Aggravated visual toxicity in zebrafish larvae upon co-exposure to titanium dioxide nanoparticles and bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate

The bioavailability and toxicity of organic pollutants in aquatic organisms can be largely affected by the co-existed nanoparticles. However, the impacts of such combined exposure on the visual system remain largely unknown. Here, we systematically investigated the visual toxicity in zebrafish larvae after single or joint exposure to titanium dioxide nanoparticles (n-TiO2) and bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH) at environmentally relevant levels. Molecular dynamics simulations revealed the enhanced transmembrane capability of the complex than the individual, which accounted for the increased bioavailability of both TBPH and n-TiO2 when combined exposure to zebrafish. Transcriptome analysis showed that co-exposure to n-TiO2 and TBPH interfered with molecular pathways related to eye lens structure and sensory perception of zebrafish. Particularly, n-TiO2 or TBPH significantly suppressed the expression of βB1-crystallin and rhodopsin in zebrafish retina and lens, which was further enhanced after co-exposure. Moreover, we detected disorganized retinal histology, stunted lens development and significant visual behavioral changes of zebrafish under co-exposure condition. The overall results suggest that combined exposure to water borne n-TiO2 and TBPH increased their bioavailability, resulted in severer damage to optic nerve development and ultimately abnormal visual behavior patterns, highlighting the higher potential health risks of co-exposure to aquatic vertebrates.

Prevotella histicola Prevented Particle-Induced Osteolysis via Gut Microbiota-Dependent Modulation of Inflammation in Ti-Treated Mice

Wear particles generated from total joint replacements induce chronic osteolysis mediated by inflammatory upregulation, which leads to implant failure. Recent studies have suggested an important role of the gut microbiota in modulating the host's metabolism and immune system, leading to alterations in bone mass. Following gavage with P. histicola, micro-CT and HE staining revealed that osteolysis was significantly reduced in titanium (Ti)-treated mice. Immunofluorescence analysis revealed an increased macrophage (M)1/M2 ratio in the guts of Ti-treated mice, which decreased when P. histicola was added. P. histicola was also found to upregulate the tight junction proteins ZO-1, occludin, claudin-1, and MUC2 in the gut, reduce the levels of inflammatory factors IL-1β, IL-6, IL-8, and TNF-α, primarily in the ileum and colon, and decrease the expression of IL-1β and TNF-α and increase the level of IL-10 in the serum and cranium. Furthermore, P. histicola treatment resulted in a significant downregulation of CTX-1, RANKL, and RANKL/OPG. These findings demonstrate that P. histicola significantly mitigates osteolysis in Ti-treated mice by improving intestinal microbiota that repairs intestinal leakage and reduces systemic and local inflammation which in turn inhibits RANKL expression for bone resorption. P. histicola treatment may thus be therapeutically beneficial for particle-induced osteolysis.

Effects of surface nanomorphology on the senescence of periodontal ligament stem cells

OBJECTIVES

The effect of TiO2 nanotube morphology on the differentiation potency of senescent periodontal ligament stem cells was investigated.

METHODS

Two types of titanium sheets with TiO2 nanotube morphology (20V-NT and 70V-NT) were prepared via anodic oxidation at 20 and 70 V separately, and their surface morphology was observed. Young periodontal ligament stem cells were cultivated in an osteogenic induction medium, and the most effective surface morphology in promoting osteogenic differentiation was selected. RO3306 and Nutlin-3a were used to induce the aging of young periodontal ligament stem cells, and senescent periodontal ligament stem cells were obtained. The osteogenic differentiation of senescent periodontal ligament stem cells was induced, and the effect of surface morphology on osteogenic differentiation was observed.

RESULTS

Nanotube morphology was achieved on the surfaces of titanium sheets through anodic oxidation, and the diameters of the nanotubes increased with voltage. A significant difference in the effect of nanotube morphology was found among nanotubes with different diameters in the young periodontal ligament stem cells. The surface nanotube morphology of 20V-NT had a more significant effect that promoted osteogenic differentiation. Compared with a smooth titanium sheet, the surface nanotube morphology of 20V-NT increased the number of alkaline phosphatase-positive senescent periodontal ligament stem cells and promoted calcium deposition and the expression of osteogenic marker genes Runt-related transcription factor 2, osteopontin, and osteocalcin.

