Lecithin Organogel with New Rheological and Scaling Behavior

Lecithin Microemulsion Lipogels Versus Conventional Gels for Skin Targeting of Terconazole: In Vitro, Ex Vivo, and In Vivo Investigation

Topical treatment of fungal infections has several superiorities over oral treatment. However, the greatest challenge for dermal delivery is the stratum corneum which is considered an effective barrier for penetration of most antifungal drugs into deeper skin layers. Terconazole (Tr), which is the first marketed triazole antifungal, was reported to be one of the most active azoles against vaginal candidiasis. Nevertheless, our work group is the first to investigate the potential of Tr in the treatment of skin mycosis via integration into lecithin microemulsion-based lipogels (LMBGs). The microemulsion regions of the investigated systems were detected through ternary phase diagrams. The in vitro characterization studies revealed promising physicochemical merits for the selected LMBGs as well as satisfactory in vitro antifungal activity. The current research work was endeavored to investigate the potential of such novel Tr-loaded LMBGs in comparison with conventional gels. Ex vivo permeation and retention studies in addition to in vivo deposition study showed a significant improvement in the permeability of Tr through animal skin from LMBGs compared to other conventional gels. Furthermore, the optimized microemulsion lipogel proved to be safe and a nonirritant to experimental animals through the acute sensitivity study and histological skin examination. Overall, lecithin-based microemulsion lipogels of different composition confirmed their potential as interesting nanocarriers for skin delivery of terconazole compared to current therapy.

Flow-induced structures observed in a viscoelastic reverse wormlike micellar system by magnetic resonance imaging and NMR velocimetry

Organogel formed by lecithin reverse wormlike micelles in the isotropic concentrated regime exhibits flow induced micro-heterogeneities detected by rheo-NMR and NMR-velocimetry.

Polymer organogelation with chitin and chitin nanocrystals

In this paper, we show that biodegradable and biocompatible organogels can be formed with chitin as the filler material and triglycerides as the continuous hydrophobic phase.

Lecithin-based nanostructured gels for skin delivery: an update on state of art and recent applications

Conventional carriers for skin delivery encounter obstacles of drug leakage, scanty permeation and low entrapment efficiency. Phospholipid nanogels have recently been recognized as prominent delivery systems to circumvent such obstacles and impart easier application. The current review provides an overview on different types of lecithin nanostructured gels, with particular emphasis on liposomal versus microemulsion gelled systems. Liposomal gels investigated encompassed classic liposomal hydrogel, modified liposomal gels (e.g. Transferosomal, Ethosomal, Pro-liposomal and Phytosomal gels), Microgel in liposomes (M-i-L) and Vesicular phospholipid gel (VPG). Microemulsion gelled systems encompassed Lecithin microemulsion-based organogels (LMBGs), Pluronic lecithin organogels (PLOs) and Lecithin-stabilized microemulsion-based hydrogels. All systems were reviewed regarding matrix composition, state of art, characterization and updated applications. Different classes of lecithin nanogels exhibited crucial impact on transdermal delivery regarding drug permeation, drug loading and stability aspects. Future perspectives of this theme issue are discussed based on current laboratory studies.

Crystalline titania nanoparticles synthesized in nonpolar Lα lecithin liquid-crystalline media in one stage at ambient conditions

High-temperature modification of titania in the form of nanoplatelets is synthesized fast in one step at ambient conditions without any additional treatment like aging or calcination. Lecithin, which is the main component of lipid matrix of biological membranes, is first used as a structure-driven template. It is demonstrated that this natural surfactant can self-organize into lamellar L(α) mesophase when small amounts of water are admixed in its solution in nonpolar solvent. The water locating mainly in lecithin polar region as hydration shell at this concentration triggers the hydrolysis-condensation reactions after the precursor addition that results in instantaneous titania formation in the form of crystalline nanoparticles. Planar lamellar sheets serve as the template specifying its crystallinity.

