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Cosmetic efficacy of topically applied hydrolysed keratin peptides and lipids derived from wool


Abstract and Figures

Skin moisturisation, elasticity, feel and appearance can all be improved through the topical application of protein hydrolysates. Recent studies suggest that supplementing intercellular lipids of the stratum corneum can enhance the functioning of the skin. In this study, a hydrolysed keratin peptide (molecular weight <1000 Da) was prepared from wool and tested on skin in two different formulations: an aqueous solution and an internal wool lipids (IWL) liposome suspension. In vivo long-term studies were performed to evaluate the water barrier function of the skin after topical application of different formulations. During the treatment period, hydration and elasticity were determined. A sorption-desorption test was also performed to assess the hygroscopic properties and water-holding capacity of the different treated skin sites. Significant differences were found between the control and treated sites, with the treated areas showing an increase in hydration and elasticity as a result of keratin peptide application. Measurements also indicated that the keratin formulations reinforce the skin barrier integrity, improving its water-holding capacity. A combination of the keratin peptide with the IWL showed beneficial effects, indicating that this combination is suitable for designing new cosmetics products.
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Cosmetic effectiveness of topically applied hydrolysed
keratin peptides and lipids derived from wool
C. Barba
, A. Roddick-Lanzilotta
, R. Kelly
, J. L. Parra
and L. Coderch
Department of Surfactant Technology, Chemical and Environmental Research Institute of Barcelona, Barcelona, Spain,
Canesis Network Limited,
Christchurch, New Zealand and
Keratec Limited, Canterbury, New Zealand
Background/purpose: Skin moisturisation, elasticity, feel
and appearance can all be improved through the topical
application of protein hydrolysates. Recent studies suggest
that supplementing intercellular lipids of the stratum cor-
neum can enhance the functioning of the skin.
Methods: In this study, a hydrolysed keratin peptide (mo-
lecular weight o1000 Da) was prepared from wool and
tested on skin in two different formulations: an aqueous
solution and an internal wool lipids (IWL) liposome suspen-
sion. In vivo long-term studies were performed to evaluate
the water barrier function of the skin after topical application
of different formulations. During the treatment period, hy-
dration and elasticity were determined. A sorption –deso-
rption test was also performed to assess the hygroscopic
properties and water-holding capacity of the different trea-
ted skin sites.
Results: Significant differences were found between the
control and treated sites, with the treated areas showing
an increase in hydration and elasticity as a result of keratin
peptide application. Measurements also indicated that the
keratin formulations reinforce the skin barrier integrity,
improving its water-holding capacity.
Conclusion: A combination of the keratin peptide with the
IWL showed beneficial effects, indicating that this combina-
tion is suitable for designing new cosmetics products.
Key words: keratin peptides – internal wool lipids – lipo-
somes – hydration – elasticity – sorption –desorption test
&Blackwell Munksgaard, 2007
Accepted for publication 24 May 2007
WOOL IS primarily (85–95%) composed of
keratin proteins that combine to give it
desirable properties such as strength, insolubility
and moisture regain. Different classes of keratin
proteins are represented in the complex macro-
molecular structure, each of which has specific
functions and characteristics. Protein hydroly-
sates from various sources have long been used
in skin and hair personal care products and are
known to confer improved compatibility, feel,
moisturisation and help maintain the natural
structure (1, 2) by interacting favourably with
the keratin and other components of skin and
hair (3).
Wool also contains a minor (1.5%) internal
lipid component that is also known to impact on
the physical, chemical and mechanical properties
of the fibre (4). Internal wool lipids (IWL) are rich
in cholesterol, free fatty acids, cholesterol sul-
phate and ceramides and are very similar in both
structure and composition to those membranes of
other keratinic tissues such as human hair and
skin stratum corneum (5).