CONCLUSIONS

A special nanotube morphology enhances the differentiation ability of senescent periodontal ligament stem cells, provides an effective method for periodontal regeneration, and further improves the performance of implants.

Physiological and transcriptomic analysis reveals the toxic and protective mechanisms of marine microalga Chlorella pyrenoidosa in response to TiO2 nanoparticles and UV-B radiation

Concerns have been raised regarding the adverse effects of nanoparticles (NPs) on marine organisms, as an increasing number of NPs inevitably enter the marine environment with the development of nanotechnology. Owing to the photocatalytic properties, TiO2 NPs' toxicity may be aggravated by enhanced UV-B resulting from stratospheric ozone depletion. However, the molecular mechanisms of phytoplankton in response to TiO2 NPs under UV-B remains poorly understood. In this study, we integrated whole transcriptome analysis with physiological data to provide understanding on the toxic and protective mechanisms of marine Chlorella pyrenoidosa in response to TiO2 NPs under UV-B. The results indicated that the changes in gene expression could be related to the growth inhibition and TiO2 NP internalization in C. pyrenoidosa, and several molecular mechanisms were identified as toxicity response to TiO2 NPs and UV-B. Differential expression of genes involved in glycerophospholipids metabolism indicated that cell membrane disruption allowed TiO2 NPs to enter the algal cell under UV-B exposure, although the up-regulation of genes involved in the general secretory dependent pathway and the ATP-binding cassette transporter family drove cellular secretion of extracellular polymeric substances, acting as a barrier that prevent TiO2 NP internalization. The absence of changes in gene expression related to the antioxidant system may be responsible for the severe oxidative stress observed in algal cells following exposure to TiO2 NPs under UV-B irradiation. Moreover, differential expression of genes involved in pathways such as photosynthesis and energy metabolism were up-regulated, including the light-harvesting, photosynthetic electron transport coupled to photophosphorylation, carbon fixation, glycolysis, pentose phosphate pathway, tricarboxylic acid cycle, and oxidative phosphorylation, indicating that more energy and metabolites were supplied to cope with the toxicity of TiO2 NPs and UV-B. The obtained results provide valuable information on the molecular mechanisms of response of marine phytoplankton exposed to TiO2 NPs and UV-B.

Bioaccumulation of Titanium in diatom Cyclotella atomus Hust

Diatomaceous earth or diatomite is a fossil rock deposit of diatoms made up of silica and other minerals. A distinguishing feature of diatoms that placed them in the single class of microalgae Bacillariophyceae, is the frustule, a transparent, hard-shelled cell wall. It's interesting to note that the diatom has specific proteins and enzymes for heavy metal detoxification and can intake and store more heavy metals in its frustule. Consequently, an attempt has been made in this study to determine the bioaccumulation of metals in the frustules of the diatom. Hence, a centric diatom was isolated from the freshwater sample collected from the Adyar River, Chennai, Tamil Nadu. The diameter of the cell was 5-7.5 µm and 20-23 striations with radial arrangement. A single, dark off-center fultoportula and marginal fultoportula on the striae are found in the diatom. Additionally, one rimoportula between two marginal fultoportula distributed on the striae between the costa was also seen. As a result, the isolated diatom was morphologically identified as Cyclotella atomus Hust. Simultaneously, the bioaccumulation study reveals that the Titanium (Ti) was found accumulated in the frustules of the diatom incubated in the Ti-supplemented culture medium based on the scanning electron microscope-energy-dispersive X-ray analysis (SEM-EDAX). Therefore, the biogenic accumulation and fabrication of Titanium frustules in diatom have advantages in enhancing the efficiency of solar cells.

