By The Cosmetic Chemist Staff
January 15, 2017
Many scientists associate the beginning of nanotechnology with the inspiring speech given by the physicist and Nobel laureate Richard P. Feynman in 1959 at the American Physical Society annual meeting held at the California Institute of Technology.1 Professor Feynman challenged a new generation of scientists to discover a “staggeringly small world” of solid state physics that would have widespread applications and change the technology landscape. More than 60 years later, nanotechnology has become an integral component of our everyday lives. Who can imagine life without the selection of electronic devices we have at our disposal? Moreover, many advances in biotechnology and medicine have been possible due to nanotechnology.
Nanotechnology is the study of small things. It can be the fabrication, application, manipulation, or measurement of objects on the nanoscale. It is difficult to imagine, but one nanometer is equal to a billionth of a meter. To give us some perspective, an average hair fiber is 70,000 nm (70 µm) in diameter. Nanoparticles are often defined as particles with a diameter greater than 1 nm but less than 100 nm. However, this definition is often extended to include particles slightly larger, and many nanoparticles are on the order of tens or hundreds of nanometers in size. It was not until the 1980s that we really began to measure and grasp the concept of the nanoworld. In a large part, this was due to the discovery of the scanning tunneling and atomic force microscopes, which allowed us to measure and image objects from the nanoscale down to atomic resolution.
The world of cosmetics is no stranger to nanotechnology. In the last ten to fifteen years there has been a flurry of activity in the development of cosmetic technology based on nanoscience.2-5 In fact, L’Oréal ranks 6th in the United States in terms of the number of nanotechnology patents filed by a company.2 A number of other cosmetic companies, including Procter & Gamble and Henkel, also produce a lot of nanotechnology intellectual property.3 In the cosmetics arena, the largest application areas for nanotechnology are centered on sunscreen or delivery system technology.
Most of the efforts in sunscreen technology have been to reduce the size of titanium dioxide and zinc oxide particles to make sunscreen formulas more transparent during application on the skin. On the other hand, nanotechnology delivery systems aim to supply key ingredients to the skin using a variety of different vesicle as well as molecular scaffold and macromolecular structures. Some of these structures include cubosomes, dendrimers, fullerenes, hydrogels, liposomes, nanocrystals, nanocapsules, nanoemulsions, solid-lipid nanoparticles, nanogold particles, nanosilver particles, niosomes, and transfersomes.2,3 Table 1 includes a short description of each of these nanostructures.
Table 1. Nanostructures with potential use in cosmetic products. For a more comprehensive description, the reader is referred to References 2 and 3.
|Cubosomes||Self-assembled liquid crystalline structures. They are made from the bicontinuous cubic liquid crystalline phase of surfactants.6|
|Dendrimers||Macromolecules that are highly branched and have well defined structure. Many of the external moieties can be functionalized.7|
|Fullerenes||Fullerenes are highly conjugated C60 hollow molecular spheres. They have free radical scavenging properties, acting as a free radical sponge.8|
|Hydrogels||A hydrophilic polymeric gel network structure capable of holding large quantities of water.9|
|Liposomes||Spherical shaped vesicles containing phospholipid bilayers comprising a hydrophobic shell with an aqueous interior capable of delivering active ingredients.10|
|Nanocrystals||Nanosized crystalline materials that have unique physicochemical properties.11|
|Nanocapsules||Small nanoparticles consisting of a polymeric shell surrounding a solid or liquid interior allowing for the delivery of active ingredients.12|
|Nanoemulsions||Emulsions (liquid-in-liquid dispersions) with a droplet size on the order of 100 nm.13|
|Solid-lipid nanoparticles||Lipid droplets that are in the solid state (a solid core) and stabilized by surfactants and emulsifiers; used to deliver molecules.14,15|
|Nanogold/nanosilver particles||Investigations of nanoparticles of gold and silver have been carried out to understate their penetration capabilities into different layers of the skin for biomedical applications. In addition, this technology is being exploited for its possible antibacterial properties in deodorant applications.3,16|
|Niosomes||Vesicles—similar to liposomes—made of surfactants and cholesterol. Niosomes have greater permeation capabilities and are more stable than liposomes.17|
|Transfersomes||Similar to niosomes and liposomes, transfersomes are lipid vesicles with an aqueous core. The transfersome membrane is more flexible than those found in other lipid vesicles.18|
The use of nanotechnology in cosmetics has not been without scrutiny. There are considerable safety concerns since there is still insufficient toxicological data on nanostructures. Regardless, it is still uncertain to what extent nanomaterials are able to penetrate into the viable layers of the epidermis.4 A more grave concern is if the penetration of such materials reaches the vascular network in the dermis and can be systemically distributed throughout the body. For example, a number of studies demonstrate that nanoparticles TiO2 and ZnO do not pose a significant risk of penetration into the deeper layers of the skin.19-21 On the other hand, many other nanomaterials are designed with the idea in mind that they could serve as delivery vehicles and provide penetration of active ingredients. These types of materials are usually designed with lipid components that allow for incorporation into the biological components of skin, specifically the lipid lamellae phase of the stratum corneum.
