Presence Of Dicetyl Phosphate Research Articles

Metformin loaded non-ionic surfactant vesicles: optimization of formulation, effect of process variables and characterization

BackgroundMetformin an oral hypoglycemic has been widely used as a fist line of treatment of Type II Diabetes but in a very high dose 2–3 times a day and moreover suffers from a number of side effects like lactic acidosis, gastric discomfort, chest pain, allergic reactions being some of them. The present work was conducted with the aim of sustaining the release of metformin so as to decrease its side effects and also reduce its dosing frequency using a novel delivery system niosomes (non-ionic surfactant vesicles). Non-ionic surfactant vesicles of different surfactants were prepared using thin film hydration technique and were investigated for morphology, entrapment, in-vitro release, TEM (transmission electron microscopy) and physical stability. Optimized formulation was further studied for the effect of Surfactant concentration, DCP (Dicetyl phosphate), Surfactant: cholesterol ratio and volume of hydration. The release studies data was subjected to release kinetics models.ResultsThe prepared vesicles were uniform and spherical in size. Optimized formulation MN3 entrapped the drug with 84.50±0.184 efficiency in the vesicles of the size 487.60±2.646 and showed the most sustained release of 73.89±0.126. Also it was resulted that 100 molar concentration of cholesterol and surfactant, Presence of DCP, equimolar ratio of span 60: cholesterol and 15 ml of volume of hydration were found to be optimum for miosome preparation.ConclusionsThe present work concluded metformin loaded niosomes to be effective in sustaining the drug release leading to decreased side effects and increased patient compliance.

Development of a topical niosomal preparation of acetazolamide: preparation and evaluation

Orally administered acetazolamide has a limited use in glaucoma due to the systemic side effects associated with its use. No topical formulation of acetazolamide is available, mainly because of it having a limited aqueous solubility and poor corneal permeation. To enhance the bioavailability of acetazolamide by the topical route and to improve the corneal permeability of the drug, niosomes of acetazolamide were prepared (employing span 60 and cholesterol) by different methods. Transmission electron microscopy (TEM) of the selected formulation was carried out to study the morphology. Niosomes were also prepared in the presence of dicetyl phosphate and stearylamine to obtain negatively and positively charged vesicles, respectively. It was found that the reverse-phase evaporation method (REV) gave the maximum drug entrapment efficiency (43.75%) as compared with ether injection (39.62%) and film hydration (31.43%) techniques. Drug entrapment efficiency varied with the charge and the percent entrapment efficiency for the REV method was 43.75, 51.23 and 36.26% for neutral, positively charged and negatively charged niosomes, respectively. Corneal permeability studies, however, showed that the percent permeation and the apparent permeability coefficient for the charged niosomes were less than for the neutral ones. A bioadhesive niosomal formulation of acetazolamide was also prepared and compared with the positively charged formulation, considering that both of them would have a prolonged stay in the cul-de-sac because of their expected interactions with mucin. The formulations were also compared based on their intraocular pressure (IOP)-lowering capacity. The positively charged niosomes (REV2), although showing good corneal permeability and pharmacodynamics, were however found to be inappropriate in terms of the corneal cell toxicity. The bioadhesive coated formulation (REV1bio) compared well with REV2 and also showed a much lesser toxicity. Further, the IOP-lowering effect of the developed formulations was compared with that of a marketed formulation of dorzolamide 2%, a topical carbonic anhydrase inhibitor. The developed niosomal formulations of acetazolamide showed a comparable physiological effect (33% reduction of IOP in REV1bio and 37% reduction in dorzolamide) with a duration of up to 6 h (the duration being 3 h for dorzolamide). Results of the study indicate that it is possible to develop a safe (as indicated by corneal toxicity studies) and physiologically active topical niosomal formulation of acetazolamide relative in efficiency to the newer local carbonic anhydrase inhibitor, dorzolamide. The developed formulations can form a cost effective treatment plan, which is especially important in the treatment of glaucoma, a chronic ailment affecting middle-aged to old patients.