The interaction between titanium dioxide nanoparticles and light can have dualistic effects on the physiological responses of plants

The model plant Arabidopsis thaliana was exposed to combined stress factors, i.e., titanium dioxide nanoparticles (TiNPs) and high light. The concentrations of TiNPs used for irrigation were 250, 500, and 1000 μg/mL. This study shows that TiNPs alter the morphology and nanomechanical properties of chloroplasts in A. thaliana, which leads to a decrease in membrane elasticity. We found that TiNPs contributed to a delay in the thermal response of A. thaliana under dynamic light conditions, as revealed by non-invasive thermal imaging. The thermal time constants of TiNP-treated plants under excessive light are determined, showing a shortening in comparison to control plants. The results indicate that TiNPs may contribute to an alleviation of temperature stress experienced by plants under exposure to high light. In this research, we observed a decline in photosystem II photochemical efficiency accompanied by an increase in energy dissipation upon exposure to TiNPs. Interestingly, concentrations exceeding 250 µg/mL TiNPs appeared to mitigate the effects of high light, as shown by reduced differences in the values of specific OJIP parameters (FV/FM, ABS/RC, DI0/RC, and Pi_Abs) before and after light exposure.

AMPK activation enhances osteoblast differentiation on a titanium disc via autophagy

PURPOSE

The acquisition of osseointegration during implant therapy is slower and poorer in patients with diabetes compared with healthy persons. The serum concentration of adiponectin in patients with type II diabetes is lower than that of healthy persons via the suppression of AMP-activated protein kinase (AMPK). Therefore, we hypothesized that the AMPK activation enhances bone formation around implants, resulting in the improved acquisition of osseointegration. The purpose of this study was to evaluate the impact of AMPK activation on osteoblast differentiation and its mechanism of downstream signaling on titanium disc (Ti).

METHODS

Confluent mouse pre-osteoblasts (MC3T3-E1) cells (1 × 105 cells/well) were cultured with BMP-2 for osteoblast differentiation, in the presence or absence AICAR, an AMPK activator. We examined the effects of AMPK activation on osteoblast differentiation and the underlying mechanism on a Ti using a CCK8 assay, a luciferase assay, quantitative RT-PCR, and western blotting.

RESULTS

Although the proliferation rate of osteoblasts was not different between a Ti and a tissue culture polystyrene dish, the addition of AICAR, AMPK activator slightly enhanced osteoblast proliferation on the Ti. AICAR enhanced the BMP-2-dependent transcriptional activity on the Ti, leading to upregulation in the expression of osteogenesis-associated molecules. AICAR simultaneously upregulated the expression of autophagy-associated molecules on the Ti, especially LC3-II. AdipoRon, an adiponectin receptor type1/type2 activator activated AMPK, and upregulated osteogenesis-associated molecules on Ti.

CONCLUSIONS

AMPK activation enhances osteoblast differentiation on a Ti via autophagy, suggesting that it promotes the acquisition of osseointegration during implant therapy.

Macrophages in the process of osseointegration around the implant and their regulatory strategies

PURPOSE/AIM OF THE STUDY

To summarize and discuss macrophage properties and their roles and mechanisms in the process of osseointegration in a comprehensive manner, and to provide theoretical support and research direction for future implant surface modification efforts.

MATERIALS AND METHODS

Based on relevant high-quality articles, this article reviews the role of macrophages in various stages of osseointegration and methods of implant modification.

RESULTS AND CONCLUSIONS

Macrophages not only promote osseointegration through immunomodulation, but also secrete a variety of cytokines, which play a key role in the angiogenic and osteogenic phases of osseointegration. There is no "good" or "bad" difference between the M1 and M2 phenotypes of macrophages, but their timely presence and sequential switching play a crucial role in implant osseointegration. In the implant surface modification strategy, the induction of sequential activation of the M1 and M2 phenotypes of macrophages is a brighter prospect for implant surface modification than inducing the polarization of macrophages to the M1 or M2 phenotypes individually, which is a promising pathway to enhance the effect of osseointegration and increase the success rate of implant surgery.

Recombinant human secretory leukocyte protease inhibitor (rhSLPI) coated titanium enhanced human osteoblast adhesion and differentiation

