Nanotechnology is the design, characterisation, production and application of structures, devices and systems by controlling shape and size at the nanometre scale which covers the size range from 1 nanometre to 100 nanometre (nm) where 1 nanometre is 1 billionth of a metre.
It is therefore the technology of the very small. To put this size into context, the diameter of a red blood cell is c.7000 nm, the average thickness of a human hair is of the order of 80,000 to 100,000 nm and human nails grow at a rate of 1 to 10 nm per second. The use of nanotechnology stretches across many areas of science from electronics to biology and has applications in many product sectors. Nanomaterials are those that have at least one dimension of size in the range 1 nm to 100 nm and they can be considered under the following three headings:
• Natural.• Anthropogenic. • Engineered.
Natural nanomaterials are created independently of man, and include a wide range of materials such as sea salt resulting from the evaporation of water from sea spray, soil dust and volcanic dust. Anthropogenic nanomaterials are created as a result of action by man with the main example of this type of nanomaterial being soot produced from the combustion of fossil fuels. The final group comprises engineered nanomaterials which have been designed and manufactured specifically by man. While there have been many such nanomaterials produced for many applications including carbon black in tyres, cerium oxide in combustion catalysts and carbon nanotubes in sports goods, there have been examples developed and manufactured specifically for use in cosmetics. Engineered nanomaterials used in cosmetics are in the form of nanoparticles and nanoemulsions. Nanomaterials can be found in sunscreens with efficient UV protection, long-lasting make-up, anti-ageing creams with an increased intake of vitamins or enzymes, toothpaste, nail treatments and hair colouring products. In 2007, BCC Research forecast that the global market for cosmetics using nanotechnology will grow by 16.6% per year reaching $155.8 million in 2012.
Nanomaterials in cosmetics
Large particle size often generates an unpleasant skin feel and size reduction can improve skin feel. Nanoparticles such as titanium dioxide and zinc oxide are minerals already present in our natural environment and are used in many sunscreen products. The nanoscale versions of these particles retain the effectiveness of their larger analogues for removing ultraviolet radiation, but do not scatter visible light, allowing them to be used in transparent formulations. Inclusion of these materials and especially nanoparticulate titanium dioxide in sunscreen formulations provides protection against UV light which is known to hasten the skin ageing process and which can induce DNA damage that can lead to skin cancer. There is a growing use of nanoparticulate titanium dioxide in a range of skin care products providing a level of sun protection for everyday use. These products generally advertise the SPF on their labels as an additional product feature. This trend is expected to continue as the general public becomes more aware of the benefits of protecting themselves against skin damage from excessive exposure to UV light. Smaller particle sizes improve the application of the product to the skin. For example the smaller the particle size used in face creams and powders, the smoother the final look of the product on the skin. In sunscreens, smaller particle size means that the product is easier to apply, coats more effectively and is less visible on the skin. The worldwide market for nanoparticulate titanium dioxide is estimated at many hundreds of tonnes per year. There have been questions regarding the possibility that nanoparticles and specifically titanium dioxide and zinc oxide will pass through the skin and enter viable tissue. Extensive studies have confirmed that neither titanium dioxide nor zinc oxide penetrates through the skin although there has been evidence for the presence of insoluble nanoparticles such as titanium dioxide in the hair follicles where they remained outside of living tissue until they could be washed off. It is important that to allay any fears or concerns regarding other nanomaterials, similar extensive studies are conducted on a case-by-case basis, just as for nano titanium dioxide and zinc oxide, prior to use in any products applied to human skin.
Nanoemulsions are widespread in nature and probably the best example is milk. In cosmetics, they contain oil and water droplets reduced to nanometre size to increase the content of nutritious oils while preserving the transparency and the lightness of the formulas. Nanoemulsions do not cross the skin barrier and public health agencies worldwide acknowledge that they are safe. Nanoparticles of silica have been proposed for use to help create stable nanoemulsions.
