Recent Progress in Hair Science and Trichology.

Hair is important to our appearance as well as to protect our heads. Human hair mainly consists of proteins (80-85%), melanin pigments (0-5%), water (10-13%), and lipids (1-6%). The physicochemical properties of hair have been studied for over 100 years. However, they are not yet thoroughly understood. In this review, recent progress and the latest findings are summarized from the following three perspectives: structural characteristics, delivery and distribution of active ingredients, and hair as a template. The structural characteristics of hair have been mainly investigated by microscopic and/or spectroscopic techniques such as atomic force microscopy integrated with infrared spectroscopy (AFM-IR) and rheological measurements. The distribution of active ingredients has been generally evaluated through techniques such as nanoscale secondary ion mass spectrometry (NanoSIMS). And finally, attempts to explore the potential of hair to be used as a substrate for flexible device fabrication will be introduced.

Controlling the formation of ionic complex vesicles through double-tailed surfactants.

OBJECTIVE: Liposomes are often used in cosmetics since they are naturally derived and have excellent texture enhancing capabilities. However, when preparing them by using phospholipids with unsaturated acyl groups, they easily suffer from oxidative degradation. Accordingly, hydrogenated phospholipids are preferred, however, it is difficult to prepare stable liposomes due to its high gel-liquid crystalline phase transition temperature. On the other hand, although dialkyl dimethyl ammonium type cationic surfactants are widely known to form vesicles, they have rarely been used for skincare products except for water-in-oil type emulsion creams stabilized by organically modified clay minerals. We decided to overcome all of the problems above through ionic complex vesicles formed by double-tailed cationic and anionic surfactants. METHODS: Distearyl dimethyl ammonium chloride (DSAC) and sodium dilauramidoglutamide lysine (DLGL) were selected as cationic and anionic surfactants, respectively. Differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering (SWAXS) measurements were performed to confirm the DSAC/DLGL/water ternary phase diagram. Newly developed ionic complex vesicle formation was confirmed by cryogenic transmission electron microscopy (cryo-TEM). The adsorbed cosmetic film structure on the skin in vivo was evaluated through the polarized infrared external reflection (PIR-ER). Finally, a cosmetic lotion formula was developed and the vesicle size was determined by dynamic light scattering (DLS). RESULTS: DSC and SWAXS data indicated that stable vesicles could be obtained at a molar ratio of DLGL to DSAC = 6:4. At this molar ratio, multi lamellar vesicles with diameters less than 100 nm were observed through cryo-TEM. PIR-ER data revealed that the developed vesicles formed a highly perpendicular orientation to the human skin surface. We have succeeded in formulating a cosmetic lotion containing developed vesicles with a mean diameter of 63.2 nm, which was stable over 1 month at 0, 37, and 50°C. CONCLUSIONS: Our newly developed vesicles can be easily obtained through a coagulation process. Also, the adsorbed film structure supported by PIR-ER experiments implies that the developed lotion has an excellent texture that is the same as cosmetic lotions containing liposomes. Therefore, it's possible that this ionic complex vesicle could take the place of liposomes.

