Ag-doping regulates the cytotoxicity of TiO2 nanoparticles via oxidative stress in human cancer cells

First extensive study of silver-doped lanthanum manganite nanoparticles for inducing selective chemotherapy and radio-toxicity enhancement

Nanoparticles have a great potential to increase the therapeutic efficiency of several cancer therapies. This research examines the potential for silver-doped lanthanum manganite nanoparticles to enhance radiation therapy to target radioresistant brain cancer cells, and their potential in combinational therapy with magnetic hyperthermia. Magnetic and structural characterisation found all dopings of nanoparticles (NPs) to be pure and single phase with an average crystallite size of approximately 15 nm for undoped NPs and 20 nm for silver doped NPs. Additionally, neutron diffraction reveals that La_0.9Ag_0.1MnO₃ (10%-LAGMO) NPs exhibit residual ferromagnetism at 300 K that is not present in lower doped NPs studied in this work, indicating that the Curie temperature may be manipulated according to silver doping. This radiobiological study reveals a completely cancer-cell selective treatment for LaMnO₃, La_0.975Ag_0.025MnO₃ and La_0.95Ag_0.05MnO₃ (0, 2.5 and 5%-LAGMO) and also uncovers a potent combination of undoped lanthanum manganite with orthovoltage radiation. Cell viability assays and real time imaging results indicated that a concentration of 50 μg/mL of the aforementioned nanoparticles do not affect the growth of Madin-Darby Canine Kidney (MDCK) non-cancerous cells over time, but stimulate its metabolism for overgrowth, while being highly toxic to 9L gliosarcoma (9LGS). This is not the case for 10%-LAGMO nanoparticles, which were toxic to both non-cancerous and cancer cell lines. The nanoparticles also exhibited a level of toxicity that was regulated by the overproduction of free radicals, such as reactive oxygen species, amplified when silver ions are involved. With the aid of fluorescent imaging, the drastic effects of these reactive oxygen species were visualised, where nucleus cleavage (an apoptotic indicator) was identified as a major consequence. The genotoxic response of this effect for 9LGS and MDCK due to 10%-LAGMO NPs indicates that it is also causing DNA double strand breaks within the cell nucleus. Using 125 kVp orthovoltage radiation, in combination with an appropriate amount of NP-induced cell death, identified undoped lanthanum manganite as the most ideal treatment. Real-time imaging following the combination treatment of undoped lanthanum manganite nanoparticles and radiation, highlighted a hinderance of growth for 9LGS, while MDCK growth was boosted. The clonogenic assay following incubation with undoped lanthanum manganite nanoparticles combined with a relatively low dose of radiation (2 Gy) decreased the surviving fraction to an exceptionally low (0.6 ± 6.7)%. To our knowledge, these results present the first biological in-depth analysis on silver-doped lanthanum manganite as a brain cancer selective chemotherapeutic and radiation dose enhancer and as a result will propel its first in vivo investigation.

Effect of ROS generation on highly dispersed 4-layer O-Ti7O13 nanosheets toward tumor synergistic therapy

Ultra-thin two-dimensional nanosheets have attracted increasing attention due to their great application prospects in nanomaterial science and biomedicine. Herein, we report the preparation of exfoliated raw and oxidized 4-layer Ti₇O₁₃ (O-Ti₇O₁₃) and their ability to produce reactive oxygen species (ROS). The results show that O-Ti₇O₁₃ nanosheets can effectively produce ROS induced by X-ray irradiation. The 4-layer nanosheets can quickly load doxorubicin (DOX) within 5 min with a high loading rate to obtain a novel nanodrug system through their electrostatic adsorption capacity, and they exhibit a sustained release behavior. In this way, chemotherapy, radiation therapy and photodynamic therapy effectively combine for cancer synergistic treatment. We evaluated the cytotoxicity, cellular uptake and intracellular location of the O-Ti₇O₁₃ nanosheet-based drug delivery system in A549 lung cancer cells. Our results show that the O-Ti₇O₁₃/DOX complex is more cytotoxic to A549 cells than free DOX since a low concentration of loaded DOX (10 μg/mL) with a low dose of X-rays can cause the complete apoptosis of tumor cells. This work reveals that the therapeutic effect of DOX-loaded O-Ti₇O₁₃ nanosheets is strongly dependent on their loading mode, and the effects of chemotherapy and photodynamic therapy are enhanced under X-ray irradiation, which allows O-Ti₇O₁₃ nanosheet use as a photo-activated drug carrier. This work provides a new strategy for preparing 2D metal oxide nanosheets toward biomedical applications.

SnO2-Doped ZnO/Reduced Graphene Oxide Nanocomposites: Synthesis, Characterization, and Improved Anticancer Activity via Oxidative Stress Pathway

BACKGROUND

Therapeutic selectivity and drug resistance are critical issues in cancer therapy. Currently, zinc oxide nanoparticles (ZnO NPs) hold considerable promise to tackle this problem due to their tunable physicochemical properties. This work was designed to prepare SnO2-doped ZnO NPs/reduced graphene oxide nanocomposites (SnO2-ZnO/rGO NCs) with enhanced anticancer activity and better biocompatibility than those of pure ZnO NPs.

MATERIALS AND METHODS

Pure ZnO NPs, SnO2-doped ZnO (SnO2-ZnO) NPs, and SnO2-ZnO/rGO NCs were prepared via a facile hydrothermal method. Prepared samples were characterized by field emission transmission electron microscopy (FETEM), energy dispersive spectroscopy (EDS), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), ultraviolet-visible (UV-VIS) spectrometer, and dynamic light scattering (DLS) techniques. Selectivity and anticancer activity of prepared samples were assessed in human breast cancer (MCF-7) and human normal breast epithelial (MCF10A) cells. Possible mechanisms of anticancer activity of prepared samples were explored through oxidative stress pathway.