Sometimes, fragile active ingredients like vitamins are protected from the air inside nanomaterial size bubbles (vesicles) or nanosomes that release the ingredient upon contact with the skin at the time of application. Nanosomes are small liposomes which are formed from soap-like molecules which self assemble in water into sheets. When these sheets curve around and make a closed surface, this creates a liposome, i.e. a bag to trap useful molecules like vitamins and vitamin precursors. The idea is that these nanosomes will both protect the active molecules and help them penetrate into the skin should that be required. Benefits of using lipid nanoparticles in cosmetics include improved stability of chemically unstable active ingredients, controlled release of active ingredients, provision of pigment effects and improved skin hydration and protection through film formation on the skin.
Iron oxides have been for many years probably the most commonly used colouring agents for cosmetics with manufacture beginning around 1900. Iron oxides have various colours which are classified into three main colour groups, yellow, red and black. Variations on these colours can be achieved by combining these materials with other pigments such as titanium dioxide and they find use in liquid foundations, face powders, and blushers. Eye shadows have been developed with more vivid colours and iridescent or metallic effects. Nanoparticulate versions of iron oxides are generally acicular in form of length c.100 nm and width 10-20 nm and colour strength is greatly increased when the particle size is reduced to such a size. Nanopigments such as iron oxides can also provide UVA protection and help boost SPF. Aluminium oxide has been specially designed in platelet form to provide soft focus properties with superior cosmetic feel and competes with talc and mica for this application. Soft focus cosmetics aim to reduce the appearance of fine lines by ensuring that light is highly diffused while remaining highly transparent to show natural skin tones giving a more natural look. Mica, like aluminium oxide is in platelet form with platelet thickness in the nano size range and gives a natural translucence when used in face powders and powder blushers. Such enhanced appearance, as can be achieved using these platelet based particles, is likely to increase in the future.
Nanosilver and nanogold
Silver is an antibacterial agent and has been shown to be effective against many different organisms. Cosmetic manufacturers are harnessing the enhanced antibacterial properties of nanosilver in a range of applications. Some manufacturers are already producing under-arm deodorants with claims that the silver in the product will provide up to 24 hour anti-bacterial protection. There have been concerns that nanosilver could pass through the skin barrier resulting in unwanted side effects, but there is currently no evidence of this. However, the use of nanosilver especially as a component of toothpaste has given rise to reasonable concern in that the mouth contains a number of so-called friendly bacteria. Over-use of substances which kill bacteria are associated with opportunistic infections and although this has not been demonstrated for nanosilver in the mouth, it needs to be considered. Nano size gold, like nanosilver, is claimed to be highly effective in disinfecting the bacteria in the mouth and has also been added to toothpaste. Titanium dioxide is often a component of toothpaste and at least part of the titanium dioxide content is of nano size. Toothpaste has also been developed containing hydroxy apatite, the compound from which bone and tooth enamel are formed. Enamel is damaged by everyday activities such as brushing and the self assembling hydroxy apatite is claimed to arrange itself in a way that mimics and binds to the natural enamel structure. The use of nanogold and in particular nanosilver is likely to come under continued scrutiny as concern about their antibacterial activity grows. Testing is ongoing to evaluate the effects of these materials both as used by humans and in the environment following removal.
Buckminster fullerene, C60, is perhaps the most iconic nanomaterial and this molecule – it is really too small to be referred to as a nanomaterial, being approximately 1 nm in diameter – has found its way into some very expensive face creams. The motivation is to capitalise on its capacity to behave as a potent scavenger of free radicals. However, given the reports of the toxic effects of some fullerenes, products based on C60 have aroused concern.
Influence of the Directive
Unlikely as it seems, the global cosmetics industry is one of the main players in the emerging field of nanotechnology with the cosmetics industry already leading the way in terms of number of patents for nanoparticles. Since 2005, there have been approximately 100 published patent documents per year having nano and cosmetic in their abstract or title. In the earlier part of the decade that number was in the range 50 to 70 so the focus on developing nanotechnology based products has increased significantly in the past few years confirming the emphasis on developing products based on this technology. A new consolidated version of the Cosmetics Directive 76/768/EEC, EU Regulation No 1223/2009, will require cosmetics manufacturers to list any nanoparticles contained in products marketed within the European Union. This new consolidation is a 397-page cosmetics regulation approved on 20 November 2009 by the Council of the European Union. The new regulation will apply in all 27 EU countries and harmonises a previously fragmented area of law. Most of the provisions of this new regulation will be applicable as from 11 July 2013 and replace the Cosmetics Directive 76/768/EEC thereafter.
