Follicular pathway role in chemical warfare simulants percutaneous penetration.

Chemical warfare (CW) exposure could be fatal to military and civilians through skin contamination. Our work and others focus on investigating stratum corneum reservoir with less regards to skin appendageal routes including hair follicles. Here, C-14 CW simulants (CWS) with specific activity of 0.1 mCi/ml were tested on abdominal and scalp human cadaver skin using flow-through diffusion system. Quantitative analysis of simulants in skin compartments were performed using scintillation counter. Scalp permeation of dipropylene glycol monomethyl ether (DPGME), diisopropyl methylphosphonate (DIMP) and methyl salicylate (MeS) exceed abdominal skin by 8%, 15%, and 6% (p value < 0.05) of applied dose, respectively. DPGME and DIMP (most hydrophilic) showed earlier permeation peak time (Tmax) through scalp skin at 2 and 4 h, respectively, comparing with 6 h with abdominal skin. The percentage of applied dose of DPGME and DIMP retained in human skin membrane (SC, epidermis, and viable dermis) showed no statistically significant difference between tested abdominal and scalp skin samples (p value >0.05). The percentage of applied dose of MeS in scalp showed higher partitioning in stratum corneum and viable epidermis than abdominal skin (p value <0.05). In conclusion, human scalp showed greater total skin absorption than abdominal skin. This work points to a qualitative importance of high follicular density body regions in percutaneous penetration and suggests that transfollicular pathway might have a significant role in early stage permeation of chemical warfare simulants. However, the difference noticed here between scalp and abdominal skin could be attributed to regional variability in anatomy, physiology, and barrier characteristics.

Binding affinity and decontamination of dermal decontamination gel to model chemical warfare agent simulants.

Six chemical warfare agent simulants (trimethyl phosphate, dimethyl adipate, 2-chloroethyl methyl sulfide, diethyl adipate, chloroethyl phenyl sulfide and diethyl sebacate) were studied in in vitro human skin to explore relationship between dermal penetration/absorption and the mechanisms of simulant partitioning between stratum corneum (SC) and water as well as between dermal decontamination gel (DDGel) and water. Both binding affinity to and decontamination of simulants using DDGel were studied. Partition coefficients of six simulants between SC and water (Log PSC/w ) and between DDGel and water (Log PDDGel/w ) were determined. Results showed that DDGel has a similar or higher binding affinity to each simulant compared to SC. The relationship between Log P octanol/water and Log PSC/w as well as between Log P octanol/water and Log PDDGel/w demonstrated that partition coefficient of simulants correlated to their lipophilicity or hydrophilicity. Decontamination efficiency results with DDGel for these simulants were consistent with binding affinity results. Amounts of percentage dose of chemicals in DDGel of trimethyl phosphate, dimethyl adipate, 2-chloroethyl methyl sulfide, diethyl adipate, chloroethyl phenyl sulfide and diethyl sebacate were determined to be 61.15, 85.67, 75.91, 53.53, 89.89 and 76.58, with corresponding amounts absorbed in skin of 0.96, 0.65, 1.68, 0.72, 0.57 and 1.38, respectively. In vitro skin decontamination experiments coupled with a dermal absorption study demonstrated that DDGel can efficiently remove chemicals from skin surface, back-extract from the SC, and significantly reduced chemical penetration into skin or systemic absorption for all six simulants tested. Therefore, DDGel offers a great potential as a NextGen skin Decon platform technology for both military and civilian use.

Sebo-pharmacokinetics: a proposed percutaneous sebum egression method.

BACKGROUND/AIMS: The sebaceous gland is widely believed a critical factor in the pathogenesis of acne vulgaris. Although extensive studies document the ability of oral and topical treatments to improve acne, little is known about the quantification and mechanism of drug delivery via the sebaceous gland. A percutaneous egression method presents a way to study how drugs reaching the bloodstream can enter the skin. METHODS: A literature search was performed across databases (PubMed, Embase, and Google Scholar) and the University of California, San Francisco (UCSF) textbook library with relevant search terms. RESULTS: This search failed to reveal data on sebo-pharmacokinetics (PK); however, many articles center on pharmacodynamics (PD) - i.e. functional improvement instigated by oral or topical treatments. Experiments on humans and hamsters - representative sebaceous gland models - demonstrate indirect PD measures of sebaceous gland function. DISCUSSION: Here, we summarize the current available data on drug delivery via the sebaceous gland and suggest a practical method to directly document sebo-PK in man and animal.

