Nanos, what’s that?
The term “nano” is a prefix used in the International System of Units (SI) when talking of a figure which is a billionth of the unit (for length, volume, mass, whatever). Strictly speaking, a nanomaterial is a material the size of which is less than a micrometer (1,000 nanometres), hence, between one and 999 nanometres.
Nanosciences and nanotechnologies are a rather recent scientific branch, which rose during the second half of the 20th century.
Nowadays, nanomaterials, with their properties very different from those that prevail at a larger scale, are present in numerous sectors: aerospace, automotive, chemistry, electronics, energy, environment… and cosmetics.
How do nanos look like in cosmetics?
In cosmetology, there are several kinds of nano-objects, be they solid, semi-solid or liquid. One can list:
• nanoparticles: mineral powders (in sunscreens, or as texture adjuvant in emulsions), polymeric or semi-solid lipid nanoparticles, metallic powders (used also in medicines), carbon-based molecules (fullerens, nanotubes), complex molecular structures (used to deliver active ingredients),
• dispersed liquid systems (micellar systems, micro-emulsions, nano-emulsions).
What nanos are used for in cosmetics?
Nano-objects have a lot of interesting applications in cosmetics.
• Encapsulation: to protect fragile active ingredients (retinol, tocopherol, coenzyme Q10, ascorbic acid…) or, in a formula, molecules that are incompatible.
This technique allows also for the controlled-release and/or the targeted-release of active ingredients, along the time, or in specific conditions of application (for instance, sebum, thanks to its peculiar physico-chemical properties, may threshold the release of an anti-oily skin ingredient.)
• To mask a taste, or to release some aromas.
• An increased solubility, or better flow-properties, as for powders.
• Sensory effects (sense of touch, of sight) that use light interferences for photochromic rendering, which makes a make-up appear the same on the skin, whatever the light intensity, during the day or in the evening.
Nanos could also help stabilise emulsions without use of surfactants, still unavoidable, in spite of their irritant potential. They are already present in cosmeto-textiles…
Which cosmetic products may contain nanos?
It is well-known that sunscreens contain nano-ingredients, especially when the protective effect is due to mineral screens, such as titanium dioxide and zinc oxide.
However, they are far from the only ones.
For instance, these active-ingredient releasers are in many skin-care products: brightening, anti-ageing and anti-wrinkles creams, regenerating serums, body balms, but also hair care…
Obviously, they are present as well in all the categories of make-up products and in micellar waters.
Are nanos dangerous to human health?
Asking the question sums-up the overall argument.
• In fact, nano-materials are suspected to be the cause of harmful effects on human tissues or cells: an increase of the oxidative stress, a production of free-radicals, enhancing inflammatory phenomena, DNA mutation and/or damage…
The main issue is to know whether if, when applied on the skin in a cosmetic product, they can go through the cutaneous barrier down to the cells.
In theory, nano-ingredients should not go deeper than the outer layers of the epidermis. In practice, it is likely that these ultra-small particles find easily their way to the inside of our body: either by swallowing (lipstick …), or by inhalation (powders dust, perfumed vapours), or even by going through the epidermis barrier, especially if injured (even slightly), as when due to eczema or spots, to a burn from sunburn, a micro-cut when shaving…
Sanitary authorities think that “the risk cannot be excluded.”
However, if it exists for the user, it is, by far, more important in occupational setting, especially when nano-powders are inhaled.
How can the regulation help?
Until recently left aside by the regulation on cosmetics, the nanos have come forward in the new Regulation 1223/2009, which was implemented on 11 July 2013.
After this document, any cosmetic product shall be notified to the authorities, and if it contains nano-ingredients, these ingredients shall be precisely described and characterized. Further, any nano-ingredient not listed in the Annexes, i.e. which has not yet been evaluated by the SCCS (a committee of scientific experts), shall be notified six months prior to the placing of the product on the market. This is the time needed by the experts to assess its file, and to allow its use, or not. This preliminary screening is a first in the cosmetic world, in which the principle is an a posteriori assessment.
As a complement, to help the consumer in his choice, since the 11 July 2013, all the nano-ingredients shall be in the list of ingredients, on the product’s packaging, with their name followed by the mention [nano], in brackets (the brackets may depend on the language).
Which nanos shall be listed?
All the nano-ingredients will not be listed on the label; the obligation deals only with those that meet the definition given in the Regulation on Cosmetics. As per this document, “nanomaterial means an insoluble or biopersistant and intentionally manufactured material with one or more external dimensions, or an internal structure, on the scale from 1 to 100 nm.”
Thus, only solid and biopersistant nanos (without any precise definition of “biopersistant”, especially in terms of time), and less than 100 nm in size, are currently considered. For instance, this excludes all liquid systems, as well as active ingredient’s releasers and the nanostructures used for encapsulation, and, also, liposomes.
Therefore, powders (silica …) and mineral screens (titanium dioxide, zinc oxide) would likely be the first nanos displayed on labels.
Nevertheless, the situation may move, thanks to a future broader European definition “Nanos: the European definition”), which could be applied to all the European Union documents, or thanks to pressure by the consumers associations.
• Professor Philippe Piccerelle is a lecturer in the Aix-Marseille (Southern France) University, in which he is the Director of the Laboratory of Industrial Galenic Pharmacy and Cosmetology.
• The Morning Meetings on Cosmetics is a monthly breakfast meeting of cosmetics professionals on a topical point.