Osseointegration is vital to success in orthopedic and dental reconstructions with implanted materials. The bone matrix or cells-particularly osteoblasts-are required to achieve functional contact on the implant surface. Osteoblast induction is therefore essential for osteogenesis to occur. Enhancement of osteoblast adhesion, proliferation, and differentiation, particularly by implant surface modifications, have been found challenging to develop. Secretory Leukocyte Protease Inhibitor (SLPI), a cation ionic protein with anti-inflammatory and anti-bacterial activities, showed activation in osteoblast proliferation and differentiation. However, the effects of coating recombinant human (rh) SLPI on a titanium alloy surface on human osteoblast adhesion, proliferation, and differentiation has never been investigated. In this study, titanium alloys (Ti-6Al-4V) were coated with rhSLPI, while human osteoblast adhesion, proliferation, differentiation, actin cytoskeletal organization, and gene expressions involved in cell adhesion and differentiation were investigated. The results indicate that coating titanium with 10-100 µg/ml rhSLPI enhanced the physical properties of the Ti surface and enhanced human osteoblast (hFOB 1.19) cell adhesion, activated actin dynamic, enhanced adhesive forces, upregulated integrins α1, α2, and α5, enhanced cell proliferation, mineralization, alkaline phosphatase activity, and upregulated ALP, OCN, and Runx2. This is the first study to demonstrate that coating SLPI on titanium surfaces enhances osseointegration and could be a candidate molecule for surface modification in medical implants.

Maternal exposure to nano-titanium dioxide impedes fetal development via endothelial-to-mesenchymal transition in the placental labyrinth in mice

BACKGROUND

Extensive production and usage of commercially available products containing TiO2 NPs have led to accumulation in the human body. The deposition of TiO2 NPs has even been detected in the human placenta, which raises concerns regarding fetal health. Previous studies regarding developmental toxicity have frequently focused on TiO2 NPs < 50 nm, whereas the potential adverse effects of large-sized TiO2 NPs received less attention. Placental vasculature is essential for maternal-fetal circulatory exchange and ensuring fetal growth. This study explores the impacts of TiO2 NPs (100 nm in size) on the placenta and fetal development and elucidates the underlying mechanism from the perspective of placental vasculature. Pregnant C57BL/6 mice were exposed to TiO2 NPs by gavage at daily dosages of 10, 50, and 250 mg/kg from gestational day 0.5-16.5.

RESULTS

TiO2 NPs penetrated the placenta and accumulated in the fetal mice. The fetuses in the TiO2 NP-exposed groups exhibited a dose-dependent decrease in body weight and length, as well as in placental weight and diameter. In vivo imaging showed an impaired placental barrier, and pathological examinations revealed a disrupted vascular network of the labyrinth upon TiO2 NP exposure. We also found an increase in gene expression related to the transforming growth factor-β (TGF-β) -SNAIL pathway and the upregulation of mesenchymal markers, accompanied by a reduction in endothelial markers. In addition, TiO2 NPs enhanced the gene expression responsible for the endothelial-to-mesenchymal transition (EndMT) in cultured human umbilical vein endothelial cells, whereas SNAIL knockdown attenuated the induction of EndMT phenotypes.

CONCLUSION

Our study revealed that maternal exposure to 100 nm TiO2 NPs disrupts placental vascular development and fetal mice growth through aberrant activation of EndMT in the placental labyrinth. These data provide novel insight into the mechanisms of developmental toxicity posed by NPs.

Micronano Titanium Accelerates Mesenchymal Stem Cells Aging through the Activation of Senescence-Associated Secretory Phenotype

Stem cell senescence is one of the most representative events of organism aging and is responsible for many physiological abnormalities and disorders. In the scenario of orthopedic disease treatment, stem cell aging may affect the implantation outcome and even lead to operation failure. To explore whether stem cell aging will affect the osteointegration effect of titanium implant, a widely used micronano titanium (MNT) was fabricated. We first verified the expected osteointegration effect of the MNT, which could be attributed to the improvement of stem cell adhesion and osteogenic differentiation. Then, we obtained aged-derived bone marrow mesenchymal stem cells (BMSCs) and studied their biological behaviors on MNT both in vitro and in vivo. We found that compared with normal rats, MNT did not significantly improve the osteointegration in aged rats. Compared with normal rats, fewer endogenous stem cells were observed at the implant-host interface, and the expression of p21 (senescence marker) was also higher. We further confirmed that MNT promoted the nuclear localization of NF-κB in senescent stem cells through the activation of p38 MAPK, thereby inducing the occurrence of the senescence-associated secretory phenotype (SASP) and ultimately leading to the depletion of the stem-cell pool at the implant-host interface. However, the activation of p38 MAPK can still promote the osteogenic differentiation of nonsenescent BMSCs. These results showed an interesting paradoxical balance between osteogenesis and senescence on MNT surfaces and also provided insights for the design of orthopedic implants for aging patients.