Reaction Products of γ-Tocopherol with (E)-4-Oxo-2-nonenal in Acidic Acetonitrile

gamma-Tocopherol was reacted with (E)-4-oxo-2-nonenal (ONE) at 37 degrees C in an acidic acetonitrile solution. The reaction products were isolated by reversed-phase high-performance liquid chromatography and their structures were characterized to be 5-substituted gamma-tocopherols: 5-(1-(furan-2-yl)pentyl)-gamma-tocopherol (1), 3-(1-butyl-4,5,7-trimethyl-7-(4,8,12-trimethyltridecyl)-8,9-dihydro-7H-furo[3,2-f]chromen-2yl)propanal (2), and 1-(1-butyl-4,5,7-trimethyl-7-(4,8,12-trimethyltridecyl)-8,9-dihydro-7H-furo[3,2-f]chromen-2-yl)-4-(furan-2-yl)octan-3-one (3). Compound 1 was the predominant product under the mild acidic conditions, whereas compounds 2 and 3 were relatively stable and accumulated during the reaction. Compound 1 was detected as the product when gamma-tocopherol and ONE were incubated in methyl linoleate in the presence of dicetyl phosphate. The results indicate that gamma-tocopherol may trap ONE under acidic conditions of lipid peroxidation.

Fatty alcohols or fatty acids as niosomal hybrid carrier: Effect on vesicle size, encapsulation efficiency and in vitro dye release

Niosomal hybrid mixtures are prepared with bilayer stabilizer cholesterol from non-ionic surfactants span 20 (HLB value 8.6), span 60 (HLB 4.7) and span 85 (HLB 1.8) in presence of dicetyl phosphate (DCP) where fatty acids or fatty alcohols (C14, C16 and C18) are used as carrier. Hybrid mixtures upon hydration with aqueous phosphate buffer (pH 7.4) spontaneously produce vesicular phase which can encapsulate 5(6)-carboxyfluorescein (CF). Effect of fatty alcohols and fatty acids on the vesicle size has been studied by dynamic light scattering (DLS), freeze-fracture scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Release rates of CF from vesicular suspensions are found to be dependent on carriers as well as surfactants used. Fatty acid coated hybrids form large multilamellar vesicles (LMV) (size range 10–15 μm) where as fatty alcohol coated hybrid systems form small multilamellar vesicles (SMV) with an average diameter of 400 nm, in all cases vesicles are polydisperse (PI ∼ 0.9) in nature.

Electrochemical determination of acetaminophen using a glassy carbon electrode coated with a single-wall carbon nanotube-dicetyl phosphate film

Single-wall carbon nanotubes (SWNT) were dispersed into water in the presence of dicetyl phosphate (DCP), and then a SWNT-DCP film-coated glassy carbon electrode (GCE) was constructed. The electrochemical behavior of acetaminophen at bare GCE and SWNT-DCP modified GCE were compared, suggesting that the SWNT-DCP-modified GCE significantly enhances the oxidation peak current of acetaminophen. A sensitive and simple electrochemical method with a good linear relationship in the range of 1.0 × 10−7–2.0 × 10−5 mol L−1, was developed for the determination of acetaminophen. The detection limit is 4.0 × 10−8 mol L−1 for 3-min accumulation. This method was successfully demonstrated with tablets.

Voltammetric determination of 2-chlorophenol using a glassy carbon electrode coated with multi-wall carbon nanotube-dicetyl phosphate film

Multi-wall carbon nanotubes (MWNT) were dispersed into water in the presence of dicetyl phosphate (DCP), and MWNT-DCP composite film coated glassy carbon electrodes (GCE) were constructed. The electrochemical properties of 2-chlorophenol at a bare GCE and MWNT-DCP modified GCE were compared. It was found that MWNT-DCP modified GCEs significantly enhance the oxidation peak current of 2-chlorophenol and lowers its oxidation overpotential, suggesting great potential in the sensitive determination of 2-chlorophenol. Finally, a sensitive and simple voltammetric method was developed for the determination of 2-chlorophenol. The oxidation peak current increases linearly with the concentration in the range of 1.0 × 10−7–2.0 × 10−5 mol L−1, and the detection limit is 4.0 × 10−8 mol L−1 for 2 min accumulation. The method was successfully used to determine 2-chlorophenol in waste water samples.

