S. B. Ruetsch

TRI/Princeton, Princeton, New Jersey, United States

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Publications (28)11.4 Total impact

  • Yash K Kamath, Sigrid B Ruetsch
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    ABSTRACT: A microfluorometric method has been developed to characterize lipid removal or "delipidation" of the human hair cuticula during light exposure and chemical grooming processes such as oxidation (bleaching) and reduction. In the case of photochemical and chemical oxidation, lipid removal ("delipidation" of the F-layer or lipid-layer) from the outer beta-layer of the exposed scale faces and generation of cysteic acid groups occurs. This "delipidation," which ultimately results in "acidification" of the scale faces, leading to a change in surface chemistry from hydrophobic to hydrophilic, can be detected and quantified by microfluorometry by tagging, e.g., with the cationic fluorochrome Rhodamine B. In the case of reduction, similar tagging of the acid sites on the scale faces is possible, but this time, Rhodamine B reacts with the mixed disulfide containing a carboxyl group that will be ionized above a pH of about 4. In addition to this, we have shown by microfluorometric scanning that the negative charges generated in the cuticle surface can be used to bind low-molecular-weight quaternary conditioners. This process can be considered as "relipidation" or "refatting" of the scale faces. We have shown in earlier studies (1) that this entire process of oxidation-induced "delipidation" and subsequent "relipidation" of the acidic scale faces with a cationic conditioning molecule can also be reliably quantified by X-ray photoelectron spectroscopy (XPS). Furthermore, single-fiber wettability scanning using the Wilhelmy technique, which is highly sensitive to any changes in surface chemistry, is well-suited to detect and characterize treatment-induced changes in the chemical nature of the hair surface from hydrophobic to hydrophilic.
    Journal of cosmetic science 01/2010; 61(1):1-12. · 0.28 Impact Factor
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    ABSTRACT: New thermosensitive, cationic hydrogels were synthesized by the dispersion copolymerization of N-isopropylacrylamide (NIPAM) and (3-acrylamidopropyl)trimethylammonium chloride (AAPTAC). In the polymerization protocol, an amide-based comonomer, (3-acrylamidopropyl)trimethylammonium chloride, was reacted as a new alternative monomer for introducing positive charges into the thermosensitive hydrogel. The hydrogels were synthesized without making any pH adjustment in the aqueous medium. These hydrogel particles exhibited colloidal stability in the pH range of 1.5 to 11.0, while similar cationic hydrogels were reported to be unstable at pHs higher than 6. The stronger cationic character of the selected comonomer provided higher colloidal stability to the poly(NIPAM-co-AAPTAC) hydrogels. Furthermore, these hydrogels displayed sensitivity towards temperature, pH, and salt concentration. Interestingly, the particle size of hydrogels was found to be decreased significantly with an increase in temperature and salt concentration. In addition, using pyrene fluorescence spectroscopy, it was established that the hydrophobicity/hydrophilicity of the hydrogel particles was largely controlled by both pH and temperature. The thermosensitive hydrogels reported in this paper may be suitable for delivering different actives for cosmetic and medical applications. Although direct application of these hydrogel particles in cosmetics has not been shown at this stage, the methodology of making them and controlling their absorption and release properties as a function of temperature and pH has been demonstrated. Furthermore, these hydrogels may also have applications in scavenging organic and inorganic toxics.
    Journal of cosmetic science 01/2010; 61(6):421-37. · 0.28 Impact Factor
  • S. B. Ruetsch, B. Yang, Y. K. Kamath
    International Journal of Cosmetic Science 01/2009; 31(3):244-245.
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    ABSTRACT: Optical probing of hair fibres is an elegant, non-invasive method to monitor the fibre surface and its changes with various grooming protocols. In this paper, a goniophotometer with a He-Ne light source was used to study reflection profiles from single hair fibres in both the root-to-tip and tip-to-root orientations of the fibre. The calculated scale angle (the inclination of the cuticle to the fibre axis) was used as a monitor to study combing damage in hair to demonstrate the usefulness of the method. It was shown that progressive dry combing of hair leads to cuticle thinning or abrasive damage, and wet combing results in cuticle breaking or ablative damage. Further, the use of a conditioner active like a polyquaternium-10 largely mitigates both types of damage. These findings were supported by the results of a parallel scanning electron microscopic study.
    International Journal of Cosmetic Science 01/2008; 30(1).