Titanium particles inhibit bone marrow mesenchymal stem cell osteogenic differentiation through the MAPK signaling pathway

Metallic implants have great application in clinical orthopedics. Implants wear out in vivo due to long-term mechanical loading. The formation of wear debris is one of the long-term complications of prosthesis. In the case of artificial joint replacement in particular, aseptic loosening is the most common reason for secondary revision surgery. Previous studies suggested that wear debris caused aseptic loosening mainly by promoting osteolysis around the prosthesis. In this study, titanium particles, the most commonly used particles in clinical practice, were selected to simulate wear debris and explore the influence of titanium particles on osteogenic differentiation of mesenchymal stem cells. Our results show that titanium particles can significantly inhibit osteogenic differentiation in a dose-dependent manner. While engaged in preliminary exploration of the underlying mechanisms, we found that titanium particles significantly affect phosphorylation of ERK1/2, a key component of MAPK signaling. This suggests that the MAPK signaling pathway is involved in the inhibition of osteogenic differentiation by titanium particles.

Effect of osteoblasts on osteoclast differentiation and activity induced by titanium with nanotopography

Titanium with nanotopography (Ti Nano) favors osteoblast differentiation and attenuates the osteoclast inhibitory effects on osteoblasts. Because the interactions between nanotopography and osteoclasts are underexplored, the aims of this study were to evaluate the effects of Ti Nano on osteoclast differentiation and activity, and the influence of osteoblasts on osteoclast-Ti Nano interaction. The discs were conditioned with a mixture of 10 N H2SO4 and 30% aqueous H2O2 to create Ti Nano and non-conditioned Ti discs were used as control (Ti Control). Osteoclasts were cultured on Ti Control and Ti Nano in the presence of osteoblasts in an indirect co-culture system. Also, osteoclasts were cultured on polystyrene and calcium phosphate plates in conditioned media by osteoblasts grown on Ti Control and Ti Nano. While Ti Control exhibited an irregular and smooth surface, Ti Nano presented nanopores distributed throughout the whole surface. Additionally, anisotropy was higher on Ti Nano than Ti Control. Nanotopography favored the gene expression of osteoclast markers but inhibited osteoclast differentiation and activity, and the presence of osteoblasts enhanced the effects of Ti Nano on osteoclasts. Such findings were mimicked by conditioned medium of osteoblasts cultured on Ti Nano, which reduced the osteoclast differentiation and activity. In conclusion, our results indicated that nanotopography regulates osteoblast-osteoclast crosstalk and further investigations should focus the impact of these bone cell interactions on Ti osseointegration.

Titanium biogenic nanoparticles to help the growth of Trichoderma harzianum to be used in biological control

BACKGROUND

The biogenic synthesis of metallic nanoparticles is a green alternative that reduces the toxicity of this nanomaterials and may enable a synergy between the metallic core and the biomolecules employed in the process enhancing biological activity. The aim of this study was to synthesize biogenic titanium nanoparticles using the filtrate of the fungus Trichoderma harzianum as a stabilizing agent, to obtain a potential biological activity against phytopathogens and mainly stimulate the growth of T. harzianum, enhancing its efficacy for biological control.

RESULTS

The synthesis was successful and reproductive structures remained in the suspension, showing faster and larger mycelial growth compared to commercial T. harzianum and filtrate. The nanoparticles with residual T. harzianum growth showed inhibitory potential against Sclerotinia sclerotiorum mycelial growth and the formation of new resistant structures. A great chitinolytic activity of the nanoparticles was observed in comparison with T. harzianum. In regard to toxicity evaluation, an absence of cytotoxicity and a protective effect of the nanoparticles was observed through MTT and Trypan blue assay. No genotoxicity was observed on V79-4 and 3T3 cell lines while HaCat showed higher sensitivity. Microorganisms of agricultural importance were not affected by the exposure to the nanoparticles, however a decrease in the number of nitrogen cycling bacteria was observed. In regard to phytotoxicity, the nanoparticles did not cause morphological and biochemical changes on soybean plants.

