The effect of nonionic surfactant structure on hemolysis

Development of novel cationic microemulsion as parenteral adjuvant for influenza vaccine

Squalene-based oil-in-water (O/W) emulsions have been used as effective and safe adjuvants in approved influenza vaccines. However, there are concerns regarding the safety and side effects of increasing risk of narcolepsy. In present study, novel O/W microemulsions (MEs) containing wheat germ oil, D-alpha tocopheryl polyethylene glycol 1000 succinate (TPGS) and Cremophor EL (CreEL) or Solutol HS15 were formulated with/without a cationic surfactant, cetyltrimethylammonium bromide (CTAB) and then sterilized by autoclaving. Their physical properties and biological efficacies were evaluated. The results demonstrated that autoclaving reduced the droplet size to ∼20 nm with narrow size distributions resulting in monodisperse systems with good stability up to 3 years. Hemolytic activity, viscosity, pH, and osmolality were appropriate for parenteral use. Bovine serum albumin (BSA), a model antigen, after mixing with MEs retained the protein integrity, assessed by SDS-PAGE and CD spectroscopy. Greater percentages of 28SC cell viability were observed from CreEL-based MEs. Uptake of FITC-BSA-MEs increased with the increasing concentration of CTAB confirmed by CLSM images. Furthermore, cationic CreEL-based MEs could induce Th1 cytokine synthesis with an increase in TNF-α and IL-12 levels and a decrease in IL-10 level. In vivo immunization study in mice of adjuvants admixed with influenza virus solution revealed that nonionic and selected cationic CreEL-MEs enhanced immune responses as measured by influenza-specific serum antibody titers and hemagglutination inhibition titers. Particularly, cationic CreEL-based ME showed better humoral and cellular immunity with higher IgG2a titer than nonionic CreEL-based ME and antigen alone. No differences in immune responses were observed between mice immunized with selected cationic CreEL-based ME and marketed adjuvant. In addition, the selected ME induced antigen-sparing while retained immune stimulating effects compared to antigen alone. No inflammatory change in muscle fiber structure was observed. Accordingly, the developed cationic CreEL-based ME had potential as novel adjuvant for parenteral influenza vaccine.

Synthesis, characterization and assessment of suitability of trehalose fatty acid esters as alternatives for polysorbates in protein formulation

Nonionic polyethylene glycol-derived surfactants are today's choice as surfactants in protein formulations. Different groups discovered that although surface-induced stresses are reduced by these excipients, the long-term stability of different proteins decreased due to polyethylene glycol-related induction of oxidation processes under static storage conditions. In this paper, the potential of polyoxyethylene-free surfactants for protein formulation was evaluated. Three different sugar-based surfactants, 6-O-monocaprinoyl-α,α-trehalose, 6-O-monolauroyl-α,α-trehalose and 6-O-monopalmitoyl-α,α-trehalose, were synthesized in four reaction steps. These substances lack polyethylene glycol residues and can be produced from renewable resources. The chemical and physical properties of these three surfactants were investigated and compared with polysorbate 20 and 80. 6-O-monopalmitoyl-α,α-trehalose was insoluble in water at room temperature and was hence excluded from some of the further tests. The critical micellar concentration of all surfactants is in a comparable range of approximately 0.001-0.01% (m/V). The sugar-based surfactants showed slightly higher hemolytic activity than the polysorbate references. The surfactants with shorter chain length proved to be comparable to polysorbates in regard to physicochemical properties. Finally for human growth hormone, the protein-stabilizing properties against shaking-induced stress were tested and compared to polysorbate-containing formulations. Whereas in the absence of surfactant, dramatic monomer loss and aggregate formation occurred, it was found that 100% monomer content was maintained when 0.1% (m/V) 6-O-monocaprinoyl-α,α-trehalose or 6-O-monolauroyl-α,α-trehalose was added to the formulation. Polysorbate 80 at a concentration of 0.1% (m/V) also significantly stabilized the protein. Lower amounts of surfactants result in only partial stabilization. Furthermore, adsorption of human growth hormone to the container surface is reduced in the presence of the surfactants. Thus, the new sugar-based surfactants offer a promising alternative and have potential for application in protein formulations.

