52, 1-11 (January/February 2001)
An in vivomethod to assess the photostability of UV filters
in a sunscreen
M. CAMBON, N. ISSACHAR, D. CASTELLI, and C. ROBERT, Johnson
and Johnson Consumer, 1 Avenue Camille Demoulins, 92187 Issy
les Moulineaux, France.
Accepted for publication February 8, 2001.
Synopsis
An in vivo method was developed in order to study the photostability
of UV filters in a sunscreen. This method assesses sunscreen
photostability in the emulsion after direct interaction with
the skin. For this purpose UV filters were recovered from volunteers'
forearms by using the stripping technique, then extracted from
tapes and quantified by high-performance liquid chromatography
(HPLC). The photostability of the filters tested was evaluated
by comparing the amount of filters recovered from the strippings
of UV-irradiated skin (40 minimal erythema dose, or MED) versus
non-irradiated skin. Sequential analysis of several successive
tapes reflected the distribution profile of the filters in the
stratum corneum. Photochemical change was observed for one filter:
it was shown to undergo a photochemical modification with the
appearance of an additional HPLC peak. Moreover, UV filters
tested displayed a high affinity for the stratum corneum but
presented different distribution profiles. This in vivo method
takes into account the interaction of the sunscreen agents with
the stratum corneum. Furthermore, unlike spectrometric methods
usually used for photostability assessment, it gives quantitative
data for each individual filter of a finished product by using
an HPLC technique.
52, 13-22 (January/February 2001)
The ability of electrical measurements to predict
skin moisturization. I. Effects of NaCl and glycerin on short-term
measurements
FANG LI, EILEEN CONROY, MARTY VISSCHER, and R. RANDALL WICKETT,
College of Pharmacy, University of Cincinnati (F.L., E.C.,
R.R.W.), and The Skin Sciences Institute, Children's Hospital
Medical Center (M.V.), Cincinnati, OH 45267. Accepted for publication
January 15, 2001. Presented as a poster at the Annual
Scientific Seminar of the Society of Cosmetic Chemists, Chicago,
May 6-7, 1999.
Synopsis
Non-invasive methods to evaluate skin hydration by measuring
electrical properties are widely used in the cosmetic industry.
However, there is still some controversy about factors that
affect measurement. For example, concerns have often been expressed
about the possible confounding effect of salts, either in the
formulation or on the skin. Ionized salts on the skin may increase
electrical conductivity and may lead to changes in electrical
properties that are not related to increased water content.
We have performed a systematic study of the effects of salt,
i.e., sodium chloride, and glycerin on the electrical properties
of skin as measured by the three most commonly used instruments,
the Novat DPM 9003, the Corneometert CM 825, and the Skicont
200. Formulations containing salt from 0-3% and glycerin from
0-10% were tested for their effects at one and two hours after
a single application. Salt lowered the readings in the absence
of glycerin and increased the reading in the presence of glycerin.
For all three instruments, there was a linear correlation between
the measurement and the glycerin level in the presence or absence
of salt.
52, 23-33 (January/February 2001)
The ability of electrical measurements to
predict skin moisturization. II. Correlation between one-hour
measurements and long-term results
FANG LI, EILEEN CONROY, MARTY VISSCHER, and R. RANDALL WICKETT,
College of Pharmacy, University of Cincinnati (F.L., E.C.,
R.R.W.), and The Skin Sciences Institute, Children's Hospital
Medical Center (M.V.), Cincinnati, OH 45267. Accepted for publication
January 15, 2001.
Synopsis We investigated the ability of short-term (one-hour)
electrical measurements with three different commonly used instruments
to predict the effects of long-term treatment with glycerin-containing
formulations on moderately dry leg skin. We report the moisturizing
effects of glycerin on healthy female adult skin in a two-week
study as measured by electrical conductance and capacitance,
transepidermal water loss (TEWL), and clinical grading of skin
dryness. The test formulations contained 1.5% NaCl and levels
of glycerin from 0% to 15%. Results obtained with a smaller
cohort of ten subjects, one hour after treatment, were predictive
of moisturizing efficacy in the two-week period among twenty
subjects with dry leg skin. Our results show that single application
tests can be predictive of longer-term results with humectant-based
moisturizers and that electrical measurements of skin conditions
correlate well with skin grades.