CONCLUSION

The production of biogenic nanoparticles was an essential factor in stimulating or maintaining structures that are important for biological control, showing that this may be an essential strategy to stimulate the growth of biocontrol organisms to promote more sustainable agriculture.

Engineered Fibrous NiTi Scaffolds with Cultured Hepatocytes for Liver Regeneration in Rats

At present, the use of alternative systems to replenish the lost functions of hepatic metabolism and partial replacement of liver organ failure is relevant, due to an increase in the incidence of various liver disorders, insufficiency, and cost of organs for transplantation, as well as the high cost of using the artificial liver systems. The development of low-cost intracorporeal systems for maintaining hepatic metabolism using tissue engineering, as a bridge before liver transplantation or completely replacing liver function, deserves special attention. In vivo applications of intracorporeal fibrous nickel-titanium scaffolds (FNTSs) with cultured hepatocytes are described. Hepatocytes cultured in FNTSs are superior to their injections in terms of liver function, survival time, and recovery in a CCl₄-induced cirrhosis rats' model. 232 animals were divided into 5 groups: control, CCl₄-induced cirrhosis, CCl₄-induced cirrhosis followed by implantation of cell-free FNTSs (sham surgery), CCl₄-induced cirrhosis followed by infusion of hepatocytes (2 mL, 10⁷ cells/mL), and CCl₄-induced cirrhosis followed by FNTS implantation with hepatocytes. Restoration of hepatocyte function in the FNTS implantation with the hepatocytes group was accompanied by a significant decrease in the level of aspartate aminotransferase (AsAT) in blood serum compared to the cirrhosis group. A significant decrease in the level of AsAT was noted after 15 days in the infused hepatocytes group. However, on the 30th day, the AsAT level increased and was close to the cirrhosis group due to the short-term effect after the introduction of hepatocytes without a scaffold. The changes in alanine aminotransferase (AlAT), alkaline phosphatase (AlP), total and direct bilirubin, serum protein, triacylglycerol, lactate, albumin, and lipoproteins were similar to those in AsAT. The survival time of animals was significantly longer in the FNTS implantation with hepatocytes group. The obtained results showed the scaffolds' ability to support hepatocellular metabolism. The development of hepatocytes in FNTS was studied in vivo using 12 animals using scanning electron microscopy. Hepatocytes demonstrated good adhesion to the scaffold wireframe and survival in allogeneic conditions. Mature tissue, including cellular and fibrous, filled the scaffold space by 98% in 28 days. The study shows the extent to which an implantable "auxiliary liver" compensates for the lack of liver function without replacement in rats.

The environmental remediation capacity of Ulva lactuca: the potential of macroalgae to reduce the threats caused by Titanium in marine invertebrate species

As a result of the wide use of Titanium (Ti) compounds in various products, Ti and Ti nanoparticles (nTi) are released into aquatic environments, inducing varying degrees of toxicity on aquatic fauna. Ulva lactuca, green macroalgae commonly found in coastal areas, has been extensively studied due to its worldwide distribution and capacity to accumulate trace elements under toxic conditions, which makes it a good universal sorbent. The present study aimed to establish the remediation properties of U. lactuca by evaluating the toxicity of Ti and nTi in bivalves, in the presence and absence of algae. Using the bivalve species Mytilus galloprovincialis, Ti toxicity was evaluated by assessing changes in mussel's metabolic capacity and oxidative status. Results evidenced cellular damage in M. galloprovincialis exposed to Ti and nTi. This was a result of the inactivation of antioxidant defences. The presence of U. lactuca limited cellular damage, however, this was not a result of the previously demonstrated bioremediation capacity, as no accumulation of Ti was verified in algal tissues. As a metabolic depression was verified for mussels exposed to Ti/nTi in the presence of algae, we hypothesise that U. lactuca may have been responsible for changes to the water quality which induced this response.

