BACKGROUND/PURPOSE: Percutaneous permeation is a frequently used approach in drug delivery, but the detailed physics process in the patch--stratum corneum (SC)--viable epidermis system remains unclear: the influence of the interphases in the multilayered structure has been little studied.

METHODS: This paper applied the finite-element method to develop a contact algorithm with an interphase element to account for the interphase barrier on drug diffusion and chemical absorption during a transdermal drug delivery process. A more realistic multilayer structure, including the patch, SC and viable epidermis, are incorporated into the algorithm. Both interphases between the patch and SC, and between SC and viable epidermis are considered.

RESULTS: Our study confirms that the interphase transfer coefficients have a direct connection with drug concentration and flux distribution along the diffusion paths. The simulation results suggested a potential for the optimal control of drug diffusion. The partition coefficients and other interphase barrier factors can be incorporated into the model.

CONCLUSIONS: The algorithm can deal with complicated geometrical conditions, which is difficult using classical analytical approaches. Furthermore, calibrated against experiments, the model may predict more realistically the drug delivery process and drug distribution profiles so as to assist in the patch and even drug design.

BACKGROUND/PURPOSE: Percutaneous permeation is a frequently used approach in drug delivery, but the detailed physics process in the patch--stratum corneum (SC)--viable epidermis system remains unclear: the influence of the interphases in the multilayered structure has been little studied. METHODS: This paper applied the finite-element method to develop a contact algorithm with an interphase element to account for the interphase barrier on drug diffusion and chemical absorption during a transdermal drug delivery process. A more realistic multilayer structure, including the patch, SC and viable epidermis, are incorporated into the algorithm. Both interphases between the patch and SC, and between SC and viable epidermis are considered. RESULTS: Our study confirms that the interphase transfer coefficients have a direct connection with drug concentration and flux distribution along the diffusion paths. The simulation results suggested a potential for the optimal control of drug diffusion. The partition coefficients and other interphase barrier factors can be incorporated into the model. CONCLUSIONS: The algorithm can deal with complicated geometrical conditions, which is difficult using classical analytical approaches. Furthermore, calibrated against experiments, the model may predict more realistically the drug delivery process and drug distribution profiles so as to assist in the patch and even drug design.

Skin and garment constitute a dynamic contact system for human body comfort and protection. Although dermatological injuries due to fabric actions during human body movement are common, there is still no general guidance or standard for measuring or evaluating skin/garment contact interactions, especially, during intense sports. A three-dimensional explicit finite element (EFE) model combined with Augmented Lagrange algorithm (ALA) is developed to simulate interactions between skin and fabric during rotation of the arm. Normalized effective shear stresses at the interface between skin and the sleeve during the arm rotation are provided to reflect the severity of the interactions. The effects due to changes in fabric properties, fabric-skin gap, and arm rotation rate are also illustrated. It has been demonstrated from our predictions that factors such as elastic modulus, friction coefficients, density of fabric, and the initial gap between skin and fabric influence significantly the shear stress and thus the discomfort and even injury potential to skin during intensive body movement such as sports and military. Thus this study for the first time confirms quantitatively that poorly chosen fabric with inappropriate garment design renders adverse actions on human skin.

This article overviews research in the interdisciplinary area of textile/skin interaction and related cutaneous intolerance. Microclimate in the skin/clothing system and especially the skin responses relates to the moisture and heat transfer within this system and plays a critical role in skin irritation from textiles. A discussion is then given on skin irritation reactions to textiles, including intolerance caused by chemicals (dyes and finishes) and physical contact/friction. Finally, two skin injuries, blisters and pressure ulcers, which are caused by physical contact, pressure, and friction, are documented. Despite the prevalent problems caused by ill textile/skin interactions, minimal efforts have been devoted to this field. In addition, the in vivo experimental studies infrequently lead to a solid conclusion. The cause may lie in the dramatic variation of skin conditions among individuals as well as among different anatomic sites of the same person. Another reason might be the lack of communications between researchers in the areas of textiles and dermatology.