Recent studies have shown that formulations
containing lipids that are similar to the natural
components of the skin and, in particular some
ceramide supplementation, can improve disturbed
skin conditions. IWL extracts have been shown to
form liposomes with a stable bilayer structure (6, 7)
and topical application of IWL liposomes on intact
and disturbed skin has been demonstrated to
improve the skin barrier properties (8, 9).
In this work, the effect on the skin of a novel
wool keratin peptide, obtained from an enzy-
matic hydrolysis of the intermediate filament
protein, is investigated. Depending on the mole-
cular weight and chemical composition, the abil-
ity of peptides to penetrate into the skin and
provide nutrition, moisturisation and skin pro-
tection, is well established (2, 10).
The aim of this work is to determine the effect
of the wool keratin peptide when applied topi-
cally on the water-holding capacity, hydration
and elasticity of undisturbed skin. Two different
formulations, an aqueous solution and IWL lipo-
some solution, have been evaluated.
Skin Research and Technology 2008; 14: 243–248
Printed in Singapore All rights reserved
doi: 10.1111/j.1600-0846.2007.00280.x
r2007 The Authors
Journal compilation r2007 Blackwell Munksgaard
Skin Research and Technology
Materials and Methods
Chloroform (Merck, Darmstadt, Germany), kera-
tin peptide (Keratec Limited, Christchurch, New
Zealand), methanol (Merck) and sodium chloride
(Panreac, Barcelona, Spain) were used.
Sample preparation
The IWL were soxhlet extracted with a chloro-
form/methanol azeotrope (11). IWL liposomes
were prepared by dissolving the IWL in chloro-
form/methanol 2:1 (v/v) and evaporating to
dryness under a stream of dry nitrogen to form
a thin film on the flask. The film was hydrated
with 0.9% NaCl solution to give a final suspen-
sion that contained 2% liposomes. Multilamellar
vesicle liposomes were formed by sonication of
the suspension in a sonicator, Labsonic 1510 (B.
Braun, Melsungen, Germany), at 100 W for about
15 min, maintaining the temperature at 65 1C.
Two different keratin formulations were pre-
pared for application on the skin: keratin sample 1,
an aqueous keratin formulation, where a 15%
solution of the keratin peptide was diluted to a
final concentration of 0.5%, and keratin sample 2,a
liposome formulation prepared by mixing the
IWL liposomes (2%) with the aqueous keratin
solution to obtain a final concentration of 0.5% of
the keratin peptide and 2% of IWL.
Six healthy Caucasian volunteers (all females)
phototype III–IV, mean age 28 6 years (range
24–36 years), participated in both studies (Table
1). The subjects were advised to avoid topical
drugs or moisturisers on the tested zones for a
week before the experiments. To obtain reliable
measurements, the volunteers were acclimatised
for 15 min in a conditioned room (20 1C, 60% RH)
before the experiments.
Biophysical measurements
Skin hydration was determined using a Corne-
ometer CM 85 (Courage & Khazaka, Colonge,
Germany), which measures skin capacitance in
arbitrary units (AU). Elasticity was determined
by a Cutometer SEM 575 (Courage & Khazaka)
using Mode 1 where the measurements are per-
formed with a constant negative pressure. Results
are visualised in a curve that points out the
viscoelastic qualities of the skin. The parameters
that were considered in these studies are: R5, the
net elasticity, and R7, portion of elasticity com-
pared with the complete curve (the closer these
parameters to 1, the more elastic the skin). All
parameters were recorded in accordance with
established guidelines (12–14).
Efficacy of the keratin peptides on healthy human skin
A long-term study was performed to test the
effect of the keratin formulations when applied
repeatedly to undisturbed skin (15). Baseline
measurements of skin capacitance and skin elas-
ticity were taken on six marked zones of the volar
forearm of the volunteers before topical applica-
tion: three zones for topical treatment of the
different samples [keratin peptide aqueous solu-
tion (keratin sample 1), keratin peptide liposome
solution (keratin sample 2), and IWL liposomes]
and two zones for the placebo solutions [water
(placebo 1) and 0.9% NaCl solution (placebo 2)].