Gemini surfactant electrospun membranes

Our research demonstrates electrospun nonwoven fibrous scaffolds from a low molar mass gemini ammonium surfactant, N,N'-didodecyl-N,N,N',N'-tetramethyl-N,N'-ethanediyldiammonium dibromide (12-2-12). Cryogenic transmission electron microscopy (cryo-TEM) and solution rheological experiments revealed micellar morphological transitions of 12-2-12 in water and water:methanol (1:1 vol). The microstructure of 12-2-12 in water transitioned from entangled, cylindrical, threadlike micelles to branched threadlike micelles, and a viscoelastic, entangled, highly branched network of threadlike micelles with increasing concentration finally formed. In sharp contrast, the solution behavior of 12-2-12 in water:methanol produced a drastically different micellar microstructure compared to that in water, and the morphology transitioned from partitioned, globular micelles to overlapped micelles at an overlap concentration (C*) of 11 wt %. Electrospinning 12-2-12 from water did not produce fibers at any concentration; however, electrospinning 12-2-12 in water:methanol at concentrations greater than 2C* produced hydrophilic continuous fibers with diameters ranging from 0.9 to 7 microm. High surface area scaffolds with hydrophilic surfaces offer potential as charged controlled-release membranes, tissue engineering scaffolds, and coatings for biologically compatible devices.

Macroscopic properties and microstructure of HSA based organogels: sensitivity to polar additives

Organogels can be formed by a large variety of different low molecular weight gelators. In our investigations we employed 12-hydroxy stearic acid (HSA) and studied its ability to gel various organic solvents, such as dodecane, paraffin oil, triglycerides, octyl palmitate, and silicone oil. Gelation typically occurs above a concentration of 0.1-0.8 wt% and the gelation concentration is related to the polarity of the oil. In a second part we investigated the influence of polar additives which can affect the gelation process due to their polar character. By doing so we varied largely the polarity conditions under which the gelation of the HSA occurs. The macroscopic gel properties were characterised by means of oscillatory rheology experiments, differential scanning calorimetry (DSC), and optical microscopy. The microstructure of the samples was studied by means of small-angle neutron scattering (SANS). The gelation of HSA mainly depends on the availability of free acidic and hydroxy groups for the formation of H-bonds. Accordingly the elastic properties and finally the gelation process become suppressed by the addition of polar additives such as alcohols. This effect depends just on the molar ratio of added alcohol and HSA, being independent of the length of the added alcohol. Evidently the added alcohol is competing for the H-bonding with the HSA and thereby effectively destroying the H-bonding necessary for the formation of the network-forming fibres. This finding is of importance for potential applications of such molecules as rheological modifiers in oil-based systems.

Distinct Kinetic Pathways Generate Organogel Networks with Contrasting Fractality and Thixotropic Properties

The kinetics of the isothermal transformation of sols, comprised of a low molecular-mass organogelator (LMOG) and an organic liquid, to their organogel phases have been followed by circular dichroism (CD), fluorescence, small angle neutron scattering (SANS), and rheological methods. The thixotropic properties (in the sense that severe shearing followed by rest lead to reestablishment of viscoelasticity) of the gels have been examined as well by rheological measurements. The compositions of the samples were either 5alpha-cholestan-3beta-yl N-(2-naphthyl) carbamate (CNC) in an n-alkane (n-octane or n-dodecane) or 3beta-cholesteryl N-(2-naphthyl) carbamate (CeNC) in ethyl acetate. Values of Df, the mass fractal dimension of the microcrystalline self-assembled fibrillar networks (SAFINs) in the gels, have been extracted from the kinetic data using a model developed by Dickinson (J. Chem. Soc., Faraday Trans. 1997, 93, 111). The Df values, 1.1-1.3 for the CeNC gels and 1.3-1.4 or 1.6-1.8 (depending on the temperature of incubation of the sol phase) for CNC gels, are consistent with the gel network structures observed by optical microscopy. In addition, comparison of the temperature dependence of both n (the Avrami component) and K (the Avrami "rate constant") for CeNC/ethyl acetate gelation with those reported previously for gelation of CNC/n-alkane sols demonstrate that the very small change of a single bond in CNC to a double bond in CeNC causes significant differences in their gelation abilities and gel properties. The rheological measurements on CNC/n-alkane gels with spherulitic SAFIN units, formed by incubation of their sols at < or =28 degrees C, indicate that they are thixotropic. Gels with the same chemical composition but formed by incubation of their sols at > or =30 degrees C, leading to fiberlike SAFIN units, remain liquidlike after shearing regardless of the periods they are at rest. The time-dependent viscoelastic properties of the gel networks are treated according to a stretched exponential model. The observations from these studies provide detailed insights into the mechanisms of formation of molecular organogel phases and demonstrate the extreme sensitivity of the SAFINs and viscoelastic properties of such organogels to slight modifications in LMOG structure or sample history.

