Preparation of titanium dioxide nanoparticles from Solanum Tuberosum peel extract and its applications

The present study describes a method for the preparation of green titanium dioxide (TiO2) nanoparticles from the peel of Solanum tuberosum, commonly known as potato, and the potato peel being a kitchen waste. The green synthesized TiO2 (G- TiO2) nanoparticles were characterized using UV-visible spectroscopy, dynamic light scattering, scanning electron microscopy, TEM, XRD, and FTIR spectroscopy. The photocatalytic activity of the G- TiO2 nanoparticles was also shown using the dye bromophenol blue. To explore the biocompatibility of the G- TiO2, the cell viability in normal as well as cancer cells was assessed. Further, the in vivo toxicity of the G- TiO2 nanoparticles was assessed using zebrafish embryos. The novelty of the present invention is to utilize kitchen waste for a useful purpose for the synthesis of titanium dioxide nanoparticles which is known to have UV light scavenging properties. Moreover, the potato peel is a natural antioxidant and possesses a skin-lightening effect. A combination of the potato peel extract and titanium dioxide prepared using the extract will have a combinatorial effect for protecting UV light exposure to the skin and lightening the skin colour.

Food-grade titanium dioxide (E171) and zinc oxide nanoparticles induce mitochondrial permeability and cardiac damage after oral exposure in rats

Food-grade titanium dioxide (E171) and zinc oxide nanoparticles (ZnO NPs) are found in diverse products for human use. E171 is used as whitening agent in food and cosmetics, and ZnO NPs in food packaging. Their potential multi-organ toxicity has raised concerns on their safety. Since mitochondrial dysfunction is a key aspect of cardio-pathologies, here, we evaluate the effect of chronic exposure to E171 and ZnO NPs in rats on cardiac mitochondria. Changes in cardiac electrophysiology and body weight were measured. E171 reduced body weight more than 10% after 5 weeks. Both E171 and ZnO NPs increased systolic blood pressure (SBP) from 110-120 to 120-140 mmHg after 45 days of treatment. Both NPs altered the mitochondrial permeability transition pore (mPTP), reducing calcium requirement for permeability by 60% and 93% in E171- and ZnO NPs-exposed rats, respectively. Treatments also affected conformational state of adenine nucleotide translocase (ANT). E171 reduced the binding of EMA to Cys 159 in 30% and ZnO NPs in 57%. Mitochondrial aconitase activity was reduced by roughly 50% with both NPs, indicating oxidative stress. Transmission electron microscopy (TEM) revealed changes in mitochondrial morphology including sarcomere discontinuity, edema, and hypertrophy in rats exposed to both NPs. In conclusion, chronic oral exposure to NPs induces functional and morphological damage in cardiac mitochondria, with ZnO NPs being more toxic than E171, possibly due to their dissociation in free Zn2+ ion form. Therefore, chronic intake of these food additives could increase risk of cardiovascular disease.

Effect of chronic prenatal exposure to the food additive titanium dioxide E171 on respiratory activity in newborn mice

Nanoparticles (NPs) possess unique properties that make their use valuable in all industries. Titanium dioxide (TiO2) NPs are extensively used as a white pigment in food (labeled under the European number E171) and personal care products, which creates a significant potential for chronic consumer exposure. Concerns about the potential toxic effects of TiO2 NPs have arisen, particularly in vulnerable populations, including pregnant women and infants. Recently, human materno-fetal transfer of E171 was demonstrated, and simultaneously, we reported that chronic prenatal exposure to reference P25 TiO2 NPs was found to alter the developing respiratory neural networks. In this study, using whole body plethysmography from postnatal day (P) 0 to P7, we assessed the respiratory function of newborn mice born to mothers fed with E171 during pregnancy. We also evaluated the potential alterations to respiratory centers by using brainstem-spinal cord electrophysiological recordings from P0 to P6. Our study reveals that E171-prenatally exposed animals displayed an abnormally elevated breathing rate from P3 onwards. From P5 to P6, the respiratory-related burst frequency generated by the isolated brainstem-spinal cord preparations was significantly higher in E171-exposed animals than in non-exposed animals. These findings demonstrate prenatal toxicity of E171 to the developing respiratory function and may contribute to policy-making regarding the use of TiO2 NPs.

Titanium dioxide nanoparticles induce apoptosis through ROS-Ca2+ -p38/AKT/mTOR pathway in TM4 cells

Titanium dioxide nanoparticles (TiO2 NPs) can cause apoptosis in TM4 cells; however, the underlying mechanism has not been entirely elucidated. The purpose of this study was to investigate the effects of TiO2 NPs on ROS, Ca2+ level, p38/AKT/mTOR pathway, and apoptosis in TM4 cells and to evaluate the role of Ca2+ in p38/AKT/mTOR pathway and apoptosis. After exposure to different concentrations (0, 50, 100, 150, and 200 μg/mL) of TiO2 NPs for 24 h, cell viability, ROS, Ca2+ level, Ca2+ -ATPase activity, p38/AKT/mTOR pathway-related proteins, apoptosis rate, and apoptosis-related proteins (Bax, Bcl-2, Caspase 3, Caspase 9, and p53) were detected. The ROS scavenger NAC was used to determine the effect of ROS on Ca2+ level. The Ca2+ chelator BAPTA-AM was used to evaluate the role of Ca2+ in p38/AKT/mTOR pathway and apoptosis. TiO2 NPs significantly inhibited cell viability, increased ROS level, and elevated Ca2+ level while suppressing Ca2+ -ATPase activity. TiO2 NPs regulated the p38/AKT/mTOR pathway via increasing p-p38 level and decreasing p-AKT and p-mTOR levels. TiO2 NPs significantly enhanced the apoptosis. NAC attenuated Ca2+ overload and reduction in Ca2+ -ATPase activity caused by TiO2 NPs. BAPTA-AM alleviated TiO2 NPs-induced abnormal expression of p38/AKT/mTOR pathway-related proteins. BAPTA-AM assuaged the apoptosis caused by TiO2 NPs. Altogether, this study revealed that TiO2 NPs elevated intracellular Ca2+ level through ROS accumulation. Subsequently, the heightened intracellular Ca2+ level was observed to exert regulation over the p38/AKT/mTOR pathway, ultimately culminating in apoptosis. These results provides a complementary understanding to the mechanism of TiO2 NPs-induced apoptosis in TM4 cells.

Pure Epigallocatechin-3-gallate-Assisted Green Synthesis of Highly Stable Titanium Dioxide Nanoparticles

Nanoparticles (NPs) are conventionally produced by using physical and chemical methods that are no longer in alignment with current society's demand for a low environmental impact. Accordingly, green synthesis approaches are considered a potential alternative due to the plant extracts that substitute some of the hazardous reagents. The general mechanism is based on the reducing power of natural products that allows the formation of NPs from a precursor solution. In this context, our study proposes a simple, innovative, and reproducible green approach for the synthesis of titanium dioxide (TiO2 NPs) that uses, for the first time, the major component of green tea (Camellia sinensis)-epigallocatechin-3-gallate (EGCG), a non-toxic, dietary, accessible, and bioactive molecule. The influence of EGCG on the formation of TiO2 NPs was analyzed by comparing the physicochemical characteristics of green synthesized NPs with the chemically obtained ones. The synthesis of bare TiO2 NPs was performed by hydrolysis of titanium isopropoxide in distilled water, and green TiO2 NPs were obtained in the same conditions, but in the presence of a 1 mM EGCG aqueous solution. The formation of TiO2 NPs was confirmed by UV-VIS and FTIR spectroscopy. SEM micrographs showed spherical particles with relatively low diameters. Our findings also revealed that green synthesized NPs were more stable in colloids than the chemically synthesized ones. However, the phytocompound negatively influenced the formation of a crystalline structure in the green synthesized TiO2 NPs. Furthermore, the synthesis of EGCG-TiO2 NPs could become a versatile choice for applications extending beyond photocatalysis, including promising prospects in the biomedical field.

8-Bromo-cAMP attenuates human airway epithelial barrier disruption caused by titanium dioxide fine and nanoparticles

Titanium dioxide fine particles (TiO2-FPs) and nanoparticles (TiO2-NPs) are the most widely used whitening pigments worldwide. Inhalation of TiO2-FPs and TiO2-NPs can be harmful as it triggers toxicity in the airway epithelial cells. The airway epithelium serves as the respiratory system's first line of defense in which airway epithelial cells are significant targets of inhaled pathogens and environmental particles. Our group previously found that TiO2-NPs lead to a disrupted barrier in the polarized airway epithelial cells. However, the effect of TiO2-FPs on the respiratory epithelial barrier has not been examined closely. In this study, we aimed to compare the effects of TiO2-FPs and TiO2-NPs on the structure and function of the airway epithelial barrier. Additionally, we hypothesized that 8-Bromo-cAMP, a cyclic adenosine monophosphate (cAMP) derivative, would alleviate the disruptive effects of both TiO2-FPs and TiO2-NPs. We observed increased epithelial membrane permeability in both TiO2-FPs and TiO2-NPs after exposure to 16HBE cells. Immunofluorescent labeling showed that both particle sizes disrupted the structural integrity of airway epithelial tight junctions and adherens junctions. TiO2-FPs had a slightly more, but insignificant impact on the epithelial barrier disruption than TiO2-NPs. Treatment with 8-Bromo-cAMP significantly attenuated the barrier-disrupting impact of both TiO2-FPs and TiO2-NPs on cell monolayers. Our study demonstrates that both TiO2-FPs and TiO2-NPs cause comparable barrier disruption and suggests a protective role for cAMP signaling. The observed effects of TiO2-FPs and TiO2-NPs provide a necessary understanding for characterizing the pathways involved in the defensive role of the cAMP pathway on TiO2-induced airway barrier disruption.

