SCC Jazzes Up its Scientific Seminar.
THE SOCIETY of Cosmetic Chemists (SCC) hosted its annual scientific seminar at the Sheraton, New Orleans in May. Eighteen speakers shared their latest findings and innovations in the personal care industry during the two days. In addition, the annual awards luncheon sponsored by Dragoco honored Eric S. Abrutyn, a product development employee of the Andrew Jergens Company, for his paper, "The ability of creams to reduce erythema, stratum corneum barrier damage and subjective itching." The paper was co-authored by Dr. Anthony Simion of Andrew Jergens and Dr. Zoe Draelos of Dermatology Consulting.
The first of the four seminar sessions featured presentations on new discoveries in hair research. Sidney B. Hornby of Martech Contract Services, Inc., Broomall, PA, discussed, "Technique for evaluating grooming and weathering damage to hair." According to Ms. Hornby, hair damage is caused by sunlight, chemicals, brushing and combing which result in split ends, breakage and loss of luster. Using a Dia-Stron cyclic tester, damage was simulated to virgin and bleached hair, with or without conditioner (JR400), at specific load-elongation cycles, resembling everyday combing or brushing. The research team studied the changes in the hair fiber structure and elasticity as a function of accumulated stress, such as hair cracks. "We used the Dia-Stron cyclic tester to simulate damage and styling stresses to see the effects of conditioning and to monitor the degradation of elasticity," explained Ms. Hornby.
Virgin hair without conditioner had a 16% chance of surviving 5,000 fatigue cycles with a 70g load and 30% relative humidity. With the addition of a JR400 conditioning agent, survival increased to 22%. Bleached hair, on the other hand, did not improve greatly with the addition of JR400; however other conditioners explored in the study improved survival probability. Overall, decreases in fiber elasticity and resilience were observed as the hair was subjected to cyclic tensile stresses. "There was a slow, progressive reduction in elasticity of fibers with increased elongation, especially with bleached hair," Ms. Hornby added.
Tao Gao, Ph.D, of Croda Inc., presented "Differential scanning calorimetry (DSC) study of hair damage and hair restructuring by protein derivatives." In his opening remarks Dr. Gao explained, "Our questions were, what is an [Alpha]-helix, where is it and what is its temperature of denaturation?"
Using strands of virgin brown, bleached blond and virgin African-American hair, structural changes of the microfibril-matrix were studied to determine the various [Alpha]-helix peaks (temperatures of denaturation), or relative helix contents (RHS). The hair was immersed in an aqueous solution for three minutes, air-dried and placed in a chamber at 23 [degrees] C and 50% humidity for 48 hours.
When the virgin hair sections were weathered (treated with photodegradation), results showed that RHC in the tip of the hair was 85.6% of that in the root end, illustrating a clear weathering effect. When bleached and relaxed, the RHC of hair decreased with increased bleaching time. The RHC of the bleached hair decreased 72.8% compared to that of virgin hair, demonstrating the severity of damage sustained by already bleached hair.
Results for the concurrent use of bleached hair and conditioner showed that RHC increased 77.5%, 72% and 88.8% for samples treated with hydrolyzed wheat protein, cystine polysiloxane and a mixture of hydrolyzed wheat protein and hydroxypropyl polysiloxane, respectively. These reactions changed the amount and structure of helix in the hair, while leave-on products showed better peak recovery effects than rinse-off products. Mr. Gao suggested that due to the high molecular weight of protein derivatives such as hydrolyzed wheat protein and hydroxypropyl polysiloxane, their large particle size prevents them from penetrating well into virgin hair pores. However, bleached hair is very porous and that may have made it possible for the polymers to penetrate and react with the bleached hair.
According to K.R. Ramaprasad of TRI, Princeton, NJ, author of "FTIR Investigation of the Ambient Dependent Photodamage in Hair," the products of oxidation of keratin fibers, mostly sulfoxides and sulfonic acid, are dependent on the chemical agents used and other reactions. Dr. Ramaprasad's experiment reinvestigated previous works on the FTIR spectra of photo-damaged hair under two different humidities. European brown and Piedmont hair fibers were used.
"By unifying established knowledge about the oxidation of the disulfide bond in keratin fibers, we may find something new," said Dr. Ramaprasad. The tests used the Q-UV weatherometer for low humidity; the Atlas Fade-O-Meter for higher humidity; a Nicolet 560 FTIR spectrometer for infrared spectra and for all spectra, an attenuated total reflectance accessory and ZnSe crystal. Test results concluded that drier Piedmont hair tresses promote photochemical reaction at the disulfide site, creating thiosulfonate end products, while more moist hair oxidizes sulfur into what is thought to be sulfinic acid.