Placebos and solutions (50 mL) were randomly
applied onto marked areas of 9 cm
using an
Exmire microsyringe (ITO Corp., Fuji, Japan).
After 24 h all biophysical parameters, skin capa-
citance and skin elasticity, were evaluated and
then 50 mL of the solutions were applied again.
The application of the solutions was repeated for
three more days and the parameters were mea-
sured on days 2, 3, 4 and 7 (3 days after the last
Sorption–desorption test
Following the long-term study, a sorption–deso-
rption test (16, 17) was performed on the sites
treated with the keratin peptides. This test is
based on a kinetic method to measure stratum
corneum water uptake and water-holding capacity
following the application of the different samples.
Baseline measurement of skin capacitance was
250 mL of distilled water was applied onto each
test area for 90 s using an Exmire microsyringe
TABLE1. Age and skin phototype of the volunteers who participated in the
Volunteer Age Phototype
1 24 III
3 24 III
Barba et al.
(ITO Corp.). Afterwards, the water droplet was
removed with a soft paper towel and the water
desorption kinetics was recorded every 90 s (t
and t
) using a
Data treatment
The mean values and standard deviations (SD)
were calculated. Dixon’s test was used for detect-
ing outliers, which were excluded from the data.
One-way analysis of variance, with the Kruskal–
Wallis test, was used to determine significant
differences between the values obtained from
the different treatments (significance level ac-
Results and Discussion
Efficacy of the keratin peptides on undisturbed skin
A long-term study was performed on undisturbed
skin to determine the efficacy of the keratin pep-
tide samples (18, 19). Evaluation of skin capaci-
tance and skin elasticity was performed 24h after
a daily application (days 1, 2, 3 and 4) and 3 days
after the last application (day 7).
The mean values of skin capacitance and elas-
ticity parameters for the different treatments were
calculated and are listed in Table 2 and Table 3.
Significant differences were obtained for skin
capacitance and elasticity parameters with appli-
cation of the keratin samples.
Values for skin capacitance (Table 2) show a
greater increase on the skin capacitance in the
sites to which keratin samples were applied
during the treatment period. Figure 1 displays
the variation of the skin capacitance after sample
application during the treatment period. Changes
were evaluated vs. both the basal and the place-
bos values. It was observed that the zones treated
with the keratin peptide samples had a higher
skin capacitance and this was maintained 3 days
after the last application. Keratin peptide samples
1 and 2 showed very similar abilities to increase
the hydration of the skin, indicating that the
peptides are effective when applied from an
aqueous solution or in liposome form.
Evaluation of the parameters R5 and R7 for the
skin elasticity (Table 3) showed a trend of
increasing elasticity for the zones to which the
keratin peptides were applied. The keratin solu-
tion 1 yielded an increase in skin elasticity that
was maintained over the duration of the treat-
TABLE2. Skin capacitance values (mean values SD) obtained before (basal) and during the treatment period
Time (days)
Basal 1 2 3 4 7
Placebo 1 37.78 4.37 39.00 5.93 39.61 4.78 41.28 6.15 38.78 5.21 38.28 5.11
Placebo 2 39.67 8.58 41.28 6.93 38.56 5.63 39.00 8.81 40.78 5.73 35.78 6.70
IWL liposomes 38.95 8.54 41.28 6.59 39.50 4.64 40.94 5.68 38.89 7.69 35.50 6.46
Keratin sample 1 35.56 5.30 39.00 5.48 38.61 5.83 41.29 4.99 41.06 5.83 41.33 5.89
Keratin sample 2 37.61 6.64 40.94 6.36 40.72 5.55 40.61 8.25 41.28 3.63 40.11 3.97
IWL, internal wool lipids; SD, standard deviation.
