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1503415 
Journal Article 
Review 
TITANIUM DIOXIDE AND ZINC OXIDE NANOPARTICLES IN SUNSCREENS: FOCUS ON THEIR SAFETY AND EFFECTIVENESS 
Smijs, TG; Pavel, S 
2011 
1 
Nanotechnology, Science and Applications
ISSN: 1177-8903 
4 
1 (2011) 
95-112 
English 
24198489 
Sunscreens are used to provide protection against adverse effects of ultraviolet (UV)B (290-320 nm) and UVA (320-400 nm) radiation. According to the United States Food and Drug Administration, the protection factor against UVA should be at least one-third of the overall sun protection factor. Titanium dioxide (TiO2) and zinc oxide (ZnO) minerals are frequently employed in sunscreens as inorganic physical sun blockers. As TiO2 is more effective in UVB and ZnO in the UVA range, the combination of these particles assures a broad-band UV protection. However, to solve the cosmetic drawback of these opaque sunscreens, microsized TiO2 and ZnO have been increasingly replaced by TiO2 and ZnO nanoparticles (NPs) (,100 nm). This review focuses on significant effects on the UV attenuation of sunscreens when microsized TiO2 and ZnO particles are replaced by NPs and evaluates physicochemical aspects that affect effectiveness and safety of NP sunscreens. With the use of TiO2 and ZnO NPs, the undesired opaqueness disappears but the required balance between UVA and UVB protection can be altered. Utilisation of mixtures of micro- and nanosized ZnO dispersions and nanosized TiO2 particles may improve this situation. Skin exposure to NP-containing sunscreens leads to incorporation of TiO2 and ZnO NPs in the stratum corneum, which can alter specific NP attenuation properties due to particle-particle, particle-skin, and skin-particle-light physicochemical interactions. Both sunscreen NPs induce (photo)cyto- and genotoxicity and have been sporadically observed in viable skin layers especially in case of long-term exposures and ZnO. Photocatalytic effects, the highest for anatase TiO2, cannot be completely prevented by coating of the particles, but silica-based coatings are most effective. Caution should still be exercised when new sunscreens are developed and research that includes sunscreen NP stabilisation, chronic exposures, and reduction of NPs' free-radical production should receive full attention. 123 Refs. 
BLOOD-BRAIN BARRIER; CHAIN; VIBRATIONAL SPECTROSCOPY; ELLIPSOMETRY; ENERGY LEVEL; SKIN; IR SPECTROMETRY; SEMI-CONDUCTOR; MICROSPONGE; CRYSTALLINITY; BAND GAP; ULCER; LIPOPHILIC; CARCINOGEN; SCATTERING; SURFACE CHEMISTRY; PHOTOACTIVITY; ELECTRON MICROSCOPY; HEALTH HAZARD; RESERVOIR; GAP WIDTH; SPECTROSCOPIC ELLIPSOMETRY; SHORT CHAIN; ESR SPECTRA; ATOMIC ORBITAL; DIRECT IMAGING; DERMATITIS; IR SPECTROSCOPY; FROZEN-IN; TAPE; COSMETICS; ELECTROMAGNETIC RADIATION; REFRACTIVE INDEX; FTIR SPECTROSCOPY; ENDOGENOUS; CONVEYING; NEEDLE-SHAPED; MIXTURE; ASSAY; RISK; X-RAY FLUORESCENCE; FOOD; FREEZING; PARTITIONING; DEGRADATION; SEMICRYSTALLINE; SUNSCREEN; ABSORPTION