RESULTS

XRD spectra of SnO2-ZnO/rGO NCs confirmed the formation of single-phase of hexagonal wurtzite ZnO. High resolution TEM and SEM mapping showed homogenous distribution of SnO2 and rGO in ZnO NPs with high quality lattice fringes without any distortion. Band gap energy of SnO2-ZnO/rGO NCs was lower compared to SnO2-ZnO NPs and pure ZnO NPs. The SnO2-ZnO/rGO NCs exhibited significantly higher anticancer activity against MCF-7 cancer cells than those of SnO2-ZnO NPs and ZnO NPs. The SnO2-ZnO/rGO NCs induced apoptotic response through the upregulation of caspase-3 gene and depletion of mitochondrial membrane potential. Mechanistic study indicated that SnO2-ZnO/rGO NCs kill cancer cells through oxidative stress pathway. Moreover, biocompatibility of SnO2-ZnO/rGO NCs was also higher against normal breast epithelial (MCF10A cells) in comparison to SnO2-ZnO NPs and ZnO NPs.

CONCLUSION

SnO2-ZnO/rGO NCs showed enhanced anticancer activity and better biocompatibility than SnO2-ZnO NPs and pure ZnO NPs. This work suggested a new approach to improve the selectivity and anticancer activity of ZnO NPs. Studies on antitumor activity of SnO2-ZnO/rGO NCs in animal models are further warranted.

Green biomimetic synthesis of Ag-TiO2 nanocomposite using Origanum majorana leaf extract under sonication and their biological activities

BACKGROUND

Studies of plant extract-mediated synthesis of nanoparticles is extensively explored and studied in recent time due to eco-friendly, cost-effectiveness and minimal use of toxic chemicals for synthesis. In this study, the synthesis of Ag-TiO2 nanocomposites (NCs) was carried out using Origanum majorana leaf extract under ultrasound irradiation. Origanum majorana leaf extract plays an important role as reducing and capping agent in synthesis of Ag-TiO2 nanocomposites (NCs). The antimicrobial activities of synthesised Ag-TiO2 NCs have been studied against Gram-positive and Gram-negative bacteria. In addition to this, the antioxidant activity of green Ag-TiO2 NCs was also evaluated on the basis of free radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS), and hydrogen peroxide free radicals.

RESULTS

Green-synthesised Ag-TiO2 NCs were successfully characterised on the basis of UV-Vis spectrophotometer, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction analysis (XRD), scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). The results revealed the spherical shape of nanocomposite with an average size 25-50 nm. The synthesised Ag-TiO2 NCs have showed significant antimicrobial activity against Escherichia coli, Bacillus subtilis and Aspergillus niger in comparison to TiO2 nanoparticles (NPs). The antioxidant evaluation of biomimetic synthesised Ag-TiO2 NCs also exhibited strong activity than TiO2 NPs and comparable to standard.

CONCLUSION

Green-synthesized Ag-TiO2 NCs provide a promising approach that can satisfy the requirement of large-scale industrial production bearing the advantage of low cost, eco-friendly and reproducible.

Toxicological effects of Ag2O and Ag2CO3 doped TiO2 nanoparticles and pure TiO2 particles on zebrafish (Danio rerio)

In this study, the toxic effects of silver oxide and silver carbonate doped TiO₂ nanoparticles (Ag₂O-TiO₂ NPs and Ag₂CO₃-TiO₂NPs), TiO₂ nanoparticles (TiO₂ NPs), and bulk TiO₂ on gene expression, lipid peroxidation, genotoxicity, and histological alterations in zebrafish (Danio rerio) was assessed. The physicochemical properties of the synthesized nanoparticles were evaluated by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), diffuse reflectance spectroscopy (DRS), dynamic light scattering (DLS), and Zeta potential analyses. TiO₂NPs after doping with Ag showed shift to higher wavelengths and decrease of band gap energy. Also, remarkable reduction in the size of Ag-doped TiO₂NPs in comparison with the TiO₂ NPs was observed. According to our results, acute toxicity increased in the order of bulk TiO₂ < TiO₂ NPs < Ag₂O-TiO₂NPs < Ag₂CO₃-TiO₂NPs, respectively. Results of sub-lethal experiments after 30 days of exposure, showed higher expression of Gpx, Hsp70, Ucp-2, and Bax genes, and lower expression of Bcl-2 gene in Ag-doped TiO₂NPs than pure TiO₂ particles (TiO₂ NPs and bulk TiO₂) treatments (p < 0.05). However, the mRNA levels of SOD and CAT genes were significantly higher in pure TiO₂ particles than doped TiO₂NPs (p < 0.05). Moreover, levels of malondialdehyde, abnormalities of peripheral blood cells and severity of histological lesions in liver, gill, intestine and kidney tissues were more evident in Ag-dopedTiO₂ NPs than pure TiO₂ particles. It can be concluded that Ag doping of TiO₂ NPs significantly increased their toxicity and resulted in more histological lesions, apoptosis and oxidative stress than pure TiO₂ particles in adult zebrafish.

Nanomedicine: Photo-activated nanostructured titanium dioxide, as a promising anticancer agent

The multivariate condition of cancer disease has been approached in various ways, by the scientific community. Recent studies focus on individualized treatments, minimizing the undesirable consequences of the conventional methods, but the development of an alternative effective therapeutic scheme remains to be held. Nanomedicine could provide a solution, filling this gap, exploiting the unique properties of innovative nanostructured materials. Nanostructured titanium dioxide (TiO₂) has a variety of applications of daily routine and of advanced technology. Due to its biocompatibility, it has also a great number of biomedical applications. It is now clear that photo-excited TiO₂ nanoparticles, induce generation of pairs of electrons and holes which react with water and oxygen to yield reactive oxygen species (ROS) that have been proven to damage cancer cells, triggering controlled cellular processes. The aim of this review is to provide insights into the field of nanomedicine and particularly into the wide context of TiO₂-NP-mediated anticancer effect, shedding light on the achievements of nanotechnology and proposing this nanostructured material as a promising anticancer photosensitizer.

