Titanium Dioxide in Food Products: Quantitative Analysis Using ICP-MS and Raman Spectroscopy

DFOB-Induced Dissolution of Anatase, Rutile, and Food-Grade TiO2 Nanoparticles

Titanium dioxide nanoparticles (TiO2 NPs) are prevalent in products of everyday use, especially in food additives, paints, and consumer products. Their favorable properties include inertness in an aqueous environment. In this study, nanosized anatase, rutile, and food-grade TiO2 particles were investigated with the treatment of the siderophore desferrioxamine B (DFOB), and their physicochemical, spectroscopic, and microscopic natures were revealed under different pH conditions. The formation of a Ti(IV)-DFOB complex in solution is evident from electrospray ionization mass spectroscopy. Dissolved Ti was analyzed by UV/visible and inductively coupled plasma optical emission spectroscopy and was found in the micromolar range (ca. 1-60 μM) over days. At all pH values, dissolution is more extensive for food-grade NP than for anatase and rutile. Near neutral pH, Fourier transform infrared spectroscopy (FTIR) data suggest that siderophore adsorption is more prominent than Ti dissolution. Scanning electron microscopy data reveals erosion of the TiO2 surface with DFOB. A comprehensive kinetic profile supports multiple dissolution steps associated with anatase and rutile, with fewer steps for food-grade NPs. The addition of small organic acids shows mostly synergistic effects toward dissolution. This study will be helpful for considering TiO2 applications in the food processing industry and for predicting its environmental fate in the presence of avid ligands.

Hepatotoxicity of titanium dioxide nanoparticles

The food additive E171 (titanium dioxide, TiO2), is widely used in foods, pharmaceuticals and cosmetics. It is a fine white powder, with at least one third of its particles sized in the nanoparticulate (˂100 nm range, TiO2 NPs). The use of E171 is controversial as its relevant risk assessment has never been satisfactorily accomplished. In vitro and in vivo studies have shown dose-dependent toxicity in various organs including the liver. TiO2 NPs have been shown to induce inflammation, cell death and structural and functional changes within the liver. The toxicity of TiO2 NPs in experimental models varies between organs and according to their physiochemical characteristics and parameters such as dosage and route of administration. Among these factors, ingestion is the most significant exposure route, and the liver is a key target organ. The aim of this review is to highlight the reported adverse effects of orally administered TiO2 NPs on the liver and to discuss the controversial state of its toxicity.

Development of a fast and low-cost aqueous based-extraction protocol for the simultaneous extraction and characterization of SiO2 and TiO2 (nano)particles in confectionary products

BACKGROUND

The determination of (nano)particulate content from food additives has been a long-standing concern for authorities since it is of vital importance for ensuring food safety, regulatory adherence, and transparent consumer information. Nonetheless, a critical step in these determinations is the refinement of a careful and quantitative extraction process for particles that may be found within complex matrices such as confectionery products. The development of new technologies and analysis methods for nanoparticles is ongoing. Whereas new technologies and analysis methods for nanoparticles are being developed, the extraction of (nano)particles of different nature has not been adequately addressed in the literature.

RESULTS

A simple aqueous extraction procedure was found to be suitable for the simultaneous extraction of TiO2 and SiO2 (nano)particles from five confectionery products. Neither the extraction agents (water, lipase, pancreatin and Tris-HCl solutions) nor the methods (manual shaking, ultrasonic bath, ultrasonic probe and ultrafiltration) altered the size, morphology, or aggregation state of either type of particle, as revealed by the micrographs obtained by Transmission Electron Microscopy (TEM). Single-particle ICP-MS (spICP-MS) determined that the optimal conditions for extracting both types of particles involve manual shaking using water as the solvent. Furthermore, the use of enzymes seemed to hinder the determination of both types of particles by spICP-MS. (Nano)particles of TiO2 and SiO2 were detected in all the confectionaries, even though the E171 additive was only labeled in one of them. The average percentage of nanoparticulate TiO2 material in the evaluated products was 30 %, while no nanometer-sized particles of SiO2 were detected.

SIGNIFICANCE

Ensuring food safety, regulatory compliance and transparent consumer information relies on getting reliable results that connect with the application of sample treatment procedures for detecting unaltered nanoparticles in food products. The presented research introduces an economical, swift, user-friendly, environmentally responsible, and harmonious extraction method for the concurrent analysis of TiO2 and SiO2 particles in confectionery samples. Furthermore, particles from additives not included in the labeling have been detected, characterized, and quantified in the confectionary products.

Challenges and potential for detecting and quantifying titanium dioxide in food

BACKGROUND

Titanium dioxide (TiO2) is banned in some countries but its use is still permitted in others. The global food supply chain is therefore challenged with the need to use rapid and reliable testing methods to either detect the presence of TiO2 or to quantify its concentration. The goal of this study was to determine the feasibility of using color, texture profile analysis, Raman microscopy, and X-ray fluorescence (XRF) spectroscopy to detect and quantify TiO2 in fillings used in the pastry and confectionery industry. In this study, two types of fillings were investigated: vanilla based and chocolate based. All fillings were prepared in four different variations - without TiO2 and with three concentrations as follows: 0.25 g*kg-1, 0.5 g*kg-1, or 0.75 g*kg-1 TiO2 per sample. The methods were selected for their ability to analyze the samples in a short period of time.

RESULTS

All of the methods showed moderate to high potential for detecting TiO2 in the samples. The results reveal how TiO2 affects the food matrix color and texture. Use of Raman microscopy confirms its detectability, although concentrations of TiO2 do not follow a pattern. X-ray fluorescence spectroscopy showed the greatest potential as it can not only detect TiO2 but can also quantify its concentration in the samples.

CONCLUSIONS

The highest potential for quantifying the concentration of this food additive was achieved with XRF. © 2024 Society of Chemical Industry.