TABLE3. Skin elasticity parameter values (mean values SD) obtained before (basal) and during the treatment period
Parameter Zones
Time (days)
Basal 1 2 3 4 7
R5 Placebo 1 0.811 0.10 0.826 0.08 0.814 0.08 0.812 0.11 0.826 0.08 0.818 0.10
Placebo 2 0.781 0.06 0.704 0.11 0.740 0.14 0.730 0.14 0.730 0.18 0.764 0.12
IWL liposomes 0.728 0.15 0.693 0.13 0.744 0.16 0.631 0.13 0.726 0.15 0.774 0.13
Keratin sample 1 0.777 0.13 0.834 0.09 0.825 0.06 0.789 0.09 0.824 0.07 0.825 0.10
Keratin sample 2 0.763 0.11 0.729 0.12 0.838 0.16 0.731 0.12 0.837 0.12 0.805 0.09
R7 Placebo 1 0.670 0.07 0.673 0.07 0.668 0.07 0.671 0.08 0.686 0.05 0.667 0.07
Placebo 2 0.640 0.04 0.589 0.08 0.629 0.10 0.605 0.10 0.613 0.12 0.643 0.10
IWL liposomes 0.520 0.10 0.622 0.07 0.565 0.10 0.569 0.11 0.605 0.12 0.629 0.07
Keratin sample 1 0.616 0.09 0.680 0.08 0.653 0.08 0.638 0.07 0.679 0.07 0.658 0.12
Keratin sample 2 0.641 0.09 0.625 0.09 0.688 0.12 0.626 0.09 0.691 0.09 0.683 0.07
IWL, internal wool lipids; SD, standard deviation.
Cosmetic effectiveness of topically applied keratin peptides and lipids
ment period. The combination of the keratin
peptide with the IWL liposomes showed a sig-
nificant beneficial effect, resulting in a 17% in-
crease in skin elasticity during the treatment
period. An increase in skin elasticity was also
obtained for the zones treated with the IWL
liposomes only, supporting the beneficial effects
of skin lipid supplementation (Fig. 2 and Fig. 3).
The results obtained in this first study show
that application of the keratin peptides conferred
beneficial effects to the skin. These effects were
demonstrated by an increase in the skin hydra-
tion and elasticity. Wool keratin peptides, with a
low molecular weight range (o1000 Da), are able
to penetrate into the skin and improve the water-
holding capacity of the skin, as demonstrated by
an increase in its hydration and elasticity. A
combination of the keratin peptides with the
IWL extract in the form of liposomes confers
similar beneficial effects on hydration and im-
proves elasticity. Therefore, this combination may
be a good approach when formulating new
cosmetic products for skin care, as it combines
the ability to increase skin hydration and elasti-
city due to the presence of keratin peptides and
also offers the potential to increase the skin
barrier and decrease transepidermal water loss
attributed to the presence of IWL (8, 9).
Sorption–desorption test
This method is a dynamic measurement of skin
capacitance using a non-invasive test (16, 17, 20).
Following the application of water to the skin, the
capacitance value increased sharply, and then
declined slowly with an almost complete recovery
to the baseline value reached after 10min (Table 4).
12 347
Skin Capacitance Change (%)
Keratin sample 1
Keratin sample 2
IWL Liposomes
Fig. 1. Variation of skin capacitance after sample application during
the treatment period. Changes were evaluated vs. both basal and
placebo values (
Po0.05, calculated between samples and placebos).
Time (Da
Elasticity R5 Change (%)
Keratin sample 1
Keratin sample 2
IWL Liposomes
Fig. 2. Variation of the elasticity parameter R5 after sample applica-
tion on volunteers during the treatment period. Changes were
evaluated vs. basal and placebos values. (
Po0.05, calculated between
samples and placebos).
Time (Days)
Elasticity R7 Change (%)
Keratin sample 1
Keratin sample 2
IWL Liposomes
Fig. 3. Variation of the elasticity parameter R7 after sample applica-
tion on volunteers during the treatment period. Changes were
evaluated vs. both basal and placebo values. (
Po0.05, calculated
between samples and placebos).
