THz Time Domain Characterization of Human Skin Tissue for Nano-Electromagnetic Communication

This paper presents an experimental investigation of excised human skin tissue material parameters by THz Time Domain Spectroscopy in the band 0.1-2.5 THz. The results are used to evaluate the channel path loss Nano-electromagnetic communication. Refractive index and absorption coefficient values are evaluated for dermis layer of the human skin. Results obtained illustrate the effect of hydrated tissue on channel parameters and provide the optimum distance, which can be utilized for effective communication inside the human skin

The use of heat and chemical penetration enhancers to increase the follicular delivery of erythromycin to the skin

Copyright © 2019. Published by Elsevier B.V.The effect of heat on the follicular absorption of drugs into the skin has not previously been investigated. In comparison to drug delivery across the continuous stratum corneum (SC), follicular absorption is known to be relatively rapid and therefore the use of short durations of heat may be particularly useful for enhancing drug delivery to the hair follicles, as well as being practical for patients to use. In this study erythromycin has been used as a model drug and the combined use of heat and chemical penetration enhancers was found to be able to synergistically increase the penetration of erythromycin into human skin via the follicular route. Moreover durations of heat application as short as 10 min in combination with particular enhancer systems were found to be sufficient to significantly increase erythromycin delivery to the skin. Overall the data indicate that the use of heat with chemical penetration enhancers offers a potentially valuable strategy for delivering drugs via the follicular route.Peer reviewedFinal Accepted Versio

Metabolism of Butoxyethanol in excised human skin in vitro

Glycol ethers are widely used in industrial and household applications because their chemical and physical properties make them versatile solvents, miscible with both water and organic media. Due to the ease with which the glycol ethers are absorbed through the skin and the potential for development of adverse health effects it is important to understand the extent to which local metabolism can contribute to local and systemic toxicity. Sections of previously frozen, full thickness excised human skin samples were placed on transwell supports and placed with the underside of the skin in contact with receptor fluid. The skin surface was dosed with 115.2 mg of neat butoxyethanol and the absorption and metabolism of butoxyethanol to butoxyacetic acid monitored over time. In total 64.94 ± 0.04 mg of butoxyethanol or its metabolites were removed from the surface of the skin at 24 hours, representing the equivalent of 56% of the applied dose, the equivalent of 17.5% of the applied dose was recovered from the receiver fluid, 3% from within the skin and the remaining 23.5% of the dose was lost to the atmosphere through evaporation. After 24 hours a total of 31.5 μg of butoxyacetic acid had been produced representing approximately 0.03% of the applied dose. Therefore approximately 0.16% (31.5 μg as a percentage of the total amount of butoxyethanol reaching the receiver fluid (20.17 mg) of the absorbed butoxyethanol was metabolised to butoxyacetic acid during its passage through the skin. This suggested that, although enzyme activities capable of converting butoxyethanol to butoxyacetic acid are present in skin, metabolic conversion during percutaneous absorption was small and systemic exposure to the parent compound rather than the metabolite would occur following dermal exposure to butoxyethanol. This experiment demonstrates that it is possible to maintain metabolic activity in skin samples in an in vitro set up for short, but experimentally useful, period.Peer reviewe

N-alkylamides : from plant to brain

Background: Plant N-alkylamides (NAAs) are bio-active compounds with a broad functional spectrum. In order to reach their pharmacodynamic targets, they have to overcome several barriers of the body in the absorption phase. The permeability kinetics of spilanthol (a diene NAA) and pellitorine (a triene NAA) across these barriers (i.e. skin, oral/gut mucosa, blood-brain barrier) were investigated. Methods: The skin and oral mucosa permeability were investigated using human skin and pig mucosa in an ex vivo in vitro Franz diffusion cell set-up. The gut absorption characteristics were examined using the in vitro Caco-2 cell monolayer test system. The initial blood-brain barrier transport kinetics were investigated in an in vivo mice model using multiple time regression and efflux experiments. Quantification of both NAAs was conducted using HPLC-UV and bio-analytical UPLC-MS methods. Results: We demonstrated that spilanthol and pellitorine are able to penetrate the skin after topical administration. It is likely that spilanthol and pellitorine can pass the endothelial gut as they easily pass the Caco-2 cells in the monolayer model. It has been shown that spilanthol also crosses the oral mucosa as well as the blood-brain barrier. Conclusion: It was demonstrated that NAAs pass various physiological barriers i.e. the skin, oral and gut mucosa, and after having reached the systemic circulation, also the blood-brain barrier. As such, NAAs are cosmenutriceuticals which can be active in the brain