  • Y K Kamath, S B Ruetsch
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    ABSTRACT: Natural weathering of hair in a relatively dry hot climate was carried out by exposing hair of different ethnicity to natural environmental conditions at a Q-Lab weathering station in Arizona. The appearance of hair fibers changed dramatically due to thinning and fusion of scales as well as fusion of individual hair fibers with each other (inter-fiber fusion) to form rod-like structures stuck together by solubilized, oozed out, gelled and finally hardened proteins. The hair became extremely rigid and brittle with radial cracks forming mostly smooth radial fractures and occasionally step fractures. There was also internal fusion of the cellular structure of the fiber. Hair fibers were characterized by scanning electron microscopy (SEM) and UV-visible microspectrophotometry. UV-visible spectra showed that natural hair color (melanin) plays an important role in protecting hair proteins, mostly by a sacrificial mechanism. Indian and Chinese black hair, which are rich in melanin, resist photochemical degradation much better than hair of European origin with moderate, low or no melanin content.
    International Journal of Cosmetic Science 05/2007; 29(2):145.
  • S B Ruetsch, Y K Kamath
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    ABSTRACT: Cationic conditioning compounds protect against hair damage caused by cosmetic chemical treatments and grooming practices. They also enhance the retention of moisture. However, the question as to whether they do this superficially by residing on the hair surface or by penetrating into the fiber remains unanswered. In this work, an attempt has been made to show the penetration of a low-molecular-weight cationic conditioning compound into the hair cortex using the time-of-flight secondary ion mass spectrometry (TOF SIMS) method, applied in earlier research to show the penetration of oils into hair. An example of the practical benefit of such penetration into the cortex in greatly improving the fatigue resistance of hair has been discussed.
    Journal of cosmetic science 01/2006; 56(5):323-30. · 0.28 Impact Factor
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    ABSTRACT: In this communication, penetration of vegetable oils into hair fibers has been investigated by the TOF-SIMS (Time-Of-Flight Secondary Ion Mass Spectrometry) method. In earlier work [1], the method was found suitable to study the penetration of coconut and mineral oils into human hair. Therefore, the study has been extended to a group of vegetable oils with different types of unsaturation in the fatty acid components. Different patterns of penetration have been observed for oils of different molecular structure. The general pattern which emerges from this study is that polyunsaturated oils do not penetrate at all, or do so only sparingly into the structure of hair. Most of these molecules seem to penetrate only into the cuticular region of the hair fiber. Oils with polyunsaturated fatty acids seem to have difficulty in penetrating hair. It is possible that these molecules do not fit into the fiber's cell membrane complexes, which are known to be the diffusion pathways in the keratin fiber. On the other hand, monounsaturated oils, such as olive oil, with more compact molecular structure seem to penetrate readily into the hair fiber.
    International Journal of Cosmetic Science 10/2005; 27(5).
  • S. B. Ruetsch, Y. K. Kamath
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    ABSTRACT: This is a multifaceted study on the characterization and quantification of damage to the hair fiber surface caused by photochemical and cosmetic chemical oxidative processes. Unique techniques were used, including a microfluorometric method that had been adapted to characterize and quantify the delipidation and acidification of the human hair surface during light exposure and cosmetic chemical grooming processes such as bleaching. During photochemical and chemical oxidation, breakdown of the lipid domains (also called the F-layer) of the outer b-layer occurs on the exposed scale faces and cysteic acid groups are generated on the cuticle cell surface. The newly formed acid functionalities can be tagged with the cationic fluorochrome Rhodamine B, allowing not only quantification of the level of progressive acidification but also localization of the newly formed acid functionalities. On the other hand, the negative charges generated on the hair surface by oxidation can also bind low molecular weight quaternary cationic conditioning compounds such as cetyltrimethylammonium bromide. This process can be considered a relipidation by adsorption. We have shown that the entire process of delipidation/acid formation and subsequent relipidation by adsorption on the scale faces can be quantified by X-ray photoelectron spectroscopy. Since X-ray photoelectron spectroscopy analysis is highly sensitive and able to detect atomic species at the very surface of the hair fibers, receiving signals from an escape depth as shallow as 25 Å, it appeared ideal for the characterization of treatment-induced changes in the hair surface. However, X-ray photoelectron spectroscopy provides an average elemental composition of the hair surface including scale faces and scale edges. The microfluorometric technique, on the other hand, can distinguish progressive delipidation of the scale faces from changes occurring at the broken scale edges. This distinction was shown and characterized in detail by slow speed microfluorometric scanning of the hair surface. Chemical and photochemical oxidative processes at the hair surface result in certain collateral effects. Particularly changes in surface wettability and fiber friction are of significance to the cosmetic chemist because they affect the spreading and wicking of products in hair as well as the managability and the body of hair assemblies. Methods of characterizing these effects are discussed briefly.
