A comparative study of the in vitro permeation characteristic of sulphadiazine across synthetic membranes and eschar tissue

Multivariate Analytical Approaches to Identify Key Molecular Properties of Vehicles, Permeants and Membranes That Affect Permeation through Membranes

There has been considerable recent interest in employing computer models to investigate the relationship between the structure of a molecule and its dermal penetration. Molecular permeation across the epidermis has previously been demonstrated to be determined by a number of physicochemical properties, for example, the lipophilicity, molecular weight and hydrogen bonding ability of the permeant. However little attention has been paid to modeling the combined effects of permeant properties in tandem with the properties of vehicles used to deliver those permeants or to whether data obtained using synthetic membranes can be correlated with those obtained using human epidermis. This work uses Principal Components Analysis (PCA) to demonstrate that, for studies of the diffusion of three model permeants (caffeine, methyl paraben and butyl paraben) through synthetic membranes, it is the properties of the oily vehicle in which they are applied that dominated the rates of permeation and flux. Simple robust and predictive descriptor-based quantitative structure-permeability relationship (QSPR) models have been developed to support these findings by utilizing physicochemical descriptors of the oily vehicles to quantify the differences in flux and permeation of the model compounds. Interestingly, PCA showed that, for the flux of co-applied model permeants through human epidermis, the permeation of the model permeants was better described by a balance between the physicochemical properties of the vehicle and the permeant rather than being dominated solely by the vehicle properties as in the case of synthetic model membranes. The important influence of permeant solubility in the vehicle along with the solvent uptake on overall permeant diffusion into the membrane was substantiated. These results confirm that care must be taken in interpreting permeation data when synthetic membranes are employed as surrogates for human epidermis; they also demonstrate the importance of considering not only the permeant properties but also those of both vehicle and membrane when arriving at any conclusions relating to permeation data.

Polymeric micelles as cutaneous drug delivery system in normal skin and dermatological disorders

The easy accessibility of skin made dermal application, one of the approaches for local drug therapy. Effectiveness of topical drug application is depended on different parameters such as skin barrier properties, physicochemical properties of drug and vehicle, and interaction between drug and its vehicle with the skin layers. In this review, an overview of skin structure and feature of polymeric micelles as topical nanocarriers is provided. We also summarized the research studies dealing with the application of polymeric micelles for cutaneous delivery. In the past decades, numerous types of nanocarriers have been widely investigated as a novel delivery approach to improve skin penetration and localization of drugs in normal skin and dermatological diseases. Polymeric micelles are one of them, with their specific ability to encapsulate hydrophilic drugs. These carriers can enhance the therapeutic efficacy and minimize the systemic side effects of the drugs. Polymeric micelles could enhance the deposition of drugs in targeted sites of the skin in the normal and dermatological diseases such as psoriasis and acne. Nevertheless, still there is a need to investigate the mechanism of action of these carriers and the fate of polymeric micelles in skin.

Immediate tangential excision accelerates wound closure but does not reduce scarring of mid-dermal porcine burns

Current evidence supports the use of excision to remove eschar from deep dermal and full-thickness burns. However, the role of excision of mid-dermal burns remains unclear. This study aimed to develop a porcine model that could produce reproducible middermal thermal burns that undergo tangential excision; and investigate the effects of immediate tangential excision (30 minutes postburn) on healing and scarring. An aluminum bar preheated in hot water (70°C) was applied for 20 or 30 s to produce a total of sixteen mid-dermal burns per pig on each of six pigs. Thirty minutes after burn creation, half of the burns were tangentially excised. Four partial- thickness wounds per pig were created as controls. Depth of burn injury (1 and 24 h), reepithelialization (7 and 10 d) and scar depth (28 d) were assessed microscopically. Total scar surface area was grossly evaluated on day 28. Exposure of porcine skin to a preheated aluminum bar at 70 °C for 20 or 30 sec resulted in reproducible mid-dermal burns, where immediate excision enhanced complete wound closure as judged by complete re-epithelialization, but did not reduce initial depth of injury, scar contraction and scar depth. Immediate surgical intervention is sufficient to enhance wound closure, but not to mitigate mid-dermal burn scar formation. This work provides a suitable animal model to evaluate novel therapies that may be used to inhibit burn progression, accelerate wound closure and decrease scarring, especially those therapies unable to penetrate burn eschar.

Optimization of Ibuprofen Delivery through Rat Skin from Traditional and Novel Nanoemulsion Formulations

The topical delivery of non-steroidal anti-inflammatory drugs (NSAIDS) such as Ibuprofen has been explored as a potential method of avoiding the first pass effects and the gastric irritation, which may occur when used orally. Ibuprofen is formulated into many topical preparations to reduce the adverse effects and simultaneously avoid the hepatic first-pass metabolism as well. However, it is difficult to obtain an effective concentration through topical delivery of Ibuprofen due to its low skin permeability. The aim of this study was to develop two types of nanoemulsions formulations and focused on the screening of Ibuprofen-loaded nanoemulsions and evaluating the influence of these types of nanoemulsions on the skin permeability of the drug. In both nanoemulsion formulations, oil was similar, but the surfactant and co-surfactant were different. The effect of independent variables on skin permeability parameters was evaluated using full factorial design. Results demonstrate that novel formulations were more effective as skin enhancer than traditional formulation. In case of the novel formulation, any increase in percentage of surfactant and co-surfactant had increasing effect on flux (Jss). On the other hand, the proportion of surfactant/co-surfactant (S/C) demonstrated reverse correlation with Jss. While, in traditional formulations, direct correlation was found between both variables, and Jss. Comparison between two types of nanoemulsion formulations revealed that, novel formulations were more effective as topical Ibuprofen carrier in contrast to traditional type due to lower amounts of surfactant and co-surfactant and less irritating effect.