and negative zeta potential. Ex vivo permeation experiments revealed 3.5-fold and 6.4-fold improvement in membrane permeability of the exenatide-SOS-loaded SEDDS vs. the exenatide-DOC-loaded SEDDS and exenatide solution, respectively. The orally administered exenatide-SOS-loaded SEDDS and exenatide-DOC-loaded SEDDS resulted in relative oral bioavailability vs. subcutaneous injection (SC) of 19.6 and 15.2%, respectively. Within this study, the key role of counterions for oral peptide delivery via HIP could be confirmed, and SOS was identified as a promising surfactant for this purpose.

Imine bond formation: A novel concept to incorporate peptide drugs in self-emulsifying drug delivery systems (SEDDS).

HYPOTHESIS: Because of its hydrophilic character the peptide drug Polymyxin B (PMB) cannot be incorporated in lipophilic nanocarrier systems such as self-emulsifying drug delivery systems (SEDDS) for oral administration. Due to the formation of imine conjugates between the primary amino groups of PMB and the carbonyl group of cinnamaldehyde, however, drug lipophilicity might be sufficiently raised for incorporation in SEDDS. METHODS: Imine bonds were formed between the primary amino groups of PMB and the carbonyl group of cinnamaldehyde. PMB-cinnamaldehyde conjugate was characterized regarding degree of substitution, log P and release of PMB due to interaction with bovine serum albumin (BSA), SEDDS loading and cell viability. RESULTS: 87.1% of primary amines formed imines with cinnamaldehyde. Log P was increased 69.183 - folds. BSA triggered release of PMB was 45.2%, 64.9% and 80.6% within 16 h. Log DSEDDS/Release medium of PMB-cinnamaldehyde conjugate was 3.4. CONCLUSION: According to these findings, the concept of imine bond formation with cinnamaldehyde can be considered as a novel concept for increasing lipophilicity of the hydrophilic antibiotic peptide PMB.

Hydrophobic ion-pairs and lipid-based nanocarrier systems: The perfect match for delivery of BCS class 3 drugs.

Membrane permeability of charged BCS class 3 drugs can be tremendously improved by the formation of hydrophobic ion-pairs (HIPs), as the lipophilic character of the drug is strongly improved so that it can move across the phospholipid bilayer of epithelial cells. This effect, however, can in most cases only be observed in in vitro studies, where the destabilizing effect of endogenous counterions on HIPs can be minimized. In vivo results were so far disappointing. Due to the incorporation of HIPs in lipid-based nanocarrier systems such as self-emulsifying drug delivery systems (SEDDS) and oil-in-water nanoemulsions, however, the stability of HIPs in the GI-tract can be substantially improved. As the dielectric constant in the oily droplets is comparatively much lower than that of GI-fluids and endogenous counterions cannot penetrate the oily droplets, HIPs can reach the absorption membrane still in intact form. Moreover, lipid-based nanocarrier systems were shown to be able to move across the mucus gel as well as unstirred water layer and to interact with the absorption membrane via various mechanisms delivering their payload to the systemic circulation. First in vivo studies utilizing the combination of HIPs and lipid-based nanocarrier systems showed a 10- up to 20-fold improved oral bioavailability of different types of drugs providing evidence for the potential of this concept. Within this review so far made achievements in this field and challenges ahead are discussed.

Oral self-emulsifying delivery systems for systemic administration of therapeutic proteins: science fiction?

Objective: The aim of this study was to develop self-emulsifying drug delivery systems (SEDDS) for oral delivery of therapeutic proteins through hydrophobic ion pairing. Method: Horseradish peroxidase (HRP), a model protein, was ion paired with sodium docusate to increase its hydrophobicity. The formed enzyme - surfactant complex was incorporated into SEDDS, followed by permeation studies across Caco-2 cell monolayer and freshly excised rat intestine. Results: Hydrophobic ion pairs (HIP) were formed between HRP and sodium docusate with the efficiency of 87.49 ± 1.35%. The formed complex maintained 60.97 ± 1.48% of the original enzyme activity. The ion pair was subsequently loaded into SEDDS with a payload of 0.1% (mass per cent, m/m). The obtained emulsion formed by SEDDS had a droplet size in the range from 20 to 200 nm with negative zeta potential. Permeation mechanism of the enzyme was energy-dependent and the encapsulation of the HIP complex in SEDDS enhanced the permeation of the enzyme through the Caco-2 cell monolayer and freshly excised rat intestine by 4 times and 2.5 times compared to the free enzyme, respectively. Conclusion: According to these findings, hydrophobic ion pairing followed by incorporation to SEDDS might be considered as a potential strategy for oral delivery of therapeutic proteins.

Self-emulsifying drug delivery systems and cationic surfactants: do they potentiate each other in cytotoxicity?

OBJECTIVES: The aim of this study was to evaluate the cytotoxicity of self-emulsifying drug delivery systems (SEDDS) containing five different cationic surfactants. METHODS: Cationic surfactants were added in a concentration of 1% and 5% (m/m) to SEDDS comprising 30% Capmul MCM, 30% Captex 355, 30% Cremophor EL and 10% propylene glycol. The resulting formulations were characterized in terms of size, zeta potential, in-vitro haemolytic activity and toxicity on Caco-2 via MTT assay and lactate dehydrogenase release assay. KEY FINDINGS: The evaluated surfactants had in both concentrations a minor impact on the size of SEDDS ranging from 30.2 ± 0.6 to 55.4 ± 1.1 nm, whereas zeta potential changed significantly from -9.0 ± 0.3 to +28.8 ± 1.6 mV. The overall cytotoxicity of cationic surfactants followed the rank order: hexadecylpyridinium chloride > benzalkonium chloride > alkyltrimethylammonium bromide > octylamine > 1-decyl-3-methylimidazolium. The haemolytic activity of the combination of cationic surfactants and SEDDS on human red blood cells was synergistic. Furthermore, cationic SEDDS exhibited higher cytotoxicity of Caco-2 cells compared to SEDDS without cationic surfactants. CONCLUSIONS: According to these results, SEDDS and cationic surfactants seem to bear an additive up to synergistic toxic risk.

Mucus permeating self-emulsifying drug delivery systems (SEDDS): About the impact of mucolytic enzymes.

This study aimed to improve the mucus permeating properties of self-emulsifying drug delivery systems (SEDDS) by anchoring lipidized bromelain, papain and trypsin using palmitoyl chloride. SEDDS containing enzyme-palmitate conjugates were characterized regarding droplet size and zeta potential. Their mucus permeating properties were evaluated by Transwell diffusion and rotating tube method using fluorescein diacetate (FDA) as marker. Degree of substitution of modified enzymes was 35.3%, 47.8% and 38.5% for bromelain-palmitate, papain-palmitate and trypsin-palmitate, respectively. SEDDS as control and SEDDS containing enzyme-palmitate conjugates displayed a droplet size less than 50nm and 180-312nm as well as a zeta potential of -3 to -4 and -4 to -5mV, respectively. The highest percentage of permeation was achieved by introducing 5% papain-palmitate into SEDDS. It could enhance the mucus permeation of SEDDS in porcine intestinal mucus 4.6-fold and 2-fold as evaluated by Transwell diffusion and rotating tube method, respectively. It is concluded that mucus permeation of SEDDS can be strongly improved by incorporation of enzyme-palmitate conjugates.