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Nanotechnology and Skin Delivery: Infinitely Small or Infinite Possibilities?
By: Johann W. Wiechers, PhD, JW Solutions
Posted: December 19, 2008, from the January 2009 issue of Cosmetics & Toiletries.
- Figure 1. Theoretical predictions of particle penetration
- Figure 2. Histological sections demonstrating the penetration depth
- Figure 3. Kinetics of the storage of nanoparticles
- Figure 4.The effect of particle size on the UV attenuating properties of titanium dioxide.
- Figure 5. Schematic representation of the size-dependent occlusive effect of lipid nanoparticles
- Figure 6: Cumulative amount of ketorolac
page 2 of 13
Apart from natural nanoparticles that occur in the environment—such as volcanic dust, lunar dust, magnetotactic bacteria and minimal composites—man-made industrial processes also create incidental nanoparticles such as diesel exhaust, coal combustion and welding fumes. A last group consists of the engineered nanoparticles that are created either top-down (via milling) or bottom-up (via crystal growth).6 Most nanoscale materials, whether engineered or natural, fall into one of four categories (although other ways of classifying them also exist6):
- Metal oxides, such as zinc and titanium oxide, that are used in ceramics, chemical polishing agents, scratch-resistant coatings, cosmetics and sunscreens;
- Nanoclays; naturally occurring plate-like clay particles that strengthen or harden materials or make them flame retardant;
- Nanotubes, which are used in coatings to dissipate or minimize static electricity (e.g., in fuel lines, in hard disk handling trays, or in automobile bodies to be painted electrostatically); and
- Quantum dots, used in exploratory medicine or in the self-assembly of nanoelectronic structures.
The cosmetic industry's contribution to the "thousands of tonnes of nano-materials" is mainly the global production of nanoparticles for sunscreen products, which was estimated to be approximately 1,000 tons during 2003-2004.7
As previously mentioned, the more flexible vesicles such as liposomes, elastosomes and other skin delivery systems are also an application of nanotechnology but their contribution to the production of "thousands of tonnes of nanomaterials" will be less--although they may have been produced over a longer period of time because liposomes were invented by Bangham8 in 1965 and have been used ever since.
The global production of engineered nanomaterials is estimated to increase from 1,100 tons in 2003-2004 to
5,700 tons in 2020, whereas the contribution of metal oxides in sunscreens is estimated to remain constant at
1,000 tons over the 2003-2020 time span investigated; the contribution of the cosmetic industry to the global production of nanomaterials will remain constant in absolute terms and reduce in relative terms.7
Therefore, nanomaterials are indeed present in the immediate environment, even in thousands of tons. But there is still a difference between the presence of nanomaterials in the environment and their getting under the skin of individuals (i.e., human exposure). The following discussion will thus focus on topical exposure and the skin penetration of nanomaterials that are used for cosmetic purposes, such as the metal oxides. Liposomes as well as other routes of exposure to nanomaterials, such as inhalation and oral uptake, will not be discussed.