    International journal of cosmetic science 03/2005; 27(2):142 - 143.
  • S. B. Ruetsch, B. Yang, Y. K. Kamath
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    ABSTRACT: This research is a multifaceted study which investigates not only the role of melanin in providing photostability to natural hair color and hair proteins, but also the claim that the presence of specific artificial colors in hair slows down the rate of photodegradation of hair proteins. In earlier studies, the extractability of protein from photodegraded hair was investigated and showed that many of the cleaved proteins could not be extracted because of photo-oxidative cross-linking. The current study investigates the effect of the amount of melanin in hair of different ethnicity and the presence of artificial hair colors on the extractability of the main classes of hair proteins. Furthermore, the data are used in the interpretation of the effect of these components in being able to prevent photo-oxidative damage to hair proteins.When exposed to sunlight, hair undergoes changes in chemical, mechanical and morphological properties. The UVB and UVA regions of the solar spectrum are the most damaging to human hair. Of these two, the UVA region is predominant in the solar spectrum at low altitudes. Hair of different ethnicity responds differently to the damaging radiation of the solar spectrum, because of different amounts of melanin present in hair. Melanin absorbs the impinging radiation (especially at the lower wavelengths (254–350 nm), and converts it by some complex internal mechanism into heat. Because of this, melanin provides a photochemical protection to natural hair color and hair proteins and prevents their photodegradation. However, the melanin pigments act sacrificially and become themselves degraded in the process of protecting the proteins from light. As a result, this «protective» effect of the melanin pigments does not last during long-term intense exposure, when, regardless of the amount of melanin in hair, most matrix, intermediate filament and high molecular weight hair proteins undergo photo-oxidative cross-linking into higher molecular weight species, and their extractability from hair decreases significantly.The goal of this study is to demonstrate how UV-radiation affects natural and artificial hair color during long-term exposures. Bright-field and UV-microspectrophotometry and an electrophoretic separation technique (SDS-PAGE) were chosen as investigative techniques for these studies, because they are well-suited to accurately and reproducibly investigate the initial properties of a specific hair sample and the changes in these properties as a result of long-term light-exposure. The goal of this paper is not to relate this to the content and type of melanin in hair. Electrophoresis, while not measuring the exact quantitative amount of protein extracted, is a semi-quantitative method, where increases in brightness of the bands represent increased amounts of proteins that were extracted of that specific protein from hair. This electrophoretic study attempts to determine whether the presence of natural or artificial color in hair influences the protein extractability in unaltered hair and the photo-oxidative cross-linking during light-exposure.The bright-field microspectrophotometric study showed that high concentrations of melanin provide protection to the melanin itself and that they prevent loss of natural hair color during light-exposure. However, neither large amounts of melanin in hair of different ethnicity, nor artificial hair colors (even a dye with an absorption in the UV region) provide protection to the hair proteins against photodegradation under the conditions used in this study.UV-microspectrophotometry has suggested the formation of high levels of photo-oxidized proteins as a result of light-exposure. Electrophoresis revealed photo-oxidative cross-linking of most matrix, intermediate filament and high molecular weight hair proteins into their higher molecular weight analogues, rendering them less extractable due to their lowered diffusivity. Only very low levels of low molecular weight matrix proteins could be extracted.
    International Journal of Cosmetic Science 10/2004; 26(5):269-269.
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    S B Ruetsch, Y K Kamath
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    ABSTRACT: The effect of curling hair with a curling iron has been investigated. Possibilities of thermal damage with repeated curling according to, and in violation of, the manufacturer's specifications have been studied. The propensity of hair surface to damage depends on the moisture content of the hair, and these experiments have been conducted in both wet and dry conditions, with and without application of tension, and with short or prolonged times. Scanning electron microscopic (SEM) examination revealed that fibers treated under the dry condition (50% RH) show radial and axial cracking along with scale edge fusion. Similar thermal treatment on wet hair resulted in severe damage of the type described above, as well as bubbling and buckling of the cuticle due to the formation and escaping of steam from the fiber. Fibers subjected to repeated curling in the dry condition show slight increases in tensile mechanical properties, characteristic of a crosslinked fiber. Fibers treated with conditioners show an improvement in characteristic life, especially in the case of low-molecular-weight conditioners, such as CETAB, which can penetrate into the hair fiber (shown by TOF-SIMS analysis).