Lecithin organogels as a potential phospholipid-structured system for topical drug delivery: a review

The purpose of this review is to give an insight into the considerable potential of lecithin organogels (LOs) in the applications meant for topical drug delivery. LOs are clear, thermodynamically stable, viscoelastic, and biocompatible jelly-like phases, chiefly composed of hydrated phospholipids and appropriate organic liquid. These systems are currently of interest to the pharmaceutical scientist because of their structural and functional benefits. Several therapeutic agents have been formulated as LOs for their facilitated transport through topical route (for dermal or transdermal effect), with some very encouraging results. The improved topical drug delivery has mainly been attributed to the biphasic drug solubility, the desired drug partitioning, and the modification of skin barrier function by the organogel components. Being thermodynamically stable, LOs are prepared by spontaneous emulsification and therefore possess prolonged shelf life. The utility of this novel matrix as a topical vehicle has further increased owing to its very low skin irritancy potential. Varied aspects of LOs viz formation, composition, phase behavior, and characterization have been elaborated, including a general discussion on the developmental background. Besides a comprehensive update on the topical applications of lecithin organogels, the review also includes a detailed account on the mechanistics of organogelling.

Aggregated Assemblies of Sodium Dodecyl Sulfate/Dimethyldodecyl Ammoniopropane Sulfonate and Phospholipids at the Interface and in the Bulk

Interactions between the binary combinations of sodium dodecyl sulfate (SDS) or dimethyldodecylammoniopropane sulfonate (DPS) with L-alpha-phosphatidylcholine (PC), 1,2-didecanoyl-sn-glycero-3-phosphacholine (DPC), and 1,2-dipalmitoyl-sn-glycero-3-phosphacholine (PPC) at the air/water interface and in aqueous bulk were evaluated with the help of interfacial tension (gamma) and pyrene fluorescence (I(1)/I(3)) measurements by studying the aggregation processes of SDS and DPS in pure water and in the presence of 7-36 microM of each lipid. The gamma measurements suggested that the interface was mainly occupied by the surfactant monomers especially in the presence of PC and PPC, and the surfactant-PC or surfactant-PPC aggregates were mainly available in the bulk with the least surface activity. Significant surface activity was observed in the case of a surfactant-DPC complex. The fluorescence measurements showed clear onset, C(1), and completion, C(2), of a vesicles solubilization process upon incorporation of surfactant monomers into the vesicles in the presence of DPC and PPC whereas this process was not visible in the presence of PC. A comparative study of all the three lipids indicated that both PC and PPC were mainly available in the aggregated form in the bulk due to their higher hydrophobicities and, hence, were the least surface active. On the other hand, DPC with relatively lower hydrophobicity showed considerable surface activity even in the monomeric form. Among both surfactants, DPS showed stronger interactions with DPC and PPC in comparison to SDS due to its zwitterionic nature, which could easily accommodate itself into the lipid-aggregated assemblies with similar headgroup natures, and helped in reducing the interhead-group repulsions.