TABLE4. Skin capacitance values (mean values SD) obtained before
(BV) and during the treatment period
Time (s)
Water Keratin sample 1 Keratin sample 2
BV 42.81 5.27 42.06 7.80 39.89 1.75
0 85.56 5.91 96.72 11.28 100.31 5.22
90 61.61 6.47 59.50 7.01 57.17 2.84
180 54.06 4.30 55.06 7.61 51.00 3.84
270 51.00 4.75 53.11 7.52 48.64 4.63
360 49.67 4.73 50.89 7.18 47.83 3.44
450 48.33 4.95 50.44 7.27 47.11 3.48
540 47.84 3.73 50.45 7.37 46.33 3.72
630 47.83 4.24 50.45 7.13 46.22 2.20
SD, standard deviation.
Barba et al.
To assess the final results, the baseline values
were subtracted to obtain the increase in capaci-
tance (in arbitrary units) at each time point
(added capacitance, AC); then, the ln(AC) was
calculated and plotted vs. time (Fig. 4). Figure 4
shows that the two zones treated with the keratin
peptides yielded a higher absorption (value at
time 0).
The sorption–desorption test demonstrated the
moisturisation properties of the keratin samples.
Higher values of initial absorption of water and a
greater capacity for retention were observed for
the areas treated with the keratin samples. There
was a slightly more pronounced effect for the
aqueous keratin peptide solution 1.
In summary, in the long-term study, the beneficial
effect of application of the wool keratin peptide
samples on healthy skin has been demonstrated.
Improved hydration and elasticity were observed
following treatment with the keratin peptide
samples. Furthermore, the moisture sorption–
desorption profile obtained showed higher va-
lues of initial absorption of water for the skin
zones treated with the two keratin formulations.
Higher skin elasticity values were observed fol-
lowing treatment with the IWL liposomes; these
results support the beneficial effects of skin lipid
supplementation with IWL, which have been
shown, in previous work, to strongly resemble
that of the stratum corneum.
Therefore, hydrolysed keratin peptides derived
from wool may be applied alone or combined
with wool internal lipids structured as liposomes,
improving in both cases the hydration, elasticity
and moisture sorption–desorption profile. This
new combination of derivatives from wool fibre
can be suitable for designing new pharmaceutical
or cosmetic products for skin care.
We thank all the volunteers who participated in
these trials. Thanks are also due to EVIC Hispa-
nia for the scholarship awarded to C. Barba.
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0 120 240 360 480 600 720 840
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ln (AC)
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Clara Barba
Department of Surfactant Technology
Chemical and Environmental Research Institute of Barcelona
Jordi Girona 18-26
Barcelona 08034
Tel: 134 93 400 6179
Fax: 134 93 204 5904
Barba et al.
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... Hydrolyzed amino acids are protein-derived substances that result in temporary increase in hair strength and hydrophobicity. 6,9,[22][23][24] Hydrolyzed amino acids are derived from animal or vegetable sources and are efficient hair restorers and natural moisturizers. Protein hydrolysates consist of positively charged amino acids with low molecular weight, usually under 1,000 Da. ...
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Medical professionals that treat patients with alopecia usually lack knowledge about hair cosmetics. Trichologists focus on hair cycling and growth problems and not on the hair shaft integrity. This may lead to abandon of the use of the prescribed treatment, such as topical minoxidil or to inadequate traumatic grooming habits that may jeopardize hair follicle health. Shampoos, hair dyes, and hair-straightening products may alter hair fiber structure, remove lipids, and elude protein. Hair procedures such as hair dying and straightening have side effects and health concerns, especially for pregnant women or sensitive hair and scalp patients. Hair breakage, follicle traction, frizz, contact dermatitis, and mutagenicity are possible side effects of hair cosmetics misuse. The proper use of hair care products may help to increase patients' adherence to alopecia treatments and avoid health problems related to inadequate application of hair cosmetics and procedures.
... Improves hydration and elasticity of healthy skin. [159] adhesion sequences, has excellent cell stability. It assisted in fibroblast attachment and proliferation for 23-43 days. ...