Fabrication of a single-walled carbon nanotube-modified glassy carbon electrode and its application in the electrochemical determination of epirubicin

In the presence of dicetyl phosphate (DCP), a kind of surfactant with two long carbon–hydrogen chains, insoluble single-walled carbon nanotube (SWNT) was successfully dispersed into water. A uniform and very stable SWNT–DCP aqueous suspension was achieved, and then a SWNT-film-modified glassy carbon electrode (GCE) was easily fabricated via water-evaporation. The SWNT-modified GCE was characterized and its application in the electrochemical determination of epirubicin was described.

Lidocaine-loaded non-ionic surfactant vesicles: characterization and in vitro permeation studies

Our research on topical application of lidocaine-loaded non-ionic surfactant vesicles (NSVs) was prompted by the great interest on new delivery systems for local anaesthetics. This study is focused on a novel formulation of NSVs entrapping lidocaine in the form of a free base (LID) and a hydrochloride (LIDHCl). NSVs were prepared from polyoxyethylene sorbitan monolaurate (Tween20™) and cholesterol. The effect of vesicle composition and environmental pH condition (8.6–5.5) on drug encapsulation efficiency (e.e.) was investigated. Experimental strategies involved: freeze-fracture, microscopy technique, dynamic light scattering, permeation through Silastic™ and mouse abdominal skin, in vitro release kinetics of vesicle-entrapped drugs, fluorescence quenching analyses. Diffusion experiments showed that the flux of charged lidocaine through Silastic™ membrane was possible only after the vesicle encapsulation. Permeation through mouse abdominal skin of LIDHCl loaded vesicles showed a higher flux and a shorter lag time with respect to classical liposome formulations, while LID permeation rate was quite similar for NSV and liposome formulations. Vesicles were also prepared in the presence of dicetylphosphate (DCP) and N-cetylpyridinium chloride (CP) to obtain negatively and positively charged vesicles respectively, but in this case the e.e. of the drug was negligible. The possible reason of the remarkable lower e.e. observed with charged vesicles was investigated by means of fluorescence quenching experiments.

Structural Analysis of the Protein/Lipid Complexes Associated with Pore Formation by the Bacterial Toxin Pneumolysin

Pneumolysin, a major virulence factor of the human pathogen Streptococcus pneumoniae, is a soluble protein that disrupts cholesterol-containing membranes of cells by forming ring-shaped oligomers. Magic angle spinning and wideline static (31)P NMR have been used in combination with freeze-fracture electron microscopy to investigate the effect of pneumolysin on fully hydrated model membranes containing cholesterol and phosphatidylcholine and dicetyl phosphate (10:10:1 molar ratio). NMR spectra show that the interaction of pneumolysin with cholesterol-containing liposomes results in the formation of a nonbilayer phospholipid phase and vesicle aggregation. The amount of the nonbilayer phase increases with increasing protein concentration. Freeze-fracture electron microscopy indicates the coexistence of aggregated vesicles and free ring-shaped structures in the presence of pneumolysin. On the basis of their size and analysis of the NMR spectra it is concluded that the rings are pneumolysin oligomers (containing 30-50 monomers) complexed with lipid (each with 840-1400 lipids). The lifetime of the phospholipid in either bilayer-associated complexes or free pneumolysin-lipid complexes is > 15 ms. It is further concluded that the effect of pneumolysin on lipid membranes is a complex combination of pore formation within the bilayer, extraction of lipid into free oligomeric complexes, aggregation and fusion of liposomes, and the destabilization of membranes leading to formation of small vesicles.

Toxic effects of antileishmanial reverse-phase evaporation liposomes containing dicetyl phosphate in monkeys

AbstractLiposomes containing or lacking encapsulated pen-tavalent antimony (Sb), a widely used antileishmanial agent, were administered to cynomolgous monkeys to investigate possible toxicity. The liposomes consisted of either reverse-phase evaporation vesicles (REV) composed of dipalmitoyl phosphatidylcholine, choles- terol (CHOL), and dicetyl phosphate (DCP) or mul- tilamellar vesicles (MLV) composed of dimyristoyl phosphatidylcholine and dimyristoyl phosphatidylglycerol, with or without CHOL. Toxicity was observed in monkeys receiving REV containing or lacking Sb as evidenced by thrombocytopenia, splenomegaly, and hemorrhage. The severity of the symptoms was potentiated by two factors, the presence of Sb in REV and the frequency of REV administration. In contrast, no significant adverse reactions were observed in animals treated with MLV containing or lacking Sb. Since the main difference between REV and MLV was the presence of DCP in REV, this observation suggested that toxicity was due, at least part...