Visible-Light-Responsive Photoreversible Multi-Color Switching for Rewritable Light-Printing and Information Display

Photoreversible color switching systems (PCSSs) exhibiting multi-color responses to visible light are favored for sustainable societal development over those relying on ultraviolet light due to safer operation and better penetration depth. Here, a PCSS capable of multi-color switching responsive to visible light based on highly photoreductive rutile-phase Sn-doped TiO2-x nanoparticles is reported. The Sn-doping significantly red-shifts the absorption band of the nanoparticles to the visible region, improving charge separation and transfer efficiencies and introducing Ti3+ species and oxygen vacancies as internal sacrificial electron donors for scavenging photogenerated holes. The resulting Sn-doped TiO2-x nanoparticles feature exceptional photoreduction ability and activity, thereby enabling photoreversible color switching of various redox dyes operational under visible light illumination. Furthermore, multi-color switching can be achieved via the color overlay effect by combining different redox dyes in one system, opening the door to many advanced applications, as demonstrated in their successful uses for developing visible-light-driven rewritable multi-color light-printing systems and visual information displays.

Titanium-Dioxide-Nanoparticle-Embedded Polyelectrolyte Multilayer as an Osteoconductive and Antimicrobial Surface Coating

Bioactive surface coatings have retained the attention of researchers and physicians due to their versatility and range of applications in orthopedics, particularly in infection prevention. Antibacterial metal nanoparticles (mNPs) are a promising therapeutic, with vast application opportunities on orthopedic implants. The current research aimed to construct a polyelectrolyte multilayer on a highly porous titanium implant using alternating thin film coatings of chitosan and alginate via the layer-by-layer (LbL) self-assembly technique, along with the incorporation of silver nanoparticles (AgNPs) or titanium dioxide nanoparticles (TiO2NPs), for antibacterial and osteoconductive activity. These mNPs were characterized for their physicochemical properties using quartz crystal microgravimetry with a dissipation system, nanoparticle tracking analysis, scanning electron microscopy, and atomic force microscopy. Their cytotoxicity and osteogenic differentiation capabilities were assessed using AlamarBlue and alkaline phosphatase (ALP) activity assays, respectively. The antibiofilm efficacy of the mNPs was tested against Staphylococcus aureus. The LbL polyelectrolyte coating was successfully applied to the porous titanium substrate. A dose-dependent relationship between nanoparticle concentration and ALP as well as antibacterial effects was observed. TiO2NP samples were also less cytotoxic than their AgNP counterparts, although similarly antimicrobial. Together, these data serve as a proof-of-concept for a novel coating approach for orthopedic implants with antimicrobial and osteoconductive properties.

Evaluation of neurotoxicity and the role of oxidative stress of cobalt nanoparticles, titanium dioxide nanoparticles, and multiwall carbon nanotubes in Caenorhabditis elegans

The widespread use of nanomaterials in daily life has led to increased concern about their potential neurotoxicity. Therefore, it is particularly important to establish a simple and reproducible assessment system. Representative nanomaterials, including cobalt nanoparticles (CoNPs), titanium dioxide nanoparticles (TiO2-NPs), and multiwall carbon nanotubes (MWCNTs), were compared in terms of their neurotoxicity and underlying mechanisms. In 0, 25, 50, and 75 μg/ml of these nanomaterials, the survival, locomotion behaviors, acetylcholinesterase (AchE) activity, reactive oxygen species production, and glutathione-S transferase 4 (Gst-4) activation in wildtype and transgenic Caenorhabditis elegans (C. elegans) were evaluated. All nanomaterials induced an imbalance in oxidative stress, decreased the ratio of survival, impaired locomotion behaviors, as well as reduced the activity of AchE in C. elegans. Interestingly, CoNPs and MWCNTs activated Gst-4, but not TiO2-NPs. The reactive oxygen species scavenger, N-acetyl-l-cysteine, alleviated oxidative stress and Gst-4 upregulation upon exposure to CoNPs and MWCNTs, and rescued the locomotion behaviors. MWCNTs caused the most severe damage, followed by CoNPs and TiO2-NPs. Furthermore, oxidative stress and subsequent activation of Gst-4 were involved in nanomaterials-induced neurotoxicity. Our study provides a comprehensive comparison of the neurotoxicity and mechanisms of typical nanomaterials, which could serve as a model for hazard assessment of environmental pollutants using C. elegans as an experimental model system.

TiO2 nanoparticles combined with polystyrene nanoplastics aggravated reproductive toxicity in female mice via exacerbating intestinal barrier disruption

BACKGROUND

TiO2 nanoparticles (NPs), a widely used food additive in the food industry, have been shown to aggravate the progress of metabolic diseases. Nanoplastics (NPLs) are an emerging contaminant widely present in the food system and have been shown to induce ovarian disorders in mammals. Noteworthy, they can be ingested by humans through 'contaminated' food, whereas the potential toxicity of NPLs and TiO2 NPs combined remains unclear. In the present study, we investigated the potential effects and mechanisms of co-exposure to polystyrene (PS) NPLs and TiO2 NPs on the ovary in female mice.

RESULTS

Our results revealed that the co-exposure of TiO2 NPs and PS NPLs caused significant injury to ovarian structure and function, but individual exposure had no effect. Moreover, compared to the TiO2 NPs group, co-exposure aggravated the intestinal barrier damage in mice, increasing the bioaccumulation of TiO2 NPs in the ovary. After being supplemented with the oxidative stress inhibitor N-acetyl-l-cysteine, the expression of ovarian antioxidant genes increased, and the ovarian structural and functional injury in co-exposure mice reverted to normal levels.

CONCLUSION

The present study demonstrated that co-exposure to PS NPLs and TiO2 NPs can cause more severe female reproductive dysfunction and deepens the toxicological insights between NPLs and NPs. © 2023 Society of Chemical Industry.

Spin-Label Electron Paramagnetic Resonance Spectroscopy Reveals Effects of Wastewater Filter Membrane Coated with Titanium Dioxide Nanoparticles on Bovine Serum Albumin

The accumulation of proteins in filter membranes limits the efficiency of filtering technologies for cleaning wastewater. Efforts are ongoing to coat commercial filters with different materials (such as titanium dioxide, TiO2) to reduce the fouling of the membrane. Beyond monitoring the desired effect of the retention of biomolecules, it is necessary to understand what the biophysical changes are in water-soluble proteins caused by their interaction with the new coated filter membranes, an aspect that has received little attention so far. Using spin-label electron paramagnetic resonance (EPR), aided with native fluorescence spectroscopy and dynamic light scattering (DLS), here, we report the changes in the structure and dynamics of bovine serum albumin (BSA) exposed to TiO2 (P25) nanoparticles or passing through commercial polyvinylidene fluoride (PVDF) membranes coated with the same nanoparticles. We have found that the filtering process and prolonged exposure to TiO2 nanoparticles had significant effects on different regions of BSA, and denaturation of the protein was not observed, neither with the TiO2 nanoparticles nor when passing through the TiO2-coated filter membranes.

Ternary nanocomposite potentiates the lysophosphatidic acid effect on human osteoblast (MG63) maturation

Aim: This study aimed to investigate the potential of ternary nanocomposite (TNC) to support MG63 osteoblast maturation to EB1089-(3S)1-fluoro-3-hydroxy-4-(oleoyloxy)butyl-1-phosphonate (FHBP) cotreatment. Materials & methods: Binary (P25/reduced graphene oxide [rGO]) nanocomposite was prepared, and silver (Ag) nanoparticles were loaded onto the surface to form TNC (P25/rGO/Ag). The influence of TNC on proliferation, alkaline phosphatase activity and osteogenic gene expression was evaluated in a model of osteoblast maturation wherein MG63 were costimulated with EB1089 and FHBP. Results: TNC had no cytotoxic effect on MG63. The addition of TNC to EB1089-FHBP cotreatment enhanced the maturation of MG63, as supported by the greater alkaline phosphatase activity and OPN and OCN gene expression. Conclusion: TNC could serve as a promising carrier for FHBP, opening up possibilities for its application in bone regeneration.

Covered Rutile-TiO2 Nanoparticles Enhance Tomato Yield and Growth by Modulating Gas Exchange and Nutrient Status

Nanotechnology has developed materials that can increase food production while reducing the use of conventional fertilizers. In this study, the effect of two forms of application (foliar and drench) as well as covering or non-covering of the surface of titanium dioxide nanoparticles (nTiO2) with maltodextrin (MDX) at 1500 ppm was investigated on tomato plants. The results show that treatment of tomato with nTiO2 increased yield (+21%), while covering the surface of the NPs resulted in a further yield increase (+27%). Similar trends were observed in the dry weight of vegetative plant parts. Fruit firmness (+33%) and total soluble solids (+36%) were enhanced by MDX-covered nTiO2. Application of nTiO2 resulted in enhanced SPAD index, photosynthesis rate, NO3-, K, and Ca concentration in the petiole sap, whereas in the fruits there was an increase in P and K in MDX-covered nTiO2. Considering the dilution effect due to the higher fruit yield, N, P, Mg, Cu, and B increased in plants treated with nTiO2. Covering the surface with MDX resulted in an enhanced response to nTiO2, as fruit yield and quality increased compared to plants treated with non-covered nTiO2.

