Zinc Oxide (ZnO) is an inert, natural mineral that is commonly used in cosmetics as a thickening, lubricating, & sunscreen active ingredient. Zinc Oxide is a physical UV filter that provides the safest, most comprehensive broad-spectrum protection against the sun’s harmful UV rays.
How mineral filters work versus how chemical filters work
Currently, in the cosmetic industry, there are two types of UV filters available, chemical or mineral. Traditionally, chemical UV filters have been the most predominant & commonly used filters. However, recently, chemical sunscreens have been coming under increasing scrutiny opening the market to mineral sunscreens.
Chemical filters operate by permeating the skin where chemical ingredients absorb & dissipate UV rays. Most chemical filters protect predominantly against UVB radiation, offering little to no protection against the arguably more harmful UVA rays. This is one of the main criticisms levelled against chemical UV filters. Another concern with chemical filters is their impact on human health & the environment.
Products containing a number of chemical UV filters, including oxybenzone & octinoxate, have already been banned in certain areas, such as Hawaii & Palau, due to their toxic effect on coral reef. Those same two ingredients, along with some other chemical filters, are also suspected of having endocrine disrupting effects in humans & cause the higher instances of allergic reactions that are associated with chemical sunscreens as opposed to mineral ones. Chemical filters also have low photostability, causing them to degrade or destabilise over time when exposed to sunlight.
Only mineral filters can offer broad spectrum UV protection by protecting against both the sun’s UVA & UVB rays. The active ingredients in mineral sunscreens operate by creating a physical filter on the surface of the skin that deflects & scatters UV rays. The two current mineral UV filters on the market are Zinc Oxide & Titanium Dioxide (TiO2). Zinc Oxide is a globally approved natural mineral ingredient, largely regarded as the most effective UV filter in broad spectrum sunscreen, providing extensive protection against both UVA & UVB rays.
CONVENTIONAL ZnO IN SUN CARE PRODUCTS
When used in cosmetics as a sunscreen active ingredient, ZnO is found in one of two forms, micron or nano. Micron formulations of ZnO contain larger particles in the size range of 2 to 10 µm, while the smaller particle size in the nano formulations range from 10 to 40 nm.
Comparison of the particle sizes of ZnO in the micron & nano forms
There are benefits & negatives to both forms of conventional ZnO. The large size of the particles in the micron form of ZnO make it the safer option of the two, since the particles are unable to permeate through the skin, as opposed to the smaller sized particles in nano ZnO. Nano ZnO is also more harmful to the environment as the small particles may accumulate in plant roots.
Despite micron ZnO being considered the safer option, nano ZnO is the form more commonly used by formulators in sunscreen. This is due to nano ZnO’s superiority as an effective UV filter additive. Nano ZnO provides a higher protection to UV rays per percentage mass & can cover a higher surface area per percentage mass when compared to micron ZnO. It also creates a more visually & aesthetically pleasing sunscreen since it has a high level of transparency.
The efficacy of ZnO as a UV filter & nano ZnO’s superiority in transparency, depend on the particles not agglomerating. This is a problem, as nano ZnO exhibits a very high level of uncontrolled agglomeration & micron ZnO has also been shown to exhibit uncontrolled agglomeration.
Entekno Materials have designed & developed the innovative MicNo® ZnO Particle Technology to allow sunscreen formulators to combine the benefits & overcome the disadvantages associated with micron & nano ZnO as a UV filter. MicNo® is a tailored, platelet shaped, micron sized particles composed of nano primary particles.
The uniquely designed morphology of MicNo® particles enables them to behave like safe micron particles over the skin & like transparent nano particles under the light.
Structure & primary particles of MicNo ZnO
MicNo® is a superior UV filter to both micron & nano ZnO. It offers a much higher UV protection per percentage mass & has proven to have a much higher absorbance of rays within the UV wavelength, especially in the UVA range. MicNo® also offers a higher sun protection factor (SPF), which is the measure of protection from UVB rays, & has exhibited a higher visible light transparency when used at the same concentration as commercial transparent nano ZnO.
MicNo® novel shape allows for better UV protection
Its novel hexagonal shape offers cover to a larger surface area per percentage mass. MicNo® can cover approximately 70% more surface area than the same amount of nano ZnO, assuming no agglomeration takes place.
Distribution of 80 nano ZnO particles compared to MicNo®
MicNo® can achieve a high transparency percentage at 440 nm wavelength, comparable to that of commercial transparent nano ZnO currently on the market. This high transparency means that the white cast effect is reduced. Its nano-porous structure naturally creates a more ivory/beige colour as opposed to the milk white colour that is currently associated with ZnO sunscreens. This occurs due to a phenomenon called structural colouration, which is the production of colour when microscopically structured surfaces are fine enough to be able to interfere with visible light. Due to MicNo’s unique morphology it is also possible that products containing it may produce an attractive shimmer effect simply through the refraction of light. No longer will ZnO have to be associated with thick, unattractive, milky white layers of sunscreen.
MicNo® nano-porous structure (right) causes a less milky white colour & creates a shimmer effect like on the butterfly wings (left)
Its nano-porous structure also creates a continuous coating over the skin with pore channels that make ventilation of the skin efficient. The pore channels even bring a cooling effect to the formulation MicNo® is used in due to this ventilation characteristic.
This unique MicNo characteristic will leave end users feeling cooler & more comfortable & could help consumers with sensitive skin avoid adverse reactions caused by bad skin ventilation.
MicNo® is not only a superior UV filter to nano ZnO, it is also a much safer option. Since MicNo® has particles in the micron range it has a safety profile comparable to micron ZnO. MicNo’s size means it doesn’t not accumulate in plant roots or permeate the skin’s epidermis, decreasing the chances of allergic reactions, & its structure ensures much higher photostability. Research has shown that MicNo presents much less cytotoxicity, genotoxicity & phototoxicity making it more biocompatible & safer when compared to commercial nano ZnO. This biocompatibility of MicNo® makes it a much kinder sunscreen for the environment as it causes less pollution & damage to marine & plant life.
Other benefits of MicNo® include its antimicrobial properties. MicNo® has exhibited broad spectrum antibacterial activity against a range of micro-organisms & a number of fungi allowing for formulations with less or no preservatives. The need for less preservatives would mean less risks of adverse reactions & a decrease in total ingredients needed for formulation, which could translate to less overall total formulation costs.
The MicNo® technology from Entekno Materials is a breakthrough innovation that provides global cosmetics companies a single ingredient to offer broad spectrum protection to consumers from the harmful effects of the sun’s UV rays. With the end consumer increasingly desiring superior sun protection with natural ingredients, that are safe for humans & environmentally friendly, MicNo® provides a cost effective opportunity for a competitive formulation that meets consumers demands.
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