Definition, detection, and tracking of nanowaste in foods: Challenges and perspectives

Commercial applications of nanotechnology in the food industry are rapidly increasing. Accordingly, there is a simultaneous increase in the amount and diversity of nanowaste, which arise as byproducts in the production, use, disposal, or recycling processes of nanomaterials utilized in the food industry. The potential risks of this nanowaste to human health and the environment are alarming. It is of crucial significance to establish analytical methods and monitoring systems for nanowaste to ensure food safety. This review provides comprehensive information on nanowaste in foods as well as comparative material on existing and new analytical methods for the detection of nanowaste. The article is specifically focused on nanowaste in food systems. Moreover, the current techniques, challenges as well as potential use of new and progressive methods are underlined, further highlighting advances in technology, collaborative efforts, as well as future perspectives for effective nanowaste detection and tracking. Such detection and tracking of nanowaste are required in order to effectively manage this type ofwasted in foods. Although there are devices that utilize spectroscopy, spectrometry, microscopy/imaging, chromatography, separation/fractionation, light scattering, diffraction, optical, adsorption, diffusion, and centrifugation methods for this purpose, there are challenges to be overcome in relation to nanowaste as well as food matrix and method characteristics. New technologies such as radio-frequency identification, Internet of things, blockchain, data analytics, and machine learning are promising. However, the cooperation of international organizations, food sector, research, and political organizations is needed for effectively managing nanowaste. Future research efforts should be focused on addressing knowledge gaps and potential strategies for optimizing nanowaste detection and tracking processes.

The distribution, fate, and environmental impacts of food additive nanomaterials in soil and aquatic ecosystems

Nanomaterials in the food industry are used as food additives, and the main function of these food additives is to improve food qualities including texture, flavor, color, consistency, preservation, and nutrient bioavailability. This review aims to provide an overview of the distribution, fate, and environmental and health impacts of food additive nanomaterials in soil and aquatic ecosystems. Some of the major nanomaterials in food additives include titanium dioxide, silver, gold, silicon dioxide, iron oxide, and zinc oxide. Ingestion of food products containing food additive nanomaterials via dietary intake is considered to be one of the major pathways of human exposure to nanomaterials. Food additive nanomaterials reach the terrestrial and aquatic environments directly through the disposal of food wastes in landfills and the application of food waste-derived soil amendments. A significant amount of ingested food additive nanomaterials (> 90 %) is excreted, and these nanomaterials are not efficiently removed in the wastewater system, thereby reaching the environment indirectly through the disposal of recycled water and sewage sludge in agricultural land. Food additive nanomaterials undergo various transformation and reaction processes, such as adsorption, aggregation-sedimentation, desorption, degradation, dissolution, and bio-mediated reactions in the environment. These processes significantly impact the transport and bioavailability of nanomaterials as well as their behaviour and fate in the environment. These nanomaterials are toxic to soil and aquatic organisms, and reach the food chain through plant uptake and animal transfer. The environmental and health risks of food additive nanomaterials can be overcome by eliminating their emission through recycled water and sewage sludge.

Identification of liquor adulteration by Raman spectroscopy method based on ICNAFS

The health of consumers can be impacted by the additives placed into the liquor. To address the issues of poor accuracy, low reliability, and complex operational procedures in identifying adulteration in existing liquor, an improved convex non-negative matrix factorization (ICNAFS) with an adaptive graph constraint for unsupervised feature extraction is proposed in this paper, with the goal of achieving rapid identification of adulteration in liquor by Raman spectroscopy through dimensionality reduction. For the sake to streamline the calculation process for effective feature extraction and increase the accuracy of the analyzed model, the proposed ICNAFS method incorporates two fundamental models, such as ridge regression and convex non-negative matrix factorization (NMF). In particular, dimensionality reduction of the original spectrum is initially conducted using Principal Component Analysis (PCA), Sequential Projection Algorithm (SPA), Convex Non-Negative Matrix Factorization with an Adaptive Graph Constraint (CNAFS), and ICNAFS respectively. k-means is subsequently employed to merge the four models for clustering analysis. The results suggest that the accuracy of the presented ICNAFS-assisted k-means model is higher than the other techniques, with a clustering accuracy of 98.67%, exhibiting a 4% improvement over the existing CNAFS, through examination of 150 sets of tainted liquor data from five categories of samples. This demonstrates the potency of the proposed ICNAFS-assisted k-means clustering model in conjunction with Raman spectroscopy as a method for detecting tainted liquor.

An innovative approach in titanium determination based on incorporating 2-amino-4-((4-nitrophenyl)diazenyl)pyridine-3-ol in a PVC membrane

A pioneering optical sensor has been effectively developed to achieve precise and reliable detection of titanium ions. The sensor employs an optode membrane composed of 2-amino-4-((4-nitrophenyl)diazenyl)pyridine-3-ol (ANPDP) and sodium tetraphenylborate (NaTPB) incorporated into a plasticized PVC matrix, with dioctyl sebacate (DOS) acting as the plasticizer. When exposed to Ti4+ ions at pH 8.25, the color of the sensing membrane undergoes a distinctive transformation from yellow-orange to violet. Extensive investigations were carried out to assess and optimize various factors influencing the efficiency of ion uptake. Through careful experimentation, the optimum conditions were determined to be 60.0% DOS, 6.0% ANPDP, 30% PVC, and 4.0% NaTPB, with a rapid response time of 5.0 min. Within these conditions, the developed optode demonstrates an impressive linear range of 3.0-225 ng mL-1, boasting detection (LOD) and quantification (LOQ) limits of 0.91 and 2.95 ng mL-1, respectively. Moreover, the precision of the sensor, as indicated by the relative standard deviation (RSD%), remained consistently below 1.55% in six replicate determinations of 100 ng mL-1 Ti4+ across diverse membranes. The selectivity of the sensor was rigorously examined for a range of cations and anions, successfully establishing the tolerance limits for interfering species. Notably, the presence of EDTA as a masking agent did not compromise the high selectivity of the sensor. Consequently, the innovative probe holds significant potential as a reliable analytical tool for quantifying titanium content in various samples, including water, geological materials, soil, plants, paints, cosmetics, and plastics.

Perinatal foodborne titanium dioxide exposure-mediated dysbiosis predisposes mice to develop colitis through life

BACKGROUND

Perinatal exposure to titanium dioxide (TiO2), as a foodborne particle, may influence the intestinal barrier function and the susceptibility to develop inflammatory bowel disease (IBD) later in life. Here, we investigate the impact of perinatal foodborne TiO2 exposure on the intestinal mucosal function and the susceptibility to develop IBD-associated colitis. Pregnant and lactating mother mice were exposed to TiO2 until pups weaning and the gut microbiota and intestinal barrier function of their offspring was assessed at day 30 post-birth (weaning) and at adult age (50 days). Epigenetic marks was studied by DNA methylation profile measuring the level of 5-methyl-2'-deoxycytosine (5-Me-dC) in DNA from colic epithelial cells. The susceptibility to develop IBD has been monitored using dextran-sulfate sodium (DSS)-induced colitis model. Germ-free mice were used to define whether microbial transfer influence the mucosal homeostasis and subsequent exacerbation of DSS-induced colitis.