In Situ Growth of Tunable Gold Nanoparticles by Titania Nanotubes Templated Electrodeposition for Improving Osteogenesis through Modulating Macrophages Polarization

Driving macrophages M2 polarization has attracted growing attention for improving osteogenesis. Here, the in situ growth of tunable gold nanoparticles (AuNPs) on titania nanotubes (TiNTs) array was realized by electrodeposition, with the guidance of TiNTs. The fabricated Au layer showed excellent biocompatibility with different osteoimmune effects. Briefly, the Au deposition on 5 and 10 V anodized TiNTs surface could induce RAW264.7 cells to M2 polarization, whereas the Au deposition on 20 V anodized TiNTs surface showed M1 polarization, as indicated by various markers determination through immunofluorescence staining, qPCR, Western blot, and ELISA. Furthermore, the osteogenic differentiation of MC3T3-E1 was significantly enhanced by the macrophages conditioned medium from the Au@10VNTs surface. The in vivo tests also confirmed denser and thicker new trabecula bone formation and more M2 macrophages infiltration both on and adjacent to the Au@10VNTs implant surface. In mechanism, the cytokine array analysis of macrophages conditioned medium from the Au@10VNTs surface revealed the upregulation of pro-healing cytokines such as IL-10 and VEGF and downregulation of pro-inflammatory cytokines such as IL-1β and MCSF. In addition, the NF-κB pathway was significantly inhibited. In conclusion, the electrodeposition of a Au layer guided by TiNTs is a promising strategy for reducing postoperative inflammatory reactions and improving osseointegration through modulating macrophages polarization.

Exosome-Functionalized Ti6Al4V Scaffolds Promoting Osseointegration by Modulating Endogenous Osteogenesis and Osteoimmunity

Periprosthetic bone defects are the most serious problem of revision total hip arthroplasty, which can easily lead to insufficient osteointegration between the prosthesis and host bone. Bone marrow mesenchymal stem cells (BMSCs) and a moderate inflammatory response at the prosthesis-bone interface play an important role in osteointegration. Here, we developed microarc oxide titanium implant loaded engineered exosomes (S-Exos) to promote osseointegration at the prosthesis-bone interface. First, Smurf1-shRNA was transferred into the BMSCs using a viral vector to prepare S-Exos, which were subsequently immobilized to the microarc oxide titanium implant surface with positively charged polyethyleneimine. The immobilized S-Exos could be slowly and uniformly released and subsequently phagocytosed by BMSCs and macrophages. Once the S-Exos were phagocytosed, they could simultaneously activate the BMP/Smad signaling pathway in the BMSCs and promote macrophage M2 polarization, both of which enhance osseointegration. Specifically, this S-Exos coating exhibits a dual effect of promoting osseointegration, including the osseointegration of BMSCs by activating the BMP/Smad signaling pathway and the macrophage M2 polarization promoting osseointegration. In summary, the construction of S-Exos modified microarc oxide titanium implants could provide a new method for promoting osteointegration between the prosthesis and host bone in revision total hip arthroplasty.

circRNA422 enhanced osteogenic differentiation of bone marrow mesenchymal stem cells during early osseointegration through the SP7/LRP5 axis

Circular RNAs (circRNAs) play an important role in biological activities, especially in regulating osteogenic differentiation of stem cells. However, no studies have reported the role of circRNAs in early osseointegration. Here we identified a new circRNA, circRNA422, from rat bone marrow mesenchymal stem cells (BMSCs) cultured on sandblasted, large-grit, acid-etched titanium surfaces. The results showed that circRNA422 significantly enhanced osteogenic differentiation of BMSCs with increased expression levels of alkaline phosphatase, the SP7 transcription factor (SP7/osterix), and lipoprotein receptor-related protein 5 (LRP5). Silencing of circRNA422 had opposite effects. There were two SP7 binding sites on the LRP5 promoter, indicating a direct regulatory relationship between SP7 and LRP5. circRNA422 could regulate early osseointegration in in vivo experiments. These findings revealed an important function of circRNA422 during early osseointegration. Therefore, circRNA422 may be a potential therapeutic target for enhancing implant osseointegration.

