Electrorheological Effects in Lecithin Organogels with Water and Glycerol

Propolis organogel as a novel topical delivery system for treating wounds

CONTEXT

Propolis has traditionally been used in curing infections and healing wounds and burns.

OBJECTIVE

The aim of this study is to formulate pluronic lecithin organogel of propolis to improve its availability and antimicrobial activity.

MATERIALS AND METHODS

Different organogels were prepared by using soybean lecithin, isopropyl palmitate, pluronic F127 and water. The effect of quantity of lecithin and pluronic F127 and percentage of oil phase was investigated. The organogels were evaluated for appearance, texture, pH, drug content and viscosity. In vitro release studies were carried out using cellophane membrane. Drug permeation through abdominal rat skin from organogels that showed high % drug release was compared to that from propolis suspension in distilled water. Finally, the antimicrobial activity of the selected propolis formulation against different bacterial isolates was compared with that of propolis suspension in water.

RESULTS AND DISCUSSION

Results showed that all organogel formulations except the formula containing 10% pluronic F127, showed acceptable physical properties. Drug content of organogel formulations was in the range of 97.5-100.2%. The pH of the formulations was in the range of 5.5-6.3 that suits the skin pH, indicating skin compatibility. The viscosity was in the range of 5366-8984 cp. A significant decrease in drug release from formulations was observed with increase in concentration of lecithin and pluronic F127. Decreasing oil phase percentage to 20% w/w led to a decrease in drug release from the formulation.

CONCLUSION

The formula containing 3% lecithin and 20% pluronic F127 exhibited superior skin permeation and antimicrobial activity over propolis suspension in water.

Preparation and evaluation of tubular micelles of pluronic lecithin organogel for transdermal delivery of sumatriptan

The present work focuses on the preparation and evaluation of lecithin organogel system of thermoreversible polymer pluronic F127, which would enhance the stability and absorption of sumatriptan succinate across the skin. Formulations were developed with and without co-surfactant (pluronic F127). The prepared organogels were evaluated for its appearance, organoleptic characteristics, and feel upon application, homogeneity, occlusivenes, washability, pH, viscosity, spreadability, gel transition temperature of formulations. The formulations were also evaluated for drug content, in vitro drug diffusion properties and skin irritation testing. In vivo evaluation of formulations was carried out by hot plate and writhing test method, and finally the optimized formulation was subjected to stability studies. The developed formulations were easily washable, smooth in feel, and showed no clogging which indicate superior texture of system. Formulation, containing pluronic showed greater spreadability and higher drug diffusion rate as compared to pluronic free organogel. Drug content of organogel formulations was in the range of 94-97%. The pH of the formulations was 6.48 ± 0.5 and 6.98 ± 0.1, reflecting no risk of skin irritation. Pluronic not only enhances the stability of organogel by increasing the viscosity (from 6,541 ± 234.76 to 7,826 ± 155.65 poise) but also increases the release of drug from 67.39 ± 1.53% to 74.21 ± 1.7%. The sumatriptan exhibits higher and long lasting antinociceptive effect as indicated by the persistent increase in reaction time in hot plate and inhibited abdominal contraction in acetic acid-induced writhing test (p < 0.05). The prepared optimized formulation was found to be stable without any significant changes at room temperature.

Wormlike micelles in mixed surfactant solutions

Small micellar aggregates of some surfactants exhibit enormous growth in one dimension and form very long and flexible wormlike micelles. Depending on the nature of the surfactant, such micellar growth can be induced in different ways, for example by adding cosurfactants or salts. Above a system-dependent concentration of surfactant, these giant micelles are entangled to form a transient network, and exhibit viscoelastic behavior analogous to a flexible polymer solution. However, unlike polymers in solutions, wormlike micelles undergo breaking and recombination, and, therefore, exhibit complex rheological behavior. Information on the evolution of aggregate morphology can be obtained from rheological study. In this article formation of wormlike micelles and the evolution of rheological properties in different mixed surfactant systems is discussed. Besides, a brief overview on the salt-induced micellar growth in ionic surfactant systems and reverse micellar systems induced by adding certain polar additives has also been presented.

Electrorheological properties of PMMA-b-PSt copolymer suspensions

In this study, a block copolymer of methyl methacrylate (MMA) and styrene (St) synthesized by combined ultrasonic irradiation and reverse atom transfer radical polymerization (RATRP) processes was used. PMMA-b-PSt was partially hydrolyzed and converted to a lithium salt, PMMA-b-PSt-Li, before the electrorheological (ER) measurements carried out. Average particle diameter of PMMA-b-PSt-Li polymeric salt was determined by dynamic light scattering (DLS) as 22 mum. Suspensions of PMMA-b-PSt-Li polymeric salts were prepared in silicone oil. ER properties of PMMA-b-PSt-Li/silicone oil suspensions were studied as a function of electric field strength, dispersed phase concentration, shear rate, shear stress, temperature, frequency, and polar promoter. Further dielectric properties of PMMA-b-PSt-Li ionomer were also investigated.

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.