RESULTS

In pregnant and lactating mice, foodborne TiO2 was able to translocate across the host barriers including gut, placenta and mammary gland to reach embryos and pups, respectively. This passage modified the chemical element composition of foetus, and spleen and liver of mothers and their offspring. We showed that perinatal exposure to TiO2 early in life alters the gut microbiota composition, increases the intestinal epithelial permeability and enhances the colonic cytokines and myosin light chain kinase expression. Moreover, perinatal exposure to TiO2 also modifies the abilities of intestinal stem cells to survive, grow and generate a functional epithelium. Maternal TiO2 exposure increases the susceptibility of offspring mice to develop severe DSS-induced colitis later in life. Finally, transfer of TiO2-induced microbiota dysbiosis to pregnant germ-free mice affects the homeostasis of the intestinal mucosal barrier early in life and confers an increased susceptibility to develop colitis in adult offspring.

CONCLUSIONS

Our findings indicate that foodborne TiO2 consumption during the perinatal period has negative long-lasting consequences on the development of the intestinal mucosal barrier toward higher colitis susceptibility. This demonstrates to which extent environmental factors influence the microbial-host interplay and impact the long-term mucosal homeostasis.

An ICP-MS-Based Analytical Strategy for Assessing Compliance with the Ban of E 171 as a Food Additive on the EU Market

A method was developed for the determination of total titanium in food and food supplements by inductively coupled plasma mass spectrometry (ICP-MS) after microwave-assisted acid digestion of samples. Five food supplements, including one certified reference material, and 15 food products were used for method development. Key factors affecting the analytical results, such as the composition of the acid mixture for sample digestion and the bias from spectral interferences on the different titanium isotopes, were investigated. Resolution of interferences was achieved by ICP-MS/MS with ammonia adduct formation and viable conditions for control laboratories equipped with standard quadrupole instruments were identified. The method was successfully validated and enables rapid screening of samples subject to confirmatory analysis for the presence of TiO2 particles. For the latter, single-particle ICP-MS (spICP-MS) analysis after chemical extraction of the particles was used. The two methods establish a viable analytical strategy for assessing the absence of titania particles in food products on the EU market following the E 171 ban as a food additive.

Characterisation of engineered titanium dioxide nanoparticles in selected food

Titanium dioxide (TiO2), an E171 manufacturer-made food additive, is extensively utilised as a colourant in drug and a food products. Some studies showed that most of confectionary and food items contain inexplicable particles. The aim of this article is to determine the size and structure of TiO2 nanoparticles in different food products. Ten food samples, including coffee cream, white chocolate concentrate, frosting, gum, yoghurt candy, hard candies and chewy candies, were investigated for this purpose. The crystalline structure and particle size of TiO2 were determined by Powder X-ray Diffraction (PXRD) and Transmission Electron Microscopy (TEM). TEM images revealed that a few of the extracted nanoparticles had a rod-like shape, but most were spherical. Also, the size of the TiO2 particle had a wide distribution between 12 and 450 nm. Thus, to avoid human health risk, crucial factors such as size, and shape should be considered and regulated by food authorities.

Raman mapping for determination of TiO2 in different solid food samples by multivariate curve resolution with alternating least squares

Titanium dioxide is a food additive commonly used as a white food coloring (E171). Its wide use by the food industry associated with the nanometric size distribution of the particles of this pigment has shown high genotoxicity associated with recurrent exposure by ingestion. Therefore, the use of E171 in food products has already been banned by some industries and in the European Union. Such banishment should soon be extended to other countries around the world, making it important to establish techniques for the efficient determination of TiO₂ in different food products. The association between hyperspectral images and chemometric tools can be useful in this sense, aiming to enable the use of a single method for sample preparation and analysis of different types of food. Thus, the present work aims to evaluate the use of Raman mapping associated with the resolution of multivariate curves with alternating least squares (MCR-ALS) for the determination of titanium dioxide in solid food samples with different compositions, without the need to introduce specific sample preparation. The proposed method allowed for the first-time quantification of TiO₂ in different food matrices without specific sample preparation, with a simple, rapid, accurate (93% of recovery), low detection limits (0.0111% m/m) and quantification (0.0370% m/m) and adequate linearity (r = 0.9990) and precise (standard deviation around 0.020-0.030% w/w) methodology. Such results highlight the potential use of Raman mapping associated with the MCR-ALS for quantification of the nano-TiO₂ in commercial samples.

Subchronic Oral Toxicity Study of Food-Related Titanium Dioxide Nanoparticles in Rats Involved in Ti Biodistribution and Gut Microbiota

The widespread use of titanium dioxide nanoparticles (TiO₂ NPs) in the food industry has brought about human safety risks related to nanotoxicity. In this study, food-related TiO₂ NPs (anatase, 40 nm) were given to rats by oral gavage for 90 days at doses of 10, 100, and 1000 mg/kg bw. An additional two satellite groups underwent the same protocol for 45 days and for 90 days followed by a 28 day recovery. TiO₂ NPs tended to agglomerate together in H₂O, AGJ, and AIJ. No systemic toxicity was observed after 90 day agglomerated TiO₂ NP exposure with no Ti distribution in major tissues/organs. Furthermore, TiO₂ NP consumption for 90 days had no impact on microbiota diversity; the community structure of the gut microbiota is shifted to some extent at the genus level. Collectively, the NOAEL of agglomerated TiO₂ NPs for 90 days of oral administration was 1000 mg/kg bw, the highest dose tested in male and female rats.

Characterization of titanium dioxide nanoparticles in confectionary products and estimation of dietary exposure level among the Chinese population

Titanium dioxide (TiO₂) is widely used in the food industry. Recently, European Commission has banned TiO₂ as a food additive, raising public concern about its health risk, especially the nanoparticles (NPs) contained therein. This study aimed to reveal the existence of TiO₂ NPs in food and further estimate the dietary exposure level among Chinese population by characterizing particle size distribution, determining Ti content and micro-distribution in food products, and calculating food consumption from the China Health and Nutrition Survey (CHNS). The results showed that TiO₂ particle size in food additives and chewing gums was 53.5-230.3 nm and 56.8-267.7 nm respectively, where NPs accounted for 34.7% and 55.6% respectively. TiO₂ was firstly in situ presented on the surface of confectionary products with hard shells. The content of TiO₂ ranged from 3.2 to 3409.3 μg/g product. Besides, the mean dietary intake was 71.31 μg/kg_bw/day for TiO₂ and 7.75 μg/kg_bw/day for TiO₂ NPs among Chinese population, affected by people's dietary habits of different regions. Children's exposure levels was the highest due to their love of sweets. More attention should be paid to risk assessment and management of TiO₂ NPs for children in China.