This review aims to trace the developments of keratin extraction techniques over the last 70 years and possibilities for future research. Keratin is a fibrous structural protein naturally present in the appendages of animals such as hair, wool, feathers, hooves and hides. Currently millions of tons of these appendages are discarded as waste products by the meat, poultry, textile and leather industries. These keratin-rich wastes lack environmental-friendly disposal methods, and are often dumped in landfills or incinerated. Over the last few years, several studies have developed various methods to repurpose these wastes as a potential source for obtaining keratin. Keratin has recently been demonstrated to have applications within the biomedical field (as a scaffold material in tissue engineering, for drug delivery and wound healing), cosmetic products and environmental remediation. To meet the demand for keratin in the above-mentioned applications, research on extracting keratin from different natural sources including keratinous wastes and improving the extraction efficiency thereof is imperative. Hence, with a brief introduction to the structure and occurrence of keratin, the present review extensively focuses on current methods of its extraction from hair, feathers, wool, hides and hooves. Also, the review identifies gaps in current research and outlines future directions in this field.
The utilization of cosmetics is not a recent practice. In ancient times, kohl was used by women to darken their eyelids, also, milk is used during bathing to get soften and whiten skin. Cosmetics have a huge market all over the world, and a business of billion dollars per annum. An extensive variety of ingredients involves polymers, minerals, chemicals, and also other materials like preservatives, color, pH stabilizers, emulsifiers, and thickeners to convey anticipated characteristics to the cosmetics products. Over the past years, biopolymeric materials have gained a lot of attraction in the global cosmetics industry because of their price, durability, and adaptability. Consumer awareness concerning the harmful influence of synthetic polymers on the atmosphere guides the path for biopolymer development from natural sources. Cosmetic polymers are utilized for the nanoparticle’s preparation for the fragrance’s delivery. Also, nanoparticles have been loaded with dermal permeation enhancers to enhance their bioactivities on the skin. Natural polymers in cosmetic formulations are of specific significance due to their eco-friendly, safe, and biocompatible characteristics. These formulations are appropriate for a number of applications such as hair, skincare, and make-up as they are highly attractive and marketable to consumers. In this review, the applications of biopolymers such as starch, chitosan, cellulose, collagen, keratin, Polyhydroxyalkanoates (PHA), etc., in cosmetic and cosmetic packaging are discussed.
Keratin-based biomaterials have been investigated extensively over the past few decades because of their intrinsic biological properties and excellent biocompatibility, as keratin contains high cysteine content (7%–13%) as compared to other structural proteins. Keratin-based biofilms open an entirely new solution space for a wide range of disciplines. In the past few decades, naturally derived biomaterials have been extensively used in tissue engineering and regenerative medicine, owing to their biological function, structural support, excellent biocompatibility, and favorable biodegradability characteristics. Traditionally, keratin has been extracted from wool, feathers, horns, and other animal sources for industrial use. It has also been used as a biomaterial to develop various useful materials, such as scaffolds, hydrogels, and other forms for biomedical applications. Recently, keratin extracted from human hair has emerged as a fascinating biomaterial that, as a human-derived protein, exhibits excellent biocompatibility, no immune reaction upon transplantation, good cellular interaction activity, and biodegradability. Keratin from human hair, feathers, and wool shows promise as an original raw material that will enable fibrous composite materials of this kind to be manufactured. In this chapter we emphasize the importance of keratin, including its history, broad classification, and properties, and how it can be functionalized to provide modified properties. This chapter also deals with the kinds of bonds in keratin and the uses of keratin-based biomaterials in various fields, such as biomedical and cosmetics applications. Finally, we emphasize the capacity of keratin for the adsorption of metals.
