Structures and Properties of Self-Assembled Phospholipids in Excess Water
E. Nigel Harris, Thomas Exner, Graham R. V. Hughes, Ronald A. Asherson in Phospholipid-Binding Antibodies, 2020
If two phospholipids, which are nearly identical in size and shape, are mixed then the two component lipids will be completely miscible over the entire composition range in both the gel- and liquid-crystalline phases. This two-component binary system containing various molar ratios of the mixtures will exhibit calorimetrically a single-endothermic phase transition, corresponding to the gel to liquid-crystalline phase transition. The transition curves for the mixtures are slightly broadened in comparison with those of the pure component lipids. Each curve, however, has characteristic onset and completion temperatures positioned at the beginning and ending of the transition curve, respectively. These characteristic temperatures can be determined by the extrapolation of the maximal peak slopes from the two sides of the phase transition curve with the baseline. The phase diagram is constructed by plotting the onset and completion temperatures, after proper correction for the finite width of the transition curves of the pure components, as a function of the relative concentration of the higher melting component; these onset and completion temperature points then define the solidus and liquidus curve, respectively, in the temperature-composition binary phase diagram.
Lipopolysaccharide Preparations in Aqueous Media: Implications for Solution Versus Suspension
Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison in Endotoxin in Health and Disease, 2020
This built-in asymmetry of LPS is characteristic of much simpler lipids, soaps, detergents, and cationic surfactants, which have been studied extensively (13–18). The basic asymmetry allows lipid monomers to be interfacially active. They pack in a bewildering variety of organized and self-assembled structures such as micelles, vesicles, and a large number of mesophases (15,17,18). To give an example, the phase diagram of a simple two-component system of sodium palmitate and water has been determined at various compositions and temperatures (18,19). It showed more than a dozen different two-phase regions along with a single-phase liquid region. If a simple compound like sodium palmitate can yield numerous phases, we can expect an even greater variety of aggregate structures to exist in the more complex LPS-water two-phase system.
Electron Microscopy in Lung Research
Joan Gil in Models of Lung Disease, 2020
The critical temperature of a fluid is the temperature above which no amount of pressure will maintain it in the liquid phase (Cohen et al., 1968). By warming a liquid under high pressure through its critical temperature, it is converted to gas. When the phase transition takes place at the critical point in the phase diagram, there is no surface tension between gas and liquid to distort the specimen. Critical point drying is carried out in a pressure chamber and a fluid with critical temperature close to room temperature is used for convenience. Several of the freons and liquid CO2 give satisfactory results, but owing to environmental concerns about the release of freons into the atmosphere, CO2 with a critical temperature of 45° is the fluid of choice. Many types of commercial apparatus are available and their manufacturers provide detailed protocols for their use.
Ganoderic acid loaded nano-lipidic carriers improvise treatment of hepatocellular carcinoma
Published in Drug Delivery, 2019
Mahfoozur Rahman, Shareefa Abdullah Al-Ghamdi, Khalid S Alharbi, Sarwar Beg, Kalicharan Sharma, Firoz Anwar, Fahad A Al-Abbasi, Vikas Kumar
The phase diagram was constructed as per the method of (Kumar et al., 2016). The lipid ratio composition of solid lipid (Cap MCM C10), liquid lipid (Capmul PG8) was 3:1. Tween 80 and PL-90G were used as surfactant and co-surfactants mixtures (Smix) in ethanol in various ratio with distilled water as aqueous phase. Furthermore, the weight amounts of Smix and the lipid mixtures were heated at same temperature. Microemulsion (ME) regions was obtained at 60 °C with fixed amount of Smix and lipid mixtures (i.e. 10:0–0:10 w/w) with further titration with aqueous phase to obtain a transparent titrated mixture. This titration was continued until turbidity was observed or vice versa. Whereas in the back titration, Smix was added in aqueous phase and titrated with lipid mixtures, for rest above procedure was followed. Overall, after obtaining resultant quantities of titrants and aqueous ratio, the weight percent was determined coinciding with boundary points in Gibbs phase triangle (Amarji et al., 2015; Kumar et al., 2016).
Solid self nano-emulsifying system for the enhancement of dissolution and bioavailability of Prasugrel HCl: in vitro and in vivo studies
Published in Pharmaceutical Development and Technology, 2021
Mai Khanfar, Suhair Al-Nimry, Shatha Attar
Depending on the solubility study, Kolliphor EL as surfactant, Maisine 35-1 as oil, and Transcutol P as co-surfactant were selected to prepare the SEDDS. A series of SEDDS preparations in different ratios were formulated. Kolliphor EL and Transcutol P (the surfactant–co-surfactant mixture Smix) were blended in the following ratios (0.25:1, 0.3:1, 0.5:1, 1:1, 2:1, 3:1, and 4:1 w/w). Volumes of each surfactant and cosurfactant mixture (Smix) were blended with the oil phase (Maisine 35-1) in the ratios of (1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, and 9:1) then water was added in a drop-wise manner to each lipid–Smix mixture under gentle shaking at 37 °C. After equilibrium, the emulsions were visually assessed for translucence, droplet size/distribution, and zeta-potential. The amounts of water, oil, surfactant, and cosurfactant to make a clear emulsion were recorded and calculated. The pseudo-ternary phase diagrams were mapped with (Microsoft excel). The microemulsion region in the diagrams were plotted and the wider region indicated the better self-micro-emulsification efficiency.
Repurposing ibuprofen-loaded microemulsion for the management of Alzheimer’s disease: evidence of potential intranasal brain targeting
Published in Drug Delivery, 2021
Ming Ming Wen, Noha Ismail Khamis Ismail, Maha M. A. Nasra, Amal Hassan El-Kamel
The selected oils, surfactants, and co-surfactants, according to the solubility studies were grouped in eight combinations and the phase diagrams constructed (SigmaPlot 14.5, Systat Software, Inc., San Jose, CA, USA) to indicate the stable area of the ME. To identify the limits of the one phase domain, a pseudoternary phase diagram was constructed with three axes representing aqueous, oil phase, and the mixture of surfactant and co-surfactant (Smix). The compositions of all studied pseudo ternary phase diagrams were presented in Table 1. In each formulation, a series of nine mixtures based on oil: Smix volume ratios (1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, and 9:1) were prepared for the initial determination of ME phase areas. Extra points were also made to define the boundaries of phases when constructing the phase diagrams. Once the ME region was identified in each phase diagram, the largest ME areas with good physical stability were selected. Finally, a point in the middle of the ME region was identified for further characterization studies.
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