Assessment of the Authenticity of Whisky Samples Based on the Multi-Elemental and Multivariate Analysis

Two hundred and five samples of whisky, including 170 authentic and 35 fake products, were analyzed in terms of their elemental profiles in order to distinguish them according to the parameter of their authenticity. The study of 31 elements (Ag, Al, B, Ba, Be, Bi, Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, Pb, Sb, Sn, Sr, Te, Tl, U, V, Ca, Fe, K, Mg, P, S, Ti and Zn) was performed using the Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Cold Vapor-Atomic Absorption (CVAAS) techniques. Additionally, the pH values of all samples were determined by pH-meter, and their isotopic ratios of ⁸⁸Sr/⁸⁶Sr, ⁸⁴Sr/⁸⁶Sr, ⁸⁷Sr/⁸⁶Sr and ⁶³Cu/⁶⁵Cu were assessed, based on the number of counts by ICP-MS. As a result of conducted research, elements, such as Mn, K, P and S, were identified as markers of whisky adulteration related to the age of alcohol. The concentrations of manganese, potassium and phosphorus were significantly lower in the fake samples (which were not aged, or the aging period was much shorter than legally required), compared to the original samples (in all cases subjected to the aging process). The observed differences were related to the migration of these elements from wooden barrels to the alcohol contained in them. On the other hand, the sulfur concentration in the processed samples was much higher in the counterfeit samples than in the authentic ones. The total sulfur content, such as that of alkyl sulfides, decreases in alcohol with aging in the barrels. Furthermore, counterfeit samples can be of variable origin and composition, so they cannot be characterized as one group with identical or comparable features. Repeatedly, the element of randomness dominates in the production of these kinds of alcohols. However, as indicated in this work, the extensive elemental analysis supported by statistical tools can be helpful, especially in the context of detecting age-related adulteration of whisky. The results presented in this paper are the final part of a comprehensive study on the influence of selected factors on the elemental composition of whisky.

Estimation of Titanium Dioxide Intake by Diet and Stool Assessment among US Healthy Adults

BACKGROUND

Titanium dioxide (TiO2/E171) is used in foods primarily as a whitening agent. Little is known regarding TiO2 exposure in the United States.

OBJECTIVES

To quantify stool TiO2 content among US adults and evaluate its association with estimated intake.

METHODS

Adults participated in phase 1 [three 24-h dietary recalls (DRs) and stool TiO2 measured from 3 matched samples (n = 52)] and/or phase 2 [tailored FFQ and stool TiO2 measured from 3 samples over 3 mo (n = 61)]. TiO2 in foods was estimated from a database, and concentration in 49 additional foods and 339 stool samples were quantified using inductively coupled plasma mass spectrometry. Associations between dietary and stool TiO2 were assessed by log-linear multivariable regression. USDA food groups (n = 49, servings/d) were related to stool TiO2 by stepwise regression.

RESULTS

TiO2 food content varied by brand. Mean TiO2 intake from three 24-h DRs [0.19 ± 0.31 mg/(kg body weight · d)] was lower than from the FFQ [0.30 ± 0.21 mg/(kg body weight · d)]. Dietary TiO2 was not predictive of stool TiO2, in phase 1 or phase 2, 10^(β) per 10 times higher dietary TiO2: 1.138 [10^(95% CI): 0.635, 2.037, P = 0.66] and 0.628 [10^(95% CI): 0.206, 1.910, P = 0.41], respectively. Food groups related to stool TiO2 were 1) milk desserts, sauces, and gravies [10^(β) per servings/d: 3.361; 10^(95% CI): 0.312, 36.163; P = 0.002] and 2) yeast breads [10^(β): 1.430; 10^(95% CI): 0.709, 2.884; P = 0.002] in phase 1 and 1) cream and cream substitutes [10^(β) = 10.925; 10^(95% CI): 1.952, 61.137; P = 0.01] and 2) milk and milk drinks [10^(β) = 0.306; 10^(95% CI): 0.086, 1.092, P = 0.07] in phase 2.

CONCLUSIONS

Intake of certain foods was associated with higher stool TiO2 content. There is a need for valid estimation of TiO2 intakes via the improvement of a dietary assessment method and a TiO2 food composition database. Future research should assess whether high stool TiO2 content is related to adverse health outcomes.

Migration of Irganox 1010, Irganox 1076, and Titanium dioxide into Doogh and corresponding food simulant from laminated packaging

PURPOSE

Doogh is a famous Iranian drink based on fermented milk. Laminated film is one of the most common packaging for this beverage in Iran. So, chemical substances of the packaging may migrate to the Doogh and endanger human health.

METHOD

In this research, High-Performance Liquid Chromatography (HPLC) was used to determine the migration of Irganox 1010 and Irganox 1076 from the contact layer and inductively coupled plasma for Titanium dioxide (TiO2) from the second layer of three-layer laminate films into Doogh and acetic acid 3% (w/v). The influence of different storage temperatures and times was investigated by evaluating the samples stored in various conditions. The morphological, thermal and mechanical properties of the film, before and after contact with food simulant were further studied.

RESULT

The highest amount of Irganox 1010 concentration of the tested samples were 0.8 ± 0.04 mg/l in acetic acid 3% (w/v), and 0.62 ± 0.04 mg/l in Doogh. The highest amount of TiO2 concentration were 0.25 ± 0.04 mg/l in acetic acid 3% (w/v), and 0.12 ± 0.02 mg/l in Doogh. The migration of Irganox 1076 was determined, but it was not detected. The results indicated that the food simulant had no significant effect on the microstructure and thermal properties of the polymer, but it reduced the mechanical properties.

CONCLUSION

The results indicate the possible migrating of Irganox 1010 and TiO2 through laminate packaging into Doogh in some storage conditions. Since the migration value was low, the mentioned film was proven safe for Doogh packaging, imposing no hazards on human health.

