Titanium dioxide (TiO2) nanoparticles (NPs) are manufactured worldwide in large quantities for use in a wide range of applications. TiO2 NPs possess different physicochemical properties compared to their fine particle (FP) analogs, which might alter their bioactivity. Most of the literature cited here has focused on the respiratory system, showing the importance of inhalation as the primary route for TiO2 NP exposure in the workplace. TiO2 NPs may translocate to systemic organs from the lung and gastrointestinal tract (GIT) although the rate of translocation appears low. There have also been studies focusing on other potential routes of human exposure. Oral exposure mainly occurs through food products containing TiO2 NP-additives. Most dermal exposure studies, whether in vivo or in vitro, report that TiO2 NPs do not penetrate the stratum corneum (SC). In the field of nanomedicine, intravenous injection can deliver TiO2 nanoparticulate carriers directly into the human body. Upon intravenous exposure, TiO2 NPs can induce pathological lesions of the liver, spleen, kidneys, and brain. We have also shown here that most of these effects may be due to the use of very high doses of TiO2 NPs. There is also an enormous lack of epidemiological data regarding TiO2 NPs in spite of its increased production and use. However, long-term inhalation studies in rats have reported lung tumors. This review summarizes the current knowledge on the toxicology of TiO2 NPs and points out areas where further information is needed.

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Titanium dioxide nanoparticles: a review of current toxicological data

Concerns with the environmental and health risk of widely distributed, commonly used nanoparticles are increasing. Nanosize titanium dioxide (TiO2) is used in air and water remediation and in numerous products designed for direct human use and consumption. Its effectiveness in deactivating pollutants and killing microorganisms relates to photoactivation and the resulting free radical activity. This property, coupled with its multiple potential exposure routes, indicates that nanosize TiO2 could pose a risk to biological targets that are sensitive to oxidative stress damage (e.g., brain). In this study, brain microglia (BV2) were exposed to a physicochemically characterized (i.e., dispersion stability, particle size distribution, and zeta potential) nanomaterial, Degussa P25, and cellular expressions of reactive oxygen species were measured with fluorescent probes. P25's zeta potentials, measured in cell culture media and physiological buffer were -11.6 +/- 1.2 mV and -9.25 +/- 0.73 mV, respectively. P25 aggregation was rapid in both media and buffer with the hydrodynamic diameter of stable P25 aggregates ranging from 826 nm to 2368 nm depending on the concentration. The biological response of BV2 microglia to noncytotoxic (2.5-120 ppm) concentrations of P25 was a rapid (<5 min) and sustained (120 min) release of reactive oxygen species. The time course of this release suggested that P25 not only stimulated the immediate "oxidative burst" response in microglia but also interfered with mitochondrial energy production. Transmission electron microscopy indicated that small groups of nanosized particles and micron-sized aggregates were engulfed bythe microglia and sequestered as intracytoplasmic aggregates after 6 and 18 h exposure to P25 (2.5 ppm). Cell viability was maintained at all test concentrations (2.5-120 ppm) over the 18 h exposure period. These data indicate that mouse microglia respond to Degussa P25 with cellular and morphological expressions of free radical formation.

Titanium Dioxide (P25) Produces Reactive Oxygen Species in Immortalized Brain Microglia (BV2): Implications for Nanoparticle Neurotoxicity†

An upper bound is estimated for the magnitude of potential exposure to nano-TiO2 with the purpose of enabling exposure assessment and, ultimately, risk assessment. Knowledge of the existing bulk TiO2 market is combined with available nano-TiO2 production data to estimate current nano-TiO2 sources as a baseline. The evolution of nano-TiO2 production as a percentage of the total TiO2 market is then projected based on material and market information along with a method that combines observations from scientific articles and patents as predictive indicators of the rate of innovative transformation.

Estimates of upper bounds and trends in nano-TiO2 production as a basis for exposure assessment.

Toxicity and bioaccumulation of TiO2 nanoparticle aggregates in Daphnia magna.

BackgroundTitanium dioxide is a widely used nanomaterial whose photo-reactivity suggests that it could damage biological targets (e.g., brain) through oxidative stress (OS).ObjectivesBrain cultures...

https://www.jstor.org/stable/info/4626985

Nanosize titanium dioxide stimulates reactive oxygen species in brain microglia and damages neurons in vitro.

Optical characteristics of titanium oxide interference film and the film laminated with oxides and their applications for cosmetics.

A composition which comprises a substrate of a thin plate form and a coating layer formed on the surface thereof, characterized in that the substrate of a thin plate form has a size of 50 to 800 μm, and the coating layer has a thickness of 0.05 to 0.6 μm and contains a titanium composition in an amount of 70 to 95 wt %. A titanium oxide composition having high brilliant color is prepared through firing the above composition comprising a coating layer and then delaminating the fired coating layer, as a delaminated composition. The titanium oxide composition is novel, and is capable of producing interference colors having excellent brightness and clearness and providing clear complementary colors and thus is useful particularly as a component of a cosmetic composition.

Titanium oxide composition having high brilliant color, composition comprising coating and cosmetic composition, and method for their preparation

Pearlescent pigments are one of the most essential materials not only in paints, plastics, and printing inks, but also in cosmetics. Pigments with higher chroma, color purity, and brightness are in high demand all over the world. In this study we developed a high chroma pearlescent pigment for powder foundation. To produce the high chroma pearlescent pigment, we have designed the layer structure of a pearlescent pigment using computer simulation. In the simulation we have considered its layer structure, the complex refractive indices of the layers, and the thickness distribution of a mica substrate that was measured with Atomic Force Microscopy (AFM). The layer thicknesses have been optimized. The feature of this design is that iron oxide having selective light absorption has been adopted as the layer material to enhance certain wavelengths of the reflected light, which is one of the properties of high chroma. Thus, we have found that a mica substrate homogeneously coated with iron oxide which is further coated with colorless titanium dioxide has a high chroma compared to ordinary pearlescent pigments. The designed pigment has been synthesized by developing a novel manufacturing method to achieve a low roughness iron-oxide surface. We believe that this simulation is useful for designing other pearlescent pigments.

High chroma pearlescent pigments designed by optical simulation

PROBLEM TO BE SOLVED: To provide a low-valent titanium oxide-based black pearlescent powder having excellent color, and a method for easily producing the black powder. SOLUTION: The black pearlescent powder prepared by covering the surface of a flaky powder with low-valent titanium oxide is characterized in that the low-valence titanium oxide is substantially free of nitrogen, and is represented by TiO X (X is 1.56 to 1.75). COPYRIGHT: (C)2008,JPO&INPIT

Black pearlescent powder and method for producing the same

A highly iridescent titanium oxide composition, which not only produces new and outstanding luster as well as color brightness within a recognized color range by interference colors but also retains clear complementary colors. The highly iridescent titanium oxide composition is a coating composition forming a coating layer over the surface of a thin flake-shaped matrix, whose size is 50-800 μm. The coating layer is 0.05-0.6 μm thick containing a titanium composition whose content is 70-95% by mass. This titanium oxide-contained coating layer is the highly iridescent titanium oxide composition exfoliated from the coating composition. The highly iridescent titanium oxide composition is a beneficial element, especially as a cosmetic ingredient.

Fukuji Suzuki

Papers

Optical characteristics of titanium oxide interference film and the film laminated with oxides and their applications for cosmetics.

Titanium oxide composition having high brilliant color, composition comprising coating and cosmetic composition, and method for their preparation

High chroma pearlescent pigments designed by optical simulation

Black pearlescent powder and method for producing the same

Method for Manufacturing Highly Iridescent Titanium Oxide Composition