Genotoxicity assessment of titanium dioxide nanoparticles using a standard battery of in vivo assays

As one representative of nanometal oxides, titanium dioxide nanoparticles (TiO2-NPs) have been widely used, particularly in the food industry. The genotoxicity of TiO2-NPs has attracted great attention over the years. This study was undertaken to investigate the chromosome and DNA damage effects of TiO2-NPs (0, 50, 150, and 500 mg/kg BW) using rodent models. After a comprehensive characterization, we conducted a standard battery of in vivo genotoxicity tests, including the chromosomal aberration test (CA), micronucleus (MN) test, and the comet test. The results of all these tests were negative. There were no structural or numerical chromosomal abnormalities in mice bone marrow cells, no increase in the frequency of micronucleated polychromatic erythrocytes in mice bone marrow cells, and no elevation in % tail DNA in rat hepatocytes. This indicated that TiO2-NPs did not cause chromosomal damage or have a direct impact on DNA. These findings suggested that TiO2-NPs did not exhibit genotoxicity and provided valuable data for risk assessment purposes.

An Eco-Friendly Approach Utilizing Green Synthesized Titanium Dioxide Nanoparticles for Leather Conservation against a Fungal Strain, Penicillium expansum AL1, Involved in the Biodeterioration of a Historical Manuscript

The main hypothesis of the present research is investigating the efficacy of titanium oxide nanoparticles (TiO₂-NPs) to prevent the growth of fungal strains when applied on leather under an experimental study. Therefore, fifteen fungal strains were isolated from a deteriorated historical manuscript (papers and leathers) and identified by traditional methods and ITS sequence analysis, including Aspergillus chevalieri (one isolate), A. nidulans (two strains), A. flavus (four strains), A. cristatus (one strain), A. niger (one strain), Paecilomyces fulvus (two strains), Penicillium expansum (two strains), and P. citrinum (two strains). The enzymes cellulase, amylase, pectinase, and gelatinase, which play a crucial role in biodegradation, were highly active in these fungal strains. TiO₂-NPs were formed using the cell-free filtrate of the probiotic bacterial strain, Lactobacillus plantarum, and characterized. Data showed that the TiO₂-NPs were successfully formed with a spherical shape and anatase phase with sizes of 2-8 nm. Moreover, the EDX analysis revealed that the Ti and O ions occupied the main component with weight percentages of 41.66 and 31.76%, respectively. The in vitro cytotoxicity of TiO₂-NPs toward two normal cell lines, WI38 and HFB4, showed a low toxicity effect against normal cells (IC₅₀ = 114.1 ± 8.1µg mL^-1 for Wi38, and 237.5 ± 3.5µg mL^-1 for HFB4). Therefore, concentrations of 100 μg mL^-1 were used to load on prepared leather samples before inoculation with fungal strain P. expansum AL1. The experimental study revealed that the loaded TiO₂-NPs have the efficacy to inhibit fungal growth with percentages of 73.2 ± 2.5%, 84.2 ± 1.8%, and 88.8 ± 0.6% after 7, 14, and 21 days, respectively. Also, the analyses including SEM, FTIR-ART, color change, and mechanical properties for leather inoculated with fungal strain AL1 in the absence of NPs showed high damage aspects compared to those inoculated with fungal strains in the presence of TiO₂-NPs.

Wide-Field and Real-Time Super-Resolution Optical Imaging By Titanium Dioxide Nanoparticle-Assembled Solid Immersion Lens

Super-resolution optical imaging techniques can break the optical diffraction limit, thus providing unique opportunities to visualize the microscopic world at the nanoscale. Although near-field optical microscopy techniques have been proven to achieve significantly improved imaging resolution, most near-field approaches still suffer from a narrow field of view (FOV) or difficulty in obtaining wide-field images in real time, which may limit their widespread and diverse applications. Here, the authors experimentally demonstrate an optical microscope magnification and image enhancement approach by using a submillimeter-sized solid immersion lens (SIL) assembled by densely-packed 15 nm TiO₂ nanoparticles through a silicone oil two-step dehydration method. This TiO₂ nanoparticle-assembled SIL can achieve both high transparency and high refractive index, as well as sufficient mechanical strength and easy-to-handle size, thus providing a fast, wide-field, real-time, non-destructive, and low-cost solution for improving the quality of optical microscopic observation of a variety of samples, including nanomaterials, cancer cells, and living cells or bacteria under conventional optical microscopes. This study provides an attractive alternative to simplify the fabrication and applications of high-performance SILs.

Effect of addition of titanium dioxide nanoparticles on the antimicrobial properties, surface roughness and surface hardness of polymethyl methacrylate: A Systematic Review

Background: Polymethyl Methacrylate (PMMA) denture-base resins have poor surface properties that facilitates microbial adhesion causing denture stomatitis. This systematic review aims to evaluate the effect of different sizes and percentages of titanium dioxide nanoparticles (TiO2NP) on the antimicrobial property, surface roughness and surface hardness of PMMA denture base resin.  Methods: A systematic search of English peer-reviewed articles, clinical trial registries, grey literature databases and other online sources was performed using the PRISMA-S Guidelines for In-Vivo and In-Vitro studies. Qualitative data synthesis was performed to analyse sample dimensions, acrylic used, treatments of nanoparticles, methods used for testing and effect of size and percentage of nanoparticle. Risk of bias assessment was done using modified Cochrane risk of bias tool. Results: Out of 1376 articles, 15 were included. TiO 2NP of size less than 30 nm was most frequently used. Both antimicrobial property and surface hardness improved irrespective of the size of the added TiO 2NP. Three studies reported increase in the surface roughness with less than 50 nm TiO 2NP.  3% TiO 2NP was most frequently used. On increasing the percentage, three studies reported an increase in antimicrobial property, while two studies found no change. With TiO 2NP greater than or equal to 3%, six studies reported an increase in surface hardness, while two reported increase in surface roughness. Large methodological variations were observed across studies. All studies except one were of moderate quality. Conclusions:   On addition of TiO 2NP to heat polymerized PMMA, the antimicrobial property and surface hardness improved irrespective of the size of the TiO 2NP, however, addition of nanoparticles less than 50 nm increased the surface roughness. Increasing the percentage of TiO 2NP increased the surface hardness but did not always increase the antimicrobial property. Addition of 3% TiO 2NP provided optimum results with regards to antimicrobial effect and surface hardness, but increase in the surface roughness.

An In Vitro Small Intestine Model Incorporating a Food Matrix and Bacterial Mock Community for Intestinal Function Testing

Consumed food travels through the gastrointestinal tract to reach the small intestine, where it interacts with the microbiota, forming a complex relationship with the dietary components. Here we present a complex in vitro cell culture model of the small intestine that includes human cells, digestion, a simulated meal, and a microbiota represented by a bacterial community consisting of E. coli, L. rhamnosus, S. salivarius, B. bifidum, and E. faecalis. This model was used to determine the effects of food-grade titanium dioxide nanoparticles (TiO₂ NPs), a common food additive, on epithelial permeability, intestinal alkaline phosphatase activity, and nutrient transport across the epithelium. Physiologically relevant concentrations of TiO₂ had no effect on intestinal permeability but caused an increase in triglyceride transport as part of the food model, which was reversed in the presence of bacteria. Individual bacterial species had no effect on glucose transport, but the bacterial community increased glucose transport, suggesting a change in bacterial behavior when in a community. Bacterial entrapment within the mucus layer was reduced with TiO₂ exposure, which may be due to decreased mucus layer thickness. The combination of human cells, a synthetic meal, and a bacterial mock community provides an opportunity to understand the implications of nutritional changes on small intestinal function, including the microbiota.

A Flexible Lithium-Ion-Conducting Membrane with Highly Loaded Titanium Oxide Nanoparticles to Promote Charge Transfer for Lithium-Air Battery

In this research, we aim to investigate a flexible composite lithium-ion-conducting membrane (FC-LICM) consisting of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and titanium dioxide (TiO2) nanoparticles with a TiO2-rich configuration. PVDF-HFP was selected as the host polymer owing to its chemically compatible nature with lithium metal. TiO2 (40-60 wt%) was incorporated into the polymer matrix, and the FC-LICM charge transfer resistance values (Rct) were reduced by two-thirds (from 1609 Ω to 420 Ω) at the 50 wt% TiO2 loading compared with the pristine PVDF-HFP. This improvement may be attributed to the electron transport properties enabled by the incorporation of semiconductive TiO2. After being immersed in an electrolyte, the FC-LICM also exhibited a Rct that was lower by 45% (from 141 to 76 Ω), suggesting enhanced ionic transfer upon the addition of TiO2. The TiO2 nanoparticles in the FC-LICM facilitated charge transfers for both electron transfer and ionic transport. The FC-LICM incorporated at an optimal load of 50 wt% TiO2 was assembled into a hybrid electrolyte Li-air battery (HELAB). This battery was operated for 70 h with a cut-off capacity of 500 mAh g-1 in a passive air-breathing mode under an atmosphere with high humidity. A 33% reduction in the overpotential of the HELAB was observed in comparison with using the bare polymer. The present work provides a simple FC-LICM approach for use in HELABs.