Intestinal toxicity of micro- and nano-particles of foodborne titanium dioxide in juvenile mice: Disorders of gut microbiota-host co-metabolites and intestinal barrier damage

The wide use of TiO₂ particles in food and the high exposure risk to children have prompted research into the health risks of TiO₂. We used the microbiome and targeted metabolomics to explore the potential mechanism of intestinal toxicity of foodborne TiO₂ micro-/nanoparticles after oral exposure for 28 days in juvenile mice. Results showed that the gut microbiota-including the abundance of Bacteroides, Bifidobacterium, Lactobacillus, and Prevotella-changed dynamically during exposure. The organic inflammatory response was activated, and lipopolysaccharide levels increased. Intestinal toxicity manifested as increased mucosal permeability, impaired intestinal barrier, immune damage, and pathological changes. The expression of antimicrobial peptides, occludin, and ZO-1 significantly reduced, while that of JNK2 and Src/pSrc increased. Compared with micro-TiO₂ particles, the nano-TiO₂ particles had strong toxicity. Fecal microbiota transplant confirmed the key role of gut microbiota in intestinal toxicity. The levels of gut microbiota-host co-metabolites, including pyroglutamic acid, L-glutamic acid, phenylacetic acid, and 3-hydroxyphenylacetic acid, changed significantly. Significant changes were observed in the glutathione and propanoate metabolic pathways. There was a significant correlation between the changes in gut microbiota, metabolites, and intestinal cytokine levels. These, together with the intestinal barrier damage signaling pathway, constitute the network mechanism of the intestinal toxicity of TiO₂ particles.

TiO2 nanoparticles negatively impact the bioavailability and antioxidant activity of tea polyphenols

This study was to investigate the influence of TiO₂ nanoparticles (NPs) on the stability, bioavailability, and antioxidant activity of co-ingested tea polyphenols extract using an in vitro digestion model. The tea polyphenol contents decreased significantly after addition of 0.5 % (w/w) TiO₂ NPs. The gallocatechin gallate level decreased the most, changing from 101.9 to 27.2 µg/mL (about 73.3%). The TiO₂ NPs also reduced the bioavailability of the tea polyphenols in a dose-dependent manner, which was ascribed to the formation of large polyphenol-TiO₂ NP complex aggregates that could not pass through the pores in the dialysis tube used to simulate the gut wall. Additionally, the TiO₂ NPs decreased the antioxidant activity of the tea polyphenols within the simulated gastrointestinal tract. In summary, our results show that high levels of TiO₂ NPs (but within the current legal limits in many countries) may negatively impact the bioavailability and bioactivity of polyphenols in foods.

Development of Colorimetric Whole-Cell Biosensor for Detection of Heavy Metals in Environment for Public Health

Heavy metals cause various fetal diseases in humans. Heavy metals from factory wastewater can contaminate drinking water, fish, and crops. Inductively coupled plasma-mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS) are commonly used to analyze heavy metal contents; however, these methods require pre-treatment processes and are expensive and complex. To overcome these limitations, three metal-sensing materials using a whole-cell biosensor in Escherichia coli (E. coli) were developed. Strains were engineered to harbor three kinds of plasmids containing the copA, zntA, and mer promoters for sensing copper, cadmium, and mercury, respectively. The luciferase (lux) gene was inserted as a reporter into the plasmid, which was later replaced with a fused protein sequence containing OmpA (1–159) and mCherry for optical detection. The constructed strains could detect mercury, cadmium, and copper at 0.1–0.75 ppm, 0.2–0.75 ppm, and 2–7.5 ppm, respectively, with linearity values of 0.99030, 0.99676, and 0.95933, respectively. The immobilization linearity value was 0.99765. Notably, these three heavy metals could be detected by visual analysis of the strains. Overall, these findings establish this novel sensor as a potential approach for heavy metal detection in biological samples and foods.

How to control fluorescent labeling of metal oxide nanoparticles for artefact-free live cell microscopy

Nanotechnologies hold great promise for various applications. To predict and guarantee the safety of novel nanomaterials, it is essential to understand their mechanism of action in an organism, causally connecting adverse outcomes with early molecular events. This is best investigated using noninvasive advanced optical methods, such as high-resolution live-cell fluorescence microscopy, which require stable labeling of nanoparticles with fluorescent dyes. However, as shown here, when the labeling is performed inadequately, unbound fluorescent dyes and inadvertently altered chemical and physical properties of the nanoparticles can result in experimental artefacts and erroneous conclusions. To prevent such unintentional errors, we introduce a tested minimal combination of experimental methods to enable artefact-free fluorescent labeling of metal-oxide nanoparticles-the largest subpopulation of nanoparticles by industrial production and applications-and demonstrate its application in the case of TiO2 nanotubes. We (1) characterize potential changes of the nanoparticles' surface charge and morphology that might occur during labeling by using zeta potential measurements and transmission electron microscopy, respectively, and (2) assess stable binding of the fluorescent dye to the nanoparticles with either fluorescence intensity measurements or fluorescence correlation spectroscopy, which ensures correct nanoparticle localization. Together, these steps warrant the reliability and reproducibility of advanced optical tracking, which is necessary to explore nanomaterials' mechanism of action and will foster widespread and safe use of new nanomaterials.

Impact of Polyphenol Interactions with Titanium Dioxide Nanoparticles on Their Bioavailability and Antioxidant Activity

Titanium dioxide is widely utilized as a pigment in the food industry to enhance the whiteness or brightness of foods and beverages. The powdered forms of titanium dioxide used as food ingredients contain a substantial fraction of nanoparticles (d < 100 nm), which may have adverse effects on human health. This is a model study that investigated the molecular interactions between TiO₂ nanoparticles and selected polyphenols, as well as their influence on the in vitro bioavailability and antioxidant activity of the polyphenols. Our results showed that the chemical structure of polyphenols significantly influenced their binding affinity to TiO₂ nanoparticle surfaces, with those possessing vicinal trihydroxy groups having the highest binding affinities. The presence of TiO₂ nanoparticles was shown to reduce the bioavailability of polyphenols using an in vitro digestion model. This effect was mainly ascribed to the formation of large TiO₂ nanoparticle-polyphenol complex agglomerates that could not pass through the pores in the dialysis tube used to simulate the epithelium layer. Additionally, the binding of polyphenols to the surfaces of TiO₂ nanoparticles reduced their antioxidant activity. This study provides valuable insights into the impact of inorganic nanoparticles on the bioavailability and bioactivity of polyphenols.

