from the better-skin-through-nanotechnology dept.
Marconi Lee writes "Chengyin Technology [in English] developed silica-coated titanium dioxide for sunscreen. Organic UV-absorbers have been used in sunscreen agents to protect against UVA. However, those organic UV-absorbers are only sparingly soluble in oil and form chelate compounds with metallic ions. It is therefore difficult to obtain a stable blend containing a large amount of those organic UV-absorbers, and this results in low protection factor of UVA (PFA)."
"In view of the above, we have developed a highly dispersed composite powder in which the surface of TiO2 fine powder is coated with dense and uniform thin-layer of silica. The features of this powder are that it enables formation of uniform and dense coating on base material's primary particles of any shape, the thickness of silica coating can be controlled at any nanometer level, and there will be no exposure of bare titanium dioxide surface even after powerful milling. Using this silica-coated TiO2, we have developed a broad-spectrum sunscreens with improved PFA , transparency and stability of cosmetic fomulation."
"The widening destruction of the ozone layer in recent years has caused concern on the noxious effect of UV-radiation on the skin, such as skin cancer, premature skin aging, and photoallergy. Two conditions, 1) prevention of adverse skin reactions and 2) prevention of product deterioration are indispensable in order to ensure protection by cosmetic products against UV-radiation. Organic UV-absorbers such as t-butyl-methoxy-dibenzoyl-methane (Parsol A) have been used in sunscreens as protection against UVA, but stable compounding has been difficult due to low solubility in oils and coloration resulting from chelation. The expected UVA protection could not be achieved because of poor photostability. Concomitant use of various organic UV-absorbers has also been tried, but use of large amounts resulted in stickiness and there were also problems with a deteriorating feeling of use. Meanwhile, an increasing awareness of the need for safety in cosmetic products has led to a trend toward inorganic UV-blockers, causing a demand for their multifunctional use."
"Here we report on the development of a hypercomposite powder that increases dispersibility, and inhibits photocatalytic activity, by coating the primary particles surface of titanium dioxide with a dense and uniform thin layer of silica. This in turn resulted in the development of a broad-spectrum sunscreen that provides excellent protection against UVA as well as outstanding transparency, stability, and safety."