TiO2 Nanoparticles in Cancer Therapy as Nanocarriers in Paclitaxel's Delivery and Nanosensitizers in Phototherapies and/or Sonodynamic Therapy

Nanomaterials have been offering improvements in different areas due to their unique characteristics, but cytotoxicity associated with their use is still a topic that concerns researchers. Causing cell death, at first glance, may seem to be a problem and the studies regarding signaling pathways involved in this toxicity are still in their infancy. However, there are scenarios in which this feature is desirable, such as in cancer treatment. Anti-cancer therapies aim to eliminate the cells of malignant tumors as selectively as possible. From this perspective, titanium dioxide (TiO2) nanoparticles (NPs) deserve to be highlighted as important and efficient tools. Besides being able to induce cell death, these NPs can also be used to deliver anti-cancer therapeutics. These drugs can originate from natural sources, such as paclitaxel (an antitumoral molecule derived from a vegetal source). The present review aims to explore the recent knowledge of TiO2 NPs as nanocarriers (promoting the nanodelivery of paclitaxel) and as nanosensitizers to be used in phototherapies and/or sonodynamic therapy aiming to treat cancer. Signaling pathways triggered by this nanomaterial inside cells leading to apoptosis (a desirable fate when targeting tumor cells) and challenges related to the clinical translation of these NPs will also receive attention in the future.

A Comparative Study of the Biodurability and Persistence of Gold, Silver and Titanium Dioxide Nanoparticles Using the Continuous Flow through System

The potential for nanoparticles to cause harm to human health and the environment is correlated with their biodurability in the human body and persistence in the environment. Dissolution testing serves to predict biodurability and nanoparticle environmental persistence. In this study, dissolution testing using the continuous flow through system was used to investigate the biodurability and persistence of gold nanoparticles (AuNPs), silver nanoparticles (AgNPs) and titanium dioxide nanoparticles (TiO₂ NPs) in five different simulated biological fluids and two synthetic environmental media to predict their behaviour in real life situations. This study examined the physicochemical properties and agglomeration state of gold, silver and titanium dioxide nanoparticles before and after dissolution tests using three different techniques (UV-vis, XRD and TEM). The UV-vis spectra revealed that all three nanoparticles shifted to higher wavelengths after being exposed to simulated fluids. The titanium powder was found to be mixed with both rutile and anatase, according to XRD examination. The average diameter of gold nanoparticles was 14 nm, silver nanoparticles were 10 nm and titanium dioxide nanoparticles were 25 nm, according to TEM images. The gold and silver nanoparticles were observed to be spherical, but the titanium dioxide nanoparticles were irregular in shape, with some being spherical. The level of dissolved nanoparticles in simulated acidic media was higher in magnitude compared to that dissolved in simulated alkaline media. The results obtained via the continuous flow through dissolution system also displayed very significant dissolution rates. For TiO₂ NPs the calculated half-times were in the range of 13-14 days, followed by AuNPs ranging between 4-12 days, significantly longer if compared to the half-times of AgNPs ranging between 2-7 days. AuNPs and TiO₂ NPs were characterized by low dissolution rates therefore are expected to be (bio)durable in physiological surroundings and persistent in the environment thus, they might impose long-term effects on humans and the environment. In contrast, AgNPs have high dissolution rates and not (bio)durable and hence may cause short-term effects. The results suggest a hierarchy of biodurability and persistence of TiO₂ NPs > AuNPs > AgNPs. It is recommended that nanoparticle product developers should follow the test guidelines stipulated by the OECD to ensure product safety for use before it is taken to the market.

Toxic effects of titanium dioxide nanoparticles on reproduction in mammals

Titanium dioxide nanoparticles (nano-TiO₂) are widely used in food, textiles, coatings and personal care products; however, they cause environmental and health concerns. Nano-TiO₂ can accumulate in the reproductive organs of mammals in different ways, affect the development of the ovum and sperm, damage reproductive organs and harm the growth and development of offspring. The oxidative stress response in germ cells, irregular cell apoptosis, inflammation, genotoxicity and hormone synthesis disorder are the main mechanisms of nano-TiO₂ toxicity. Possible measures to reduce the harmful effects of nano-TiO₂ on humans and nontarget organisms have emerged as an underexplored topic requiring further investigation.

Effect of Nanomaterials on Gut Microbiota

Nanomaterials are widely employed in everyday life, including food and engineering. Food additives on a nanoscale can enter the body via the digestive tract. The human gut microbiota is a dynamically balanced ecosystem composed of a multitude of microorganisms that play a crucial role in maintaining the proper physiological function of the digestive tract and the body's endocrine coordination. While the antibacterial capabilities of nanomaterials have received much interest in recent years, their impacts on gut microbiota ought to be cautioned about and explored. Nanomaterials exhibit good antibacterial capabilities in vitro. Animal studies have revealed that oral exposure to nanomaterials inhibits probiotic reproduction, stimulates the inflammatory response of the gut immune system, increases opportunistic infections, and changes the composition and structure of the gut microbiota. This article provides an overview of the impacts of nanomaterials, particularly titanium dioxide nanoparticles (TiO₂ NPs), on the gut microbiota. It advances nanomaterial safety research and offers a scientific foundation for the prevention, control, and treatment of illnesses associated with gut microbiota abnormalities.

Innovative Antibacterial, Photocatalytic, Titanium Dioxide Microstructured Surfaces Based on Bacterial Adhesion Enhancement

Bacterial colonization and biofilm formation are found on nearly all wet surfaces, representing a serious problem for both human healthcare and industrial applications, where traditional treatments may not be effective. Herein, we describe a synergistic approach for improving the performance of antibacterial surfaces based on microstructured surfaces that embed titanium dioxide nanoparticles (TiO₂ NPs). The surfaces were designed to enhance bacteria entrapment, facilitating their subsequent eradication by a combination of UVC disinfection and TiO₂ NPs photocatalysis. The efficacy of the engineered TiO₂-modified microtopographic surfaces was evaluated using three different designs, and it was found that S2-lozenge and S3-square patterns had a higher concentration of trapped bacteria, with increases of 70 and 76%, respectively, compared to flat surfaces. Importantly, these surfaces showed a significant reduction (99%) of viable bacteria after just 30 min of irradiation with UVC 254 nm light at low intensity, being sixfold more effective than flat surfaces. Overall, our results showed that the synergistic effect of combining microstructured capturing surfaces with the chemical functionality of TiO₂ NPs paves the way for developing innovative and efficient antibacterial surfaces with numerous potential applications in the healthcare and biotechnology market.

Titanium Dioxide Nanoparticles Modulate Systemic Immune Response and Increase Levels of Reduced Glutathione in Mice after Seven-Week Inhalation

Titanium dioxide nanoparticles (TiO₂ NPs) are used in a wide range of applications. Although inhalation of NPs is one of the most important toxicologically relevant routes, experimental studies on potential harmful effects of TiO₂ NPs using a whole-body inhalation chamber model are rare. In this study, the profile of lymphocyte markers, functional immunoassays, and antioxidant defense markers were analyzed to evaluate the potential adverse effects of seven-week inhalation exposure to two different concentrations of TiO₂ NPs (0.00167 and 0.1308 mg TiO₂/m³) in mice. A dose-dependent effect of TiO₂ NPs on innate immunity was evident in the form of stimulated phagocytic activity of monocytes in low-dose mice and suppressed secretory function of monocytes (IL-18) in high-dose animals. The effect of TiO₂ NPs on adaptive immunity, manifested in the spleen by a decrease in the percentage of T-cells, a reduction in T-helper cells, and a dose-dependent decrease in lymphocyte cytokine production, may indicate immunosuppression in exposed mice. The dose-dependent increase in GSH concentration and GSH/GSSG ratio in whole blood demonstrated stimulated antioxidant defense against oxidative stress induced by TiO₂ NP exposure.

Polymer Membrane Modified with Photocatalytic and Plasmonic Nanoparticles for Self-Cleaning Filters

In this study, we developed a filtering material for facial masks, which is capable of trapping and subsequent inactivation of bacteria under white light emitting diodes (LED) or sunlight irradiation. Such a functionality is achieved via the modification of the composite membrane based on porous polymer with photocatalytic (TiO₂) and plasmonic (Ag) nanoparticles. The porous polymer is produced by means of a computer numerical control machine, which rolls a photoresist/thermoplastic mixture into a ~20-µm-thick membrane followed by its thermal/ultraviolet (UV) hardening and porosification. TiO₂ nanoparticles are prepared by hydrothermal and sol-gel techniques. Colloidal synthesis is utilized to fabricate Ag nanoparticles. The TiO₂ photocatalytic activity under UV excitation as well as a photothermal effect generated by plasmonic Ag nanoparticles subjected to LED irradiation are studied by the assessment of methylene blue (MB) decomposition. We demonstrate that, in contrast to the filter of the standard facial medical mask, the polymer membrane modified with spray-coated TiO₂ and Ag nanoparticles prevents the penetration of bacillus subtilis from its top to bottom side and significantly inhibits bacterial growth when exposed to LED or sunlight.