EFSA Panel on Food Additives and Flavourings (FAF), Younes M, Aquilina G, Castle L, Engel K, Fowler P, Frutos Fernandez MJ, Fürst P, Gundert‐Remy U, Gürtler R, Husøy T, Manco M, Mennes W, Moldeus P, Passamonti S, Shah R, Waalkens‐Berendsen I, Wölfle D, Corsini E, Cubadda F, De Groot D, FitzGerald R, Gunnare S, Gutleb AC, Mast J, Mortensen A, Oomen A, Piersma A, Plichta V, Ulbrich B, Van Loveren H, Benford D, Bignami M, Bolognesi C, Crebelli R, Dusinska M, Marcon F, Nielsen E, Schlatter J, Vleminckx C, Barmaz S, Carfí M, Civitella C, Giarola A, Rincon AM, Serafimova R, Smeraldi C, Tarazona J, Tard A, Wright M. Safety assessment of titanium dioxide (E171) as a food additive

The present opinion deals with an updated safety assessment of the food additive titanium dioxide (E 171) based on new relevant scientific evidence considered by the Panel to be reliable, including data obtained with TiO2 nanoparticles (NPs) and data from an extended one-generation reproductive toxicity (EOGRT) study. Less than 50% of constituent particles by number in E 171 have a minimum external dimension < 100 nm. In addition, the Panel noted that constituent particles < 30 nm amounted to less than 1% of particles by number. The Panel therefore considered that studies with TiO2 NPs < 30 nm were of limited relevance to the safety assessment of E 171. The Panel concluded that although gastrointestinal absorption of TiO2 particles is low, they may accumulate in the body. Studies on general and organ toxicity did not indicate adverse effects with either E 171 up to a dose of 1,000 mg/kg body weight (bw) per day or with TiO2 NPs (> 30 nm) up to the highest dose tested of 100 mg/kg bw per day. No effects on reproductive and developmental toxicity were observed up to a dose of 1,000 mg E 171/kg bw per day, the highest dose tested in the EOGRT study. However, observations of potential immunotoxicity and inflammation with E 171 and potential neurotoxicity with TiO2 NPs, together with the potential induction of aberrant crypt foci with E 171, may indicate adverse effects. With respect to genotoxicity, the Panel concluded that TiO2 particles have the potential to induce DNA strand breaks and chromosomal damage, but not gene mutations. No clear correlation was observed between the physico-chemical properties of TiO2 particles and the outcome of either in vitro or in vivo genotoxicity assays. A concern for genotoxicity of TiO2 particles that may be present in E 171 could therefore not be ruled out. Several modes of action for the genotoxicity may operate in parallel and the relative contributions of different molecular mechanisms elicited by TiO2 particles are not known. There was uncertainty as to whether a threshold mode of action could be assumed. In addition, a cut-off value for TiO2 particle size with respect to genotoxicity could not be identified. No appropriately designed study was available to investigate the potential carcinogenic effects of TiO2 NPs. Based on all the evidence available, a concern for genotoxicity could not be ruled out, and given the many uncertainties, the Panel concluded that E 171 can no longer be considered as safe when used as a food additive.

Separation and size characterization of highly polydisperse titanium dioxide nanoparticles (E171) in powdered beverages by using Asymmetric Flow Field-Flow Fractionation hyphenated with Multi-Angle Light Scattering and Inductively Coupled Plasma Mass Spectrometry

The application of titanium dioxide as E171 food additive has become an issue of debate due to numerous reports that titanium dioxide nanoparticles (TiO₂ NPs) inside the products may pose risks to human health. However, there is still a lack of an official standardized methodology for the detection and size characterization of TiO₂ particles in foods containing E171. In this study, a method was presented for size characterization of TiO₂ particles with various independent verifications in coffee creamer and instant drink powders, using Asymmetric Flow Field-Flow Fractionation hyphenated with Multi-Angle Light Scattering and Inductively Coupled Plasma Mass Spectrometry (AF4-MALS-ICP-MS). TiO₂ particles from these products were well extracted, followed by their optimized AF4 separation using anionic surfactant Sodium Dodecyl Sulfate (SDS) (0.05%, pH 9) and mixed surfactant NovaChem (0.2%), respectively. Size determination of TiO₂ NPs was conducted based on AF4 calibration with polystyrene nanospheres and verification with TiO₂ NPs standard suspension of 100 nm under two different AF4 conditions. The TiO₂ particle sizes detected ranged from 24.4 - 544.3 nm for coffee creamer and 27.7 - 574.3 nm for instant drink powders, with the TiO₂ NPs detection recoveries of 75% and 92%, respectively. Hydrodynamic diameters from AF4 size calibration could be independently validated by the gyration diameters from online MALS measurement. The established approach was demonstrated to be reliable and pragmatic for size profiling of highly polydisperse TiO₂ particles and thus useful for monitoring E171 in similar foodstuffs.

Optimisation and application of an analytical approach for the characterisation of TiO2 nanoparticles in food additives and pharmaceuticals by single particle inductively coupled plasma-mass spectrometry

This study was designed to optimise an analytical method for characterising TiO₂ nanoparticles (NPs) in food additives and pharmaceuticals by inductively coupled plasma-mass spectrometry in single particle mode (spICP-MS). Several parameters, including transport efficiency (TE), were assessed and optimised using the NM-100 reference material. We found that self-aspiration for sample intake and use of the concentration-based method for TE was optimal for characterising TiO₂ NPs. No spectral interference was observed with either ⁴⁹Ti or ⁴⁸Ti isotopes. The optimised Excel spreadsheet developed for this study not only provided additional parameters but gave results closer to the NM-100 reference value than the ICP-MS software. The method was then applied to the analysis of a selection of food samples and pharmaceuticals. The average diameter of TiO₂ particles ranged from 86 to 179 nm in the food samples and from 131 to 197 nm in the pharmaceuticals, while the nanoparticular fraction was between 19 and 68% in food, and between 13 and 45% in pharmaceuticals.

Possible Adverse Effects of Food Additive E171 (Titanium Dioxide) Related to Particle Specific Human Toxicity, Including the Immune System

Titanium dioxide (TiO₂) is used as a food additive (E171) and can be found in sauces, icings, and chewing gums, as well as in personal care products such as toothpaste and pharmaceutical tablets. Along with the ubiquitous presence of TiO₂ and recent insights into its potentially hazardous properties, there are concerns about its application in commercially available products. Especially the nano-sized particle fraction (<100 nm) of TiO₂ warrants a more detailed evaluation of potential adverse health effects after ingestion. A workshop organized by the Dutch Office for Risk Assessment and Research (BuRO) identified uncertainties and knowledge gaps regarding the gastrointestinal absorption of TiO₂, its distribution, the potential for accumulation, and induction of adverse health effects such as inflammation, DNA damage, and tumor promotion. This review aims to identify and evaluate recent toxicological studies on food-grade TiO₂ and nano-sized TiO₂ in ex-vivo, in-vitro, and in-vivo experiments along the gastrointestinal route, and to postulate an Adverse Outcome Pathway (AOP) following ingestion. Additionally, this review summarizes recommendations and outcomes of the expert meeting held by the BuRO in 2018, in order to contribute to the hazard identification and risk assessment process of ingested TiO₂.