Rationale and decision rules behind the ECETOC NanoApp to support registration of sets of similar nanoforms within REACH

New registration requirements for nanomaterials under REACH consider the possibility to form 'sets of similar nanoforms' for a joined human health and environmental hazard, exposure and risk assessment. We developed a tool to create and justify sets of similar nanoforms and to ensure that each of the nanoforms is sufficiently similar to all other nanoforms. The decision logic is following the ECHA guidance in a transparent and evidence-based manner. For each two nanoforms the properties under consideration are compared and corresponding thresholds for maximal differences are proposed. In tier1, similarity is assessed based on intrinsic properties that mostly correspond to those required for nanoform identification under REACH: composition, impurities/additives, size, crystallinity, shape and surface treatment. Moreover, potential differences in the agglomeration/aggregation state resulting from different production processes are considered. If nanoforms were not sufficiently similar based on tier1 criteria, additional data from functional assays are required in tier2. In rare cases, additional short-term in vivo rodent data could be required in a third tier. Data required by tier 2 are triggered by the intrinsic properties in the first tier that did not match the similarity criteria. Most often this will be data on dissolution and surface reactivity followed by in vitro toxicity, dispersion stability, dustiness. Out of several nanoforms given by the user, the tool concludes which nanoforms could be justified to be in the same set and which nanoforms are outside. It defines the boundaries of sets of similar nanoforms and generates a justification for the REACH registration.

Preparation, characterization and antibacterial mechanism of the chitosan coatings modified by Ag/ZnO microspheres

BACKGROUND

To improve the physicochemical and antibacterial properties of coatings, the chitosan (CS) coatings were respectively prepared by a casting method with zinc oxide (ZnO) and silver (Ag)/ZnO microspheres as modifiers. The chemical structures and micromorphology of ZnO, Ag/ZnO microspheres and CS coatings were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. Furthermore, using the dominant spoilage bacteria of aquatic products, Shewanella putrefaciens and Pseudomonas aeruginosa, as objects, the antibacterial activities and mechanism of the CS coatings were investigated.

RESULTS

The results show that ZnO and Ag/ZnO microspheres are dispersed homogeneously in the CS coatings. After modified by ZnO and Ag/ZnO microspheres, the mechanical properties and antibacterial abilities of the CS coatings are improved, and that of 0.5% Ag/ZnO-CS coating is the optimal. For pure CS coating, the bacterial cell membrane is damaged slightly because of the electrostatic interaction between NH³⁺ of CS and the negative charge on bacterial surface. After treated by ZnO-CS composite coating, the bacterial cell membrane is destroyed badly on account of the earlier-mentioned ion interaction and disturbing the synthesis of high molecular weight total protein.

CONCLUSION

With regard to Ag/ZnO-CS composite coating, the bacterial cell membrane is damaged seriously and cell contents are completely released due to ion interaction, disturbing the synthesis of high molecular weight total protein and low molecular weight membrane protein. Hence, Ag/ZnO-CS composite coatings are antimicrobial materials and food preservative materials with great potential application. © 2020 Society of Chemical Industry.

Barium Titanate (BaTiO3) Nanoparticles Exert Cytotoxicity through Oxidative Stress in Human Lung Carcinoma (A549) Cells

Barium titanate (BaTiO3) nanoparticles (BT NPs) have shown exceptional characteristics such as high dielectric constant and suitable ferro-, piezo-, and pyro-electric properties. Thus, BT NPs have shown potential to be applied in various fields including electro-optical devices and biomedicine. However, very limited knowledge is available on the interaction of BT NPs with human cells. This work was planned to study the interaction of BT NPs with human lung carcinoma (A549) cells. Results showed that BT NPs decreased cell viability in a dose- and time-dependent manner. Depletion of mitochondrial membrane potential and induction of caspase-3 and -9 enzyme activity were also observed following BT NP exposure. BT NPs further induced oxidative stress indicated by induction of pro-oxidants (reactive oxygen species and hydrogen peroxide) and reduction of antioxidants (glutathione and several antioxidant enzymes). Moreover, BT NP-induced cytotoxicity and oxidative stress were effectively abrogated by N-acetyl-cysteine (an ROS scavenger), suggesting that BT NP-induced cytotoxicity was mediated through oxidative stress. Intriguingly, the underlying mechanism of cytotoxicity of BT NPs was similar to the mode of action of ZnO NPs. At the end, we found that BT NPs did not affect the non-cancerous human lung fibroblasts (IMR-90). Altogether, BT NPs selectively induced cytotoxicity in A549 cells via oxidative stress. This work warrants further research on selective cytotoxicity mechanisms of BT NPs in different types of cancer cells and their normal counterparts.

Single-Walled Carbon Nanotubes Attenuate Cytotoxic and Oxidative Stress Response of Pb in Human Lung Epithelial (A549) Cells

Combined exposure of single-walled carbon nanotubes (SWCNTs) and trace metal lead (Pb) in ambient air is unavoidable. Most of the previous studies on the toxicity of SWCNTs and Pb have been conducted individually. There is a scarcity of information on the combined toxicity of SWCNTs and Pb in human cells. This work was designed to explore the combined effects of SWCNTs and Pb in human lung epithelial (A549) cells. SWCNTs were prepared through the plasma-enhanced vapor deposition technique. Prepared SWCNTs were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, and dynamic light scattering. We observed that SWCNTs up to a concentration of 100 µg/mL was safe, while Pb induced dose-dependent (5-100 µg/mL) cytotoxicity in A549 cells. Importantly, cytotoxicity, cell cycle arrest, mitochondrial membrane potential depletion, lipid peroxidation, and induction of caspase-3 and -9 enzymes following Pb exposure (50 µg/mL for 24 h) were efficiently attenuated by the co-exposure of SWCNTs (10 µg/mL for 24 h). Furthermore, generation of Pb-induced pro-oxidants (reactive oxygen species and hydrogen peroxide) and the reduction of antioxidants (antioxidant enzymes and glutathione) were also mitigated by the co-exposure of SWCNTs. Inductively coupled plasma-mass spectrometry results suggest that the adsorption of Pb on the surface of SWCNTs could attenuate the bioavailability and toxicity of Pb in A549 cells. Our data warrant further research on the combined effects of SWCNTs and Pb in animal models.