OBJECTIF: Les liposomes sont souvent utilisés dans les cosmétiques, car ils sont d'origine naturelle et ont d'excellentes capacités d'amélioration de la texture. Cependant, lorsqu'ils sont préparés en utilisant des phospholipides avec des groupes acyles insaturés, ils souffrent facilement de dégradation oxydative. Par conséquent, les phospholipides hydrogénés sont préférés, mais il est difficile de préparer des liposomes stables en raison de la température élevée pour la transition de gel à liquide cristal. D'autre part, bien que les tensioactifs cationiques de type dialkyle diméthylammonium soient largement connus pour former des vésicules, ils ont rarement été utilisés pour les produits de soins de la peau, à l'exception des crèmes émulsifiées de type eau dans l'huile stabilisées par des minéraux d'argile organiquement modifiés. Nous avons décidé de surmonter tous les problèmes susmentionnés grâce à des vésicules complexes ioniques formées par des tensioactifs cationiques et anioniques à double queue. MÉTHODES: le chlorure de distéaryl­diméthyl­ammonium (DSAC) et la lysine de dilauramidoglutamide (DLGL) ont été sélectionnés comme agents de surface cationiques et anioniques, respectivement. Des mesures de calorimétrie différentielle à balayage (DSC) et de diffraction des rayons X à petit angle et à grand angle (SWAXS) ont été effectuées pour confirmer le diagramme de phase ternaire en DSAC/DLGL/eau. La formation de vésicules complexes ioniques nouvellement développées a été confirmée par microscopie électronique à transmission cryogénique (cryo­TEM). La structure du film cosmétique adsorbé sur la peau in vivo a été évaluée par réflexion externe infrarouge polarisée (PIR­ER). Enfin, une formule de lotion cosmétique a été développée et la taille de la vésicule a été déterminée par diffraction dynamique de la lumière (DLS). RÉSULTATS: les données DSC et SWAXS ont indiqué que des vésicules stables pouvaient être obtenues à un rapport molaire de DLGL sur DSAC = 6:4. À ce rapport molaire, des vésicules pluri­lamellaires de diamètre inférieur à 100 nm ont été observées par cryo­TEM. Les données PIR­ER ont révélé que les vésicules développées forment une orientation très perpendiculaire à la surface de la peau humaine. Nous avons réussi à formuler une lotion cosmétique contenant des vésicules développées d'un diamètre moyen de 63,2 nm, qui était stable pendant un mois à 0°C, 37°C et 50°C. CONCLUSIONS: Nos vésicules nouvellement développées peuvent être facilement obtenues grâce à un processus de coagulation. De plus, la structure du film adsorbé soutenue par les expériences PIR­ER implique que la lotion développée a une excellente texture qui est la même que celles des lotions cosmétiques contenant des liposomes. Il est donc possible que cette vésicule complexe ionique puisse remplacer les liposomes.

Microscopic Analysis of the Water/Glycerol/EO30PS System in Bulk and on a Solid Substrate.

Surfactant systems are often employed in cosmetic formulations where they dry on skin as a surface, thereby becoming increasingly concentrated systems. To better understand this drying process, we focused on the difference of self-assembled structures of the water/glycerol/polyoxyethylene (30) phytosteryl ether (EO30PS) system in bulk and on a solid substrate because the interaction between the substrate and the surfactant may have a substantial effect on the self-assembly, which may be related to the bulk structure but in detail may also differ strongly from the bulk situation. In bulk, small-angle neutron scattering (SANS) experiments showed that with increasing loss of water, the degree of ordering increases but changes of the aggregate structure are rather small. The results indicate that ellipsoidal micelles of EO30PS are densely packed and simply become more ordered in bulk during the drying process. On the other hand, neutron reflectometry revealed that EO30PS molecules adsorb onto a Si surface in the form of bilayers and analysis indicates that at a high concentration (c = 20 wt %), there are on average two bilayers (a double bilayer) on the Si substrate. The adsorbed membrane structure of EO30PS is rather thin with respect to its hydrophobic part, indicating tilted molecules, containing only some solvent, and being not highly ordered. These experimental results then allow for a much deeper understanding of the structural properties of practical formulations as they are applied, for instance, in cosmetic lotions.

Novel O/W Emulsions by Utilizing a Vesicle/Disc Transformation of Polyether Modified Silicone.

