In the ever-changing landscape of sun protection products, consumers are struggling to keep up & understand the cosmetic industry’s current sun protection message. The high mortality rate from UV ray associated melanomas, one person dies of melanoma every hour & 86% of melanomas are caused by UV rays from the sun, means that it is widely accepted by consumers that protection of the skin from the sun is a necessity. However, not everyone is clear on all the terminology surrounding sun protection. SPF & UVA are not well understood by the normal sunscreen user.
The sun emits two types of UV radiation, UVA & UVB, that can reach & damage the skin. UVA rays are present at all daytime hours & can penetrate clouds & even glass. They have long wavelengths & can penetrate deep into the skin’s surface, releasing free radicals that cause long term damage & can lead to skin cancers & contribute to aging. UVB rays have shorter wavelengths than UVA rays but still penetrate the skin’s epidermis causing surface tanning, burning & signs of aging. They can also play a part in skin cancers like melanoma. Regular daily use of an SPF 15 or higher sunscreen can reduce the risk of developing melanoma by 50%.
SPF, or Sun Protection Factor, is the measure of protection a sun cream can provide against UVB rays. It is determined according to how long it takes for skin treated with sunscreen to burn compared to untreated skin. If skin would begin to burn after 10 minutes of exposure to the sun, then applying an SPF 15 sunscreen would provide protection from the sun’s UVB rays by a factor of 15 times longer, so for approximately 150 minutes. The SPF scale is not linear since SPF 15 blocks 93% of UVB rays, SPF 30 blocks 97% & SPF 50 blocks 98%. The SPF numbering system does not account for protection against UVA rays.
SPF protection of the skin
UV Filters in Sunscreens
There are two types of UV-filters used in sunscreens currently on the market, chemical or mineral. Chemical sunscreens use chemical ingredients to absorb & dissipate UV rays while the active ingredients in mineral sunscreens form a physical filter that deflects & scatters UV rays. Hawaii has recently passed legislation that bans certain chemical sunscreens to protect their marine ecosystems, since chemical sunscreens have been shown to have harmful effects on the environment & an impact on human reproductive health.
Chemical sunscreens are also coming under increasing scrutiny lately because of their narrow spectrum of sun ray protection. They predominantly protect against UVB rays & not the perhaps more harmful UVA rays that can cause skin cancers. There are also higher instances of allergic reactions to sunscreens with chemical UV filters, resulting in skin irritations. Chemical filters also have low photostability, so they degrade or destabilise over time when exposed to sunlight.
These limitations of chemical UV filters have increased the popularity of mineral sunscreens with consumers & the market’s openness to using them. Broad spectrum sunscreens that can protect against UVA & UVB rays are seen by many to be the future in sun protection philosophy for formulators. Only sunscreens with physical mineral filters can offer broad spectrum protection. They also result in less instances of allergic reactions & have considerably higher photostability than those with chemical filters. There are currently two mineral UV filters available on the market Zinc Oxide (ZnO) & Titanium Dioxide (TiO2). Zinc Oxide, as a globally approved natural mineral ingredient, is largely considered the most effective broad-spectrum UV filter, providing extensive protection against both UVA & UVB rays.
Conventional ZnO Forms In Sunscreens
Current sun protection products use one of two conventional forms of ZnO, those being ZnO in micron or nano particle size. In the micron ZnO formulations, particles are bigger in size ranging from 2 to 10 µm while in the nano formulations the smaller particle size ranges from 10 to 40 nm.
Particle size comparison of the micron & nano ZnO formulations
Both forms have benefits & disadvantages. Micron ZnO is considered by some formulators to have better health & safety features but nano ZnO is considered to be a more effective sunscreen, making it more commonly used by formulators.
Nano ZnO’s ability to provide a higher protection to UV rays per percentage mass & cover a higher surface area per percentage mass is what makes it a more effective sunscreen additive compared to micron ZnO. It also forms a more visually & aesthetically pleasing sunscreen since it has a high level of transparency. However, these beneficial features are dependent on the particles not agglomerating, which is a problem for nano ZnO, as it exhibits a very high level of uncontrolled agglomeration. Micron ZnO has also been shown to exhibit uncontrolled agglomeration.
Micron ZnO’s larger particle size is the reason it is considered the safer of the two conventional ZnO formulations. The small particles in the nano formulations may be highly toxic to humans & particularly phytotoxic as they are able to penetrate through the skin of humans & accumulate in the roots of plants. Micron ZnO is also more effective than nano ZnO in the protection against high energy visible light & blue light. While this is not a major area of focus in the current sun protection market it is developing into a recent trend & provides a possible area of expansion for the future.
