Comparing methods for detecting and characterizing metal oxide nanoparticles in unmodified commercial sunscreens.

Aims: To determine if commercial sunscreens contain distinct nanoparticles and to evaluate analytical methods for their ability to detect and characterize nanoparticles in unmodified topical products using commercial sunscreens as a model.

Methods: A total of 20 methods were evaluated for their ability to detect and characterize nanoparticles in unmodified commercial sunscreens.

Results: Variable-pressure scanning-electron microscopy, atomic-force microscopy, laser-scanning confocal microscopy and X-ray diffraction were found to be viable and complementary methods for detecting and characterizing nanoparticles in sunscreens.

Conclusions: It was determined that several of the commercial sunscreens contained distinct nanoparticles. No one method was able to completely characterize nanoparticles in the unmodified products but the viable methods provided complementary information regarding the nanoparticles and how they were interacting with the sunscreen matrix.