Food additives containing nanoparticles induce gastrotoxicity, hepatotoxicity and alterations in animal behavior: The unknown role of oxidative stress

Food additives such as titanium dioxide (E171), iron oxides and hydroxides (E172), silver (E174), and gold (E175) are highly used as colorants while silicon dioxide (E551) is generally used as anticaking in ultra-processed foodstuff highly used in the Western diets. These additives contain nanosized particles (1-100 nm) and there is a rising concern since these nanoparticles could exert major adverse effects due to they are not metabolized but are accumulated in several organs. Here, we analyze the evidence of gastrotoxicity, hepatotoxicity and the impact of microbiota on gut-brain and gut-liver axis induced by E171, E172, E174, E175 and E551 and their non-food grade nanosized counterparts after oral consumption. Although, no studies using these food additives have been performed to evaluate neurotoxicity or alterations in animal behavior, their non-food grade nanosized counterparts have been associated with stress, depression, cognitive and eating disorders as signs of animal behavior alterations. We identified that these food additives induce gastrotoxicity, hepatotoxicity and alterations in gut microbiota and most evidence points out oxidative stress as the main mechanism of toxicity, however, the role of oxidative stress as the main mechanism needs to be explored further.

Toxicity Assessment of SiO2 and TiO2 in Normal Colon Cells, In Vivo and in Human Colon Organoids

We conducted systemic assessments on the toxicity of silicon dioxide (SiO₂) and titanium dioxide (TiO₂) nanoparticles using different forms of normal colon cells (CCD-18Co), in vivo and in human colon organoids. The in vivo acute oral toxicity data showed that the LD₅₀ values are greater than 2000 mg/kg for both the SiO₂ and TiO₂ nanoparticles; however, the SiO₂ and TiO₂ nanoparticles induced cytotoxicity in two-dimensional CCD-18Co cells and three-dimensional CCD-18Co spheroids and human colon organoids, with IC₅₀ values of 0.6, 0.8 and 0.3 mM for SiO₂ and 2.5, 1.1 and 12.5 mM for TiO₂ nanoparticles, respectively. The data suggest that, when SiO₂ and TiO₂ are in nanoparticle form, cytotoxicity is induced; thus, care should be taken with these materials.

Charge-switchable magnetic separation and characterization of food additive titanium dioxide nanoparticles from commercial food

Growing concerns about the potential health effects of nanoscale titanium dioxide (TiO₂) have necessitated the need for monitoring the size distribution and physicochemical properties of food additive TiO₂ that are present in commercial food. Acid digestion is by far the most widely used method to remove interfering food matrices, but the highly corrosive nature of the reaction could alter the physicochemical properties of the TiO₂, which may give a skewed information about the materials. Here, we report an effective approach to extract intact form of food additive TiO₂ nanoparticles from processed food through charge-charge interaction between TiO₂ particles and charge-switchable starch magnetic beads (PL@SMBs), of which the captured TiO₂ is readily harvested by switching the surface charge of PL@SMBs to neutral. The size and surface property of extracted TiO₂ were shown to be well maintained due to the mild nature of the reaction. The extracted TiO₂ particles from 10 commercial processed food showed a size distribution from 40 to 250 nm with a mean diameter of 115 nm, of which 22 % of them were less than 100 nm. The extracted TiO₂ did not exhibit short-term cytotoxicity, but induced cellular oxidative stress at high concentration.

Inactivation Kinetics and Membrane Potential of Pathogens in Soybean Curd Subjected to Pulsed Ohmic Heating Depending on Applied Voltage and Duty Ratio

The aim of this research was to investigate the efficacy of the duty ratio and applied voltage in the inactivation of pathogens in soybean curd by pulsed ohmic heating (POH). The heating rate of soybean curd increased rapidly as the applied voltage increased, although the duty ratio did not affect the temperature profile. We supported this result by verifying that electrical conductivity increased with the applied voltage. Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in soybean curd were significantly (P < 0.05) inactivated by more than 1 log unit at 80 Vrms (root mean square voltage). To elucidate the mechanism underlying these results, the membrane potential of the pathogens was examined using DiBAC4(3) [bis-(1,3-dibutylbarbituric acid)trimethine oxonol] on the basis of a previous study showing that the electric field generated by ohmic heating affected the membrane potential of cells. The values of DiBAC4(3) accumulation increased under increasing applied voltage, and they were significantly (P < 0.05) higher at 80 Vrms, while the duty ratio had no effect. In addition, morphological analysis via transmission electron microscopy showed that electroporation and expulsion of intracellular materials were predominant at 80 Vrms Moreover, electrode corrosion was overcome by the POH technique, and the textural and color properties of soybean curd were preserved. These results substantiate the idea that the applied voltage has a profound effect on the microbial inactivation of POH as a consequence of not only the thermal effect, but also the nonthermal effect, of the electric field, whereas the duty ratio does not have such an effect.IMPORTANCE High-water-activity food products, such as soybean curd, are vulnerable to microbial contamination, which causes fatal foodborne diseases and food spoilage. Inactivating microorganisms inside food is difficult because the transfer of thermal energy is slower inside than it is outside the food. POH is an adequate sterilization technique because of its rapid and uniform heating without causing electrode corrosion. To elucidate the electrical factors associated with POH performance in the inactivation of pathogens, the effects of the applied voltage and duty ratio on POH were investigated. In this study, we verified that a high applied voltage (80 Vrms) at a duty ratio of 0.1 caused thermal and nonthermal effects on pathogens that led to an approximately 4-log-unit reduction in a significantly short time. Therefore, the results of this research corroborate database predictions of the inactivation efficiency of POH based on pathogen control strategy modeling.

The long-term oral exposure to titanium dioxide impaired immune functions and triggered cytotoxic and genotoxic impacts in rats

BACKGROUND

Titanium dioxide "TiO₂, E171″ is a widely used food additive that exists in various everyday food products all over the world together with vast applications in cosmetics and industry. However, many toxicological aspects particularly following oral exposure still unclear.

METHODS

Hence, this study was planned to examine the effect of oral exposure of male Wistar rats to two doses of TiO₂ (20 or 40 mg/kg b.wt.) through oral gavage once daily for 90 consecutive days on the blood components, immunity, cytotoxic, and genotoxic indicators.

