224 JOURNAL OF COSMETIC SCIENCE (2) P. Elias, Epidermal barrier function: lntercellular lamellar lipid structures, origin, composition and metabolism,]. Control. Release, 15, 199-208 (1991). (3) G. lmokawa, S. Akasaki, Y. Minematsu, and M. Kaway, Importance of intercellular lipids in water retention properties of the stratum corneum, Arch. Dermatol. Res, 281, 45-51 (1989). (4) S. E. Friberg, I. Kayali, L. D. Rhein, F. A. Simion, and R. H. Cagan, The importance oflipids for water uptake in stratum corneum, Int.]. Cosmet. Sci., 12, 5-12, (1990). (5) M. Denda, New strategies to improve skin barrier homeostasis, Adv. Drug Del. Rev., 54, S123-S130 (2002). (6) K. De Paepe, D. Roseeuw, and V. Rogiers, Repair of acetone and sodium lauryl sulphate-damaged human skin barrier function using topically applied emulsion containing barrier lipids, JEADV, 16, 587-594, (2002). (7) M. Q. Man, K. R. Feingold, C.R. Thornfeld, and P. M. Elias, Optimization of physiologic lipid mixtures for barrier repair,]. Invest. Dermatol., 106, 1096-1101 (1996). (8) S. Hatziantoniou, M. Rallis, C. Demetzos, and G. T. Papaioannou, Pharmacological activity of natural lipids on a skin barrier disruption model, Pharmacol. Res., 42, 55-59 (2000). (9) L. Yang, M. Mao-Qiang, M. Taljebini, P. M. Elias, and K. R. Feingold, Topical stratum corneum lipids accelerate barrier repair after tape stripping, solvent treatment and some but not all types of detergent treatment, Br.]. Dermatol., 133, 679-685 (1995). (10) F. Bonina, C. Puglia, M. Avogadro, E. Baranelli, and G. Cravotto, The topical protective effect of soybean-germ oil against DVB-induced cutaneous erythema: An in vivo evaluation, Arch. Pharm. Chem. Life. Sci., 338, 598-601 (2005). (11) S. R. Georgetti, R. Casagrande, F. T. Moura-de-Carvalho Vicentini, W. A. Verri, and M. J. Fonseca, Evaluation of the antioxidant activity of soybean extract by different in vitro methods and investigation of this activity after its incorporation in topical formulations, Eur.]. Pharm. Biopharm., 64, 99-106 (2006). (12) K. M. Si.idel, K. Venzke, H. Mielke, U. Breitenbach, C. Mundt, S. Jaspers, U. Koop, K. Sauermann, E. Knussman-Harcig, I. Moll, G. Gercken, A. R. Young, F. Stab, H. Wenck, and S. Gallinat, Novel aspects of intrinsic and extrinsic aging of human skin: Beneficial effects of soy extract, Photochem. Photobiol., 81, 581-587 (2005). (13) B. I. Bettzuege-Pfaff and A. Melzer, Treating dry skin and pruritus with a bath oil containing soya oil and lauromacrogols, Curr. Med. Res. Opin., 21, 1735-1739 (2005). (14) F. P. Bonina, L. Montenegro, N. Scorfani, E. Esposito, R. Cortesi, E. Menegatti, and C. Nastruzzi, Effects of phospholipid based formulations on in vitro and in vivo percutaneous absorption of methyl nicotinate,J. Control. Release, 34, 53-63 (1995). (15) M. Ricci, C. Puglia, F. Bonina, C. Di Giovanni, S. Giovagnoli, and C. Rossi, Evaluation of indo­ methacin percutaneous absorption from nanostructured lipid carriers (NLC): In vitro and in vivo studies, ]. Pharm. Sci., 94, 1149-1159 (2005). (16) E. Boelsma, C. Anderson, A. M. J. Karlsson, and M. Ponec, Microdialysis technique as a method to study the percutaneous penetration of methyl nicotinate through excised human skin, reconstructed epidermis, and human skin in-vivo, Pharm. Res., 17, 141-147, (2000). (17) K. V. Roskos, A. J. Bircher, H. I. Maibach, and R.H. Guy. Pharmacodynamic measurements of methyl nicotinate percutaneous absorption: The effect of aging on microcirculation, Br. J. Dermatol., 122, 165-171 (1990). (18) P. Fernandes and J. M. S. Cabral, Phytosterols: Application and recovery methods, Bioresource Technol., 98, 2335-2350 (2007). (19) A. K. Bhattacharyya, W. E. Connor, and D. S. Lin, The origin of plant sterols in the skin surface lipids in humans: From diet to plasma to skin,]. Invest. Dermatol., 80, 294-296 (1983). (20) J. A. Bouwstra and M. Ponec. The skin barrier in healthy and diseased state, EBA Biomemebranes, 1758, 2080-2095 (2006).

]. Cosmet. Sci., 59, 225-232 (May/June 2008) AFM capabilities in characterization of particles and surfaces: From angstroms to microns N. STAROSTINA, M. BRODSKY, S. PRIKHODKO, C. M. HOO, M. L. MECARTNEY, and P. WEST, Pacific Nanotechnology Inc., 17981 Sky Park Circle, Irvine, CA 92614 (N.S, P. W.), University of California Los Angeles, UCLA Center for East-West Medicine, Los Angeles, CA 90095-1736 (M.B.), University of California Los Angeles, Department of Materials Science and Engineering, Los Angeles, CA 90095-1595 (S.P.), and University of California Irvine, Chemical Engineering and Material Science, Irvine, CA 92627-2575 (C.M.H., M.L.M.). Accepted for publication January 8, 2008. Presented at the Annual Scientific Meeting and Technology Showcase of the Society of Cosmetic Chemists, New York, December 7-8, 2006. Synopsis Scanning probe microscopy (SPM), invented 25 years ago, is now routinely employed as a surface charac­ terization technique. Atomic force microscopy (AFM) is the most widely used form of SPM, since AFM can be used in ambient conditions with minimal sample preparation. Examples of applications relevant to cosmetics include, but are not limited to, hair and skin roughness measurements and powder particle and nano-emulsion characterization. AFM is well suited for individual particle characterization, especially for measurements of volume, height, size, shape, aspect ratio, and particle surface morphology. Statistical distributions for a large set of particles can be generated through single-particle analysis techniques (i.e., ensemble-like information). AFM is better capable of resolving complex particle-size distributions than dynamic light-scattering (DLS). Single-particle analysis techniques with AFM can be more cost- and time-effective than analyses using scanning electron microscopy (SEM). However, AFM offers resolution that is comparable to or greater than SEM or transmission electron microscopy (TEM) and routinely allows direct measurements of the particle height and volume and produces images easily displayed in a quantified 3D format. INTRODUCTION AFM has been successfully employed for surface topography characterization over the last two decades. IBM researchers developed scanning tunneling microscopy (STM), which is considered an antecedent to AFM, in 1982 (1,2). AFM was invented in 1986 Address all correspondence to N. Starostina at Emerson Process Management, Rosemount Analytical Inc., Liquids, 2400 Barranca Parkway, Irvine, CA 92606. 225