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Abstract We proposed a novel approach to prepare high‐performance continuous regenerated keratin fibers with wool‐like structure by using the cortical cells and linear keratin from wool waste as reinforcement and adhesive, respectively. The spindle‐shaped cortical cells were taken from wool waste based on the different responses of cortical cells and mesenchyme in wool to the treatments of H2O2 oxidation and ultrasonication. The linear keratin was yielded through dissolving wool waste in the green solution consisting of starch derived dithiothreitol and protein denaturant sodium dodecyl sulfate. The recycled keratin fibers were produced by wet‐spinning of the mixture solution comprising of cortical cells, linear keratin and toughener poly(ethylene glycol) diacrylate, and crosslinked by glutaraldehyde and 4,4′‐methylenebis‐(phenyl isocyanate). The cortical cells were aligned along the regenerated fibers axis and retained quite a few α‐helical crystals of the intermediate filaments, benefitting improvement of mechanical properties. Consequently, the valuable chemical compositions and hierarchical microstructures of wool were largely inherited. Their mechanical properties, thermal stability, dyeing property, moisture absorption capability, and antistatic resistance resembled those of wool. The regenerated fibers contained 93.3 wt.% components of wool, and the amount of synthetic chemicals in the regenerated fibers was controlled to as low as 6.7 wt.%.
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Amphiphilic molecules like phospholipids show a tendency to form bilayers in aqueous media. In 1961 Bangham was the first to demonstrate by electron microscopy the formation of liposomes from phospholipids. Internal lipids of wool and human hair are - analogous to stratum corneum lipids - capable of bilayer formation, so it is probable that they also are present in keratin fibres as bilayers in the cell membrane complex.
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This study sought to obtain internal wool lipid extracts rich in ceramides from different wool types. Extraction methods, i.e., Soxhlet extraction with different organic solvents and supercritical fluid extraction with CO2 using several polarity modifiers such as MeOH or EtOH, were optimized. The internal wool lipid content varied from 0.2 to 1.9% (based on wool weight) with a ceramide content ranging from 15 to 30% (based on extract weight). The Spanish and Russian Merino wool extracts were the richest in ceramide compounds. TLC-FID was used to quantify the different internal wool lipid extracts. A new experimental protocol that enabled us to identify most of the different ceramide types is presented. These internal wool lipid extracts, especially the ones with a high ceramide content, may be regarded as an alternative source of animal ceramides, which could be of value in the cosmetic and dermopharmaceutical industries.
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The bilayer-forming capability of internal wool lipids and their physicochemical properties were studied in an attempt to enhance our understanding of the lipid structure, present in wool and other keratinized tissues. Internal wool lipids were extracted and analyzed, and the mixture obtained [sterol esters (10%), free fatty acids (24%), sterols (11%), ceramides (46%), and cholesteryl sulfate (9%)] was shown to form stable liposomes. A phase-transition temperature of 60°C was obtained from nuclear magnetic resonance spectra for this lipid mixture. The spontaneous permeability of these vesicles was lower than that of phosphatidylcholine liposomes but slightly higher than that of the vesicles formed with lipids extracted from other keratinized tissues with higher amounts of cholesterol. The transmission electron micrographs showed large vesicular aggregates of approximately 300 nm, which seem to be made up of smaller structures of approximately 20 nm in size. This particular structure could account for the large diameters and small internal volumes found by dynamic light-scattering and spectrofluorometric measurements.
This review defines the cell membrane complex component of structure in wool fibres and summarizes knowledge of this histological component, discussing its importance and potential influence on the fundamental and technological properties of wool fibres and fabrics. The review cites 125 references.
Dry skin is a frequent problem in dermatology and a sign of dysfunction of the epidermis, especially of the stratum corneum as the morphological equivalent of the skin barrier. It may occur as an individual disposition or as the leading symptom of atopic dermatitis or ichthyosis. Besides the visual examination of the skin, various bioengineering methods have been developed to assess the different pathological and adaptive changes in the skin. In addition to the assessment of skin humidity, barrier function and desquamation, the quantification of skin surface topography and the mechanical properties of skin are suitable methods to characterize a dry skin condition. For clinical assessment of moisturizing products and emollients the parameters of investigation have to be defined and integrated in an adapted study design depending on the composition and content of the active agent in the test product. Newly developed cosmetic products have to be investigated for safety and efficacy. Modern bioengineering methods are suitable to fulfill these challenges.
