Nanoscale titanium dioxide particle sunscreens effective, nontoxic
MedWire News: Research suggests that recently developed sunscreens containing nano-sized titanium dioxide (TiO2) particles are likely to have better efficacy than older creams containing micron-sized TiO2 particles, with no increase in toxicity.
Nakissa Sadrieh (Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, USA) and colleagues evaluated the effects of the two types of TiO2 particles in sunscreen in terms of ultraviolet (UV) light attenuation, product stability, and possible skin barrier damage.
They tested uncoated TiO2 with a primary particle size of 21 nm (nanoscale), coated TiO2 with a primary particle size of 50 nm (nanoscale), and submicron, coated TiO2 with a primary particle size of 250 nm (microscale).
The research was carried out to address safety concerns about the recent increase in use of nanoscale TiO2 particles in sunscreen, which has primarily focused on the possibility that the smaller size of such particles might result in increased dermal penetration of the skin barrier, resulting in increased toxicity.
In fact, as reported in the International Journal of Cosmetic Science, the researchers found that none of the formulations tested decreased skin barrier function.
They observed that the best blockage of UV light was achieved with smaller, more evenly distributed TiO2 particles that are stabilized with a coating. Non-agglomerated formulations were also shown to provide better blockage of UV light than highly agglomerated systems.
"This result makes intuitive sense as agglomeration will effectively reduce the amount of surface area available to absorb UV light," write Sadrieh et al.
"By contrast, a well-dispersed system with individually stabilized particles provides greater functional surface area to scatter and absorb UV radiation."
The team explains, however, that, once formulated, the stability of the particles in the sunscreen is the key feature that can impact on its ability to block UV light.
"Particles coated to minimize surface effects provided greater UV attenuation and stability than uncoated particles," explain Sadrieh and co-authors.
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By Helen Albert