Katsunori Yoshida of the Shiseido Research Center, Yokohama, Japan presented "Curdlan: style memorizing polymer for hair fixative," which proposes that curdlan, or [Beta]-1,3 glucan, bears both a soft application feeling and high humidity resistance, which is lacking in the market. "Polymers as hair fixatives are predominantly PVP," Mr. Yoshida noted. "They either have less humidity resistance with a soft feel or effective resistance and a very hard feel. But how can you get both?"
Using a dynamic viscoelastic analyzer RSA II to study film properties at 80 [degrees] C, the research team discovered that curdlan forms an aqueous gel when heated. Interestingly, curdlan actually has two different gel temperatures which is not fully understood, according to Mr. Yoshida. Regardless, curdlan in its sol state has a higher breakdown stress than polyquaternium-10 film. In its gel state, however, curdlan has less stress breakdown, indicating it is more elastic than conventional hair fixatives and showing no change even when hair is bent, proving its superior elasticity and curl retention. In addition, application feel of curdlan was soft and light despite its humidity resistance and caused no buildup, as seen under a scanning electron microscope.
Skin Delivery Seminar
Gerald B. Kasting, Ph.D of the University of Cincinnati College of Pharmacy presented "Dye localization and estimation of lipid pathlength in human stratum corneum." Based on the assumption that the primary transport in the stratum corneum is intracellular, the experiment was conducted to re-examine the mechanism of percutaneous absorption using a microtransport approach to improve predictive models of topical/transdermal drug delivery, dermal exposure and risk assessment. "Our objective was the construction of a three-dimensional model of the stratum corneum, corneocyte arrangements and lipid pathlengths," said Dr. Kasting.
Using modern confocal microscopy and both 2-D and 3-D fluorescence microscopy with corrected values for cellular swelling, it was found that corneocyte arrangement showed partial column-like alignments, but less than that assumed in earlier structural models. Dr. Kasting insisted that these findings contend contemporary transcellular transport theories.
Poster winner and student at the University of Cincinnati College of Pharmacy Wael Youssef examined the barrier function of vernix caseosa, the proteolipid biofilm that covers fetal skin in the last trimester before birth and during birth, in his paper entitled "Vernix and infant skin: interfacing biology and aesthetics." Vernix is a thick detached substance comprised of mostly water that prevents the penetration of amniotic fluid while the fetus is in the womb.
The rheology of vernix was plastic according to a dynamic stress rheomoeter, and was easier to spread in utero and difficult to rub off after birth. A mixture of vernix and saline was compared to a mixture of vernix and Survanta (a bovine lung surfactant), which caused a dramatic drop in viscosity. In terms of liquid water diffusion, the permeability coefficient of vernix was less water-diffusive with results at double the rate of Aquaphor and 25 times higher than petrolatum. Vernix was also more permeable to water vapor diffusion than either substance, especially between 25-37 [degrees] C, according to Mr. Youssef. These results support the hypothesis that vernix has a skin protective role before and after birth--in utero, vernix does not act as a totally occlusive biofilm but rather forms a semiocclusive barrier overlying the developing stratum corneum. After birth, however, it is less permeable to the new environment, aiding in the infant's overall health, he said. "This is, in essence, nature's skin cream," insisted Mr. Youssef.
Vitthal Kulkarni, Ph.D of The Collaborative Group investigated the role of sphingolipids in skin delivery systems in his multiple-authored paper, "Lipid nanotubes as skin penetration modulators." Recent research revealed that certain sphingolipids, including cerebrosides and ceramides, form tubular microstructures upon hydration. Though they are limited in application, in combination with phospholipids they can be effective penetration enhancers or retardants depending on the topical delivery system. For example, results showed that retinol palmitate had a 20% increase in skin penetration with a nanotubular formulation over a nano-dispersion, while ODF dye in a nano-dispersion did not penetrate epidermis treated with nanotubes.
According to Diana Smith of Philadelphia-based Inolex Chemical Company in the paper, "Delivery of active ingredients in and throughout the stratum corneum via polymeric ester technology," polyesters can either improve performance of hydrophilic or hydrophobic biological actives for delivery to the upper and lower levels of the stratum corneum, respectively. Ms. Smith explained that cosmetic polymeric liquid reservoir technologies use a partitioning mechanism where actives are released by controlled diffusion in the epidermis.
Results from Inolex's experiments concluded that high molecular weight, cross-linked polyesters are most effective at mitigating skin penetration of actives to the upper layers of skin. Using specifically designed polyesters, however, lactic acid could act as a skin lightener with the inclusion of polyester TL-8 (hydroxyl terminated, 800 MW) at a 2.5-5% concentration to the lower layers of skin. Hydroquinone was also an effective skin lightener with a more polar polyester, TL-8, instead of TC-8. Studies conducted with formulations containing 2.5% polyester TL-8 in combination with MAP and arbutin showed that less active was needed to be effective and non-irritating. Therefore, low molecular weight linear polar polyesters offer a lower cost potential for water-soluble skin lightening actives.