Influence of dicarboxylic phosphatidylcholines on phosphatidylcholine liposomes as revealed by gel chromatography and electron microscopy

The effect of dicarboxylic phosphatidylcholines (glutarylphosphatidylcholine) on the structural changes of phosphatidylcholine liposomes is examined by using multilamellar liposomes prepared with egg phosphatidylcholine or dipalmitoylphosphatidylcholine and by varying the surface charge by addition of dicetyl phosphate. Investigations are performed by gel chromatography and electron microscopy. Glutarylphosphatidylcholine is in micellar form (rod-like micelles or globular micelles). The structures obtained depend on the fatty acid saturation of liposomes and on the charge of liposome (addition or not of dicetyl phosphate). With egg phosphatidylcholine/glutarylphosphatidylcholine dispersions, an aspect more similar to myelinic figures than liposomes is observed, while in the presence of dicetyl phosphate, liposomes similar to control egg phosphatidylcholine liposomes are obtained. Gel chromatography on Sepharose 4B and turbidity measurements prove that dicetyl phosphate increases the stability of egg phosphatidylcholine/glutarylphosphatidylcholine mixtures. On the other hand, in dipalmitoylphosphatidylcholine/glutarylphosphatidylcholine dispersions, incorporation of dicetyl phosphate destabilizes bilayer structure and the formation of mixed micelles occurs. Viscosity measurement shows, in the presence of dicetyl phosphate, an increased fluidity for dipalmitoylphosphatidylcholine/glutarylphosphatidylcholine dispersions, in agreement with the micellar organization. These data confirm that the disorganization of liposomal membranes by dicarboxylic phosphatidylcholine depends on the fatty acid composition of phosphatidylcholine and on the presence of dicetyl phosphate.

Influence of dicarboxylic phosphatidylcholines on the stability and phase transition of phosphatidylcholine liposomes

The effect of dicarboxylic phosphatidylcholines (glutaryl phosphatidylcholine) on the stability and phase transition of phosphatidylcholine liposomes is examined by using liposomes prepared with egg phosphatidylcholine or dipalmitoyl phosphatidylcholine and by varying the surface charge by addition of dicetyl phosphate. Light-scattering and osmotic behaviour studies showed that the stability of liposomes containing dicarboxylic phosphatidylcholine is influenced by the charge and the fatty acid saturation of the liposomes. Increasing the glutaryl phosphatidylcholine-to-phosphatidylcholine molar ratio in liposomes caused the formation of mixed glutaryl phosphatidylcholine/phosphatidylcholine micelles. The sensitivity of the lipid bilayers towards glutaryl phosphatidylcholine action increases with the fatty acid saturation of liposomes. Dipalmitoyl phosphatidylcholine liposomes are most sensitive to the dicarboxylic phosphatidylcholine effect. Dicetyl phosphate addition enhances the solubilization of liposomes prepared from saturated phospholipids. The effect of increasing concentrations of glutaryl phosphatidylcholine on the gel-to-liquid crystal thermal transition of dipalmitoyl phosphatidylcholine was observed. Glutaryl phosphatidylcholine modifies the thermal phase transition of the constituents of the liposome. The presence of dicetyl phosphate in liposomes affects the phase transition temperature of these liposomes. It is suggested that the formation of the mixed micelles is responsible for the phase transition modifications. These data show that the solubilization of liposomes by dicarboxylic phosphatidylcholines depends on the fatty acid composition of phosphatidylcholine and on the presence of dicetyl phosphate.

Interaction of liposomes with polymorphonuclear leukocytes: I. Studies on the mode of interaction

Summary Amphipathic long chain anions (dicetylphosphate) or cations (stearylamine) were inserted into the lipid lamellae of multilayered lecithin-cholesterol liposomes so as to obtain liposomes with varying surface charge. These liposomes were then analysed with respect to their interaction with polymorphonuclear leukocytes (PMN cells) at 37°C. The different liposomes showed different tendencies to associate to the cells: the more negatively charged, the greater the tendency to associate. The association was insensitive to metabolic inhibitors and proceeded without activation of the hexose monophosphate shunt. It was not influenced by omitting divalent cations from the medium. However, lowering the temperature below 30°C and further down inhibited the association. The kinetics of the association process suggests that the presence of dicetylphosphate on the liposome surface increased the maximal rate of association, whereas lowering the temperature decreased the accessibility to appropriate receptor sites in the PMN cell membrane. The results lend support to the hypothesis that controlled manipulations of the liposome composition may be used to engineer the introduction of lipids into PMN cells by different rates and mechanisms. This should have relevance to the possible modification of PMN cell behavior by introduction of components derived from liposomes.