In vitro human skin permeation and decontamination of diisopropyl methylphosphonate (DIMP) using Dermal Decontamination Gel (DDGel) and Reactive Skin Decontamination Lotion (RSDL) at different timepoints.

This study compared the efficiency for in vitro human skin decontamination using DDGel and RSDL when applied at different timepoints (5 min and 90 min). Experiments were performed using in vitro human skin models, in which skin was mounted onto Flow-Through diffusion cells. The mass of 14-C DIMP removed from skin surface after decontamination was quantitated by measuring radioactivity with a liquid scintillation spectrometer. Both decontaminants removed more than 90% recovery dose of DIMP from skin compared to control group (p < 0.05). DDGel skin decontamination reduced more toxicant amount when compared to RSDL. DDGel showed slight higher decontamination ability of DIMP than RSDL and efficiently removed chemicals from the skin surface, also reduced the amount of DIMP in receptor fluid. A similar decontamination regimen with RSDL and DDGel at 90 min showed that both were still might effectively increase the time window of opportunity for treatment. Thus, DDGel can offer a potential as a next generation skin decontamination platform technology for military and civilian applications.

In vitro human skin permeation and decontamination of 2-chloroethyl ethyl sulfide (CEES) using Dermal Decontamination Gel (DDGel) and Reactive Skin Decontamination Lotion (RSDL).

This study compared the efficiency for in vitro human skin decontamination using DDGel and RSDL. Experiments were performed using in vitro human skin models, in which skin was mounted onto Flow-Through diffusion cells. The mass of 14-C CEES removed from skin surface after decontamination was quantitated by measuring radioactivity with a liquid scintillation spectrometer. Both decontaminants removed more than 82% of CEES from skin. DDGel skin decontamination significantly reduced toxicant amount when compared to RSDL. Mean CEES remaining in stratum corneum (SC), viable epidermis, dermis, and systemic absorption of DDGel and RSDL were, 0.12 and 0.55% (P < 0.01), 0.31 and 0.95% (p < 0.01), 1.08 and 2.92% (p < 0.05), 3.13 and 6.34% (p < 0.05), respectively. DDGel showed higher decontamination efficiency (twice decontamination efficacy factor, DEF) than RSDL and efficiently removed chemicals from the skin surface, importantly back-extracted from the SC, and significantly reduced both chemical penetration into skin and systemic absorption. Thus, DDGel can offer a potential as a next generation skin decontamination platform technology for military and civilian applications.

Confocal laser scanning microscopy to estimate nanoparticles' human skin penetration in vitro.

OBJECTIVE: With rapid development of nanotechnology, there is increasing interest in nanoparticle (NP) application and its safety and efficacy on human skin. In this study, we utilized confocal laser scanning microscopy to estimate NP skin penetration. METHODS: Three different-sized polystyrene NPs marked with red fluorescence were applied to human skin, and Calcium Green 5N was used as a counterstain. Dimethyl sulfoxide (DMSO) and ethanol were used as alternative vehicles for NPs. Tape stripping was utilized as a barrier-damaged skin model. Skin biopsies dosed with NPs were incubated at 4°C or 37°C for 24 hours and imaged using confocal laser scanning microscopy. RESULTS: NPs were localized in the stratum corneum (SC) and hair follicles without penetrating the epidermis/dermis. Barrier alteration with tape stripping and change in incubation temperature did not induce deeper penetration. DMSO enhanced NP SC penetration but ethanol did not. CONCLUSION: Except with DMSO vehicle, these hydrolyzed polystyrene NPs did not penetrate intact or barrier-damaged human "viable" epidermis. For further clinical relevance, in vivo human skin studies and more sensitive analytic chemical methodology are suggested.