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The gastrointestinal tract is a complex barrier/exchange system, and is the most important route by which macromolecules can enter the body. The main absorption takes place through villi and microvilli of the epithelium of the small and large intestines, which have an overall surface of about 200 m2. Already in 1922, it was recognized by Kumagai, that particles can translocate from the lumen of the intestinal tract via aggregation of intestinal lymphatic tissue (Peyer’s patch, containing M-cells (phagocytic enterocytes)). Uptake can also occur via the normal intestinal enterocytes. Solid particles, once in the sub-mucosal tissue, are able to enter both the lymphatic and blood circulation.
Titanium dioxide (TiO2) is considered as an inert and safe material and has been used in many applications for decades. However, with the development of nanotechnologies TiO2 nanoparticles, with numerous novel and useful properties, are increasingly manufactured and used. Therefore increased human and environmental exposure can be expected, which has put TiO2 nanoparticles under toxicological scrutiny. Mechanistic toxicological studies show that TiO2 nanoparticles predominantly cause adverse effects via induction of oxidative stress resulting in cell damage, genotoxicity, inflammation, immune response etc. The extent and type of damage strongly depends on physical and chemical characteristics of TiO2 nanoparticles, which govern their bioavailability and reactivity. Based on the experimental evidence from animal inhalation studies TiO2 nanoparticles are classified as “possible carcinogenic to humans” by the International Agency for Research on Cancer and as occupational carcinogen by the National Institute for Occupational Safety and Health. The studies on dermal exposure to TiO2 nanoparticles, which is in humans substantial through the use of sunscreens, generally indicate negligible transdermal penetration; however data are needed on long-term exposure and potential adverse effects of photo-oxidation products. Although TiO2 is permitted as an additive (E171) in food and pharmaceutical products we do not have reliable data on its absorption, distribution, excretion and toxicity on oral exposure. TiO2 may also enter environment, and while it exerts low acute toxicity to aquatic organisms, upon long-term exposure it induces a range of sub-lethal effects.
In a 2017 study published in Scientific Reports, researchers exposed rats to human-relevant levels of E171 to examine the effects of intestinal inflammation and carcinogenesis. They saw that “a 100-day E171 treatment promoted colon microinflammation and initiated preneoplastic lesions while also fostering the growth of aberrant crypt foci in a chemically induced carcinogenesis model.” They continued: “Stimulation of immune cells isolated from Peyer’s Patches [which are clusters of lymphoid follicles found in the intestine] showed a decrease in Thelper (Th)-1 IFN-γ secretion, while splenic Th1/Th17 inflammatory responses sharply increased,” researchers wrote. “A 100-day titanium dioxide treatment promoted colon microinflammation and initiated preneoplastic lesions.” The scientists concluded: “These data should be considered for risk assessments of the susceptibility to Th17-driven autoimmune diseases and to colorectal cancer in humans exposed to TiO2 from dietary sources.”
China has emerged as a dominant force in the global titanium dioxide (TiO2) industry, accounting for nearly 40% of the world's production. This significant contribution is not only a testament to China's industrial prowess but also highlights the country's strategic importance in meeting the growing demand for TiO2 across various applications.
Fig. 4. Hemolysis (%) values of samples, A: 0.2 mg/mL P25TiO2NPs; B: 0.02 mg/mL P25TiO2NPs; C: 0.2 mg/mL VitaminB2@P25TiO2NPs; D: 0.02 mg/mL VitaminB2@P25TiO2NPs after 3 h of irradiation (red) and 6 h (blue). SD <5 for all samples and p <0.05 between C-D and A-B.
Résumé–Cet article traite de la découverte de lithopone phosphorescent sur des dessins à l'aquarelle, datés entre 1890 et 1905, de l'artiste Américain John La Farge et de l'histoire du lithopone dans l'industrie des pigments à la fin du 19e et au début du 20e siècle. Malgré de nombreuses qualités souhaitables pour une utilisation en tant que blanc dans les aquarelles et les peintures à l'huile, le développement du lithopone comme pigment pour artistes a été compliqué de par sa tendance à noircir lorsqu'il est exposé au soleil. Sa disponibilité et son usage par les artistes demeurent incertains parce que les catalogues des marchands de couleurs n'étaient généralement pas explicites à indiquer si les pigments blancs contenaient du lithopone. De plus, lors d'un examen visuel, le lithopone peut être confondu avec le blanc de plomb et sa phosphorescence de courte durée peut facilement être ignorée par l'observateur non averti. À ce jour, le lithopone phosphorescent a seulement été documenté sur une autre œuvre: une aquarelle de Van Gogh. En plus de l'histoire de la fabrication du lithopone, cet article décrit le mécanisme de sa phosphorescence et son identification à l'aide de la spectroscopie Raman et de la spectrofluorimétrie.
To address these challenges, researchers are exploring alternative production methods that are more energy-efficient and environmentally friendly. For example, the use of solar energy to power the oxidation of titanium ore has been proposed as a way to reduce the energy consumption of the sulfate process. Other approaches include the development of new catalysts that can replace sulfuric acid in the oxidation step, as well as the exploration of bio-based feedstocks for TiO2 production.Scrap zinc or concentrated zinc ores are dissolved in sulfuric acid, the solution is purified and the two solutions are reacted. A heavy mixed precipitate results that is 28 to 30% zinc sulfide and 72 to 70% barium sulfate.
As a food additive, titanium dioxide and its nanoparticles in particular have been associated with DNA damage and cell mutations, which in turn, have potential to cause cancer. When used as a food coloring, it is known as E171.
China's consumption of talc and titanium dioxide has also surged in recent years, driven by the country's rapidly growing economy and increasing demand from various industries. The construction sector, which accounts for a significant portion of China's GDP, is one of the largest consumers of titanium dioxide, using it extensively in paints and coatings The construction sector, which accounts for a significant portion of China's GDP, is one of the largest consumers of titanium dioxide, using it extensively in paints and coatingsEurope
ROS were detected through the colorimetric assay employing the nitro-blue tetrazolium salt (NBT salt) by reading the absorbance of the reduced blue molecule.
Fig. 2. SEM micrograph and EDS map of the same area of a vitaminB2@P25TiO2NPs.
In recent years, the manufacturing industry has come under scrutiny for its environmental impact. The production process of titanium dioxide is no exception. Traditional methods often involve energy-intensive procedures and the use of chemicals that can pose risks to both human health and the environment. As awareness grows about these issues, manufacturers are compelled to reevaluate their processes and adopt more eco-friendly techniques.