Phyto-Mediated Synthesis of Porous Titanium Dioxide Nanoparticles From Withania somnifera Root Extract: Broad-Spectrum Attenuation of Biofilm and Cytotoxic Properties Against HepG2 Cell Lines

There is grave necessity to counter the menace of drug-resistant biofilms of pathogens using nanomaterials. Moreover, we need to produce nanoparticles (NPs) using inexpensive clean biological approaches that demonstrate broad-spectrum inhibition of microbial biofilms and cytotoxicity against HepG2 cell lines. In the current research work, titanium dioxide (TiO2) NPs were fabricated through an environmentally friendly green process using the root extract of Withania somnifera as the stabilizing and reducing agent to examine its antibiofilm and anticancer potential. Further, X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron micrograph (TEM), energy-dispersive X-ray spectroscopy (EDS), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) techniques were used for determining the crystallinity, functional groups involved, shape, size, thermal behavior, surface area, and porosity measurement, respectively, of the synthesized TiO2 NPs. Antimicrobial potential of the TiO2 NPs was determined by evaluating the minimum inhibitory concentration (MIC) against Escherichia coli, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, Listeria monocytogenes, Serratia marcescens, and Candida albicans. Furthermore, at levels below the MIC (0.5 × MIC), TiO2 NPs demonstrated significant inhibition of biofilm formation (43-71%) and mature biofilms (24-64%) in all test pathogens. Cell death due to enhanced reactive oxygen species (ROS) production could be responsible for the impaired biofilm production in TiO2 NP-treated pathogens. The synthesized NPs induced considerable reduction in the viability of HepG2 in vitro and could prove effective in controlling liver cancer. In summary, the green synthesized TiO2 NPs demonstrate multifarious biological properties and could be used as an anti-infective agent to treat biofilm-based infections and cancer.

Reduced graphene oxide mitigates cadmium-induced cytotoxicity and oxidative stress in HepG2 cells

Numerous applications of reduced graphene oxide (RGO) and pervasive cadmium (Cd) have led concern about their co-exposure to the environment and human. We studied the combined effects of RGO and Cd in human liver (HepG2) cells. Initially, we found that RGO (up to 50 μg/ml) did not harm to HepG2 cells while Cd induced dose-dependent (1-10 μg/ml) cytotoxicity. Exciting observations were that a non-cytotoxic concentration of RGO (25 μg/ml) effectively mitigates the toxic effects of Cd (2 μg/ml) such as cell viability reduction, lactate dehydrogenase release, and irregular cell morphology. Cd-induced cell cycle arrest, induction of caspases (3 and 9) enzymes activity, and loss of mitochondrial membrane potential were also significantly alleviated by RGO co-exposure. Moreover, generation of pro-oxidants (reactive oxygen species and hydrogen peroxide levels) and depletion of antioxidants (glutathione level and superoxide dismutase activity) due to Cd exposure was effectively attenuated by RGO co-exposure. Mitigating effect of RGO could be due to strong adsorption of Cd on the large surface area of RGO sheets, which decrease the cellular uptake and bioavailability of Cd for HepG2 cells. This study warrants future research on potential mechanisms of mitigating effects of RGO against Cd-induced toxicity in animal models.

Anti-bacterial activity of inorganic nanomaterials and their antimicrobial peptide conjugates against resistant and non-resistant pathogens

This review details the antimicrobial applications of inorganic nanomaterials of mostly metallic form, and the augmentation of activity by surface conjugation of peptide ligands. The review is subdivided into three main sections, of which the first describes the antimicrobial activity of inorganic nanomaterials against gram-positive, gram-negative and multidrug-resistant bacterial strains. The second section highlights the range of antimicrobial peptides and the drug resistance strategies employed by bacterial species to counter lethality. The final part discusses the role of antimicrobial peptide-decorated inorganic nanomaterials in the fight against bacterial strains that show resistance. General strategies for the preparation of antimicrobial peptides and their conjugation to nanomaterials are discussed, emphasizing the use of elemental and metallic oxide nanomaterials. Importantly, the permeation of antimicrobial peptides through the bacterial membrane is shown to aid the delivery of nanomaterials into bacterial cells. By judicious use of targeting ligands, the nanomaterial becomes able to differentiate between bacterial and mammalian cells and, thus, reduce side effects. Moreover, peptide conjugation to the surface of a nanomaterial will alter surface chemistry in ways that lead to reduction in toxicity and improvements in biocompatibility.

Susceptibility of HepG2 Cells to Silver Nanoparticles in Combination with other Metal/Metal Oxide Nanoparticles

The fast-growing use of nanomaterials in everyday life raises the question about the safety of their use. Unfortunately, the risks associated with the use of nanoparticles (NPs) have not yet been fully assessed. The majority of studies conducted so far at the molecular and cellular level have focused on a single-type exposure, assuming that NPs act as the only factor. In the natural environment, however, we are likely exposed to a mixture of nanoparticles, whose interactions may modulate their impact on living organisms. This study aimed to evaluate the toxicological effects caused by in vitro exposure of HepG2 cells to AgNPs in combination with AuNPs, CdTe quantum dot (QD) NPs, TiO₂NPs, or SiO₂NPs. The results showed that the toxicity of nanoparticle binary mixtures depended on the type and ratio of NPs used. In general, the toxicity of binary mixtures of NPs was lower than the sum of toxicities of NPs alone (protective effect).

Complex cytotoxicity mechanism of bundles formed from self-organised 1-D anodic TiO2 nanotubes layers

The present study reports on a comprehensive investigation of mechanisms of in vitro cytotoxicity of high aspect ratio (HAR) bundles formed from anodic TiO₂ nanotube (TNT) layers. Comparative cytotoxicity studies were performed using two types of HAR TNTs (diameter of ∼110 nm), differing in initial thickness of the nanotubular layer (∼35 μm for TNTs-1 vs. ∼10 μm for TNTs-2). Using two types of epithelial cell lines (MDA-MB-231, HEK-293), it was found that nanotoxicity is highly cell-type dependent and plausibly associates with higher membrane fluidity and decreased rigidity of cancer cells enabling penetration of TNTs to the cell membrane towards disruption of membrane integrity and reorganization of cytoskeletal network. Upon penetration, TNTs dysregulated redox homeostasis followed by DNA fragmentation and apoptotic/necrotic cell death. Both TNTs exhibited haemolytic activity and rapidly activated polarization of RAW 264.7 macrophages. Throughout the whole study, TNTs-2 possessing a lower aspect ratio manifested significantly higher cytotoxic effects. Taken together, this is the first report comprehensively investigating the mechanisms underlying the nanotoxicity of bundles formed from self-organised 1-D anodic TNT layers. Except for description of nanotoxicity of industrially-interesting nanomaterials, the delineation of the nanotoxicity paradigm in cancer cells could serve as solid basis for future efforts in rational engineering of TNTs towards selective anticancer nanomedicine.

