8 JOURNAL OF COSMETIC SCIENCE
describing the interaction between sorbate and sorbent at the strong binding sites should
be more clearly temperature-dependent. The threefold lower value of b for our data vs
Baden's (which arises from lower water sorption in the range of x =0.1-0.2) may reflect
this temperature dependence.
Our analyses do not imply that adsorbed water in nail may be strictly classified as
"bound" and "free." A range of energy states for adsorbed water molecules is highly
probable, and multilayer water is not the equivalent of bulk water (8,25). The analysis
is consistent with findings for nail (32) and other hard keratins (26) that most of the
adsorbed water in these tissues is strongly bound to protein fibers and that the contri-
bution made by multilayer formation is small.
CONCLUSION
Human nail is saturated with -30% water at 100% RH and 32°C and shows a char-
acteristic hysteresis between uptake and desorption. Of the several models tested, the
sorption isotherm is best described by the D'Arcy-Watt model.
ACKNOWLEDGMENTS
We acknowledge a research assistantship for HBG provided by the University of Cin-
cinnati.
REFERENCES
(1) J. A. Barrie, "Water in Polymers," in Diffusion in Polymers, J. Crank and G. S. Park, Eds. (Academic
Press, New York, 1968), pp. 259-313.
(2) H. Yasuda, C. Lamaze, and A. Peterlin, Diffusive nad hydraulic permeabilities of water in water-
swollen polymer membranes,]. Polymer Sci., 9, 1117-1131 (1971).
(3) H. Yasuda, J. Olf, B. Crist, C. Lamaze, and A. Peterlin, "Movement of Water in Homogeneous
Water-Swollen Polymers," in Water Structure at the Water-Polymer Interface, H. H. G. Jellinek, Ed.
(Plenum Press, New York, 1972), pp. 39-55.
(4) G. B. Kasting, N. D. Barai, T. F. Wang, and J.M. Nitsche, Mobility of water in human stratum
corneum,J. Pharm. Sci., 92, 2326-2340 (2003).
(5) A. B. Cassie, Absorption of water by wool, Trans. Faraday Soc., 41, 458-464 (1945).
(6) I. C. Watt, Sorption of organic vapors by wool keratin,]. Appl. Polymer Sci., 8, 1737-1750 (1964).
(7) I. C. Watt, Determination of diffusion rates in swelling systems,]. Appl. Polymer Sci., 8, 2835-2842
(1964).
(8) I. C. Watt, Sorption of water vapor by keratin,]. Macromol. Sci.-Rev. Macro. Chem., Cl8, 169-245
(1980).
(9) G. King, Permeability of keratin membranes to water vapor, Trans. Faraday Soc., 41, 479-487 (1945).
(10) R. C. Wester and H. I. Maibach, "Penetration Enhancement by Skin Hydration," in Percutaneous
Penetration Enhancers, E. W. Smith and H. I. Maibach, Eds. (CRC Press, Boca Raton, FL, 1995 ),pp.
21-28.
(11) R.R. Warner, Y. L. Boissy, N. Lilly, M. J. Spears, K. L. McKillop, and K. J. Stone, Water disrupts
stratum corneum lipid lamellae,]. Invest. Dermatol., 108, 644 (1997).
(12) H. Tang, D. Blankschtein, and R. Langer, Prediction of steady-state skin permeabilities of polar and
nonpolar permeants across excised pig skin based on measurements of transient diffusion: Character-
ization of hydration of effects on the skin porous pathway,]. Pharm. Sci., 91, 1891-1907 (2002).
(13) R. J. Scheuplein and I. H. Blank, Permeability of the skin, Physiol. Rev., 51, 702-747 (1971).
(14) Y. Kobayashi, M. Miyamoto, K. Sugibayashi, and Y. Morimoto, Enhancing effect of N-acetyl-L-
describing the interaction between sorbate and sorbent at the strong binding sites should
be more clearly temperature-dependent. The threefold lower value of b for our data vs
Baden's (which arises from lower water sorption in the range of x =0.1-0.2) may reflect
this temperature dependence.
Our analyses do not imply that adsorbed water in nail may be strictly classified as
"bound" and "free." A range of energy states for adsorbed water molecules is highly
probable, and multilayer water is not the equivalent of bulk water (8,25). The analysis
is consistent with findings for nail (32) and other hard keratins (26) that most of the
adsorbed water in these tissues is strongly bound to protein fibers and that the contri-
bution made by multilayer formation is small.
CONCLUSION
Human nail is saturated with -30% water at 100% RH and 32°C and shows a char-
acteristic hysteresis between uptake and desorption. Of the several models tested, the
sorption isotherm is best described by the D'Arcy-Watt model.
ACKNOWLEDGMENTS
We acknowledge a research assistantship for HBG provided by the University of Cin-
cinnati.
REFERENCES
(1) J. A. Barrie, "Water in Polymers," in Diffusion in Polymers, J. Crank and G. S. Park, Eds. (Academic
Press, New York, 1968), pp. 259-313.
(2) H. Yasuda, C. Lamaze, and A. Peterlin, Diffusive nad hydraulic permeabilities of water in water-
swollen polymer membranes,]. Polymer Sci., 9, 1117-1131 (1971).
(3) H. Yasuda, J. Olf, B. Crist, C. Lamaze, and A. Peterlin, "Movement of Water in Homogeneous
Water-Swollen Polymers," in Water Structure at the Water-Polymer Interface, H. H. G. Jellinek, Ed.
(Plenum Press, New York, 1972), pp. 39-55.
(4) G. B. Kasting, N. D. Barai, T. F. Wang, and J.M. Nitsche, Mobility of water in human stratum
corneum,J. Pharm. Sci., 92, 2326-2340 (2003).
(5) A. B. Cassie, Absorption of water by wool, Trans. Faraday Soc., 41, 458-464 (1945).
(6) I. C. Watt, Sorption of organic vapors by wool keratin,]. Appl. Polymer Sci., 8, 1737-1750 (1964).
(7) I. C. Watt, Determination of diffusion rates in swelling systems,]. Appl. Polymer Sci., 8, 2835-2842
(1964).
(8) I. C. Watt, Sorption of water vapor by keratin,]. Macromol. Sci.-Rev. Macro. Chem., Cl8, 169-245
(1980).
(9) G. King, Permeability of keratin membranes to water vapor, Trans. Faraday Soc., 41, 479-487 (1945).
(10) R. C. Wester and H. I. Maibach, "Penetration Enhancement by Skin Hydration," in Percutaneous
Penetration Enhancers, E. W. Smith and H. I. Maibach, Eds. (CRC Press, Boca Raton, FL, 1995 ),pp.
21-28.
(11) R.R. Warner, Y. L. Boissy, N. Lilly, M. J. Spears, K. L. McKillop, and K. J. Stone, Water disrupts
stratum corneum lipid lamellae,]. Invest. Dermatol., 108, 644 (1997).
(12) H. Tang, D. Blankschtein, and R. Langer, Prediction of steady-state skin permeabilities of polar and
nonpolar permeants across excised pig skin based on measurements of transient diffusion: Character-
ization of hydration of effects on the skin porous pathway,]. Pharm. Sci., 91, 1891-1907 (2002).
(13) R. J. Scheuplein and I. H. Blank, Permeability of the skin, Physiol. Rev., 51, 702-747 (1971).
(14) Y. Kobayashi, M. Miyamoto, K. Sugibayashi, and Y. Morimoto, Enhancing effect of N-acetyl-L-