COEFFICIENT; SEMICONDUCTING; STRATUM CORNEUM; PEROXIDATION; CARRIER SYSTEM; OPTICAL TRANSPARENCY; EPR SPECTROSCOPY; FREE RADICAL; CONGO RED; ANISOTROPY; SHOCK; MICROSCOPY; LIGHT MICROSCOPY; CELL MORPHOLOGY; LIGHT-SCATTERING; WHITENING; AMPHIPHILIC; FOURIER TRANSFORM INFRARED SPECTROSCOPY; MICRONUCLEUS; ELECTRICAL PROPERTIES; ULTRAVIOLET IRRADIATION; IRRADIATION; TEM; FTIR; IR SPECTRUM; SCATTERING COEFFICIENT; TRILAYER; SPONGE; ARC; WATER TREATMENT; TABLES; HIGH RESOLUTION TRANSMISSION ELECTRON MICROSCOPY; SEM; X-RAY SCATTERING; MOLECULAR ORBITAL; X-RAY DIFFRACTION; MECHANICAL PROPERTIES; UNCOATED; ESR; INFRARED SPECTROPHOTOMETRY; OPAQUE; UV RADIATION; NUCLEAR; REVIEW; SEMICONDUCTOR; PLATELET; SAFETY; EPITAXIAL; TISSUE SAMPLE; PHOTOTOXICITY; STRIPPING; PHOTODEGRADATION; ELECTRON PARAMAGNETIC RESONANCE; BROAD BAND; LIPID; ELECTRONIC STRUCTURE; COMPLEMENT; PHOTOELECTRON SPECTROSCOPY; LOTION; INTERFACIAL ENERGY; IMAGING; AUTHORISATION; ELECTRON TRANSFER; WHITENESS; POLYMETHYLSILSESQUIOXANE; PROPERTIES; ACCEPTOR; EFFLUENT; TRANSPARENCY; ULTRAFINE; TECHNICAL; CELL CULTURE; GENOTOXICITY; REFRACTIVE INDICES; SWEAT; LONG-TERM; HRTEM; X-RAY SPECTRA; PLACEBO; STABILIZATION; CANCER; DUCT; PARACRYSTALLINE; GENOTOXIC; BACKSCATTERING; REGISTRATION; INORGANIC; TRANSMISSION ELECTRON SPECTROSCOPY; FREE-RADICAL; DELIVERY SYSTEM; PLASTIC SURGERY; NANOPARTICLE; PHOTON CORRELATION SPECTROSCOPY; MICROPROBE; STIMULATION; ENERGY BAND; INFRA-RED SPECTRA; ENERGY ABSORPTION; PMAA; VISIBLE LIGHT; UV IRRADIATION; INTRACELLULAR; NANOCOMPOSITE; ENVIRONMENTAL APPLICATION; DISPERSION; QUENCH; PRODUCTION; SINGLE-PHASE; SCANNING ELECTRON MICROGRAPH; ANISOTROPIC; AUTHORIZATION; SURFACE COATING; ENVELOPE; RADIOACTIVITY; SYNERGISTIC; PHOTOSTABILITY; TRANSMISSION ELECTRON MICROSCOPY; EXCISION; SURFACE REACTIVITY; LIGHT SCATTERING; PHOTOCATALYTIC; GLAND; ELECTRON SCANNING MICROSCOPY; INFRARED SPECTRA; VALENCE BAND; SPECTROSCOPY; SIZE REDUCTION; STABILISATION; CELL VIABILITY; POLYCRYSTALLINE; CRYSTAL STRUCTURE; DYNAMIC LIGHT SCATTERING; ESR SPECTROSCOPY; CYTOPLASM; COATING; UV-IRRADIATION; PIG; DYE INTERACTION; PHYSICOCHEMICAL PROPERTIES; ENVIRONMENTAL PROTECTION; REDOX REACTION; SPA; HEXAGONAL; PHOTOREACTIVITY; MODALITY; DRUG ADMINISTRATION; IMPERMEABLE; PERCUTANEOUS; THREE-LAYER; POLYMERIC MICROSPHERE; SEMI-CRYSTALLINE; WASTE WATER; ELECTRON SPIN RESONANCE; X-RAY PHOTOELECTRON SPECTROSCOPY; UNSATURATED; APPLICATION; REACTIVITY; FTIR SPECTRA; OIL PHASE; UV ABSORPTION; EROSION; LIGHT ABSORPTION; ATTENUATION; ION MICROSCOPY; TOXICITY; METHACRYLIC ACID POLYMER; OINTMENT; ELECTRONIC ENERGY; SINGLET; LIPOSOME; BLOCKING AGENT; BLOOD; DUST; POLYMETHACRYLIC ACID; PIGMENT; ELECTRON PARAMAGNETIC RESONANCE SPECTROSCOPY; INFRARED SPECTROSCOPY; CARCINOGENIC; CYTOTOXICITY; KERATINOCYTE; IR SPECTRA; FLUORESCENCE; SPLEEN; UV TRANSMISSION; DIFFRACTION; ECOTOXICITY; COHESION; SCANNING ELECTRON MICROSCOPY; EXCITON; OIL-IN-WATER; CLEARANCE; DERMAL; X-RAY SPECTROSCOPY