Investigation of the interactions of cationic guar with human hair by electrokinetic analysis.

OBJECTIVE: Cationic guar is an important polysaccharide used as a hair conditioning agent in personal care products. In this article, we report streaming potential data demonstrating its behaviour as it interacts electrostatically with hair. Several cationic guar variants with different molecular weights (MWs) and charge densities (CDs) were examined. METHODS: All experiments were carried out with a custom-designed streaming potential instrument so that in situ, real-time data were monitored during the treatment of a hair plug with aqueous solutions of cationic guar and subsequent treatment with anionic surfactants-sodium laureth sulfate (SLES) and cocamidopropyl betaine (CAPB)-commonly found in contemporary shampoo formulations. RESULTS: The MW of the cationic guar variants plays an integral role in determining the thickness of the adsorbed polymer layer on the hair surface while CD influences the zeta potential. Data were also generated for the treatment of hair with a cationic flexible polymer (polyquaternium-28) and cationic conditioning surfactant (behentrimonium chloride) to provide a frame of reference. The deposition behaviour on hair of high MW cationic guar variants is distinct from these conventional molecules in terms of its electrokinetic properties. We also examined the electrokinetic behaviour of cationic guar on hair types from different racial backgrounds. While the cationic guar treatment yielded similar results for the different hair types, anionic surfactant treatment resulted in quicker sorption and desorption from African, European 65% grey, and Mulatto hair as compared to Chinese, European dark brown, and Indian hair. CONCLUSION: We introduce an in situ technique for measuring the dynamic sorption/desorption of charged molecules on the surface of human hair. Evaluation of a series of cationic guar species revealed varying behaviour depending on the MW and CD of the polysaccharide. Our data also demonstrate differences in the desorption properties of typical shampoo surfactants for hair from diverse racial backgrounds.

OBJECTIF: Le guar cationique est un polysaccharide important utilisé comme conditionneur capillaire dans les produits cosmétiques. Dans ce rapport, nous démontrons l'utilisation de la technique du potentiel de streaming pour étudier comment le guar cationique interagit électrostatiquement avec les cheveux. Plusieurs variantes del guar cationique avec différents poids moléculaires et densités de charge ont été examinés. MÉTHODES: Nous avons utilisé un instrument de potentiel de streaming pour les expériences. Les études ont été réalisées en temps réel pour surveiller le traitement de cheveu avec des solutions aqueuses de guar cationique suivi d'un traitement ultérieur avec tensioactifs anioniques comment le sulfate de laureth de sodium et le cocamidopropyle bétaïne, des ingrédients généralement trouvés dans les formulations de shampooing. RÉSULTATS: Le poids moléculaire des variants du guar cationique joue un rôle intégral dans la détermination l'épaisseur de la couche de polymère adsorbée sur la surface des cheveux tandis que le densité de charge influence le potentiel zêta. Des données ont également été générées pour le traitement des cheveux avec un polymère flexible (polyquaternium-28) et tensioactif de conditionnement cationique (behentrimonium chlorure) pour fournir un cadre de référence. Le comportement de dépôt sur les cheveux des variants de guar cationiques à poids moléculaire élevé est distinct de ces molécules conventionnelles en termes de ses propriétés électrocinétiques. Nous avons également examiné le comportement électrocinétique de guar cationique sur des types de cheveux de différents milieux raciaux. Le traitement avec le guar cationique a donné des résultats similaires pour les différents types de cheveux. En contraste avec ceci, le traitement avec le tensioactif anionique a entraîné une sorption et une désorption plus rapides de cheveux africains, de cheveux européens (65% gris) et de cheveux mulâtres en comparaison à les cheveux chinois, européens et indiens. CONCLUSION: Nous introduisons une technique in situ pour mesurer la sorption et la désorption dynamique de molécules chargées à la surface des cheveux humains. L'évaluation d'une série des espèces de guar cationiques ont révélé un comportement variable en fonction du poids moléculaires et densités de charge de le polysaccharide. Nos données démontrent également des différences dans les propriétés de désorption de tensioactifs de shampooing typiques pour les cheveux de diverses origines raciales.

Determination of physicochemical properties of delipidized hair.