Emulsification is an important technology in the field of cosmetics and household products. Emulsions are in non-equilibrium state; therefore, the products vary depending on the preparation process, and their state changes with time. Furthermore, it is known empirically that different types of oils have different emulsification properties (preparation and stability). For these reasons, the variables in emulsification research are numerous and complicated to analyze. As a result, many industrial applications have had to rely on empirical rules. In this study, emulsions with a lamellar liquid crystalline phase as an adsorption layer at the emulsion interface were investigated. The characteristics of O/W emulsions formed with the excess solvent phases (aqueous and oil phases) separated from the lamellar liquid crystalline phase were investigated based on the phase equilibrium of the ternary system.As a result, it was found that by agitating the aqueous phase containing dispersed vesicles of emulsifier (polyether modified silicone) together with the oil phase, an emulsion with a uniform interfacial membrane of lamellar liquid crystalline phase could be obtained. The emulsions prepared by this method were found to have good stability against coalescence. The process of transformation from vesicles to the uniform liquid crystal interfacial membrane during the emulsification process was clarified by a freeze-fracture transmission electron micrograph and the calculation of interfacial membrane thickness based on precise particle size analysis. Furthermore, the emulsification properties of polyether-modified silicones were clarified using polar oils and silicone oils, which are a combination of high/low and low/high compatibility with hydrophilic (polyethylene glycol) and lipophilic (polydimethylsiloxane) groups of polyether modified silicone, respectively. It is expected that this research will lead to the evolution of various functionalities in products in the fields of cosmetics, household products, food, pharmaceuticals, paint and others.

Promotion of glyoxylic acid penetration into human hair by glycolic acid.

OBJECTIVE: Glyoxylic acid (GA) is widely used as a straight perming agent for hair care products, however, advanced GA penetration-enhancing agents are desired due to the peculiar odour and hair colour fading caused by the continuous use of GA products. Hence, it is important to develop a penetration-enhancing agent that helps minimize the GA concentration. We have found that the combined use of GA and glycolic acid (GCA) has a strong hair straightening effect. METHODS: Straightening hair test was carried out to the evaluation of the effect of additives. Liquid chromatography-mass spectrometry (LC/MS) was performed to quantify the GA penetration amount into human hair. Attenuated total reflection (ATR) Fourier transform-infrared spectroscopy (FT-IR) and FT-IR microscope were implemented to estimate the localization of GA in the hair. RESULTS: Straightening hair tests indicated that the hair straightening effect by GA was enhanced by the presence of GCA. LC/MS results showed that the addition of GCA enhanced the amount of GA that penetrated human hair by about four times. ATR FT-IR and FT-IR microscope measurements indicated that GA was localized more in the innermost region of hair (medulla) than the cortex and cuticle. The GA accumulated in the medulla disappeared after a hair straightener treatment at 180°C due to the chemical reaction. CONCLUSIONS: The GA penetration-enhancing effect of GCA is worth investigating to reduce the GA concentration in products for more comfortable use.

OBJECTIF: L'acide glyoxylique (AG) est largement utilisé en tant qu'agent de lissage pour les produits de soins capillaires. Cependant, des agents avancés améliorant la pénétration de l'AG sont souhaités en raison de l'odeur particulière et de la décoloration des cheveux causées par l'utilisation continue de produits à base d'AG. Il est donc important de mettre au point un agent améliorant la pénétration qui contribue à minimiser la concentration d'AG. Nous avons constaté que l'utilisation combinée de l'AG et de l'acide glycolique (AGC) a un fort effet lissant sur les cheveux. MÉTHODES: Un test de lissage des cheveux a été effectué pour évaluer l'effet des additifs. Une chromatographie en phase liquide avec spectrométrie de masse (liquid chromatography-mass spectrometry, LC/MS) a été réalisée pour quantifier le volume de pénétration de l'AG dans les cheveux humains. Une spectroscopie infrarouge à transformée de Fourier (Fourier transform-infrared spectroscopy, FT-IR) à réflexion totale atténuée (RTA) et un microscope FT-IR ont été adoptés pour estimer la localisation de l'AG dans les cheveux. RÉSULTATS: Les tests de lissage des cheveux ont indiqué que l'effet de lissage des cheveux de l'AG était renforcé par la présence d'AGC. Les résultats de la LC/MS ont montré que l'ajout d'AGC augmentait d'environ quatre fois la quantité d'AG pénétrant dans les cheveux humains. Les mesures de la FT-IR à RTA et du microscope FT-IR ont indiqué que l'AG était plus localisé dans la région la plus interne du cheveu (médulla) que dans le cortex et la cuticule. L'AG accumulé dans la médulla a disparu après un traitement au lisseur à cheveux à 180 °C en raison de la réaction chimique. CONCLUSIONS: L'effet d'amélioration de la pénétration de l'AG observé avec l'AGC mérite d'être étudié afin de réduire la concentration d'AG dans les produits pour une utilisation plus confortable.

