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Titanium dioxide nanoparticles observed in dermal layers after sunscreen application

Researchers found limited evidence that repetitive application of sunscreen with titanium dioxide provides a layer of deep dermal penetration, but suggest that further studies are needed, according to recent data.

“Our findings depend on selected ‘regions of interest,’ which does not allow a detailed quantitative assessment of dermal penetration of TiO₂ nanoparticles,” Sergio G. Coelho, PhD, from the Laboratory of Cell Biology of the National Cancer Institute, NIH, in Bethesda, Maryland, and colleagues wrote. “Notwithstanding its limitations, however, the study described here provides valuable data on the dermal penetration of TiO₂ nanoparticles and the parameters for informing the design of future clinical studies.”

Coelho and colleagues evaluated six patients (four women, two men; mean age, 37 years) who underwent daily application of sunscreen with and without TiO₂ nanoparticles (2 mg/cm² concentration) at two sites on the lower back. Two participants applied the sunscreens once daily for 3 days and the other four participants applied the sunscreens once a day for 8 days. The researchers took five shave specimens from each participant 1 day after the final application: two from each sunscreen site and one from a control site.

The researchers found a higher concentration of TiO₂ nanoparticles in in the dermis of the sites that received the sunscreen with TiO₂ nanoparticles.

“The deep epidermis and dermis of the control sites and at the sunscreen-only sites were not examined because the level of in the stratum corneum of these samples was much lower than in the sunscreen plus TiO₂ skin samples,” Coelho and colleagues wrote. “The TiO₂ nanoparticles were confirmed with [scanning electron microscopy and energy dispersive X-ray spectroscopy] as present mainly in the dermis surrounding hair follicles but at very low qualitative levels and with no obviously decreasing gradient with skin depth.” – by Jeff Craven

Disclosure: The researchers report no relevant financial disclosures.