Dynamics of the Hydrocarbon Layer in Liposomes of Lecithin and Sphingomyelin Containing Dicetylphosphate

Physical properties of the hydrocarbon region in lipid bilayers were studied in a series of liposomes of lecithin and sphingomyelin containing different concentrations of dicetylphosphate. The technique used was described previously and is based on fluorescence polarization analysis of a specific probe embedded in the analyzed region. The two probes employed in this study were perylene and 1,6-diphenyl-1,3,5-hexatriene, which simulate a rotating disc and a rotating rod, respectively. The determined dynamic properties of the hydrocarbon region in the lecithin liposomes differ markedly from those of the sphingomyelin liposomes. The hydrocarbon region of the lecithin liposomes is of an invariant phase between 0° and 60° characterized by a microviscosity at 25°, η (25°), of 0.8 ± 0.1 poise and a fusion activation energy, ΔE, of 8 ± 2 Cal per mole. In contradistinction to lecithin, the hydrocarbon region of the sphingomyelin liposomes displays a distinct phase transition at 32° ± 2°. The phase at temperatures above the transition point, presumably a liquid crystalline phase, is characterized by ΔE = 16 ± 4 Cal per mole, whereas the phase below it, presumably a gel state, possesses a ΔE value lower than 3 Cal per mole. In addition to that, the·hydrocarbon layer in sphingomyelin liposomes is much more viscous than in lecithin liposomes as shown by η (25°) = 6 ± 1 poise. All of the above characteristics are only slightly and irregularly affected by the presence of dicetylphosphate, despite the strong effects it exerts on the surface charge potential of the liposomes. This indicates that the forces which dictate the dynamic properties of the hydrocarbon region in lipid bilayers predominantly originate from hydrophobic interactions.

Enzymic hydrolysis of various lecithin monolayers employing surface pressure and potential technique

Enzymic hydrolysis of dipalmitoyl, egg, soybean, and dioleoyl lecithin monolayers was studied by measuring the changes in surface pressure (π) and surface potential (Δ V) upon injection of snake venom ( Naja Naja) into the subsolution. The presence of Ca ++, which could not be substituted by Mg ++, Sr ++, or Ba ++, was essential for hydrolysis. Thin layer chromatography of monolayers removed after injection of venom into the subsolution showed that the snake venom indeed hydrolyzed lecithin monolayers into lysolecithin and free fatty acid. The rates of hydrolysis of different lecithins were in the order: dioleoyl lecithin > soybean lecithin > egg lecithin > dipalmitoyl lecithin, which is also the order of their molecular areas and hence their intermolecular spacings in monolayers. The solubility of lysolecithin molecules in the subsolution depends upon the chain length and unsaturation of the fatty acyl chains, which affects the changes in Δ V and π upon hydrolysis. The presence of citrate buffer or chelating agents with excess of Ca ++ in the subsolution increased the rate of hydrolysis by decreasing the binding of Ca ++ to lecithin monolayers. The hydrolysis of egg lecithin monolayers on different buffers was in the order, tris > veronal > collidine; which is the reverse of that found in the bulk reaction. Curves of π -area and Δ V - area of egg lecithin on these buffers indicated penetration of veronal and collidine ions into monolayers; this prevents the formation of the enzyme-substrate complex at the surface. In bulk reactions, these buffer ions act as lipid dispersants increasing the lipid/water interfacial area and consequently increase the rate of hydrolysis. Anionic, cationic, and neutral spacer molecules (15 mole %) were introduced in egg lecithin monolayers. The rate of hydrolysis increased in the presence of eicosanyl trimethylammonium, decreased in the presence of dicetyl phosphate or dipalmitin, and remained unchanged in the presence of cholesterol, indicating the importance of surface charge and state of the monolayer.