Neutron Reflectometry & Simultaneous Measurements of Rheology and Small Angle Neutron Scattering Studies for Polyether Modified Silicone Vesicle Systems.

Polyethyleneglycol 12 mol / polydimethylsiloxane co-polymer (PEG-12 dimethicone) is a type of polyether modified silicone (PEMS), which can form a lamellar liquid crystalline phase, and is widely used in cosmetics. The structural changes of PEG-12 dimethicone caused by water contents as well as shear flow were evaluated using simultaneous measurements of rheology and small angle neutron scattering (Rheo-SANS) and neutron reflectometry (NR). At high PEG-12 dimethicone concentrations (≥ 36 wt%), a reorientation of plate-like lamellar structures were observed and the neutral orientation was the most favorable. However, lamella-to-vesicle transitions were hardly observed. PEG-12 dimethicone turned out to form a bi-layer on a hydrophilized Si-wafer in a similar manner to that in bulk though the structure had a certain level of roughness.

Control of Lipid Self-Assembled Structures & Assessment of Lipid Membrane Fluidity by Fluorescence Spectroscopy.

It is well known that lipids form various kinds of self-assembled structures. First, lipid nanoparticles dispersed with hydroxy propyl methyl cellulose acetate succinate (HPMCAS) were introduced. The influence of polymers on the lipid self-assembled structures was evaluated by small and wide angle X-ray scattering (SWAXS). Self-assembled structures containing higher alcohols have attracted much attention in the cosmetic industry. The α-form hydrated crystalline phase (often called α-gel) is one of the hydrated crystalline phases which can be exhibited by surfactants and higher alcohols. As surfactants in this study, an ionic complex or a silicone type were used. This review also reports the lipid membrane fluidity by using fluorescence spectroscopy.

Novel Cubosome System Resistant to Lipid Removal by Serum Albumin.

Cubosomes are lipidic nanoparticles containing bicontinuous cubic structures. Their unique architecture and potential as drug delivery vehicles have attracted researchers' attention. However, cubosome systems that are more robust in the presence of plasma components are being sought after for applications in intravenous administration. In this study, we prepared cubosomes consisting of 1,2-dioleoyl-sn-glycero-3-hexylphosphocholine (hexyl-DOPC) and compared their interaction with bovine serum albumin (BSA), the most abundant protein in plasma, with that of conventional cubosome systems consisting of several bicontinuous cubic phase-forming lipids, including 1-monoolein (MO), 1-O-(5,9,13,17-tetramethyloctadecanoyl)erythritol (EROCO C22), or 1-O-(5,9,13,17-tetramethyloctadecyl)-ß-D-xylopyranoside (ß-XP). The average number of lipids bound to each BSA molecule was between 1.2-4.0 for MO, EROCO C22, and ß-XP. On the other hand, hexyl-DOPC exhibited negligible binding to BSA. This result suggests that hexyl-DOPC, which was shown to resist removal from particles by BSA, can be used as a new lipid component of cubosomes, and has higher plasma stability than the other cubic phase-forming lipids.

Physicochemical Properties of α-Form Hydrated Crystalline Phase of 3-(10-Carboxydecyl)-1,1,1,3,5,5,5-heptamethyl Trisiloxane/Higher alcohol/Polyoxyethylene (5 mol) Glyceryl monostearate/Water System.

The α-form hydrated crystalline phase (often called as an α-gel) is one of the hydrated crystalline phases which can be exhibited by surfactants and lipids. In this study, a novel system of an α-form hydrated crystal was developed, composed of 3-(10-carboxydecyl)-1,1,1,3,5,5,5-heptamethyl trisiloxane (CDTS), polyoxyethylene (5 mol) glyceryl monostearate (GMS-5), higher alcohol. This is the first report to indicate that a silicone surfactant can form an α-form hydrated crystal. The physicochemical properties of this system were characterized by small and wide angle X-ray scattering (SWAXS), differential scanning calorimetry (DSC), and diffusion-ordered NMR spectroscopy (DOSY) experiments. SWAXS and DSC measurements revealed that a plurality of crystalline phases coexist in the CDTS/higher alcohol/water ternary system. By adding GMS-5 to the ternary system, however, a wide region of a single α-form hydrated crystalline phase was obtained. The self-diffusion coefficients (Dsel) from the NMR measurements suggested that all of the CDTS, GMS-5, and higher alcohol molecules were incorporated into the same α-form hydrated crystals.

