Optimizing the dispersion of nanoparticulate TiO2-based UV filters in a non-polar medium used in sunscreen formulations – The roles of surfactants and particle coatings

Assessing Sunscreen Lifecycle to Minimize Environmental Risk Posed by Nanoparticulate UV-Filters – A Review for Safer-by-Design Products

“…This determining role is given to the outermost nanoparticle coating. Organic additives are grafted to the inorganic surface to improve the compatibility with the dispersing medium and thus favor the nanoparticle dispersion in the cream (Catalano et al, 2020). A hydrophilic, amphiphilic or lipophilic feature is given to the nanoparticles via this coating process, in order to preferentially enhance their dispersion in the aqueous or the oil phase of the emulsion (Faure et al, 2013).…”

“…Some formulation ingredients can unintentionally interact with the nanoparticulate UV-filters and alter their properties (Rossano et al, 2014). For example, Catalano et al (2020) found that an emulsifying agent containing a glucosidic moiety can adsorb onto the nanoparticulate UV-filter and alter its dispersion, finally affecting the UV absorption of the sunscreen (Figure 3). A mixture effect exists and must be considered and optimized in a safe-by-design approach, not only at the fabrication stage of product quality control, but also at further lifecycle stages because certain ingredient combinations affect weathering and environmental dispersion of the product (Botta et al, 2011;Tovar-Sanchez et al, 2019).…”

“…O/W and W/O sunscreens are formulated in the laboratory with 5% nano-TiO 2 , respectively hydrophilic (i.e., TiO 2 /SiO 2 ) or hydrophobic (TiO 2 /Al 2 O 3 /stearic acid). These UV filters were characterized elsewhere (Catalano et al, 2020;Slomberg et al, 2020). A real solid waste leachate is recovered from the settling pond of a municipal landfill.…”

Safety Evaluation of TiO2 Nanoparticle-Based Sunscreen UV Filters on the Development and the Immunological State of the Sea Urchin Paracentrotus lividus

“…The mixture was gently homogenized by magnetic stirring for 10 min. The emulsifying agent contained two surfactant molecules (Octyldodecyl xyloside and PEG30 dipolyhydroxystearate) known to play a role in the exposure route of the hydrophobic NPs via the creation of oil droplets containing the NPs that are stable in pure water [ 13 ].…”

“…The nanoparticulate form of ZnO and TiO 2 (size < 100 nm) is generally used in sunscreens because their small size leads to a more transparent film on the skin after application, which enhances user acceptance. Moreover, these metal oxides are also more efficient UV blockers when finely dispersed in the sunscreen product [ 12 , 13 ], which also contributes to the considerable use of nanoparticles (NPs).…”