Using various physicochemical methods of analysis, we examined human hair in its virgin and delipidized state. Free lipids were removed by a solvent extraction technique (covalently bound lipids were not removed) using a series of solvents with varying polarity. We analyzed the surface properties of hair by conducting mechanical combing and dynamic contact angle analysis. In addition, we used inverse gas chromatography surface energy analysis to explore the chemical composition of the hair surface based on interactions of various nonpolar and polar probes with biological molecules residing on the hair surface. Further, we investigated the importance that free lipids play in the internal structural properties of hair using dynamic scanning calorimetry and tensile strength measurements. The microstructure of the hair surface was probed by atomic force microscopy, whereas the lipid content of hair's morphological components was determined by infrared spectroscopic imaging. We also monitored the water management properties of virgin and delipidized hair by dynamic vapor sorption, which yielded unique water sorption isotherms for each hair type. Using all these techniques, differences were found in the chemical composition and physical behavior of virgin and delipidized hair. To better understand the influence of hair lipid composition on hair styling treatments, we conducted mechanical analyses of hair shaped into omega loops to determine the stiffness, elasticity, and flexibility of hair-polymer assemblies. Although there were no discernible differences between untreated virgin and delipidized hair, in terms of stiffness and elasticity, we found that treatment with hair styling agents produced different effects depending on the hair type used. Likewise, streaming potential measurements were carried out to monitor the binding capacity of rinse-off treatments on virgin and delipidized hair. Using this technique, we monitored the surface potential of hair and found significant differences in the binding behavior of cationic polymers and surfactants (polyquaternium-55 and quaternium-26) on both hair types.

Influence of various environmental parameters on sweat gland activity.

The choice of environmental conditions when conducting antiperspirant studies greatly affects the quantity of sweat output. Our initial goal in this work was to develop an in-house procedure to test the efficacy of antiperspirant products using replica techniques in combination with image analysis. To ameliorate the skin replica method, we conducted rheological studies using dynamic mechanical analysis of the replica formulation. In terms of sweat output quantification, our preliminary results revealed a considerable amount of variation using the replica technique, leading us to conduct more fundamental studies of the factors that influence sweating behavior and how to best design the experimental strategy. In accordance with the FDA's protocol for antiperspirant testing, we carried out gravimetric analyses of axillae sweating under a variety of environmental conditions including temperature and humidity control. Subjects were first acclimatized in an environmentally controlled room for 30 min, and then placed in a sauna for an additional 30 or 45 min, depending on which test we administered. In Test 1 (30 min total in the sauna), the first 10 min in the sauna was another equilibration period, followed by a 20 min sweat production stage. We monitored axillae sweating during the last 20 min in the sauna by gravimetric analysis. At time (t) = 30 min in the sauna, skin replicas were taken and later analyzed using imaging and image analysis techniques. Test 1 was carried out on over 25 subjects, both male and female, from various racial backgrounds. In Test 2, subjects spent 45 min in the sauna after the initial 30-min period in the environmental room. During the 45 min, we obtained gravimetric readings of absorbent pads placed in the axillae. We conducted studies at various temperature and relative humidity settings. We also studied the influence of several external parameters on sudoriferous activity. Test 2 was a range-finding experiment on two subjects to determine the optimized environmental conditions for the hot room procedure. In addition to the replica and gravimetric techniques, we also measured flux density to determine the onset of firing of sweat glands to ensure that our environmental preconditioning step (30 min in the environmental room) brought subjects to the point that their sweat glands were activated. Although flux density measurements are usually carried out to determine transepidermal water loss (TEWL), we found that they can be equally useful for monitoring the onset of sweat production. Thermal infrared imaging experiments were also carried out allowing us to generate full-body images of subjects containing anatomical thermal distribution data with high accuracy. Overall, we conclude that our in-house hot room procedure offers much potential as an effective and cost-efficient screening tool for narrowing copious antiperspirant formulations to a select few for expensive clinical evaluation.

Infrared spectroscopy and differential scanning calorimetry studies of binary combinations of cis-6-octadecenoic acid and octadecanoic acid.

Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) studies are reported for combinations of cis-6-octadecenoic acid (also termed petroselinic acid, PSA) and octadecanoic acid (also termed stearic acid, SA) across a wide range of binary mole ratio combinations. The data are then used to plot the phase diagram which is found to be montotectic with the PSA reducing the melting temperature of SA at all compositions. The relevance of these experiments to stratum corneum (SC) biophysical behavior, particularly the influence and potential mechanisms of PSA on dermal permeation, is discussed. The potential role of cis-6-octadecenoic acid as a permeation enhancer is discussed in the context of these studies of its interaction with saturated fatty acids.