Preparation and characterization of polysilsesquioxane particles containing UV-absorbing groups

Biodegradable bioadhesive nanoparticle incorporation of broad-spectrum organic sunscreen agents

Conventional emulsion-based sunscreen formulations are limited by postapplication epicutaneous penetration that increases the risk of allergic dermatitis, cellular damage, and filter photodegradation upon ultraviolet radiation (UVR) exposure. Encapsulation of the UVB filter padimate O within bioadhesive biodegradable nanoparticles (BNPs) composed of poly(d,l-lactic acid)-hyperbranched polyglycerol was previously shown to enhance UVR protection while preventing skin absorption. Herein, we assess the capacity of BNP co-incorporation of avobenzone and octocrylene to provide broad-spectrum UVR protection. The ratio of UV filters within nanoparticles (NPs) was optimized for filter-filter stabilization upon UV irradiation and maximum drug loading. In vitro water-resistance test showed significant particle retention at 85% over 3 hr. In a pilot clinical study, protection against UVR-induced erythema of BNPs was found to be comparable to the FDA standard P2. Thus, sunscreen formulations utilizing BNP incorporation of a combination of organic filters may offer key safety and performance advantages.

Organosilica hybrid nanomaterials with a high organic content: syntheses and applications of silsesquioxanes

Organic-inorganic hybrid materials garner properties from their organic and inorganic matrices as well as synergistic features, and therefore have recently attracted much attention at the nanoscale. Non-porous organosilica hybrid nanomaterials with a high organic content such as silsesquioxanes (R-SiO_1.5, with R organic groups) and bridged silsesquioxanes (O_1.5Si-R-SiO_1.5) are especially attractive hybrids since they provide 20 to 80 weight percent of organic functional groups in addition to the known chemistry and stability of silica. In the organosilica family, silsesquioxanes (R-SiO_1.5) stand between silicas (SiO₂) and silicones (R₂SiO), and are variously called organosilicas, ormosil (organically-modified silica), polysilsesquioxanes and silica hybrids. Herein, we comprehensively review non-porous silsesquioxane and bridged silsesquioxane nanomaterials and their applications in nanomedicine, electro-optics, and catalysis.

Biobased Nanoparticles for Broadband UV Protection with Photostabilized UV Filters

Sunscreens rely on multiple compounds to provide effective and safe protection against UV radiation. UV filters in sunscreens, in particular, provide broadband UV protection but are heavily linked to adverse health effects due to the generation of carcinogenic skin-damaging reactive oxygen species (ROS) upon solar irradiation. Herein, we demonstrate significant reduction in the ROS concentration by encapsulating an antioxidant photostabilizer with multiple UV filters into biobased ethyl cellulose nanoparticles. The developed nanoparticles display complete broadband UV protection and can form transparent and flexible films. This system therefore shows significant potential toward effective and safe nanoparticle-based UV protective coatings.

New Hybrid Organic/Inorganic Polysilsesquioxane-Silica Particles as Sunscreens

Effectiveness of organic sunscreens is limited by phototoxicity and degradation. Both of which can be significantly reduced by encapsulation in hollow particles or covalent incorporation into the solid structure of particles, but direct comparisons of the two methods have not been reported. In this study, physical encapsulation and covalent incorporation of sunscreens were compared with 1 mol % salicylate and curcumeroid sunscreens. 2-Ethylhexyl salicylate was physically encapsulated in hollow silica nanoparticles prepared by oil-in-water (O/W) microemulsion polymerizations (E-Sal). Some of these particles were coated with an additional shell or cap of silica to reduce leaking of sunscreen (cap-E-Sal). Covalent incorporation involved co-polymerizing tetraethoxysilane (TEOS) with 0.2 mol % of new salicylate and curcuminoid sunscreen monomers with triethoxsilyl groups. Particles were prepared with the salicylate attached to the silica matrix through single silsesquioxane groups (pendant; P-Sal) and two silsesquioxane groups (bridged; B-Sal). Particles based on a new curcuminoid-bridged monomer were also prepared (B-Curc). Sunscreen leaching, photodegradation, and sunscreen performance were determined for the E-Sal, cap-E-Sal, P-Sal, B-Sal, and B-Curc particles. Covalent attachment, particularly with bridged sunscreen monomers, reduced leaching and photodegradation over physical encapsulation, even with capping.