    Journal of cosmetic science 08/2004; 55(1):13-27. · 0.28 Impact Factor
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    ABSTRACT: Hair is routinely twisted during grooming processes, which can cause tangles and lead to breakage of hair fibers. To evaluate the damage caused by twisting hair, the tensile stress-strain properties of single twisted hair fibers were measured by two different experimental procedures: (A) twist at constant length, followed by extension to break (without untwisting); and (B) twist and untwist at constant length, followed by extension to break. In procedure (A), the strength, extension, and initial modulus decreased with increase in twist factor, whereas in procedure (B), the strength and extension did not significantly change from control values, although the initial modulus decreased with increase in twist factor. Furthermore, the degree of recovery from torsional deformation was studied by a variant of procedure (B), where the fiber after untwisting was relaxed for 5 and 10 minutes, respectively, prior to extension to break. The major conclusion from this study was that at low and moderate twist levels, the tensile mechanical properties of human hair are recoverable.
    Journal of cosmetic science 02/2004; 55 Suppl:S79-90. · 0.28 Impact Factor
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    ABSTRACT: Although adhesion failure in hair fibers can occur inside cells, it occurs more frequently in the cell membrane complex (CMC), often involving the rupture of interlayer bonds. Therefore, a model of the CMC is presented, based on prior research in which we propose interconnecting bonds between the layers to assist in our interpretation of hair-fracturing mechanisms for cuticle chipping, deep transverse cuticle cracks, cracks during heat drying, scale lifting by surfactants, and catastrophic failure. Failure in the wet state generally involves hydrophilic layers, e.g., the contact zone of the CMC or the endocuticle or bonding to these hydrophilic layers, whereas failure in the dry state generally involves bonding between hydrophobic layers, e.g., beta-delta failure. Chemical damage by perms, bleaches, and sunlight, by breaking specific chemical bonds, influences the sites of initial failure and increases the number of routes for crack propagation, leading to more complex fracture patterns.
    Journal of cosmetic science 01/2004; 55(4):351-71. · 0.28 Impact Factor
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    S B Ruetsch, B Yang, Y K Kamath
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    ABSTRACT: Microspectrophotometric and electrophoretic methods were used to characterize and quantify the effects of primary damage to hair from chemical and photochemical oxidative processes. The diffusion of molecules proceeding from the fiber surface to the center of untreated and modified (by chemical and photochemical oxidative processes) hair fibers was mapped by fluorescence microscopy and quantified by calculating diffusion coefficients of a fluorescent molecule. In addition, an electrophoretic separation technique, namely, SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis), was used not only to substantiate the results obtained in the microfluorometric study, but also to show how the main classes of proteins of unaltered hair are modified by cosmetic chemical treatments, light exposure, and combinations of these two processes. UV microspectrophotometry is an alternate analytical method to evaluate photo-oxidative damage in hair, and supports the results obtained by microfluorometry.
    Journal of cosmetic science 01/2003; 54(4):379-94. · 0.28 Impact Factor
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    ABSTRACT: Spin finishes are applied to melt-spun fibers to protect them from abrasion during processing. The principal component of the fiber finish is a lubricant, which generally is a random or block copolymer of ethylene oxide/propylene oxide. Although these polymers do not penetrate the fiber because of their high molecular weight, depending on the nature of the fiber polymer, they interact to cause changes in the hardness of the fiber surface. This happens to be the case with acidic polymer fibers such as nylon-6 and polyester [poly(ethylene terephthalate], both of which are softened by the ethylene oxide/propylene oxide lubricant. We used atomic force microscopy with nanoindentation capability to study the effect of lubricants on the microhardness of nylon-6 and poly(ethylene terephthalate) fiber surfaces. Softening of the fiber surface by plasticization generally results in an increase in fiber friction because of shear deformation at the interface. We made an effort to determine the friction of fibers against a hard stainless steel surface after coating them with the finish lubricant for different lengths of time. The relevance of these results to fiber processing is discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 394–414, 2002
    Journal of Applied Polymer Science 04/2002; 85(2):394 - 414. · 1.40 Impact Factor
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    ABSTRACT: Surface energy of nylon 66 fibers is of considerable importance in the conversion of these fibers into consumer products such as tirecord, carpets, and various composite materials in combination with other polymers. Adhesion of nylon 66 fibers to rubber or the coupling agent in tirecord, or to the fluoropolymer used as a soil resist finish in carpets, depends on the surface energy of these fibers. If produced undrawn, nylon 66 fibers can be drawn later, up to 8×, to attain desirable fiber properties. Since hydrogen bonds rearrange during drawing it would be of interest to see if these changes also result in changes in surface energy. An attempt has been made to understand this aspect in this article. We have determined the dispersion and the acid–base (donor–acceptor) components of the surface energy of nylon 66 fibers by wettability measurements in appropriate probe liquids using the Wilhelmy principle, as well as by inverse gas chromatography (IGC), where interactions between the fiber surface and the probe molecules are studied in a chromatography column in which fibers form the stationary phase. By suitable data treatment these chromatograms could be converted to adsorption isotherms. The probe molecules were reasonably well matched to give comparable values by the two methods. Adsorption of site-specific fluorescent dyes showed increases in acid and basic surface groups by microfluorometry on drawn fibers. The density of the surface groups depended on the drawing environment, especially the one involving liquid water. The apparent discrepancy between microfluorometry results and the surface energy by wettability measurements resolved itself when the surface energy components were calculated by assuming that the entire work of adhesion results from hydrogen bonding interactions only, in solids with functional groups capable of forming strong hydrogen bonds, such as nylons, as suggested by Gutowski.