Sam Shefer, Ph.D of Salvona, LLC, presented the co-authored paper, "Controlled release systems for skin care application." Dr. Shefer noted that the process of developing a new controlled release system (CRS) for skin involves several steps such as screening and selection of materials, processing optimization and performance evaluation. The key to success is tailoring the CRS to the specific application, he noted. For example, sub-micron nanospheres such as Salvona's NanoSal can readily reach the deeper layer of the skin due to its small size and hydrophobic properties. NanoSal can be tailored to meet final performance requirements such as good skin feel, conventional application and cost effectiveness.
Ken Klein of Cosmetech Laboratories, Fairfield, NJ, outlined several "dos and don'ts" on combination sunscreen products in the presentation, "Sunscreen combination products--sense or nonsense?" Mr. Klein displayed many label claims that he referred to as consumer hype and others that represent substantial claims in the marketplace. These products either cross the paths of two FDA drug monographs or involve two completely separate government agencies. Mr. Klein noted that sunscreen and insect repellant combos are logical and valid products, but sunscreen and antiacne products could have questionable combinations, such as sunscreen with benzoyl peroxide.
In the presentation "Improvements in SPF can be achieved through optimization of surface film interactions," The Collaborative Group's Jennifer Corwin compared the SPF activity of a conventional sunscreen to a nano-dispersion surfactant-free sunscreen containing 12% Parsol 1789 and 30% OMC. Results concluded that the nano-dispersion sunscreen had SPF 15 as compared to the conventional sunscreen's SPF 8.1, suggesting that particle size, population homogeneity and spreading behavior may have a significant influence on UV protection. Also, it was found that there is a direct relationship between UV protection of sunscreen agents and the size, homogeneity and stability of the particles after application. The study suggested that the formation of a uniform film with intact nano-particles is the key to achieving nearly two-fold SPF improvement over conventional lotions.
Bill Stanfield of Memphis, TN-based Suncare Research Laboratories, presented the paper, "Sunscreen photostability and UVA protection." Researchers in the study used an in vitro method to assess a sunscreen's UVA protection and photostability on an artificially prepared substrate. "Determining photestability is important because when using a sunscreen, a formula that is not stable will lose SPF more quickly in the presence of sunlight," Mr. Stanfield explained.
The SPF of the substrate and the SPF of the sunscreen can be calculated by measuring the UV transmission of the substrate alone and the substrate containing the sunscreen. The sunscreen's SPF value in vitro must be approximately equal to the SPF measured in vivo for validity. Suncare executives recommend that the linear relationship ([Beta]) between the sunscreen's UV dose and the effective dose applied to the surface of the sunscreen on the substrate (at 290-400nm) have a limit of 1.1. A sunscreen can only be considered photostable if [Beta] is less than 1.1, Mr. Stanfield noted.
The APF (UVA protection factor) can then be measured in the same manner as SPF for wavelengths ranging from 320-400nm. According to Mr. Stanfield, there is a general agreement that the contribution of UVA to the acute effects of sunlight is about 20%. Therefore, Suncare executives have proposed that if the ratio of APF to SPF is at least 20%, the sunscreen should be labeled "broad spectrum."
Presenter Klaus Kwetkat, Ph.D of Sasol Olefins & Surfactants GmbH in Marl, Germany, discussed the company's twin surfactants in his paper entitled "Gemini surfactants for sunscreens." Twin surfactants, a combination of a hydrophilic group, a hydrophobic chain and a spacer, are known for their superior interfacial activity, high electrolyte tolerance, mildness, high flexibility and stable aggregates. Dr. Kwetkat insisted that Sasol's twin surfactants (Ceralution H and F) have many uses in stable liquid crystalline gels with low interfacial tension, third phase emulsion viscosity and water resistance; as dispersions for sunscreens and as sprays with low interfacial tension giving a protective lamellar layer around dispersed oil droplets.
Heather Eyre of Ashford, UK-based Quest International reported recent findings on a process used to prove the mosquito repellency of menthyl pyrrolidone carboxylate (MPC) in the presentation, "New method for testing mosquito repellency: highlighting a new benefit for an existing ingredient." Though some attraction factors of mosquitoes are known, such as lactic acid present on skin and carbon dioxide exhalation, mosquito preferences are largely unknown. Quest International's definition for an ideal mosquito repellent was one that lasts 8 hours, does not stain, is volatile enough, cosmetically pleasant, non-toxic and does not wash off, Ms. Eyre said.