RESULTS

A dose-dependent leukopenia, eosinophilia, neutrophilia, and thrombocytopenia were noted. Also, the immunoglobins G (IgG) and IgM were significantly elevated in TiO₂ treated rats. The phagocytic activities, lysozyme, nitric oxide, and immunoglobulin levels were significantly depleted following TiO₂ exposure. A significantly reduced lymphocyte proliferation but elevated LDH activity was prominent in TiO₂ treated rats. Different pathological perturbations were observed in both splenic tissue and bone marrow. A marked increase in CD4⁺ and CD8⁺ immunolabeling was evident. A significant increase in the comet variables was recorded in response to the exposure of rats to the increasing level of TiO₂ at both levels.

CONCLUSION

Overall, these results indicated that TiO₂ could induce hematotoxicity, genotoxic, and immunotoxic alterations with exposure for long durations.

[Effect of subchronic combined oral exposure of titanium dioxide nanoparticles and glucose on levels of serum folate and vitamin B12 in young SD rats]

OBJECTIVE

To explore the effect of subchronic combined oral exposure of titanium dioxide nanoparticles and glucose on levels of serum folate and vitamin B₁₂ in young SD rats.

METHODS

At first, the physical and chemical properties of titanium dioxide nanoparticles, such as particle size, shape, crystal form and agglomeration degree in solution system, were characterized in detail. Eighty 4-week-old young SD rats were randomly divided into 8 groups (10 rats in each group, half male and half female). The rats were exposed to titanium dioxide nanoparticles through intragastric administration at 0, 2, 10 and 50 mg/kg body weight with or without 1.8 g/kg glucose daily for 90 days. At last, the concentrations of serum folate and vitamin B₁₂ were detected.

RESULTS

Titanium dioxide nanoparticles were anatase crystals, closely spherical shape, with an average particle size of (24±5) nm. In male young rats, compared with the control group, the serum folate concentration was significantly increased when exposed to titanium dioxide nanoparticles (10 mg/kg) and glucose. The difference was statistically significant (P<0.05). However, in female and male young rats, compared with glucose (1.8 g/kg) exposure group, titanium dioxide nanoparticles (50 mg/kg) and glucose significantly reduced the serum folate concentration. The difference was statistically significant (P<0.05). Through statistical analysis of factorial design and calculation of interaction, obvious antagonistic effect was observed between titanium dioxide nanoparticles and glucose on the serum folate concentration in the young female SD rats. The combined oral exposure of titanium dioxide nanoparticles and glucose had little effect on the concentration of serum vitamin B₁₂ in the young SD rats, with no significant interaction between the two substances. It was only found that titanium dioxide nanoparticles (2 mg/kg) and glucose significantly increased the serum vitamin B₁₂ concentration, compared with glucose (1.8 g/kg) exposure group. The difference was statistically significant (P<0.05).

CONCLUSION

Subchronic combined oral exposure of titanium dioxide nanoparticles and glucose had an obvious antagonistic effect on serum folate concentrations in young SD rats.

Determination of titanium dioxide nanoparticles used in various foods

Titanium dioxide (TiO₂) is commonly used in foods with code E171. There is information on the food packaging that it contains E171 in the ingredients section. However, there is no information on the amount of E171 used as ingredient. Therefore, determination of TiO₂ content of foods is extremely important for human health. In this study, confectionary foods, chewing gums, chocolates and white colored foods were investigated. TiO₂ levels of investigated foods were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The average titanium dioxide concentrations were found ranging from 3 to 2400 mg kg^-1. The size of TiO₂ particles in the foods samples was determined with transmission electron microscopy (TEM). Titanium dioxide nanoparticles in the studied foods were found to vary in size from 30 to 410 nm.

Characterisation of food grade titania with respect to nanoparticle content in pristine additives and in their related food products

Titanium dioxide is a white colourant authorised as food additive E171 in the EU and is applied in a range of food products. Currently the EU specifications for E171 do not refer to the characterisation of particle size distribution; however, this may be requested in the near future. Only a few studies have been published to date reporting data on the size distribution of food grade titanium dioxide. The aim of this study was to characterise the size distribution of titanium dioxide particles contained in eight confectionery products and the pristine titanium dioxide samples used in each of the products. This allowed the direct comparison of the particle size distribution in both the pristine and the extracted materials. By using various analytical techniques, such as transmission electron microscopy, single particle inductively coupled plasma mass spectrometry (sp-ICPMS) and centrifuge liquid sedimentation (CLS) for the characterisation and quantification of the titanium dioxide particle sizes, the impact of the instrumentation on the results was systematically studied. The volume-specific surface area (VSSA) and crystalline structure were also determined for all additives.

Preparation of TiO2 and Fe-TiO2 with an Impinging Stream-Rotating Packed Bed by the Precipitation Method for the Photodegradation of Gaseous Toluene

Nano-TiO₂ has always been one of the most important topics in the research of photocatalysts due to its special activity and stability. However, it has always been difficult to obtain nano-TiO₂ with high dispersion, a small particle size and high photocatalytic activity. In this paper, nano-TiO₂ powder was prepared by combining the high-gravity technique and direct precipitation method in an impinging stream-rotating packed bed (IS-RPB) reactor followed by Fe³⁺ in-situ doping. TiOSO₄ and NH₃·H₂O solutions were cut into very small liquid microelements by high-speed rotating packing, and the mass transfer and microscopic mixing of the nucleation and growth processes of nano-TiO₂ were strengthened in IS-RPB, which was beneficial to the continuous production of high quality nano-TiO₂. Pure TiO₂ and iron-doped nano-TiO₂ (Fe-TiO₂) were obtained in IS-RPB and were investigated by means of X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) and Brunauer-Emmett-Teller (BET) analysis, which found that pure TiO₂ had a particle size of about 12.5 nm, good dispersibility and a complete anatase crystal at the rotating speed of packing of 800 rpm and calcination temperature of 500 °C. The addition of Fe³⁺ did not change the crystalline structure of TiO₂. Iron was highly dispersed in TiO₂ without the detection of aggregates and was found to exist in a positive trivalent form by XPS. With the increase of iron doping, the photoresponse range of TiO₂ to visible light was broadened from 3.06 eV to 2.26 eV. The degradation efficiency of gaseous toluene by Fe-TiO₂ under ultraviolet light was higher than that of pure TiO₂ and commercial P25 due to Fe³⁺ effectively suppressing the recombination of TiO₂ electrons and holes; the highest efficiency produced by 1.0% Fe-TiO₂ was 95.7%.

A TiO2–SnS2 nanocomposite as a novel matrix for the development of an enzymatic electrochemical glucose biosensor

A TiO₂–SnS₂ nanocomposite was prepared and for the first time used to construct a novel electrochemical enzymatic glucose biosensor based on the direct electrochemistry of glucose oxidase (GOx).