Titanium dioxide nanoparticles induce endoplasmic reticulum stress-mediated apoptotic cell death in liver cancer cells

Objective

Titanium oxide (TiO₂) acts as a photosensitizer in photodynamic therapy by mediating reactive oxygen species (ROS)-induced endoplasmic reticulum (ER) stress. This study aimed to investigate the effect of TiO₂ on ER stress in liver cancer cells.

Methods

Normal human liver and human hepatocarcinoma cell lines were incubated with various concentrations of TiO₂ nanotubes for 48 hours. Cell growth, apoptosis, cell cycle, and cellular ROS were detected. Expression levels of ER stress sensors (PERK and ATF6) and Bax were evaluated by western blot. The effect of TiO₂ on liver cancer growth was also investigated in mice in vivo.

Results

TiO₂ inhibited cell growth, increased apoptosis and cellular ROS levels, and arrested the cell cycle in G1 stage in liver cancer cells. TiO₂ also increased PERK, ATF6, and Bax expression levels in liver cancer cells in dose-dependent manners. TiO₂ had no significant effect on cell growth, apoptosis, ROS level, cell cycle distribution, or PERK, ATF6, or Bax expression in normal liver cells. TiO₂ administration reduced tumor volume and increased PERK, Bax, and ATF6 expression levels in tumor tissues in vivo.

Conclusions

TiO₂ nanoparticles increased ROS-induced ER stress and activated the PERK/ATF6/Bax axis in liver cancer cells in vitro and in vivo.

TiO2 nanoparticles potentiated the cytotoxicity, oxidative stress and apoptosis response of cadmium in two different human cells

Widespread application of titanium dioxide nanoparticles (nTiO₂) and ubiquitous cadmium (Cd) pollution may increase their chance of co-existence in the natural environment. Toxicological information on co-exposure of nTiO₂ and Cd in mammalian models is largely lacking. Hence, we studied the combined effects of nTiO₂ and Cd in human liver (HepG2) and breast cancer (MCF-7) cells. We observed that nTiO₂ did not produce toxicity to HepG2 and MCF-7 cells. However, moderate concentration of Cd exposure caused cytotoxicity to both cells. Interestingly, non-cytotoxic concentration of nTiO₂ effectively enhanced the oxidative stress response of Cd indicated by pro-oxidants generation (reactive oxygen species, hydrogen peroxide, and lipid peroxidation) and antioxidants depletion (glutathione level and glutathione reductase, superoxide dismutase, and catalase enzymes). Moreover, nTiO₂ potentiated the Cd-induced apoptosis in both cells suggested by altered expression of p53, bax, and bcl-2 genes along with low mitochondrial membrane potential. Cellular uptake results demonstrated that nTiO₂ facilitates the internalization of Cd into the cells. Overall, this study demonstrated that non-cytotoxic concentration of nTiO₂ enhanced the toxicological potential of Cd in human cells. Therefore, more attention should be paid on the combine effects of nTiO₂ and Cd on human health.

Alleviating effects of reduced graphene oxide against lead-induced cytotoxicity and oxidative stress in human alveolar epithelial (A549) cells

Broad application of reduced graphene oxide (rGO) and ubiquitous lead (Pb) pollution may increase the possibility of combined exposure of humans. Information on the combined effects of rGO and Pb in human cells is scarce. This work was designed to explore the potential effects of rGO on Pb-induced toxicity in human alveolar epithelial (A549) cells. Prepared rGO was polycrystalline in nature. The formation of a few layers of visible creases and silky morphology due to high aspect ratio was confirmed. Low level (25 μg/mL) of rGO was not toxic to A549 cells. However, Pb exposure (25 μg/mL) induced cell viability reduction, lactate dehydrogenase enzyme leakage with rounded morphology in A549 cells. Remarkably, Pb-induced cytotoxicity was significantly mitigated by rGO co-exposure. Pb-induced mitochondrial membrane potential loss, cell cycle arrest and higher activity of caspase-3 and -9 enzymes were also alleviated by rGO co-exposure. Moreover, we observed that Pb exposure causes generation of pro-oxidants (e.g., reactive oxygen species, hydrogen peroxide and lipid peroxidation) and antioxidant depletion (e.g., glutathione and antioxidant enzymes). In addition, the effects of Pb on pro-oxidant and antioxidant markers were significantly reverted by GO co-exposure. Inductively coupled plasma-mass spectrometry suggested that due to the adsorption of Pb on rGO sheets, accessibility of Pb ions for A549 cells was limited. Hence, rGO reduced the toxicity of Pb in A549 cells. This research warrants further study to work on detailed underlying mechanisms of the mitigating effects of rGO against Pb-induced toxicity on a molecular level.

In vitro and in vivo toxicological evaluation of transition metal-doped titanium dioxide nanoparticles: Nickel and platinum

Transition metal-doped titanium dioxide nanoparticles (M-TiO₂ NPs) have been studied to enhance the activity of TiO₂ NPs in biomedical applications. In this study, in vitro and in vivo toxicological aspects of M-TiO₂ NPs were reported to assess the safety of these materials. M-TiO₂ NPs were synthesized via a photo-deposition technique. Nickel (Ni) and platinum (Pt) were used as dopants. Physicochemical properties, cytotoxicity, phototoxicity, gene ontology (GO) and dermal toxicity of M-TiO₂ NPs were investigated. Ni-TiO₂ (Ni, 1.02%) and Pt-TiO₂ (Pt, 0.26%) NPs were sphere shape crystals with nanoscale size. ARPE-19 cells were more susceptible to Pt-TiO₂ NPs (EC50, 0.796 mg/mL) than Ni-TiO₂ NPs (EC50, 2.945 mg/mL). M-TiO₂ NPs were rated as probably phototoxic to phototoxic. GO suggested binding function and metabolic processes as a risk mechanism of M-TiO₂ NPs. In vivo toxicological effects of Ni-TiO₂ NPs were not observed on body weight, serum aspartate transaminase/alanine transaminase levels, and skin histology at 61.5-6150 mg/kg. Specifically, skin thickness was not significantly modified (max. 33.2 ± 8.7 μm) and inflammation grade was less than level 2 (max. 1.2 ± 0.4). From these results, Ni-TiO₂ and Pt-TiO₂ NPs show promise as enhanced photocatalysts for safe and sustainable usage.