    Journal of Colloid and Interface Science 02/1996; 177(2):579–588. · 3.55 Impact Factor
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    SIGRID B. RUETSCH, HANS-DIETRICH WEIGMANN
    01/1996;
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    ABSTRACT: Ultraviolet microspectrophotometry is used to monitor the radial diffusion of three uv stabilizers in high molecular weight PET fibers. Under identical application con ditions, the benzotriazole and benzotriazine derivative stabilizers show peripheral penetration only, whereas the benzophenone derivative stabilizer diffuses throughout the fiber cross section. Peripheral penetration of the benzotriazole and benzotriazine derivatives does not prevent polymer photodegradation in the unprotected interior, whereas all regions of the fiber are protected by the more uniformly distributed ben zophenone stabilizer. Heavy peripheral deposition of the benzotriazole stabilizer pre vents these highly protected regions from polymer photodegradation.
    Textile Research Journal 01/1996; 66(4):185-195. · 1.14 Impact Factor
  • Y. K. Kamath, S. B. Ruetsch, H.-D. Weigmann
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    ABSTRACT: A microfluorometric method is presented for studying the distribution of finishes on textile substrates. The method is based on the effect of microenvironment (such as microviscosity and micropolarity ) in preserving the excited states of fluorescent tracer molecules introduced into the finish. Different methods for introducing tracers into finishes are described, with a critical appraisal of their merits. Fluorescence intensity is shown to be related to the thickness of the finish film up to about 3 μm. Above this, the intensity levels off due to autoquenching effects. Various microfluorometric scanning modes suitable for studying filaments, yarns, and fabrics are described, and their relevance to the nature of the distribution of finish is discussed in detail. The importance of selecting an appropriate tracer is illustrated by applying the method to an autofluorescent substrate.
    Textile Research Journal 01/1993; 63(1):19-32. · 1.14 Impact Factor
  • 7th Int. Wool Textile Research Conference, 1985, Tokyo/Japan, Tokyo/Japan; 01/1985
  • Y. K. Kamath, S. B. Ruetsch, H.-D. Weigmann
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    ABSTRACT: The fading of disperse-dyed nylon by atmospheric ozone can pose a problem at high environmental temperatures and humidities. In attempting to devise ways to inhibit such fading, researchers have suggested that the reaction between ozone and dye occurs chiefly at the fiber surface—that ozone does not penetrate inward, but that the dye diffuses outward from the fiber interior due to the concentration gradient set up as surface dye is destroyed. This mechanism has been supported, though not proved, by observations that dye diffusion is also sensitive to humidity in such systems, that rates of dye loss due to ozone exposure correlate with dye desorption rates into water, and that dye loss, like dye diffusion, depends on the square root of time and on the size of the dye molecule. These findings were based on determinations of total dye content in fiber specimens; however, adapting the techniques of microspectro photometry to fibers, as described in this paper, makes it possible to observe directly the locus of dye destruction in the fiber and to determine the relative dye loss at selected locations, such as at the edge and center of a fiber cross section. The coefficient of diffusion of the dye within the fiber can also be evaluated using the micropho tometer. These capabilities have been applied to the ozone fading of nylon 6 dyed with C.I. Disperse Blue 3, and the experimental results do not correlate with a math ematical model based on the hypothesis of dye destruction exclusively at the fiber surface. On this basis it is postulated that, in addition to dye diffusion toward the fiber surface, ozone penetration into the fiber contributes substantially to the fading process.
    Textile Research Journal 01/1983; 53(7):391-402. · 1.14 Impact Factor