The experiment compared repellents such as DEET and Merck IR 3535 in addition to MPC. The test cages contained four breath-warmed moist chicken skin "biting targets" with applied repellents and a control. The mosquito biting behavior was recorded on video and bites were counted at introduction and after one hour. MPC, a menthol-derived ingredient largely used in cosmetics for its cooling, moisturizing and soothing effects, achieved 80% repellency initially and 59% after one hour, meeting the objectives of a "good" material achieving at least 50% repellency at both time intervals. The new testing method does not require people to subject themselves to bites. Ms. Eyre also noted that MPC would be most effective as a repellent when combined with other bite inhibitors for improved performance.
Engelhard Corporations' Gabriel Uzunian presented "The impact of skin tone on the color generated by effect pigments" to discuss the visual appearance of effect pigments on various skin tones using a skin tone color chart developed by The Leneta Company. A goniospectrophotometer measured reflected light at the specular angle (0 [degrees]) and two aspecular angles (20 [degrees] and 45 [degrees]) to calculate values and visual effects seen by the eye. The pigments (titanium dioxide and mica) were applied to the color chart. Due to the incidence light, the pigments reflected part of the incident light and transmitted the portion that is not reflected, resulting in complementary colors. It was found that colors generated by effect pigments are highly dependent on the background and viewing angle. For example, on a white background, both a reflection and a transmission color are seen depending on the viewing angle; however, a black background only shows the reflection color.
In the presentation "Structure and property relationship of nonionic surfactants and emulsifiers," Sasol's Silke Hoppe, Ph.D, discussed the comparison of five nonionic surfactants based on structurally distinct hydrophobes to emulsify difficult ingredients such as silicones or lactates. Results concluded that the behavior of alcohol ethoxylates and wetting depend on the hydrophobe and degree of ethoxylation, more ethylene oxide (EO) results in more foam and critical micelle concentration (CMC) and equilibrium surface tension depend on hydrophobe structure (higher CMC is more effective in lowering surface tension). Sasol will soon introduce a new set of emulsifiers, Guerbet 12 ethoxylates, propoxylates and alkoxylates to emulsify a variety of esters and silicone oils.
Jon J. Kabara, Ph.D of Technology Exchange, Inc., Galena, IL, presented "Hurdle technology: principles for formulating preservative-free cosmetics," highlighting the latest technologies to prevent microorganism growth in personal care products. Water amounts can control microbial growth, as well as surfactants due to their solubilizing effects. Fatty acids have had a long history, and lauric acids in particular have been found to have both moisturizing and germicidal action, Dr. Kabara said. A new family of phospholipids with a reverse phosphate and quaternary arrangement has been found to be a potent antioxidant without significant toxicity or skin irritation. Antioxidants, spices, essential oils and potential chelating agents are also antimicrobial. Packaging, such as dispensers that prevent contamination, are also useful in preserving products.
On the topic of understanding the sense of smell, recognition and response, Stephen Herman of AFF International, Fairfield, NJ, discussed his paper, "Recent developments in chemoreception." He noted that Buck and Axel (1991) found the odor binding protein was a 7-transmembrane domain protein similar to hormone receptors to recognize and decode odors. Other developments have recently been in aromascience, or the temporary effects of aromatherapy-type products on emotion, and synthesia, the relation between the senses and the color of packages to match an aroma. Research on pheromones has offered new knowledge about copulins, short chain fatty acids found in vaginal secretions during the fertile times of the female cycle, which are now present in commercial pheromone fragrances. Pherins, pheromonal chemicals that cause a response in the volmeronasal organ (VNO), can apparently affect the olfactory system even when the VNO is blocked. Mr. Herman noted that the perception that pheromones are only for high priced items. He insisted that developments will lead to more economical choices and will open a new sensory dimension.
The SCC annual meeting will be held Dec. 6 and 7 in New York. The next scientific seminar will be held on May 5 and 6, 2002 in San Antonio, TX. An International Federation of Societies of Cosmetic Chemists (IFSCC) meeting will be held in September in Taipei, Taiwan and the IFSCC congress will be held in Edinburgh, next year. In 2004, the IFSCC congress will be held in Orlando, FL, at the Walt Disney World Dolphin Hotel. More info: www. scconline.org.
RELATED ARTICLE: Students Compete in Poster Contest
NINE students from American universities competed in a poster contest at the SCC seminar. The winner, Wael Youssef from the University of Cincinnati, displayed his poster, "A simple in vitro method for measuring formulation occlusivity correlation with in vivo transepidermal water loss." Mr. Youssef was also a featured speaker and received a certificate, rosette and a check, as did second and third place winners, Penpan Saiyasombati and Lory Z. Santiago.