This new Cosmetics Directive states that all ingredients present in the product in the form of nanomaterials should be clearly indicated in the list of ingredients, by inserting the word “nano” in brackets after the ingredient listing. The ruling defines nanomaterial as: “...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” and states that: “All ingredients present in the form of nanomaterials shall be clearly indicated in the list of ingredients”. This definition is in line with the one quoted at the beginning of this article. It should be emphasised that there is no established specific risk for nanomaterials. Size alone is not in itself an indicator of toxicity. Authorities in Germany have taken the view1 that highlighting the fact that a product contains nanomaterials could be viewed by consumers as a warning. German officials noted that cosmetic products that are for sale in the EU must already pass stringent safety tests. Thus, the inclusion of nano-scale materials should not warrant additional scrutiny. Alongside this, Green MEPs and environmental lobby groups have been pushing for the application of the “no data, no market” principle to nanotechnologies. Industry groups fear this would put the onus on them to prove nanomaterials do not carry any additional risk – a process that could lead to hundreds of products being taken off the market. Germany’s position is that information on nano-scale materials may be important for consumers where the particle size results in altered properties. This is closer to the industry’s preference for defining nanotechnology based on function rather than size. However, for all consumers throughout Europe, it will be important that they understand that this new labelling requirement does not mean that there is added danger from using the product, but rather that the label is simply providing further information to describe the ingredient more precisely.
Establishing consumer confidence
In the UK, the previous Government published its UK Nanotechnologies Strategy, “Small Technologies, Great Opportunities” in March 2010. There, they noted that the Department for Business, Innovation and Skills (BIS) will act as the Competent Authority for the EU Cosmetics Regulation and they will keep a watching brief on developments involving nanomaterials which may require further legislative amendments. BIS had collected views from all stakeholders on nanotechnology in preparation for publication of this strategy. It was clear from these views that to ensure the success of nanotechnology based cosmetics and to maintain and improve consumer confidence in the use of nanomaterials in cosmetic products, the Commission must administer the new regulations in the Cosmetics Directive in an effective and transparent way. Cosmetics companies will need to be prepared to respond to questions and challenges from consumers and from NGOs regarding the new information on the labels. It needs to be made clear that potential risks associated with nanomaterials have been considered and tests have been conducted rigorously to ensure that cosmetics and personal care products continue to be safe for the consumer to use with confidence. On the other hand it behoves NGOs to provide technical data in support of any concerns that they may express regarding the safety of nanomaterial containing cosmetics. This way, debates on the safety of cosmetics containing nanomaterials will be based on data and not speculation. In the US, the FDA rejected labelling of nanomaterials under food and cosmetics law in 2007. So in contrast to Europe, the US has shown no enthusiasm to require labelling for nanomaterials in consumer goods such as food and cosmetics. The debate surrounding this new European regulatory framework suggests that in the interest of all stakeholders, i.e. consumers, regulatory bodies and producers there is an opportunity for international harmonisation on ensuring consistent and effective testing for safety of cosmetics and personal care products and, of course, their ingredients. Such harmonisation would assist in instilling confidence in the consumer on a worldwide basis.
So, in conclusion, nanotechnology is here to stay. It will continue to be the basis for new cosmetics products and along with applications in many other product areas will result in significant improvements in products that enhance the quality of life as we know it.
Notes The Nanotechnology Knowledge Transfer Network (NanoKTN), one of the UK’s primary knowledgebased networks for Micro and Nanotechnologies, was set up by the Technology Strategy Board, to promote and facilitate knowledge exchange, support the growth of UK capabilities, raise nanotechnology awareness and provide thoughtleadership and input to UK policy strategy.
Membership of the NanoKTN is free. For further information visit www.nanoktn.com .
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