Differential effects of N-TiO2 nanoparticle and its photo-activated form on autophagy and necroptosis in human melanoma A375 cells

The manipulation of autophagy provides a new opportunity for highly effective anticancer therapies. Recently, we showed that photodynamic therapy (PDT) with nitrogen-doped titanium dioxide (N-TiO₂ ) nanoparticles (NPs) could promote the reactive oxygen species (ROS)-dependent autophagy in leukemia cells. However, the differential autophagic effects of N-TiO₂ NPs in the dark and light conditions and the potential of N-TiO_2- based PDT for the treatment of melanoma cells remain unknown. Here we show that depending on the visible-light condition, the autophagic response of human melanoma A375 cells to N-TiO₂ NPs switches between two different statuses (ie., flux or blockade) with the opposite outcomes (ie., survival or death). Mechanistically, low doses of N-TiO₂ NPs (1-100 µg/ml) stimulate a nontoxic autophagy flux response in A375 cells, whereas their photo-activation leads to the impairment of the autophagosome-lysosome fusion, the blockade of autophagy flux and consequently the induction of RIPK1-mediated necroptosis via ROS production. These results confirm that photo-controllable autophagic effects of N-TiO₂ NPs can be utilized for the treatment of cancer, particularly melanoma.

Visible-Light Active Titanium Dioxide Nanomaterials with Bactericidal Properties

This article provides an overview of current research into the development, synthesis, photocatalytic bacterial activity, biocompatibility and cytotoxic properties of various visible-light active titanium dioxide (TiO2) nanoparticles (NPs) and their nanocomposites. To achieve antibacterial inactivation under visible light, TiO2 NPs are doped with metal and non-metal elements, modified with carbonaceous nanomaterials, and coupled with other metal oxide semiconductors. Transition metals introduce a localized d-electron state just below the conduction band of TiO2 NPs, thereby narrowing the bandgap and causing a red shift of the optical absorption edge into the visible region. Silver nanoparticles of doped TiO2 NPs experience surface plasmon resonance under visible light excitation, leading to the injection of hot electrons into the conduction band of TiO2 NPs to generate reactive oxygen species (ROS) for bacterial killing. The modification of TiO2 NPs with carbon nanotubes and graphene sheets also achieve the efficient creation of ROS under visible light irradiation. Furthermore, titanium-based alloy implants in orthopedics with enhanced antibacterial activity and biocompatibility can be achieved by forming a surface layer of Ag-doped titania nanotubes. By incorporating TiO2 NPs and Cu-doped TiO2 NPs into chitosan or the textile matrix, the resulting polymer nanocomposites exhibit excellent antimicrobial properties that can have applications as fruit/food wrapping films, self-cleaning fabrics, medical scaffolds and wound dressings. Considering the possible use of visible-light active TiO2 nanomaterials for various applications, their toxicity impact on the environment and public health is also addressed.

A titanium dioxide/nitrogen-doped graphene quantum dot nanocomposite to mitigate cytotoxicity: synthesis, characterisation, and cell viability evaluation

Titanium dioxide nanoparticles (TiO₂ NPs) have attracted tremendous interest owing to their unique physicochemical properties. However, the cytotoxic effect of TiO₂ NPs remains an obstacle for their wide-scale applications, particularly in drug delivery systems and cancer therapies. In this study, the more biocompatible nitrogen-doped graphene quantum dots (N-GQDs) were successfully incorporated onto the surface of the TiO₂ NPs resulting in a N-GQDs/TiO₂ nanocomposites (NCs). The effects of the nanocomposite on the viability of the breast cancer cell line (MDA-MB-231) was evaluated. The N-GQDs and N-GQDs/TiO₂ NCs were synthesised using a one- and two-pot hydrothermal method, respectively while the TiO₂ NPs were fabricated using microwave-assisted synthesis in the aqueous phase. The synthesised compounds were characterised using Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM) and UV-visible spectrophotometry. The cell viability of the MDA-MB-231 cell line was determined using a CellTiter 96® AQueous One Solution Cell Proliferation (MTS) assay. The obtained results indicated that a monodispersed solution of N-GQDs with particle size 4.40 ± 1.5 nm emitted intense blue luminescence in aqueous media. The HRTEM images clearly showed that the TiO₂ particles (11.46 ± 2.8 nm) are square shaped. Meanwhile, TiO₂ particles were located on the 2D graphene nanosheet surface in N-GQDs/TiO₂ NCs (9.16 ± 2.4 nm). N-GQDs and N-GQDs/TiO₂ NCs were not toxic to the breast cancer cells at 0.1 mg mL⁻¹ and below. At higher concentrations (0.5 and 1 mg mL⁻¹), the nanocomposite was significantly less cytotoxic compared to the pristine TiO₂. In conclusion, this nanocomposite with reduced cytotoxicity warrants further exploration as a new TiO₂-based nanomaterial for biomedical applications, especially as an anti-cancer strategy.

Cytotoxicity mitigation using titanium dioxide/nitrogen-doped graphene quantum dot nanocomposites.