52, 35-50 (January/February 2001)
Kinetics of permeation and metabolism of a-tocopherol
and a-tocopheryl acetate in micro-Yucatan pig sin
MEERA RANGARAJAN and JOEL L. ZATZ, Rutgers-The State University
of New Jersey, Department of Pharmaceutics, College of Pharmacy,
160 Frelinghuysen Road, Piscataway, NJ 08854-8020. Accepted
for publication January 15, 2001
Synopsis
The objective of this research was to investigate the permeation
and metabolism of a-tocopheryl acetate (a-TAc) and a-tocopherol
(a-T) from solution and emulsion formulations and to delineate
the kinetics of such metabolism. Simple formulations containing
a-TAc and a-T were applied to fresh, viable micro-Yucatan skin
dermatomed to a thickness of 250-300 µm, as a finite dose in
a flow-through diffusion system. The experiments were stopped
at time intervals of 2, 6, 12, and 24 hours. At the end of each
time interval, the amounts removed by washing, retained in the
stratum corneum (SC), and penetrated into the viable skin and
receptor were determined by a validated HPLC method. Receptor
concentrations were below the limit of detection. a-TAc underwent
metabolism in pig skin to the active antioxidant a-T. The metabolite
appeared as early as two hours after application. The extent
of metabolism was highest at 6-12 hours after application. No
metabolism was detected in the stratum corneum. Delivery of
a-T from isopropyl myristate (IPM) solution was more efficient
than utilization of a-TAc from the same solution. Approximately
1.5% of a-T yielded the same viable skin concentration as 5%
a-TAc. Topical application of a-tocopherol or its prodrug acetate
was capable of enhancing the overall antioxidant capacity of
pig skin. The hydrolytic pathway of a-TAc leading to the active
antioxidant a-T could possibly be saturable.
52, 51-65 (January/February 2001)
Quantitative methods for evaluating optical and frictional properties
of cationic polymers
WENJUN WU, JOY ALKEMA, GREG D. SHAY, and DAVID R. BASSET,
Union Carbide Corporation, Cary, NC 27511. Accepted for publication
January 15, 2001. Presented in part at the annual Scientific
Seminar of the Society of Cosmetic Chemists, Chicago, May 6-7,
1999.
Synopsis
This paper presents three quantitative methods to examine gloss,
opacity, and friction of cationic polymers. The adsorption of
cationic polymers onto hair and skin can be regarded as a thin
film coating. Therefore, optical and frictional properties of
polymer films are of significant relevance to the applications
of cationic polymers in hair care products. Such properties
reflect the desirable hair condition attributes consumers seek
in shampoo and conditioner products. Using these test methods,
polyquaternium-10 and cationic guar samples of varying molecular
weight and cationic substitution were compared. The effect of
an anionic surfactant, sodium dodecyl sulfate (SDS), on polymer
film properties was also investigated. Neat guar hydroxypropyl
trimonium chloride imparts less friction than polyquaternium-10
but dulls the substrate employed in this study. The optical
data show that polyquaternium-10 provides greater film clarity
and gloss than cationic guars. In the presence of SDS, polyquaternium-10
also displays similar or lower friction than cationic guar.
The comparative optical and frictional results are in good agreement
with the visual assessment of the cationic polymer films. These
results clearly demonstrate that polyquaternium-10 exhibits
superior film properties in the forms of both neat polymer and
polymer/surfactant complex. In addition, microscopic techniques
such as scanning electron microscopy (SEM) and atomic force
microscopy (AFM) provide powerful explanations for the differences
noted between the two popular classes of cationic polymers.
The test methods described in this paper can be utilized to
differentiate the upper performance potential of cationic polymers.
These objective and standardized test methods derived from the
coatings industry are not affected by the variability of hair
or the formulation complexity of end products. They can be useful
tools in the product development process in quickly screening
the relative performance of different polymers.
52, 67-88 (January/February 2001)
Papers Presented at the 2000 Annual Scientific Meeting (Thursday's
Program) December 7-8, 2000 New York Hilton New York, NY
Letter from the Editor
TO OUR READERS: I have anxiously begun my three-year
term as editor of the Journal of Cosmetic Science. My first
task was to select an associate editor, and I have chosen Dr.
Mindy Goldstein from Bath & Body Works. Dr. Goldstein has had
experience on both the supplier and the marketed cosmetic product
side, which I felt would be valuable to help broaden the journal's
appeal to both sides. We plan to incorporate several reviews
a year on relevant topics of interest to the readership. Dr.
Brian Costello from Collaborative Research has agreed to prepare
the first one, on antioxidants. We also plan to have special
issues, probably at least one a year. Dr. Robert Lockhead has
agreed to put together the first one for this year. My personal
goal for the journal is to accelerate the review process and
to respond to authors within ten weeks. Over the years we have
had many complaints that the process is too slow, and many very
good submissions have failed to be published due to the long
lead time, as the authors have either changed companies or simply
given up. The society continues to encourage submission of quality
manuscripts from any area of cosmetic and OTC research that
(1) gives new insights into a specific research area, (2) provides
a review of special interest topics for the readership, and/or
(3) provides a source for the readership to quickly become well-versed
in a new area of cosmetic science for that reader. I hope you
enjoy the journal during my term. Any suggestions for improvement
are welcome and will be considered.
—Linda D. Rhein
BACK