Protective effects of lycopene on TiO2 nanoparticle-induced damage in the liver of mice

Titanium dioxide nanoparticles (nano-TiO₂ ) is one of the most widely used and produced nanomaterials. Studies have demonstrated that nano-TiO₂ could induce hepatotoxicity through oxidative stress, and lycopene has strong antioxidant capacity. The present study aimed to explore if lycopene protects the liver of mice from nano-TiO₂ damage. Ninety-six ICR mice were randomly divided into eight groups. They were control group, nano-TiO₂ -treated group (50 mg/kg BW), lycopene-treated groups (5, 20, and 40 mg/kg BW), and 50 mg/kg BW nano-TiO₂ - and lycopene-co-treated groups (nano-TiO₂  + 5 mg/kg BW of lycopene, nano-TiO₂  + 20 mg/kg BW of lycopene, nano-TiO₂  + 40 mg/kg BW of lycopene). After treated by gavage for 30 days, the histopathology of the liver was observed. Liver function was evaluated using changes in serum biochemical indicators of the liver (AST, ALT, ALP); and the level of ROS was indirectly reflected by the level of SOD, GSH-Px, MDA, GSH, and T-AOC. TUNEL assay was performed to examine the apoptosis of hepatocytes. Proteins of p53, cleaved-caspase 9, cleaved-caspase 3, Bcl-2, and Bax as well as p38 were detected. Results showed that lycopene alleviated the liver pathological damage and reduced the injury to liver function induced by nano-TiO₂ , as well as decreased nano-TiO₂ -induced ROS. Meanwhile, lycopene mitigated apoptosis resulting from nano-TiO₂ , accompanied by the reversed expression of apoptosis-related proteins. Furthermore, lycopene significantly reversed the upregulation of p-p38 induced by nano-TiO₂ . In conclusion, this study demonstrated that nano-TiO₂ resulted in hepatocyte apoptosis through ROS/ROS-p38 MAPK pathway and led to liver function injury. Lycopene protected mice liver against the hepatotoxicity of nano-TiO₂ through antioxidant property.

Novelty Cosmetic Filters Based on Nanomaterials Composed of Titanium Dioxide Nanoparticles

The following work describes the synthesis of new physical filters based on TiO₂/SiO₂ and TiO₂/Ag nanostructures. Titanium dioxide nanoparticles (TiO₂ NPs) were applied as control material and a popular physical UV filter. The advantage of using materials on the nanometer scale is the elimination of the skin whitening effect that occurs when using photoprotective cosmetics containing titanium dioxide on a macro scale. In addition, the silica coating makes the material less harmful, and the silver coating enriches the material with antibacterial properties. Nanoparticles and nanostructures have been characterized by Energy Dispersive X-Ray Analysis (EDX), the Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), and Fourier-Transform Infrared Spectroscopy (FT-IR) methods. Due to the use of physical filters in anti-radiation protection cosmetics, water-in-oil (W/O) emulsion has been prepared. All cosmetic formulations have been tested for stability. The sun protection research with the Sun Protection Diagnostic SP37 was carried out. These studies made it possible to determine the natural sun protection time and to compare the synthesized materials. Furthermore, one of the most important parameters when describing this type of cosmetic is water resistance, which has also been measured. The results show that the new type of material of TiO₂/Ag used as a new physical filter in emulsion W/O shows the best sun protection compared with other obtained nanomaterials. It is most likely due to the improved optical properties of the combination of noble metals, for example, silver with TiO₂.

Titanium Dioxide Nanoparticles Altered the lncRNA Expression Profile in Human Lung Cells

Respiration is considered to be the main occupational or environmental exposure pathway of titanium dioxide nanoparticles (TiO2 NPs), and the lung is considered to be the target organ of respiratory exposure; however, the mechanism of respiratory toxicity is not fully understood. In this study, the effect of TiO2 NPs on the expression profile of long non-coding RNA (lncRNA) in bronchial epithelial cells (BEAS-2B) was investigated to understand their potential toxic mechanism. BEAS-2B cells were treated with 100 μg/mL TiO2 NPs for 48 h, then RNA sequencing was performed to screen the differential lncRNAs compared with the control group, and the enrichment pathways of the differentially expressed lncRNAs were further analyzed using the Kyoto Encyclopedia of Genes and Genomes (KEGG). The results identified a total of 45,769 lncRNAs, and 277 different lncRNAs were screened. KEGG pathway analysis showed that the targeted mRNAs of these different lncRNAs were enriched in the pyrimidine metabolism pathway. This work demonstrates that TiO2 NPs could alter the lncRNA expression profile in BEAS-2B cells, and epigenetics may play a role in the mechanism of respiratory toxicity induced by TiO2 NPs.

Impairment of ovarian follicular development caused by titanium dioxide nanoparticles exposure involved in the TGF-β/BMP/Smad pathway

Titanium dioxide nanoparticles (TiO₂ NPs) have been shown to induce reproductive system damages in animals. To better underline how TiO₂ NPs act in reproductive system, female mice were exposed to 2.5, 5, or 10 mg/kg TiO₂ NPs by gavage administration for 60 days, the ovary injuries, follicle stimulating hormone (FSH) and luteinizing hormone (LH) levels as well as ovarian follicular development-related molecule expression were investigated. The results showed that TiO₂ NPs exposure resulted in reduction of ovary weight and inhibition of ovarian follicular development. Furthermore, the suppression of follicular development was demonstrated to be closely related to higher FSH and LH levels, and higher expression of activin, follistatin, BMP2, BMP4, TGF-β1, Smad2, Smad3, and Smad4 as well as decreased inhibin-α expression in mouse ovary in a dose-dependent manner. It implies that the impairment of ovarian follicular development caused by TiO₂ NPs exposure may be mediated by TGF-β signal pathway.

Oxidative damage induced by combined exposure of titanium dioxide nanoparticles and cypermethrin in rats for 90 days

Titanium dioxide nanoparticles (TiO₂NPs) and cypermethrin (CPM) are widely used in various fields, and they can enter the environment in different ways. Combined exposure of TiO₂NPs and CPM may increase the accumulation of pollutants in organisms and affect human health. This study was undertaken to evaluate the oxidative and inflammatory parameters associated with the combined exposure of TiO₂NPs and CPM in rats. Twenty-four healthy male adult SD rats were randomly divided into four groups. The first group served as the control, while groups 2, 3, and 4 were treated with TiO₂NPs (450 mg/m³); CPM (6.67 mg/m³) or combined exposure of TiO₂NPs and CPM by inhalation for 90 days. We investigated the oxidative damage induced through combined exposure of TiO₂NPs and CPM in rats by evaluating hematology of the rats and determining the blood biochemical index. Our results demonstrated that inhalation of TiO₂NPs and CPM increased the levels of oxidative stress markers such as malondialdehyde and alkaline phosphatase in the serum of rats. These were accompanied by a decreased glutathione peroxidase and total superoxide dismutase levels. Furthermore, the level of glutathione peroxidase was further decreased while malondialdehyde was increased in the combined exposure of TiO₂NPs and CPM. Interestingly, pathological sections showed that different degrees of tissue injury could be seen in the liver and lung tissues of each exposure group. In summary, the combined exposure of TiO₂NPs and CPM can cause increased oxidative damage in rats and damage the tissue structure of the liver and lung.

The effect and underlying mechanisms of titanium dioxide nanoparticles on glucose homeostasis: A literature review

Titanium dioxide (TiO₂ ) is used extensively as a white pigment in the food industry, personal care, and a variety of products of everyday use. Although TiO₂ has been categorized as a bioinert material, recent evidence has demonstrated different toxicity profiles of TiO₂ nanoparticles (NPs) and a potential health risk to humans. Studies indicated that titanium dioxide enters the systemic circulation and accumulates in the lungs, liver, kidneys, spleen, heart, and central nervous system and may cause oxidative stress and tissue damage in these vital organs. Recently, some studies have raised concerns about the possible detrimental effects of TiO₂ NPs on glucose homeostasis. However, the findings should be interpreted with caution due to the methodological issues. This article aims to evaluate current evidence regarding the effects of TiO₂ NPs on glucose homeostasis, including possible underlying mechanisms. Furthermore, the limitations of current studies are discussed, which may provide a comprehensive understanding and new perspectives for future studies in this field.

Spectroscopic Investigations of Porphyrin-TiO(2) Nanoparticles Complexes

This study presents the spectral characterization of TiO₂ nanoparticles (NPs) functionalized with three porphyrin derivatives: 5,10,15,20-(Tetra-4-aminophenyl) porphyrin (TAPP), 5,10,15,20-(Tetra-4-methoxyphenyl) porphyrin (TMPP), and 5,10,15,20-(Tetra-4-carboxyphenyl) porphyrin (TCPP). UV-Vis absorption and Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) spectroscopic studies of these porphyrins and their complexes with TiO₂ NPs were performed. In addition, the efficiency of singlet oxygen generation, the key species in photodynamic therapy, was investigated. UV-Vis absorption spectra of the NPs complexes showed the characteristic bands of porphyrins. These allowed us to determine the loaded porphyrins on TiO₂ NPs functionalized with porphyrins. FTIR-ATR revealed the formation of porphyrin-TiO₂ complexes, suggesting that porphyrin adsorption on TiO₂ may involve the pyrroles in the porphyrin ring, or the radicals of the porphyrin derivative. The quantum yield for singlet oxygen generation by the studied porphyrin complexes with TiO₂ was higher compared to bare porphyrins for TAPP and TMPP, while for the TCPP-TiO₂ NPs complex, a decrease was observed, but still maintained a good efficiency. The TiO₂ NPs conjugates can be promising candidates to be tested in photodynamic therapy in vitro assays.