Enhanced photocatalysis and anticancer activity of green hydrothermal synthesized Ag@TiO2 nanoparticles

Titanium dioxide (TiO₂) nanoparticles (NPs) have been doped with varying amounts (0.005, 0.010 and 0.015 M) of silver nanoparticles (Ag NPs) using hydrothermal method. Further, in this work, a green approach was followed for the formation of Ag@TiO₂ NPs using Aloe vera gel as a capping and reducing agent. The structural property confirmed the presence of anatase phase TiO₂. Increased peak intensity was observed while increasing the Ag concentration. Further, the morphological and optical properties have been studied, which confirmed the effective photocatalytic behavior of the prepared Ag@TiO₂ NPs. The photocatalytic performance of Ag@TiO₂ has been considered for the degradation of picric acid in the visible light region. The concentration at 0.010 M of the prepared Ag@TiO₂ has achieved higher photocatalytic performance within 50 min, which could be attributed to its morphological behavior. Similarly, anticancer activity against lung cancer cell lines (A549) was also determined. The Ag@TiO₂ NPs generated a large quantity of reactive oxygen species (ROS), resulting in complete cancer cell growth suppression after their systemic in vitro administration. Ag@TiO₂ NPs was adsorbed visible light that leads to an enhanced anticancer sensitivity by killing and inhibiting cancer cell reproduction through cell viability assay test. It was clear that 0.015 M of Ag@TiO₂ NPs were highly effective against human lung cancer cell lines and showed increased production of ROS in cancer cell lines due to the medicinal behavior of the Aloe vera gel.

Green synthesis and structural classification of Acacia nilotica mediated-silver doped titanium oxide (Ag/TiO2) spherical nanoparticles: Assessment of its antimicrobial and anticancer activity

Current exanimation reports, green fabrication of silver doped TiO2 nanoparticles (Ag/TiO2) using aqueous extract of Acacia nilotica as bio-reductant and assess its potential as antimicrobial and anticancer agent. The obtained spherical Ag/TiO2 were characterized by various analytical techniques including FTIR, (XRD), (FE-SEM EDS), and (TEM). Synthesized Ag/TiO2 demonstrated broad spectrum antibacterial and anticandidal activity. The order of antimicrobial activity was found to be E. coli > C. albicans > MRSA > P. aeruginosa. In addition, cytotoxicity and oxidative stress of Ag/TiO2 nanoparticles in (MCF-7) cells was also investigated. Outcomes of MTT assay showed concentration dependent reduction in cell viability. Further, synthesized NPs reduced the level of glutathione, induced ROS generation and lipid peroxidation in the treated cells. Therefore, it is envisaged that these spherical nanoparticles may be exploited in drug delivery, pharmaceutical, and food industry.

Appraisal of Comparative Therapeutic Potential of Undoped and Nitrogen-Doped Titanium Dioxide Nanoparticles

Nitrogen-doped and undoped titanium dioxide nanoparticles were successfully fabricated by simple chemical method and characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray (EDX), and transmission electron microscopy (TEM) techniques. The reduction in crystalline size of TiO2 nanoparticles (from 20-25 nm to 10-15 nm) was observed by TEM after doping with N. Antibacterial, antifungal, antioxidant, antidiabetic, protein kinase inhibition and cytotoxic properties were assessed in vitro to compare the therapeutic potential of both kinds of TiO2 nanoparticles. All biological activities depicted significant enhancement as a result of addition of N as doping agent to TiO2 nanoparticles. Klebsiella pneumoniae has been illuminated to be the most susceptible bacterial strain out of various Gram-positive and Gram-negative isolates of bacteria used in this study. Good fungicidal activity has been revealed against Aspergillus flavus. 38.2% of antidiabetic activity and 80% of cytotoxicity has been elucidated by N-doped TiO2 nanoparticles towards alpha-amylase enzyme and Artemia salina (brine shrimps), respectively. Moreover, notable protein kinase inhibition against Streptomyces and antioxidant effect including reducing power and % inhibition of DPPH has been demonstrated. This investigation unveils the more effective nature of N-doped TiO2 nanoparticles in comparison to undoped TiO2 nanoparticles indicated by various biological tests. Hence, N-doped TiO2 nanoparticles have more potential to be employed in biomedicine for the cure of numerous infections.

Small extracellular vesicles convey the stress-induced adaptive responses of melanoma cells

Exosomes are small extracellular vesicles (sEVs), playing a crucial role in the intercellular communication in physiological as well as pathological processes. Here, we aimed to study whether the melanoma-derived sEV-mediated communication could adapt to microenvironmental stresses. We compared B16F1 cell-derived sEVs released under normal and stress conditions, including cytostatic, heat and oxidative stress. The miRNome and proteome showed substantial differences across the sEV groups and bioinformatics analysis of the obtained data by the Ingenuity Pathway Analysis also revealed significant functional differences. The in silico predicted functional alterations of sEVs were validated by in vitro assays. For instance, melanoma-derived sEVs elicited by oxidative stress increased Ki-67 expression of mesenchymal stem cells (MSCs); cytostatic stress-resulted sEVs facilitated melanoma cell migration; all sEV groups supported microtissue generation of MSC-B16F1 co-cultures in a 3D tumour matrix model. Based on this study, we concluded that (i) molecular patterns of tumour-derived sEVs, dictated by the microenvironmental conditions, resulted in specific response patterns in the recipient cells; (ii) in silico analyses could be useful tools to predict different stress responses; (iii) alteration of the sEV-mediated communication of tumour cells might be a therapy-induced host response, with a potential influence on treatment efficacy.

Mechanoregulation of titanium dioxide nanoparticles in cancer therapy

Titanium dioxide (TiO₂) nanoparticles (NPs), first developed in the 1990s, have been applied in numerous biomedical fields such as tissue engineering and therapeutic drug development. In recent years, TiO₂-based drug delivery systems have demonstrated the ability to decrease the risk of tumorigenesis and improve cancer therapy. There is increasing research on the origin and effects of pristine and doped TiO₂-based nanotherapeutic drugs. However, the detailed molecular mechanisms by which drug delivery to cancer cells alters sensing of gene mutations, protein degradation, and metabolite changes as well as its associated cumulative effects that determine the microenvironmental mechanosensitive metabolism have not yet been clearly elucidated. This review focuses on the microenvironmental influence of TiO₂-NPs induced various mechanical stimuli on tumor cells. The differential expression of genome, proteome, and metabolome after treatment with TiO₂-NPs is summarized and discussed. In the tumor microenvironment, mechanosensitive DNA mutations, gene delivery, protein degradation, inflammatory responses, and cell viability affected by the mechanical stimuli of TiO₂-NPs are also examined.