Tensile functions of the skin and subcutaneous tissues contribute to the appearance of the aged and photodamaged skin and to the effects of various other pathophysiological processes. The assessment of tensile functions of skin can be performed by distinct approaches mainly characterized by the orientation and magnitude of the imposed stress and strain over time. Testing methods are basically grouped into five major classes which include tensile, torsional, indentation, impact and elevation modes. Computed tensile variables are reproducible when the experimental procedure occurs under fully controlled conditions. Consistent and relevant information is yielded when the limitations and pitfalls typical for each test method are taken into consideration.
Wool internal polar lipids were isolated and separated into different fractions based on polarity. Qualitative and quantitative analyses of the different fractions were performed by thin-layer chromatography and thin-layer chromatography coupled to flame-ionization detection, respectively. Cholesterol esters, free fatty acids, sterols, ceramides, glycosylceramides, and cholesterol sulfate were the main components, with ceramides being in the highest proportion. The fatty acid composition of ceramides and glycosylceramides was determined by gas chromatography/mass spectrometry. As for other keratinized tissues, long-chain fatty acids predominated in comparison to either free fatty acids or phospholipid-linked fatty acids; in both cases, stearic and lignoceric acids were the most abundant fatty acids, and a low amount of 18-methyleicosanoic acid was found. This work opens new avenues in the study of lipid rearrangement in more complex and realistic vesicle structures than conventional liposomes.
The improvement of stratum corneum hydration is one of the most important claims in the cosmetic industry. Objective assessment of moisturization can be done with devices based on electrical methods provided these instruments are used in an appropriate manner. This paper deals with the biophysical basis behind these techniques and describes the most important variables, pitfalls and drawbacks related to measurements and current instrumentation. Individual-related and environment-related variables are also analyzed as well as study designs for predictive or use tests. Practical suggestions for standardization of measurements are given.
Synopsis The cutaneous tolerability of detergent formulations can be improved by means of suitable additives. Exogenous proteins, for example, are able to reduce the skin irritation potential of surfactants according to a double mechanism: they complex the surfactant molecules lowering the concentration of their free monomeric species; they link to the skin keratin forming a protective colloidal layer that shields the denaturing attack of surfactants. Protein derivatives used as additives for detergency are usually prepared by partial hydrolysis of animal scleroproteins or plant reserve proteins. The main purpose of the hydrolytic cleavage is to make them water soluble and suitable for liquid products. Native, non hydrolysed wheat proteins have been recently introduced as active ingredients for detergents. Water solubility and stability are obtained by means of complexation with surfactants which also increases their actual hydrophobicity, an important parameter affecting cosmetic properties of proteins. The anti-irritant properties of these new derivatives of detergents have been evaluated by in vitro predictive tests (swelling response of collagen membranes), by acute irritancy in vivo methods (occlusive patch tests) and by use tests (forearm washing test). Transepidermal water loss and electric capacitance have been adopted as investigation techniques to evaluate the skin integrity/damage after the in vivo tests. The performance of native wheat protein-surfactant complexes has been compared with traditional protein hydrolysates and to amphoteric surfactants as detergent additives. The results show a noticeable reduction of skin irritation in surfactant formulations with addition of native wheat proteins.
Transepidermal water loss (TEWL) and water content of the stratum corneum, when measured simultaneously, provide important information regarding skin function. On the basis of the model presented, it is possible to differentiate dry senile skin from dry pathological skin (such as psoriasis, atopic dermatitis, irritant reaction), clinically involved or uninvolved. Pathological dry skin, because of the impaired barrier function is associated with increased TEWL and low corneum water content. Senile skin, on the other hand, shows both, decreased TEWL and stratum corneum water content. It is suggested that with this model it may be possible to differentiate uninvolved pathologic from healthy skin.