1. R. Feynman, There's plenty of room at the bottom, J. Microelectromech. Syst., 1, 60-66 (1992). The original transcript of the speech was published as a chapter in the book Miniaturization, Ed. H.D. Gilbert, Van Nostrand Reinhold: New York (1961).
2. T.G. Singh and N. Sharma, “Nanobiomaterials in cosmetics: current status and future prospects” in Nanobiomaterials in Galenic Formulations and Cosmetics: Applications of Nanobiomaterials, Vol. 10, Ed. A.M. Grumezescu, Elsevier: Amsterdam (2016).
3. S. Raj, S. Jose, U.S. Sumod, and M. Sabitha, Nanotechnology in cosmetics: opportunities and challenges, J. Pharm. Bioallied Sci., 4, 186-193 (2012).
4. L.M. Katz, K. Dewan, and R.L. Bronaugh, Nanotechnology in cosmetics, Food Chem. Toxicol., 85, 127-137 (2015).
5. I.P. Kaur and R. Agrawal, Nanotechnology: A new paradigm in cosmeceuticals, Recent Pat. Drug Deliv. Form., 1, 171-182 (2007).
6. G. Garg, S. Saraf, and S. Saraf, Cubosomes: an overview, Biol. Pharm. Bull., 30, 350-353 (2007).
7. P. Kesharwani, K. Jain, and N.K. Jain, Dendrimer as nanocarrier for drug delivery, Prog. Polym. Sci., 39, 268-307 (2014).
8. The Cosmetic Chemist Staff, Fullerenes and their use in cosmetics, www.TheCosmeticChemist.com (2016).
9. M.E. Parente, A. Ochoa Andrade, G. Ares, F. Russo, and Á. Jiménez-Kairuz, Bioadhesive hydrogels for cosmetic applications, Int. J. Cosmet. Sci., 37, 511-518 (2015).
10. Y. Rahimpour and H. Hamishehkar, Liposomes in cosmeceutics, Expert Opin. Drug Deliv., 9, 443-455 (2012).
11. X. Zhai, J. Lademann, C.M. Keck, and R.H. Müller, Nanocrystals of medium soluble actives—novel concept for improved dermal delivery and production strategy, Int. J. Pharm., 470, 141-150 (2014).
12. S.S. Guterres, M.P. Alves, and A.R. Pohlmann, Polymeric nanoparticles, nanospheres and nanocapsules for cutaneous applications, Drug Target Insights, 2, 147-157 (2007).
13. A. Gupta, H.B. Eral, T.A. Hattona and P.S. Doyle, Nanoemulsions: formation, properties and applications, Soft Matter, 12, 2826-2841 (2016).
14. S.A. Wissing and R.H. Müller, Cosmetic applications for solid lipid nanoparticles (SLN), Int. J. Pharm., 254, 65-68 (2003).
15. E.B. Souto and R.H. Müller, Cosmetic features and applications of lipid nanoparticles (SLN, NLC), Int. J. Cosmet. Sci., 30, 157-65 (2008).
16. R. Fernandes, N.R. Smyth, O.L. Muskens, S. Nitti, A. Heuer-Jungemann, M.R. Ardern-Jones, and A.G. Kanaras, Interactions of skin with gold nanoparticles of different surface charge, shape, and functionality, Small, 11, 713–721 (2015).
17. M.J. Choi and H.I. Maibach, Liposomes and niosomes as topical drug delivery systems, Skin Pharmacol. Physiol., 18, 209-219 (2005).
18. R. Rajan, S. Jose, V.P.B. Mukund, and D.T. Vasudevan, Transfersomes - A vesicular transdermal delivery system for enhanced drug permeation, J. Adv. Pharm. Technol. Res., 2, 138-143 (2011).
19. A.O. Gamer, E. Leibold, B. van Ravenzwaay, The in vitro absorption of microfine zinc oxide and titanium dioxide through porcine skin, Toxicol. In Vitro, 20, 301-307 (2006).
20. N.A. Monteiro-Riviere, K. Wiench, R. Landsiedel, S. Schulte, A.O. Inman, and J.E. Riviere, Safety evaluation of sunscreen formulations containing titanium dioxide and zinc oxide nanoparticles in UVB sunburned skin: an in vitro and in vivo study, Toxicol. Sci., 123, 264-280 (2011).
21. G.J. Nohynek and E.K. Dufour, Nano-sized cosmetic formulations or solid nanoparticles in sunscreens: a risk to human health? Arch. Toxicol., 86, 1063-1075 (2012).