An in vitro skin penetration model for compromised skin: estimating penetration of polyethylene glycol [¹⁴C]-PEG-7 phosphate.

Background/aims: Establishing dermal penetration rates is important to better understand the safety of topically applied materials, especially for premature infant skin with compromised skin barrier function. Skin prematurity involves thinner stratum corneum and underdeveloped epidermis/dermis resulting in decreased barrier function, higher transepidermal water loss and greater chemical penetration, when compared to healthy full-term neonate/adult skin.

Methods: We developed an in vitro skin penetration model using human ex vivo skin to estimate penetration for premature/compromised skin barrier conditions by tape stripping.

Effect of essential oils, hydrating agents, and ethanol on hair removal efficiency of thioglycolates.

Background: The required time for hair removal by chemical depilatories has always been a concern and depends on different parameters including permeation into the hair shaft.

Objectives: In an attempt to improve this process, it was decided here to investigate the possibility of decreasing depilation time of thioglycolates, widely used depilatories, using penetration enhancers.

Methods: Urea, sodium dodecyl sulfate, dimethylsulfoxide (DMSO), ethanol (75 and 96%), NaCl, and peppermint and orange oils were used as penetration enhancers, and their effect on depilatory time of thioglycolates, represented as tear resistance time (TRT) of hair shaft under a constant tensile stress, was studied.

Measuring human skin buffering capacity: an in vitro model.

Background/purpose: It has been thought that skin possesses buffering capacity. This study measured the skin buffering capacity against two model solutions of acid and base at three concentrations with an in vitro system.

Methods: Ten microliters of model base (sodium hydroxide--NaOH) and acid (hydrochloric acid--HCl) solutions at concentrations of 0.

Measuring transepidermal water loss: a comparative in vivo study of condenser-chamber, unventilated-chamber and open-chamber systems.

Background/aims: Two main systems have been utilized for measuring transepidermal water loss (TEWL): open chamber and closed chamber. Yet, further validation and standardization studies may be necessary to reveal the sensitivity, precision, and robustness of these instruments.

Methods: Three instruments are compared for their applicability to assess TEWL: unventilated chamber, open chamber and condenser chamber.

Correlating percutaneous absorption with physicochemical parameters in vivo in man: agricultural, steroid, and other organic compounds.

In vitro data are currently used to predict cutaneous chemical exposure based on physicochemical parameters. However, this in vitro data may not sufficiently account for what occurs in vivo. Previously, we modeled (via multivariate analysis) percutaneous absorption with physicochemical parameters using in vivo human transdermal patch-based data.

Estimating skin permeability from physicochemical characteristics of drugs: a comparison between conventional models and an in vivo-based approach.

This study evaluates the correlation of some widely used skin permeability predictive models with a recently proposed empirical model based on human in vivo dermatopharmacokinetic data. Drug fluxes through the skin have been calculated using in vitro- and in vivo-based models, and observed in vivo data, and the values compared. Most in vitro-based models underestimate the in vivo data by 1-100-fold.

Comparison of tissue viability imaging and colorimetry: skin blanching.

Background: Operator-independent assessment of skin blanching is important in the development and evaluation of topically applied steroids. Spectroscopic instruments based on hand-held probes, however, include elements of operator dependence such as difference in applied pressure and probe misalignment, while laser Doppler-based methods are better suited for demonstration of skin vasodilatation than for vasoconstriction.

Objective: To demonstrate the potential of the emerging technology of Tissue Viability Imaging (TiVi) in the objective and operator-independent assessment of skin blanching.

Tissue viability imaging: mapping skin erythema.

Background: Tissue Viability Imaging (TiVi) is an emerging bioengineering technology intended for two-dimensional mapping of skin erythema and blanching. Before TiVi can be effectively used in studies of diseased or damaged skin, the variability in normal skin red blood cell concentration (RBC(conc)) requires evaluation.

Objective: To demonstrate how TiVi maps spatial and temporal variations in normal skin RBC(conc) at the dorsal side of the hand at rest and during post-occlusive hyperemia.

Cutaneous bioengineering instrumentation standardization: the Tissue Viability Imager.

Background: Tissue Viability Imaging (TiVi) is a new bioengineering technology intended for remote two-dimensional mapping of skin red blood cell concentration (RBC(conc)). Before use in the laboratory, work-site and dermatology clinic, critical performance parameters of this emerging technology require careful evaluation.

Objective: To assess short- and long-term stability, image uniformity, distance and image size dependence, ambient light and curvature influence in a production batch of Tissue Viability Imagers.

Transdermal drug pharmacokinetics in man: Interindividual variability and partial prediction.

A database of human dermatopharmacokinetic parameters of 12 transdermal patches is established. The effect of system design, application site, and metabolism on pharmacokinetic data is discussed, and interindividual variability of data and its possible sources evaluated. Using multiple regression analysis, two equations based on drugs physicochemical characteristics are suggested for partial prediction of peak plasma concentration (C(max)) after patch application.