Use of the percutaneous route may avoid some of the undesirable side effects that occur following oral administration in estrogen replacement therapy. At present, knowledge of estradiol transdermal properties relating to delivery of drugs in the skin is lacking. One reason is that in the existing transport models of estradiol, the skin is regarded as a single layer. This study revealed a significant difference of effects on estradiol delivery in the 3 sublayers of the skin and has caused us to believe that if we can obtain information about the transfer properties of estradiol in human skin (3 sublayers), we will not only increase our understanding of the estradiol biotransport mechanism, but also benefit clinical application. Accordingly, radioactive 17beta-estradiol was used to clarify the percutaneous absorption of estradiol into the 3 sublayers of the skin (stratum corneum, epidermis, and dermis) and to evaluate the effect of drugs delivered in each sublayer. Based on data thereby obtained, mathematical models were built to further obtain transport parameters (diffusivity, permeability, lag time, and partition coefficients) for the 3 layers of the skin.

Huanglongbing (HLB) is a highly destructive, fast spreading disease of citrus that causes substantial economic losses to the citrus industry worldwide. Nutrient levels and their cellular distribution patterns in HLB-affected grapefruit were analyzed after graft-inoculation with infected lemon scions containing ‘Candidatus Liberibacter asiaticus’, the heat-tolerant Asian type of HLB bacterium. After 12 months, infected plants showed typical HLB symptoms including leaf curling and blotchy mottle on leaves. Zinc (Zn) concentrations in young, mature, and old leaves of grapefruit significantly decreased by HLB infection. Micro-XRF imaging of Zn and other elements showed that preferential distribution of Zn was observed in the phloem tissues of leaves and stems collected from healthy grapefruit plants but was absent from HLB-affected samples. Quantitative analysis of Zn intensity in the cross-sections of leaves using standard samples revealed that Zn concentration in phloem tissues of healthy grapefruit leaves was more than 10 times higher than that in the HLB-affected leaves. No significant variation was observed in the distribution patterns of other elements such as K and Ca in stems and leaves of grapefruit plants before or after graft-inoculation withHLB infected lemon scions. These results suggest that reduced phloem transport of Zn is one of the most important constraints that contribute to HLB-induced Zn deficiency in citrus such as grapefruit. Our report provides the first in situ visualization of elements’ variation within the tissues of HLB-infected citrus at cellular level.

BACKGROUND/PURPOSE: Percutaneous permeation is a frequently used approach in drug delivery, but the detailed physics process in the patch--stratum corneum (SC)--viable epidermis system remains unclear: the influence of the interphases in the multilayered structure has been little studied. METHODS: This paper applied the finite-element method to develop a contact algorithm with an interphase element to account for the interphase barrier on drug diffusion and chemical absorption during a transdermal drug delivery process. A more realistic multilayer structure, including the patch, SC and viable epidermis, are incorporated into the algorithm. Both interphases between the patch and SC, and between SC and viable epidermis are considered. RESULTS: Our study confirms that the interphase transfer coefficients have a direct connection with drug concentration and flux distribution along the diffusion paths. The simulation results suggested a potential for the optimal control of drug diffusion. The partition coefficients and other interphase barrier factors can be incorporated into the model. CONCLUSIONS: The algorithm can deal with complicated geometrical conditions, which is difficult using classical analytical approaches. Furthermore, calibrated against experiments, the model may predict more realistically the drug delivery process and drug distribution profiles so as to assist in the patch and even drug design.

This article overviews research in the interdisciplinary area of textile/skin interaction and related cutaneous intolerance. Microclimate in the skin/clothing system and especially the skin responses relates to the moisture and heat transfer within this system and plays a critical role in skin irritation from textiles. A discussion is then given on skin irritation reactions to textiles, including intolerance caused by chemicals (dyes and finishes) and physical contact/friction. Finally, two skin injuries, blisters and pressure ulcers, which are caused by physical contact, pressure, and friction, are documented. Despite the prevalent problems caused by ill textile/skin interactions, minimal efforts have been devoted to this field. In addition, the in vivo experimental studies infrequently lead to a solid conclusion. The cause may lie in the dramatic variation of skin conditions among individuals as well as among different anatomic sites of the same person. Another reason might be the lack of communications between researchers in the areas of textiles and dermatology.