MicNo® ZnO FROM ENTEKNO, A NOVEL ZnO TECHNOLOGY
Entekno Materials have developed a novel mineral-based UV filter, MicNo-ZnO, by using patented MicNo particle technology. MicNo-ZnO is a tailored, platelet shaped, micron sized particles composed of nano primary particles. MicNo combines the benefits of both micron & nano ZnO. It acts like micron ZnO over the skin, since it does not penetrate through the skin, but it still offers the transparent protection of nano ZnO.
MicNo exhibits a much higher protection from UV rays by percentage mass than both nano & micron ZnO. It has been proven to have a much higher absorbance of rays within the UV wavelength, especially in the UVA range, & a higher visible light transparency than commercial nano ZnO. In a formulation of 1% (standard market available) ZnO, acting as the single UV filter, an SPF of 0.8 to 1.2 can be achieved.
The SPF contribution of 1% MicNo, with MicNo as the only UV filter, is 1.5 to 2.0, depending on the formulation characteristics. With the ideal formulation, it may be possible to create a sunscreen with the same SPF but with half the concentration of standard ZnO currently required in the formulation.
SPF contribution of MicNo to formulations containing MicNo-ZnO as the only UV filter
MicNo® also offers a higher SPF than commercial transparent nano ZnO (CTN-ZnO) formulations at the same concentrations. Sunscreen formulations of 5% chemical UV-filters with an SPF of 25 & differenet MicNo & CTN-ZnO were prepared at Yeditepe University Cosmetic Research Centre (YUKOZ) & tested by an Independent Lab. The formulations containing MicNo® exhibited a considerably higher SPF value than the CTN-ZnO formulations at the same concentrations. MicNo® formulations also had a better UVA/UVB absorption ratio & transparency percentage at 440nm wavelenght.
MicNo also offers a higher SPF than commercial transparent nano ZnO (CTN-ZnO) formulations at the same concentrations. Sunscreen formulations of 5% chemical UV-filters with an SPF of 25 & differenet MicNo & CTN-ZnO were prepared at Yeditepe University Cosmetic Research Centre (YUKOZ) & tested by an Independent Lab. The formulations containing MicNo exhibited a considerably higher SPF value than the CTN-ZnO formulations at the same concentrations. MicNo formulations also had a better UVA/UVB absorption ratio & transparency percentage at 440nm wavelenght.
|ZnO content in the sunscreen formulation
||Critical Wavelength (nm)
||Transparency at 440 nm wavelength (%)
||SPF Boosting Effect
Characteristics of MicNo sunscreen formulations compared to CTN-ZnO
MicNo’s designed platelet shape ZnO particles means it can cover more surface area by percentage mass compared to the spherical commercial micron & nano ZnO particles.
MicNo novel shape allows for better UV protection
MicNo’s novel hexagonal shape can cover approximately 70% more surface area than the same amount of nano ZnO, assuming no agglomeration takes place. While uncontrolled agglomeration is a problem with commercially available versions of ZnO in both micron & nano formulations, MicNo has a low level of uncontrolled agglomeration. Thus, less MicNo is required in sunscreens to achieve the same sun protection as with nano & micron ZnO. With the right formulation using MicNo it is possible to create an SPF 50 product with broad spectrum & transparent protection with a significant reduction in the ZnO concentration & cost of the final formulation.
The ZnO particles created by the novel & patented MicNo particle technology are in the micron size range, meaning they are not able to penetrate the skin easily, as opposed to the smaller nano particles. Thus, MicNo has a much lower toxicity level than nano ZnO, similar to that of micron ZnO. It also exhibits less phytotoxicity since, unlike nano ZnO, it does not accumulate in plant roots. Overall, MicNo has been shown through research to present much less cytotoxicity, genotoxicity & phototoxicity making it more biocompatible & safer when compared to commercial ZnO.
A very important added benefit of MicNo is its antimicrobial properties. MicNo exhibits broad spectrum antibacterial activity against a range of micro-organisms & fungi. It also offers high protection to high energy visible light & blue light.
|UV Protection per mass
|Transparency (unless they are aglomerated)
|Surface cover per mass
|High energy visible light / Blue light protection
|Level of toxicity
|Level of phototoxicity
|Broad spectrum antibacterial activity
Table comparing the main attributes of micron, nano & MicNo ZnO particles
MicNo is a novel & innovative particle that can harness the benefits & overcome the problems associated with the conventional micron & nano ZnO forms currently used in sunscreens. With its unique designed structure, it can offer an even better protection against the sun’s UV rays with a higher SPF than conventional nano ZnO, while still maintaining the safety of micron ZnO.
At a time when customers are demanding more from their cosmetics, MicNo provides consumers high SPF for protection they can depend upon with the MicNo UV filter additive.
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