Jairajh Mattai

Human Cutaneous Response to a Mixed Surfactant System: Role of Solution Phenomena in Controlling Surfactant Irritation

Exposure of the skin to surfactant-based products can result in irritation. To control this effect researchers are probing mechanisms of surfactant action. In vitro studies show that mixing surfactants often results in less denaturation (swelling) of stratum corneum. We have explored the in vivo human irritation response (using a 21-day cumulative irritation test) to two of these surfactants-sodium lauryl sulfate (SLS) and (C12-C14) alkyl, 7-ethoxy sulfate (AEOS-7EO). Results demonstrate that addition of AEOS-7EO to a constant dose of SLS results in a significant reduction in erythema, hence producing a milder system. The reason for the synergism is unclear, but may related to experimentally determined alterations in the micellar solution properties of the SLS upon addition of AEOS-7EO.

Encapsulated recyclable porous materials: an effective moisture-triggered fragrance release system

A moisture-triggered release system was developed using porous metal-organic materials as encapsulating agents. Release of both hydrophilic (ethyl butyrate) and hydrophobic (D-limonene) fragrance compounds was investigated by gas adsorption measurement, thermogravimetric analysis and gas chromatography-mass spectroscopy. These materials exhibit exceptional fragrance compatibility and controlled release compared to the current leading encapsulation technology.

Detection and quantification of apocrine secreted odor-binding protein on intact human axillary skin.

A proposed mechanism of axillary malodor formation is bacterial interaction with secreted odor carrier proteins leading to the release of volatile odor molecules. One primary volatile odor molecule, 3‐methyl‐2‐hexenoic acid, is secreted into the apocrine glandular lumen bound to two carrier proteins known as apocrine secretion odor‐binding proteins (ASOB1 and ASOB2). The objective of this study was to develop a biologic method to detect and quantify ASOB2 in vitro and on intact axillary skin. The proteins present in pure apocrine secretion were separated via SDS–polyacrylamide gel electrophoresis (PAGE), electro‐blotted, and reacted with antibodies to detect ASOB2. The results of this study demonstrate that ASOB2 shares immunologically homologous epitopes with the human serum protein, apolipoprotein‐D (apo‐D). Axillary secretions and baseline microflora were collected from two groups of panelists 6 h after showering with a non‐antibacterial soap. The extracts were fractionated by SDS–PAGE. ASOB2 was detected selectively by Western blot using a monoclonal mouse‐antihuman apo‐D antibody and quantified on human axillary skin using the presented methods. Axillary ASOB2 concentration varied among individuals (<0.1–4.1 µg cm−2) with significant differences (P < 0.05, anova) seen between those of Chinese descent and non‐Chinese descent. Panelists of Chinese ancestry did not show significantly lower baseline microflora levels when compared to non‐Chinese panelists.

Development of a stratum corneum lipid model to study the cutaneous moisture barrier properties

Abstract A skin lipid model to study barrier properties of stratum corneum has been developed. Research that led to the evolution of this model is presented along with highlights of recent findings. At normal water content of skin, the model lipid exists as a liquid crystal with only a small amount of solid crystals present. As the water content is reduced, for example by exposure to a low humidity environment, more of the solid crystal phase is found. Further X-ray diffraction studies identified the location of specific lipids in the model layered structure. Triglycerides and squalene are found in the hydrophobic methyl layer, while fatty acids, cholesterol and ceramides are located between the fatty acid chains. Water uptake was significantly enhanced when extracted stratum corneum lipids or model lipids were combined with the delipidated corneocytes, compared with water uptake of the lipids or delipidated corneocytes alone. Water uptake of the combined system was similar to that of isolated, intact stratum corneum. We determined the effect of glycerol, a well known skin moisturizer, on the model. While glycerol did not alter the water loss of the model at low relative humidity (6% RH), it maintained the liquid crystalline state of the lipid at the extreme condition; in the absence of glycerol the model showed substantial crystallization and exhibited multiple phases at 6% RH. Glycerol did not exhibit humectant behavior under these conditions. This study suggests that an alternate mechanism for moisturization may be to maintain the liquid crystalline structure under dry environmental conditions. Future studies using the model will examine the role of specific lipids and proteins in enhancing barrier properties; parameters measured will be phase behavior, water uptake/loss and alterations in diffraction patterns under different environmental conditions. Additives will be sought that improve the moisturization capacity of skin by altering biophysical properties of the lipid.