Phytosynthesized metal oxide nanoparticles for pharmaceutical applications

Developments in nanotechnology field, specifically, metal oxide nanoparticles have attracted the attention of researchers due to their unique sensing, electronic, drug delivery, catalysis, optoelectronics, cosmetics, and space applications. Physicochemical methods are used to fabricate nanosized metal oxides; however, drawbacks such as high cost and toxic chemical involvement prevail. Recent researches focus on synthesizing metal oxide nanoparticles through green chemistry which helps in avoiding the involvement of toxic chemicals in the synthesis process. Bacteria, fungi, and plants are the biological sources that are utilized for the green nanoparticle synthesis. Due to drawbacks such as tedious maintenance and the time needed for the nanoparticle formation, plant extracts are widely used in nanoparticle production. In addition, plants are available all over the world and phytosynthesized nanoparticles show comparatively less toxicity towards mammalian cells. Secondary metabolites including flavonoids, terpenoids, and saponins are present in plant extracts, and these are highly responsible for nanoparticle formation and reduction of toxicity. Hence, this article gives an overview of recent developments in the phytosynthesis of metal oxide nanoparticles and their toxic analysis in various cells and animal models. Also, their possible mechanism in normal and cancer cells, pharmaceutical applications, and their efficiency in disease treatment are also discussed.

Bi0.9Ho0.1FeO3/TiO2 Composite Thin Films: Synthesis and Study of Optical, Electrical and Magnetic Properties

A visible light active Bi_0.9Ho_0.1FeO₃ nanoparticles/TiO₂ composite thin films with different mol.% of Bi_0.9Ho_0.1FeO₃ were successfully prepared via non-aqueous sol-gel method. The incorporation of 5, 10 and 20 mol.% Bi_0.9Ho_0.1FeO₃ nanoparticles in the precursor solution of TiO₂ brings modifications in the functional properties of the composite thin films. XPS analysis indicates that interdiffusion of Fe³⁺, Ho³⁺, Bi³⁺/Ti⁴⁺ ions through the interfaces between Bi_0.9Ho_0.1FeO₃ nanoparticles and TiO₂ matrix reduces the concentration of Ti³⁺ ions. X-ray diffraction analysis affirms that TiO₂ and Bi_0.9Ho_0.1FeO₃ retain anatase and orthorhombic phase respectively in composite films. The composite thin film containing 20 mol.% Bi_0.9Ho_0.1FeO₃ nanoparticles exhibits the most prominent absorption phenomenon in visible region and has significantly reduced indirect band gap of 2.46 eV compared to that of pure TiO₂ (3.4 eV). Hall effect measurements confirm that the resistivity of composite film increases by ∼2.33 orders of magnitude and its carrier concentration decreases by 1.8 orders of magnitude at 5 mol.% Bi_0.9Ho_0.1FeO₃ nanoparticles addition compared to those of pure TiO₂ film. Moreover, the pure film exhibits diamagnetism, whereas the composite films have both large ferromagnetic and small diamagnetic components. The findings in this research justify that the composite film can be a potential candidate for making improved photocatalyst, resistors and spintronic devices.

The impact of photocatalytic Ag/TiO2 and Ag/N-TiO2 nanoparticles on human keratinocytes and epithelial lung cells

The potential human health risks following the exposure to inorganic nanoparticles (NPs) is a very important issue for their application in leather finishing industry. The aim of our study was to investigate the cytotoxic effect of silver (Ag)/titanium dioxide (TiO₂) NPs on human cells. Photocatalytic NPs were prepared by electrochemical deposition of Ag on the surface of TiO₂ and nitrogen (N)-TiO₂ NPs and, subsequently, physico-chemical characterized. Then, a set of experiments have been performed to study the cytotoxicity and cell death mechanisms involved, the changes in cell morphology and the production of ROS induced in human keratinocytes (HaCaT) and human lung epithelial cells (A549) by exposure to NPs. Moreover, the changes in major signaling pathways and the inflammatory response induced by Ag/N-TiO₂ NPs in A549 cells were investigated. The data showed that cell death by late apoptosis/necrosis is induced in cells as function of the dose and the type of NPs and is characterized by morphological changes and cytoskeletal disorganization and an increase in reactive oxygen species (ROS) production. The exposure of A549 cells to Ag/N-TiO₂ NPs determine the activation of ERK1/2 MAP-kinase pathway and the release of pro-inflammatory mediators CXCL1, GM-CSF and MIF, known to be involved in the recruitment of circulating neutrophils and monocytes.

Oxidative stress mediated cytotoxicity of tin (IV) oxide (SnO2) nanoparticles in human breast cancer (MCF-7) cells

Due to unique optical and electronic properties tin oxide nanoparticles (SnO₂ NPs) have shown potential for various applications including solar cell, catalyst, and biomedicine. However, there is limited information concerning the interaction of SnO₂ NPs with human cells. In this study, we explored the potential mechanisms of cytotoxicity of SnO₂ NPs in human breast cancer (MCF-7) cells. Results demonstrated that SnO₂ NPs induce cell viability reduction, lactate dehydrogenase leakage, rounded cell morphology, cell cycle arrest and low mitochondrial membrane potential in dose- and time-dependent manner. SnO₂ NPs were also found to provoke oxidative stress evident by generation of reactive oxygen species (ROS), hydrogen peroxide (H₂O₂) and lipid peroxidation, while depletion of glutathione (GSH) level and lower activity of several antioxidant enzymes. Remarkably, we observed that ROS generation, GSH depletion, and cytotoxicity induced by SnO₂ NPs were effectively abrogated by antioxidant N-acetylcycteine. Our data have shown that SnO₂ NPs induce toxicity in MCF-7 cells via oxidative stress. This study warrants further research to explore the genotoxicity of SnO₂ NPs in different types of cancer cells.

Polystyrene-heterojunction semiconductor composite spheres prepared by a hydrothermal synthesis process: a recyclable photocatalyst under visible light irradiation for removing organic dyes from aqueous solution

The composite photocatalyst can absorb both insoluble and soluble organic dyes and can be recycled easily by filtering.