Synthesis, Characterization, and Optimization Studies of Polycaprolactone/Polylactic Acid/Titanium Dioxide Nanoparticle/Orange Essential Oil Membranes for Biomedical Applications

The development of scaffolds for cell regeneration has increased because they must have adequate biocompatibility and mechanical properties to be applied in tissue engineering. In this sense, incorporating nanofillers or essential oils has allowed new architectures to promote cell proliferation and regeneration of new tissue. With this goal, we prepared four membranes based on polylactic acid (PLA), polycaprolactone (PCL), titanium dioxide nanoparticles (TiO₂-NPs), and orange essential oil (OEO) by the drop-casting method. The preparation of TiO₂-NPs followed the sol-gel process with spherical morphology and an average size of 13.39 nm ± 2.28 nm. The results show how the TiO₂-NP properties predominate over the crystallization processes, reflected in the decreasing crystallinity percentage from 5.2% to 0.6% in the membranes. On the other hand, when OEO and TiO₂-NPs are introduced into a membrane, they act synergistically due to the inclusion of highly conjugated thermostable molecules and the thermal properties of TiO₂-NPs. Finally, incorporating OEO and TiO₂-NPs promotes tissue regeneration due to the decrease in inflammatory infiltrate and the appearance of connective tissue. These results demonstrate the great potential for biomedical applications of the membranes prepared.

Aggregation Kinetics of TiO2 Nanoparticles in Human and Artificial Sweat Solutions: Effects of Particle Properties and Sweat Constituents

Dermal penetration potentials of titanium dioxide nanoparticles (TiO₂ NPs) may be affected by aggregation upon contact with sweat. This study investigated the aggregation kinetics of three TiO₂ NPs in thirty human sweat samples and four artificial sweat standards. Effects of particle concentration, sweat type, and inorganic (sodium chloride, disodium hydrogen phosphate, and sodium dihydrogen phosphate) and organic (l-histidine, lactic acid, and urea) constituents were examined. Three TiO₂ NPs remained colloidally stable in >20/30 human sweat samples and showed significant negative correlations (P < 0.01) between aggregation rates and |zeta potentials|. They aggregated rapidly over 20 min to >750 nm in three artificial sweat standards, while remained more stable in the International-Standard-Organization-pH-5.5 standard. Aggregation behaviors of three TiO₂ NPs mostly followed the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, allowing for determining their critical coagulation concentrations in inorganic constituents (15-491 mM) and Hamaker constants (3.3-7.9 × 10^-21 J). Higher concentrations of particles, inorganic constituents, and l-histidine destabilized three TiO₂ NPs, whereas urea inhibited aggregation. Three TiO₂ NPs adsorbed organic sweat constituents via complexation with amino or carboxyl groups, with isotherms following the Langmuir model. Correlation analyses further suggested that the adsorbed organic constituents may stabilize three TiO₂ NPs against aggregation in sweat by steric hindrance.

Long Non-Coding RNA Expression Profile Alteration Induced by Titanium Dioxide Nanoparticles in HepG2 Cells

The liver is considered the major target organ affected by oral exposure to titanium dioxide nanoparticles (TiO₂ NPs), but the mechanism of hepatotoxicity is not fully understood. This study investigated the effect of TiO₂ NPs on the expression profile of long non-coding RNA (lncRNA) in hepatocytes and tried to understand the potential mechanism of hepatotoxicity through bioinformatics analysis. The human hepatocellular carcinoma cells (HepG2) were treated with TiO₂ NPs at doses of 0-200 μg/mL for 48 h and then RNA sequencing was implemented. The differential lncRNAs between the control and TiO₂ NPs-treated groups were screened, then the lncRNA-mRNA network and enrichment pathways were analyzed via multivariate statistics. As a result, 46,759 lncRNAs were identified and 129 differential lncRNAs were screened out. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that the targeted mRNAs of those differential lncRNAs were enriched in the Hedgehog signaling pathway, Vasopressin-regulated water reabsorption, and Glutamatergic synapse. Moreover, two lncRNA-mRNA networks, including lncRNA NONHSAT256380.1-JRK and lncRNA NONHSAT173563.1-SMIM22, were verified by mRNA detection. This study demonstrated that an alteration in the lncRNA expression profile could be induced by TiO₂ NPs and epigenetics may play an important role in the mechanism of hepatotoxicity.

A Novel Method for the Background Signal Correction in SP-ICP-MS Analysis of the Sizes of Titanium Dioxide Nanoparticles in Cosmetic Samples

We discuss the features involved in determining the titanium dioxide nanoparticle (TiO₂NP) sizes in cosmetic samples via single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) in the millisecond-time resolution mode, and methods for considering the background signal. In the SP-ICP-MS determination of TiO₂NPs in cosmetics, the background signal was recorded in each dwell time interval due to the signal of the Ti dissolved form in deionized water, and the background signal of the cosmetic matrix was compensated by dilution. A correction procedure for the frequency and intensity of the background signal is proposed, which differs from the known procedures due to its correction by the standard deviation above the background signal. Background signals were removed from the sample signal distribution using the deionized water signal distribution. Data processing was carried out using Microsoft Office Excel and SPCal software. The distributions of NP signals in cosmetic product samples were studied in the dwell time range of 4-20 ms. The limit of detection of the NP size (LOD_size) with the proposed background signal correction procedure was 71 nm. For the studied samples, the LOD_size did not depend on the threshold of the background signal and was determined by the sensitivity of the mass spectrometer.

Adverse Outcome Pathways Associated with the Ingestion of Titanium Dioxide Nanoparticles-A Systematic Review

Titanium dioxide nanoparticles (TiO₂-NPs) are widely used, and humans are exposed through food (E171), cosmetics (e.g., toothpaste), and pharmaceuticals. The oral and gastrointestinal (GIT) tract are the first contact sites, but it may be systemically distributed. However, a robust adverse outcome pathway (AOP) has not been developed upon GIT exposure to TiO₂-NPs. The aim of this review was to provide an integrative analysis of the published data on cellular and molecular mechanisms triggered after the ingestion of TiO₂-NPs, proposing plausible AOPs that may drive policy decisions. A systematic review according to Prisma Methodology was performed in three databases of peer-reviewed literature: Pubmed, Scopus, and Web of Science. A total of 787 records were identified, screened in title/abstract, being 185 used for data extraction. The main endpoints identified were oxidative stress, cytotoxicity/apoptosis/cell death, inflammation, cellular and systemic uptake, genotoxicity, and carcinogenicity. From the results, AOPs were proposed where colorectal cancer, liver injury, reproductive toxicity, cardiac and kidney damage, as well as hematological effects stand out as possible adverse outcomes. The recent transgenerational studies also point to concerns with regard to population effects. Overall, the findings further support a limitation of the use of TiO₂-NPs in food, announced by the European Food Safety Authority (EFSA).

Sediment Bacteria and Phosphorus Fraction Response, Notably to Titanium Dioxide Nanoparticle Exposure

Titanium dioxide nanoparticle (TiO₂ NP) toxicity to the growth of organisms has been gradually clarified; however, its effects on microorganism-mediated phosphorus turnover are poorly understood. To evaluate the influences of TiO₂ NPs on phosphorus fractionation and the bacterial community, aquatic microorganisms were exposed to different concentrations of TiO₂ NPs with different exposure times (i.e., 0, 10, and 30 days). We observed the adhesion of TiO₂ NPs to the cell surfaces of planktonic microbes by using SEM, EDS, and XRD techniques. The addition of TiO₂ NPs resulted in a decrease in the total phosphorus of water and an increase in the total phosphorus of sediments. Additionally, elevated TiO₂ NPs enhanced the sediment activities of reductases (i.e., dehydrogenase [0.19–2.25 μg/d/g] and catalase [1.06–2.92 μmol/d/g]), and significantly decreased the absolute abundances of phosphorus-cycling-related genes (i.e., gcd [1.78 × 10⁴–9.55 × 10⁵ copies/g], phoD [5.50 × 10³–5.49 × 10⁷ copies/g], pstS [4.17 × 10²–1.58 × 10⁶ copies/g]), and sediment bacterial diversity. TiO₂ NPs could noticeably affect the bacterial community, showing dramatic divergences in relative abundances (e.g., Actinobacteria, Acidobacteria, and Firmicutes), coexistence patterns, and functional redundancies (e.g., translation and transcription). Our results emphasized that the TiO₂ NP amount—rather than the exposure time—showed significant effects on phosphorus fractions, enzyme activity, phosphorus-cycling-related gene abundance, and bacterial diversity, whereas the exposure time exhibited a greater influence on the composition and function of the sediment bacterial community than the TiO₂ NP amount. Our findings clarify the responses of phosphorus fractions and the bacterial community to TiO₂ NP exposure in the water–sediment ecosystem and highlight potential environmental risks of the migration of untreated TiO₂ NPs to aquatic ecosystems.