Effect of Dialkyl Ammonium Cationic Surfactants on the Microfluidity of Membranes Containing Raft Domains.

It has been reported that a lot of receptors localize in lipid raft domains and that the microfluidity of these domains regulates the activation of these receptors. In this study, we focused on the lipid raft and in order to evaluate the physicochemical effects of surfactants on microfluidity of lipid membranes, we used liposomes comprising of egg-yolk L-α-phosphatidylcholine, egg-yolk sphingomyelin, and cholesterol as a model of cell membranes containing raft domains. The microfluidity of the domains was characterized by fluorescence spectrometry using 1,6-diphenyl-1,3,5-hexatriene and 2-dimethylamino-6-lauroylnaphthalene. Among several surfactants, dialkylammonium-type cationic surfactants most efficiently increased the microfluidity. It is therefore concluded that (1) the electrostatic interaction between the cationic surfactant and eggPC/eggSM/cholesterol liposome could be important, (2) surfactants with alkyl chains more effectively inserted into membranes than those with acyl chains, and (3) cationic surfactants with lower Tm values have a greater ability to increase the fluidity.

Viscosity stability of O/W emulsion containing α-gel through an ionic-complex system.

Although many active ingredients are used in cosmetic products for moisturizing and whitening the skin, they are often electrolytes, and the stabilities of oil in water (O/W) type emulsion formulae containing electrolytes are generally difficult to control. To solve this problem, formulae containing an α-crystalline phase (α-gel) consisting of water, higher alcohols, and anionic surfactants such as sodium N-stearoyl-N-methyl-taurate (SMT) have been developed. However, in spite of their excellent salt tolerance, these formulae have poor viscosity stability under non-electrolyte conditions, and the viscosity decreases over time. To obtain adequate viscosity stability, the required electrolyte concentration is approximately 1wt%, which is somewhat high for cosmetic applications. To replace the salts, distearyl dimethyl ammonium chloride (DSAC), a cationic surfactant, with an opposite electric charge to SMT, was used in O/W emulsion formulae, resulting in improved viscosity stability at a lower concentration than that of salts. The stabilization mechanism with DSAC was found to be different from that of salts.

Protonation-assisted conjugate addition of axially chiral enolates: asymmetric synthesis of multisubstituted ß-lactams from α-amino acids.

ß-Lactams with contiguous tetra- and trisubstituted carbon centers were prepared in a highly enantioselective manner through 4-exo-trig cyclization of axially chiral enolates generated from readily available α-amino acids. Use of a weak base (metal carbonate) in a protic solvent (EtOH) is the key to the smooth production of ß-lactams. Use of the weak base is expected to generate the axially chiral enolates in a very low concentration, which undergo intramolecular conjugate addition without suffering intermolecular side reactions. Highly strained ß-lactam enolates thus formed through reversible intramolecular conjugate addition (4-exo-trig cyclization) of axially chiral enolates undergo prompt protonation by EtOH in the reaction media (not during the work-up procedure) to give ß-lactams in up to 97% ee.

Useful modified cellulose polymers as new emulsifiers of cubosomes.

This report introduces modified cellulose polymers as new emulsifiers of cubosomes. We prepared novel nanoparticles containing cubic-phase-forming lipids using hydroxypropyl methylcellulose acetate succinate (HPMCAS). Small-angle X-ray scattering showed a much lower incorporation of HPMCAS into the cubic structure of monoolein than did a conventional emulsifier, Pluronic F127, which is known to modify the cubic structure. Cubosomes prepared with HPMCAS showed roughly equal stability as nanoparticles with Pluronic F127. These results suggest that HPMCAS can be a novel emulsifier of cubosomes, which brings about no internal structure modification.