Composition optimization and stability testing of a parenteral antifungal solution based on a ternary solvent system

An intravenous solution is a dosage forms intended for administration into the bloodstream. This route is the most rapid and the most bioavailable method of getting drugs into systemic circulation, and therefore it is also the most liable to cause adverse effects. In order to reduce the possibility of side effects and to ensure adequate clinical dosage of the formulation, the primarily formulated composition should be optimized. It is also important that the composition should retain its therapeutic effectiveness and safety throughout the shelf-life of the product. This paper focuses on the optimization and stability testing of a parenteral solution containing miconazole and ketoconazole solubilized with a ternary solvent system as model drugs. Optimization of the solvent system was performed based on assessing the risk/benefit ratio of the composition and its properties upon dilution. Stability tests were conducted based on the EMEA (European Medicines Agency) "guideline on stability testing: stability testing of existing active substances and related finished products". Experiments show that both the amount of co-solvent and surface active agent of the solvent system could substantially be reduced, while still maintaining adequate solubilizing power. It is also shown that the choice of various containers affects the stability of the compositions. It was concluded that by assessing the risk/benefit ratio of solubilizing power versus toxicity, the concentration of excipients could be considerably decreased while still showing a powerful solubilizing effect. It was also shown that a pharmaceutically acceptable shelf-life could be assigned to the composition, indicating good long-term stability.

Relationship between structure and antibacterial activity of lipophilic N-acyldiamines

We report in this work the preparation and antibacterial evaluation of a series of N-monoacylated diamines against six Gram-positive and 11 Gram-negative bacteria. The results obtained showed the existence of relationship between lipophilicity and antibacterial activity of the tested compounds. The best results were obtained against Gram-positive bacteria for compounds having a 10-12 carbons alkyl chain. Compound 4e was the most active against Microccus lentus (MIC=2 microg/mL), Staphylococcus aureus ATCC 29213 (MIC=4 microg/mL) and Enterobacter aerogenes CDC 1680 (MIC=8 microg/mL).

Alcohol ethoxylates mediate their bacteriostatic effect by altering the cell membrane of Escherichia coli NCTC 8196

The minimum inhibitory concentration (MIC) of a homologous series of alcohol ethoxylates with the same head group size (E6) but differing in the number of carbon atoms in their 'tail group' from 10 to 16 was determined for Staphylococcus aureus NCTC 4163 and Escherichia coli NCTC 8196 using a turbidimetric assay. All the surfactants tested demonstrated bacteriostatic activity against both organisms. A tetrazolium assay showed that C14E6 and C16E6 had little effect on the membrane-bound dehydrogenase enzyme activity of E. coli NCTC 8196 compared with C10E6 and C12E6. C10E6 caused leakage both of K(+) and nucleotides in a concentration-dependent manner above its MIC of 0.2 mM. C12E6 caused some leakage at concentrations below its MIC (0.12 mM).

Synthesis of New Sugar-Based Surfactants and Evaluation of Their Hemolytic Activities

The synthesis of four sugar-based surfactants derived from glucose and (R)-12-hydroxystearic acid is described. The surfactants have a hydroxy group in the hydrophobic part, which is either free or acylated using acetyl chloride, hexanoyl chloride, or myristoyl chloride. Three of the synthesized surfactants are water-soluble and are evaluated with respect to their CMCs and hemolytic activities. The fourth surfactant has limited water solubility and is not further included in the study. The investigated surfactants are all hemolytic close to their respective CMC indicating that their use in parenteral formulations may be limited. Nevertheless, surfactants having the proposed structure appear as promising alternatives to existing solubilizing agents for pharmaceutical applications.

Toxicological evaluation of mixtures of nonionic surfactants, alone and in combination with oil