Visible-Light Activation of a Dissolved Organic Matter-TiO2 Complex Mediated via Ligand-to-Metal Charge Transfer

Given the widespread use of TiO₂, its release into aquatic systems and complexation with dissolved organic matter (DOM) are highly possible, making it important to understand how such interactions affect photocatalytic activity under visible light. Here, we show that humic acid/TiO₂ complexes (HA/TiO₂) exhibit photoactivity (without significant electron-hole activation) under visible light through ligand-to-metal charge transfer (LMCT). The observed visible-light activities for pollutant removal and bacterial inactivation are primarily linked to the generation of H₂O₂via the conduction band. By systematically considering molecular-scale interactions between TiO₂ and organic functional groups in HA, we find a key role of phenolic groups in visible-light absorption and H₂O₂ photogeneration. The photochemical formation of H₂O₂ in river waters spiked with TiO₂ is notably elevated above naturally occurring H₂O₂ generated from background organic constituents due to LMCT contribution. Our findings suggest that H₂O₂ generation by HA/TiO₂ is related to the quantity and functional group chemistry of DOM, which provides chemical insights into photocatalytic activity and potential ecotoxicity of TiO₂ in environmental and engineered systems.

Exogenous Application of Green Titanium Dioxide Nanoparticles (TiO2 NPs) to Improve the Germination, Physiochemical, and Yield Parameters of Wheat Plants under Salinity Stress

Agriculture is the backbone of every developing country. Among various crops, wheat (Triticum aestivum L.) belongs to the family Poaceae and is the most important staple food crop of various countries. Different biotic (viruses, bacteria and fungi) and abiotic stresses (water logging, drought and salinity) adversely affect the qualitative and quantitative attributes of wheat. Among these stresses, salinity stress is a very important limiting factor affecting the morphological, physiological, biochemical attributes and grain yield of wheat. This research work was carried out to evaluate the influence of phytosynthesized TiO₂ NPs on the germination, physiochemical, and yield attributes of wheat varieties in response to salinity. TiO₂ NPs were synthesized using TiO₂ salt and a Buddleja asiatica plant extract as a reducing and capping agent. Various concentrations of TiO₂ nanoparticles (20, 40, 60 and 80 mg/L) and salt solutions (NaCl) (100 and 150 mM) were used. A total of 20 mg/L and 40 mg/L improve germination attributes, osmotic and water potential, carotenoid, total phenolic, and flavonoid content, soluble sugar and proteins, proline and amino acid content, superoxide dismutase activity, and reduce malondialdhehyde (MDA) content at both levels of salinity. These two concentrations also improved the yield attributes of wheat varieties at both salinity levels. The best results were observed at 40 mg/L of TiO₂ NPs at both salinity levels. However, the highest concentrations (60 and 80 mg/L) of TiO₂ NPs showed negative effects on germination, physiochemical and yield characteristics and causes stress in both wheat varieties under control irrigation conditions and salinity stress. Therefore, in conclusion, the findings of this research are that the foliar application of TiO₂ NPs can help to improve tolerance against salinity stress in plants.

Polymethylmethacrylate denture base layering as a new approach for the addition of antifungal agents

PURPOSE

To introduce a new technique, denture base layering, for the addition of titanium dioxide nanoparticles (TiO₂ NPs) to polymethylmethacrylate (PMMA) and to investigate the effects of the layering technique on Candida albicans (C. albicans) adhesion and on surface roughness, hardness, translucency, and flexural strength.

MATERIALS & METHODS

In total, 210 heat-polymerized acrylic resin specimens were prepared as discs (15 × 2 mm) for testing C. albicans adhesion (n = 70) and surface roughness, hardness, and translucency (n = 70); and as acrylic plates (65 × 10 × 2.5 mm) for testing flexural strength (n = 70). Specimens were divided into 4 groups: control (n = 30), one-layer (n = 60), double-layer (n = 60), and dotted-layer (n = 60) according to the packing and layering technique. Each group was divided according to the concentration of TiO₂ NPs 1% and 2.5% (n = 10). The control group comprised one layer of unmodified resin. The one-layer group comprised one layer of a mixture of PMMA/TiO₂ NPs packed conventionally. The double-layer group consisted of two different layers packed in two steps, as follows: unmodified resin first, followed by a continuous thin layer of the PMMA/TiO₂ NPs mixture. Similarly, the dotted-layer group consisted of two different layers packed in two steps, as follows: unmodified resin first, followed by a thin layer of the PMMA/TiO₂ NPs. However, the second mixture was added in a dotted manner. The direct culture method for C. albicans adhesion before and after ultraviolet light activation, and surface roughness, hardness, translucency, and flexural strength were measured. An analysis of variance and Tukey's post hoc test were used for data analysis (α = 0.05).

RESULTS

The addition of TiO₂ NPs reduced C. albicans adhesion (P ˂.001). However, no significant difference was found between both concentrations within the same group before and after ultraviolet light activation (P >0.05), except in the 1% dotted-layer (P = .022). Surface roughness and hardness were not affected by the additions of different concentrations of TiO₂ NPs (P = .905) and (P = .059), respectively. Translucency was significantly reduced in all the groups (P ˂.001) except in the 1% dotted-layer (P = .332). Flexural strength decreased as the TiO₂ NPs concentration increased, with the greatest reduction in strength observed in the one-layer group (P ˂.001).

CONCLUSIONS

The double and dotted layering techniques were effective in reducing C. albicans adhesion, without affecting surface roughness, hardness, or flexural strength. However, translucency was reduced in all the groups, except the 1% dotted-layer group. This article is protected by copyright. All rights reserved.

Effects of Titanium Dioxide Nanoparticles on Cell Growth and Migration of A549 Cells under Simulated Microgravity

With the increasing application of nanomaterials in aerospace technology, the long-term space exposure to nanomaterials especially in the space full of radiation coupled with microgravity condition has aroused great health concerns of the astronauts. However, few studies have been conducted to assess these effects, which are crucial for seeking the possible intervention strategy. Herein, using a random positioning machine (RPM) to simulate microgravity, we investigated the behaviors of cells under simulated microgravity and also evaluated the possible toxicity of titanium dioxide nanoparticles (TiO₂ NPs), a multifunctional nanomaterial with potential application in aerospace. Pulmonary epithelial cells A549 were exposed to normal gravity (1 g) and simulated gravity (~10⁻³ g), respectively. The results showed that simulated microgravity had no significant effect on the viability of A549 cells as compared with normal gravity within 48 h. The effects of TiO₂ NPs exposure on cell viability and apoptosis were marginal with only a slightly decrease in cell viability and a subtle increase in apoptosis rate observed at a high concentration of TiO₂ NPs (100 μg/mL). However, it was observed that the exposure to simulated microgravity could obviously reduce A549 cell migration compared with normal gravity. The disruption of F-actin network and the deactivation of FAK (Tyr397) might be responsible for the impaired mobility of simulated microgravity-exposed A549 cells. TiO₂ NPs exposure inhibited cell migration under two different gravity conditions, but to different degrees, with a milder inhibition under simulated microgravity. Meanwhile, it was found that A549 cells internalized more TiO₂ NPs under normal gravity than simulated microgravity, which may account for the lower cytotoxicity and the lighter inhibition of cell migration induced by the same exposure concentration of TiO₂ NPs under simulated microgravity at least partially. Our study has provided some tentative information on the effects of TiO₂ NPs exposure on cell behaviors under simulated microgravity.

Nitric Oxide Release and Antibacterial Efficacy Analyses of S-Nitroso-N-Acetyl-Penicillamine Conjugated to Titanium Dioxide Nanoparticles

Therapeutic agents can be linked to nanoparticles to fortify their selectivity and targeted delivery while impeding systemic toxicity and efficacy loss. Titanium dioxide nanoparticles (TiNPs) owe their rise in biomedical sciences to their versatile applicability, although the lack of inherent antibacterial properties limits its application and necessitates the addition of bactericidal agents along with TiNPs. Structural modifications can improve TiNP's antibacterial impact. The antibacterial efficacy of nitric oxide (NO) against a broad spectrum of bacterial strains is well established. For the first time, S-nitroso-N-acetylpenicillamine (SNAP), an NO donor molecule, was covalently immobilized on TiNPs to form the NO-releasing TiNP-SNAP nanoparticles. The TiNPs were silanized with 3-aminopropyl triethoxysilane, and N-acetyl-d-penicillamine was grafted to them via an amide bond. The nitrosation was carried out by t-butyl nitrite to conjugate the NO-rich SNAP moiety to the surface. The total NO immobilization was measured to be 127.55 ± 4.68 nmol mg^-1 using the gold standard chemiluminescence NO analyzer. The NO payload can be released from the TiNP-SNAP under physiological conditions for up to 20 h. The TiNP-SNAP exhibited a concentration-dependent antimicrobial efficiency. At 5 mg mL^-1, more than 99.99 and 99.70% reduction in viable Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria, respectively, were observed. No significant cytotoxicity was observed against 3T3 mouse fibroblast cells at all the test concentrations determined by the CCK-8 assay. TiNP-SNAP is a promising and versatile nanoparticle that can significantly impact the usage of TiNPs in a wide variety of applications, such as biomaterial coatings, tissue engineering scaffolds, or wound dressings.