The influence of water mixtures on the dermal absorption of glycol ethers

Original article can be found at: http://www.sciencedirect.com/science/journal/0041008X Copyright Elsevier Inc. DOI: 10.1016/j.taap.2006.09.019Glycol ethers are solvents widely used alone and as mixtures in industrial and household products. Some glycol ethers have been shown to have a range of toxic effects in humans following absorption and metabolism to their aldehyde and acid metabolites. This study assessed the influence of water mixtures on the dermal absorption of butoxyethanol and ethoxyethanol in vitro through human skin. Butoxyethanol penetrated human skin up to sixfold more rapidly from aqueous solution (50%, 450 mg/ml) than from the neat solvent. Similarly penetration of ethoxyethanol was increased threefold in the presence of water (50%, 697 mg/ml). There was a corresponding increase in apparent permeability coefficient as the glycol ether concentration in water decreased. The maximum penetration rate of water also increased in the presence of both glycol ethers. Absorption through a synthetic membrane obeyed Fick's Law and absorption through rat skin showed a similar profile to human skin but with a lesser effect. The mechanisms for this phenomenon involves disruption of the stratum corneum lipid bilayer by desiccation by neat glycol ether micelles, hydration with water mixtures and the physicochemical properties of the glycol ether–water mixtures. Full elucidation of the profile of absorption of glycol ethers from mixtures is required for risk assessment of dermal exposure. This work supports the view that risk assessments for dermal contact scenarios should ideally be based on absorption data obtained for the relevant formulation or mixture and exposure scenario and that absorption derived from permeability coefficients may be inappropriate for water-miscible solvents.Peer reviewe

Giant microwave absorption in fine powders of superconductors

Enhanced microwave absorption, larger than that in the normal state, is observed in fine grains of type-II superconductors (MgB$_2$ and K$_3$C$_{60}$) for magnetic fields as small as a few $\%$ of the upper critical field. The effect is predicted by the theory of vortex motion in type-II superconductors, however its direct observation has been elusive due to skin-depth limitations; conventional microwave absorption studies employ larger samples where the microwave magnetic field exclusion significantly lowers the absorption. We show that the enhancement is observable in grains smaller than the penetration depth. A quantitative analysis on K$_3$C$_{60}$ in the framework of the Coffey--Clem (CC) theory explains well the temperature dependence of the microwave absorption and also allows to determine the vortex pinning force constant

Near-infrared parameters extraction: A potential method to detect skin cancer

The wavelength-dependent absorption coefficients can be used to analyse optical properties of human skin. Existing absorption models for narrow ranges in the visible and near infrared are insufficient to simultaneously incorporate the spectral contrast produced by differences in chromophores, water and lipid content of skin tissue into skin cancer detection. In the broad range up to 1600 nm, recent analysis approaches for absorption spectra do not consistently provide significant differences between healthy and cancerous skins. We propose an absorption model to fit the absorption coefficient spectra of skin samples over the range from 400 nm to 1600 nm and an advanced algorithm to find the optimal estimation. The extracted parameters of this model are analysed by a statistical t-test. The test results demonstrate the significant differences between all pairs of tumour-normal skin. Therefore, our approach has strong potential for early skin cancer detection using near infrared spectroscopy (NIRS). © 2013 IEEE

Further studies of the efficacy of military, commercial and novel skin decontaminants against the chemical warfare agents sulphur mustard, soman and VX

Background/Aims: Following an incident involving toxic chemicals, deployment of countermeasures before the arrival of specialised services at the scene may provide a “therapeutic” window in which to mitigate skin absorption. Methods: Five potential candidates (itaconic acid, N,N′-methylenebisacrylamide, 2-trifluoromethylacrylic acid, fuller's earth and Fast-Act®) previously found effective against a simulant (methyl salicylate) were evaluated against a 10 μL droplet of 14C-sulphur mustard (HD), soman (GD) or VX applied to the surface of porcine skin mounted on static skin diffusion cells. Results: All the decontaminants applied to the skin 5 min post exposure achieved a marked reduction in the amount of 14C contaminant remaining within the skin at 24 h. Itaconic acid significantly (p <.05) reduced the amount of 14C-HD, GD and VX remaining in the skin at 24 h. Additionally, 2-trifluoromethylacrylic acid significantly reduced the amount of 14C-HD, whilst fuller's earth significantly reduced the amounts of 14C-HD and VX recovered within the skin at 24 h. Conclusion: All of the products evaluated in this study performed well in reducing the dermal absorption of all the chemical warfare agents tested.Peer reviewe