The toxicity to human bronchial (16-HBE14o-) epithelium cells of nonionic surfactants, polyoxyethylene-10-oleyl ether (C(18:1)E(10)), polyoxyethylene-10-dodecyl ether (C(12)E(10)), and N,N-dimethyl-dodecylamine-N-oxide (C(12)AO) alone or in combination with a range of pharmaceutically acceptable oils (namely, ethyl esters and triglyceride oils), was determined with the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay. Regardless of the presence of oil, all C(12)E(10)- and C(12)AO-containing systems were toxic at concentrations around or below their critical aggregation concentrations (as determined by surface tension measurements), suggesting that surfactant toxicity was due to the disruption caused by the partitioning of monomeric surfactant into the cell membrane. Systems prepared from C(18:1)E(10) alone or in combination with a low-molecular-weight oil, such as ethyl butyrate or tributyrin, were toxic above their critical aggregation concentration. In contrast, systems prepared from C(18:1)E(10) in combination with a high-molecular-volume oil (e.g., ethyl oleate, Miglyol 812, or soybean oil) were toxic only at concentrations significantly greater than their critical aggregation concentration, suggesting that in these cases surfactant toxicity was mediated by the aggregated form of the surfactant solubilizing components of the cell membrane. In the C(18:1)E(10)-stabilized system, it is proposed that toxicity was significantly reduced on incorporation of high-molecular-volume oils because these oils cause formation of a distinct oil core in the aggregates that leads to a reduction in the ability of the system to solubilize components of the cell membrane.

Solubilization of human erythrocyte membranes by non-ionic surfactants of the polyoxyethylene alkyl ethers series

In the present study, we investigated the interaction of the non-ionic surfactants polyoxyethylene alkyl ethers (C(n)E(m)) with erythrocyte membranes. For this purpose we have performed hemolytic assays under isosmotic conditions with five surfactants in the 8 polyoxyethylene ether series. By applying to the hemolytic curves a quantitative treatment developed for the study of surface-active compounds on biomembranes, we could calculate the surfactant/lipid molar ratios for the onset of hemolysis (R(e)(sat)) and for complete hemolysis (R(e)(sol)). This approach also allowed the calculation of the binding constants for each surfactant to the erythrocyte membrane. Results in the C(n)E(m) series were compared to those obtained for Triton X-100, a well-known non-ionic surfactant with values of cmc and HLB in the range of the alkyl ethers studied. Inside the series the lytic effect increased with the more hydrophobic homologues (C(10)E(8)<C(12)E(8)<C(14)E(8)<C(16)E(8)<C(18)E(8)), with Re values between 3:1 and 0.03:1. The effect of C(10)E(8) and C(12)E(8) was found to be in the range of that caused by Triton X-100, proving that C(n)E(m) surfactants are strongly hemolytic.

Effects of polyoxyethylene chain length on erythrocyte hemolysis induced by poly[oxyethylene (n) nonylphenol] non-ionic surfactants

The effects of three different poly[oxyethylene (n) nonylphenols], n = 9.5, 20 and 100 oxyethylene (EO) units, on erythrocyte hemolysis and on the fluidity of the erythrocyte membrane were studied. The three different surfactants showed different effects. The surfactant with average n = 9.5 EO units (C9E9) shows a biphasic effect: at low concentrations it protects erythrocytes against hypotonic hemolysis, but at higher concentrations it induces hemolysis both in isotonic and hypotonic buffers. C9E20 does not affect the erythrocyte membrane resistance to hemolysis, independent of the buffer osmolarity; this detergent did not show a hemolytic effect. C9E100 is an effective protective agent against hypotonic hemolysis, in concentration > 2 x 10(-4) M. EPR spectroscopy of spin-labeled stearic acid indicated that the three different surfactants increase the fluidity of erythrocyte ghost membranes. At the higher C9E20 and C9E100 surfactant concentrations in the presence of membrane ghosts, spin-label is located in the surfactant micelles. In the case of the hemolytic concentrations of C9E9, mixed (surfactant plus phospholipid) micelles are formed. These results suggest that C9E9 has a higher affinity for membrane phospholipids, which accounts for its lytic activity. The protective effect of C9E100 is assigned to the osmotic buffering of the liquid surrounding the cell membrane, due to the large polar chains anchored to the membrane outer monolayer but other mechanisms previously considered in the literature may also be effective.

Lysis of human red blood cells. 4. Comparison of in vitro and in vivo hemolysis data

The dynamic in vitro method developed by the authors and other available in vitro methods were used to determine the degree of hemolysis induced by several cosolvent vehicles that have previously been evaluated in vivo. The in vitro data generated for each of these vehicles was compared with the in vivo hemolysis data to assess the ability of the method to estimate in vivo hemolysis. The results show that the in vitro data generated by the dynamic method are in agreement with the in vivo data for each vehicle. Therefore, the potential for formulations to induce intravascular hemolysis after injection can be determined by this dynamic in vitro method. With this information, hemolytically safe formulations can more easily be prepared.