Photoinduced Superhydrophilicity of Gd-Doped TiO2 Ellipsoidal Nanoparticles Boosts T1 Contrast Enhancement for Magnetic Resonance Imaging

The unsatisfactory performance of current gadolinium chelate based T₁ contrast agents (CAs) for magnetic resonance imaging (MRI) stimulates the search for better alternatives. Herein, we report a new strategy to substantially improve the capacity of nanoparticle-based T₁ CAs by exploiting the photoinduced superhydrophilic assistance (PISA) effect. As a proof of concept, we synthesized citrate-coated Gd-doped TiO₂ ellipsoidal nanoparticles (GdTi-SC NPs), whose r₁ increases significantly upon UV irradiation. The reduced water contact angle and the increased number of surface hydroxyl groups substantiate the existence of the PISA effect, which considerably promotes the efficiency of paramagnetic relaxation enhancement (PRE) and thus the imaging performance of GdTi-SC NPs. In vivo MRI of SD rats with GdTi-SC NPs further demonstrates that GdTi-SC NPs could serve as a high-performance CA for sensitive imaging of blood vessels and accurate diagnosis of vascular lesions, indicating the success of our strategy.

Poly(ethylene-Co-vinyl Alcohol)/Titanium Dioxide Nanocomposite: Preparation and Characterization of Properties for Potential Use in Bone Tissue Engineering

A series of poly(ethylene-co-vinyl alcohol)/titanium dioxide (PEVAL/TiO2) nanocomposites containing 1, 2, 3, 4 and 5 wt% TiO2 were prepared by the solvent casting method. These prepared hybrid materials were characterized by Fourier-transform infrared (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The pores and their interconnections inside these nanocomposites were created using naphthalene microparticles used as a porogen after having been extracted by sublimation under a high vacuum at temperatures slightly below the glass transition temperature. A cellular activity test of these hybrid materials was performed on human gingival fibroblast cells (HGFs) in accordance with ISO 10993-5 and ISO 10993-12 standards. The bioviability (cell viability) of HGFs was evaluated after 1, 4 and 7 days using Alamar Blue®. The results were increased cell activity throughout the different culture times and a significant increase in cell activity in all samples from Day 1 to Day 7, and all systems tested showed significantly higher cell viability than the control group on Day 7 (p < 0.002). The adhesion of HGFs to the scaffolds studied by SEM showed that HGFs were successfully cultured on all types of scaffolds.

In Vitro Hepatotoxic and Neurotoxic Effects of Titanium and Cerium Dioxide Nanoparticles, Arsenic and Mercury Co-Exposure

Considering the increasing emergence of new contaminants, such as nanomaterials, mixing with legacy contaminants, including metal(loid)s, it becomes imperative to understand the toxic profile resulting from these interactions. This work aimed at assessing and comparing the individual and combined hepatotoxic and neurotoxic potential of titanium dioxide nanoparticles (TiO₂NPs 0.75–75 mg/L), cerium oxide nanoparticles (CeO₂NPs 0.075–10 μg/L), arsenic (As 0.01–2.5 mg/L), and mercury (Hg 0.5–100 mg/L) on human hepatoma (HepG2) and neuroblastoma (SH-SY5Y) cells. Viability was assessed through WST-1 (24 h) and clonogenic (7 days) assays and it was affected in a dose-, time- and cell-dependent manner. Higher concentrations caused greater toxicity, while prolonged exposure caused inhibition of cell proliferation, even at low concentrations, for both cell lines. Cell cycle progression, explored by flow cytometry 24 h post-exposure, revealed that TiO₂NPs, As and Hg but not CeO₂NPs, changed the profiles of SH-SY5Y and HepG2 cells in a dose-dependent manner, and that the cell cycle was, overall, more affected by exposure to mixtures. Exposure to binary mixtures revealed either potentiation or antagonistic effects depending on the composition, cell type and time of exposure. These findings prove that joint toxicity of contaminants cannot be disregarded and must be further explored.

Effects of Titanium Dioxide Nanoparticles on Porcine Prepubertal Sertoli Cells: An "In Vitro" Study

The increasing use of nanomaterials in a variety of industrial, commercial, medical products, and their environmental spreading has raised concerns regarding their potential toxicity on human health. Titanium dioxide nanoparticles (TiO2 NPs) represent one of the most commonly used nanoparticles. Emerging evidence suggested that exposure to TiO2 NPs induced reproductive toxicity in male animals. In this in vitro study, porcine prepubertal Sertoli cells (SCs) have undergone acute (24 h) and chronic (from 1 up to 3 weeks) exposures at both subtoxic (5 µg/ml) and toxic (100 µg/ml) doses of TiO2 NPs. After performing synthesis and characterization of nanoparticles, we focused on SCs morphological/ultrastructural analysis, apoptosis, and functionality (AMH, inhibin B), ROS production and oxidative DNA damage, gene expression of antioxidant enzymes, proinflammatory/immunomodulatory cytokines, and MAPK kinase signaling pathway. We found that 5 µg/ml TiO2 NPs did not induce substantial morphological changes overtime, but ultrastructural alterations appeared at the third week. Conversely, SCs exposed to 100 µg/ml TiO2 NPs throughout the whole experiment showed morphological and ultrastructural modifications. TiO2 NPs exposure, at each concentration, induced the activation of caspase-3 at the first and second week. AMH and inhibin B gene expression significantly decreased up to the third week at both concentrations of nanoparticles. The toxic dose of TiO2 NPs induced a marked increase of intracellular ROS and DNA damage at all exposure times. At both concentrations, the increased gene expression of antioxidant enzymes such as SOD and HO-1 was observed whereas, at the toxic dose, a clear proinflammatory stress was evaluated along with the steady increase in the gene expression of IL-1α and IL-6. At both concentrations, an increased phosphorylation ratio of p-ERK1/2 was observed up to the second week followed by the increased phosphorylation ratio of p-NF-kB in the chronic exposure. Although in vitro, this pilot study highlights the adverse effects even of subtoxic dose of TiO2 NPs on porcine prepubertal SCs functionality and viability and, more importantly, set the basis for further in vivo studies, especially in chronic exposure at subtoxic dose of TiO2 NPs, a condition closer to the human exposure to this nanoagent.

Push-out bond strength of mineral trioxide aggregate with addition of titanium dioxide, silver, and silicon dioxide nanoparticles: An in vitro comparative study

Background

The ultimate goal of endodontic therapy is to eliminate all microorganisms present inside root canal and thereby sealing all the possible communicating pathways between pulpal and periradicular tissues, which prevents all the factors that cause recontamination and reinfection of the root canal system. If endodontic treatment fails, next approach is surgical endodontics. Bioceramics are recently introduced materials specifically designed for their potential use in medical field and dentistry.

Aim

To evaluate and compare the push-out bond strength of mineral trioxide aggregate (MTA) by adding titanium dioxide (TiO2), silver, and silicon dioxide nanoparticles.

Materials and Methods

Totally, 60 single-rooted human teeth were used. Middle third of the root was sectioned to obtain 2-mm thick root section. Acrylic was adapted to the section to obtain disks of 5 mm diameter and 2 mm thickness. Canal was prepared by GG Drill. Samples were divided into four groups of 15 each (n = 15): • Group I (control): MTA • Group II: MTA + TiO₂ nanoparticles. • Group III: MTA + silver nanoparticles. • Group IV: MTA + silicon dioxide nanoparticles. The cement mixture was compacted into the canal. Samples were subjected to push-out bond strength using universal testing machine.

Statistical Analysis Used

The data were analyzed statistically by analysis of variance and post hoc comparison by Tukey's t-test.

Results

The highest push-out bond strength was shown by Group II (MTA with TiO2 nanoparticles), followed by Group III (MTA with silver nanoparticles) and Group I (MTA control group). The lowest push-out bond strength was shown by Group III (MTA with silicon dioxide nanoparticles).

Conclusions

TiO₂ and silver nanoparticles when added into MTA lead to an increase in push-out bond strength of MTA.

Phosphate Group-Derivated Bipyridine-Ruthenium Complex and Titanium Dioxide Nanoparticles for Electrochemical Sensing of Protein Kinase Activity

Monitoring of protein kinase activity is of significance for fundamentals of biochemistry, biomedical diagnose, and drug screening. To reduce the usage of a relatively complicated bio-labeled signal probe, the phosphate group-derivated bipyridine-ruthenium (Pbpy-Ru) complex and titanium dioxide nanoparticles (TiO₂ NPs) were employed as signal probes to develop an electrochemical sensor for evaluating the protein kinase A (PKA) activity. Through the specific interaction between the phosphate groups and TiO₂ NPs, the preparation of a Pbpy-Ru-TiO₂ NP signal probe and its linkage with the phosphorylated PKA substrate peptides could be performed in a simple and effective way. The tethering of Pbpy-Ru onto the TiO₂ NP surface does not degrade the electrochemical property of the complex. The Pbpy-Ru-TiO₂ NP probe exhibits well-defined redox signals at about 1.0 V versus Ag/AgCl reference and notably has about fivefold current response than that of the TiO₂ NPs with physically adsorbed tris-(bipyridine)-Ru. The PKA activity evaluation was realized by measuring the electrochemical response of the Pbpy-Ru-TiO₂ NPs at the phosphorylated peptide-assembled electrode. Operating at optimal conditions, the cathodic signals at the potential of 1.03 V exhibit a good linearity with the PKA concentrations of 0.5-40 U mL^-1. The electrochemical sensor shows good selectivity, low detection limit (0.2 U mL^-1, signal/noise = 3), qualified reproducibility, and satisfactory applicability for PKA determination in the cell lysate. The Pbpy-Ru-TiO₂ NPs/electrode system would be an excellent electrochemical platform for protein phosphorylation monitoring and sensing.