Effects of Stress on Osteoblast Proliferation and Differentiation Based on Endoplasmic Reticulum Stress and Wntβ-Catenin Signaling Pathway

In order to investigate the effect of fluid shear stress on the proliferation of osteoblasts and the regulatory role of the Wnt/β-catenin signaling pathway in cell proliferation, a new method based on endoplasmic reticulum stress and Wnt/β-catenin signaling pathway stress-mediated was proposed. Taking MG63 osteoblasts as the research object, they were inoculated on glass slides (G group), polished titanium sheets (P group), and sandblasted acid-base treated pure titanium sheets (S group). In addition, FSS of 0 dunes/cm2 (static group) and 12 dunes/cm2 (stress group) were given, respectively. Then, quantitative reverse transcription-PCR (RT-qPCR) and western blot were used to detect the mRNA and protein expressions of low-density lipoprotein receptor-related protein 5 (LRP5) and β-catenin in MG63 cells. The results showed that the expression levels of β-catenin mRNA and protein in cells in the stress group were significantly increased (P < 0.05), and the protein expression level of LRP5 was significantly decreased (P < 0.05). The expression level of LRP5 in group S was greatly inhibited, while the expression level of β-catenin was significantly upregulated. Therefore, FSS can stimulate the expression of LRP5 and β-catenin in osteoblasts. Fluid shear stress can promote osteoblast proliferation in vitro; the Wnt/β-catenin signaling pathway is involved in regulating fluid shear stress to promote osteoblast proliferation.

Smoothies Reduce the “Bioaccessibility” of TiO2 (E 171) in the Model of the In Vitro Gastrointestinal Tract

The food colorant E171 (TiO₂) containing nano fractions can cause potential health problems. In the presented work, we used a “gastrointestinal tract” model (oral→large intestine) to “digest” a fruit smoothie in the presence of TiO₂ nanoparticles and the Lactiplantibacillus plantarum B strain. The TiO₂ migration was measured using the microfiltration membrane (0.2 µm; model of “TiO₂ bioacessability”). We observed that the addition of the smoothie reduced the Ti content in the microfiltrate (reduced “bioacessability”) at the “mouth”, “stomach” and “large intestine” stages, probably due to the entrapment of Ti by the smoothie components. A significant decrease in Ti “bioaccessibility” at the “gastric” stage may have resulted from the agglomeration of nanoparticles at a low pH. Additionally, the presence of bacterial cells reduced the “bioaccessibility” at the “large intestine” stage. Microscopic imaging (SEM) revealed clear morphological changes to the bacterial cells in the presence of TiO₂ (altered topography, shrunk-deformed cells with collapsed walls due to leakage of the content, indentations). Additionally, TiO₂ significantly reduced the growth of the tested bacteria. It can be stated that the interactions (most probably entrapment) of TiO₂ in the food matrix can occur during the digestion. This can influence the physicochemical properties, bioavailability and in vivo effect of TiO₂. Research aimed at understanding the interactions between TiO₂ and food components is in progress.

TiO2 Nanotopography-Driven Osteoblast Adhesion through Coulomb's Force Evolution

Nanotopography is an effective method to regulate cells' behaviors to improve Ti orthopaedic implants' in vivo performance. However, the mechanism underlying cellular matrix-nanotopography interactions that allows the modulation of cell adhesion has remained elusive. In this study, we have developed novel nanotopographic features on Ti substrates and studied human osteoblast (HOb) adhesion on nanotopographies to reveal the interactive mechanism regulating cell adhesion and spreading. Through nanoflat, nanoconvex, and nanoconcave TiO₂ nanotopographies, the evolution of Coulomb's force between the extracellular matrix and nanotopographies has been estimated and comparatively analyzed, along with the assessment of cellular responses of HOb. We show that HObs exhibited greater adhesion and spreading on nanoconvex surfaces where they formed super matured focal adhesions and an ordered actin cytoskeleton. It also demonstrated that Coulomb's force on nanoconvex features exhibits a more intense and concentrated evolution than that of nanoconcave features, which may result in a high dense distribution of fibronectin. Thus, this work is meaningful for novel Ti-based orthopaedic implants' surface designs for enhancing their in vivo performance.

Response of Saponaria officinalis L. hairy roots to the application of TiO2 nanoparticles in terms of production of valuable polyphenolic compounds and SO6 protein

Saponaria officinalis L. is a perennial plant from the Caryophyllaceae family whose various parts are used in traditional medicine as the treatment agent of skin diseases, blood purifier, diuretic, sudorific, and bile purifier. The cultivation system of hairy roots is a proper alternative for improving the valuable pharmaceutical compounds production compared to other in-vitro methods. The extensive nanotechnology applications in hairy roots cultivation is a sustainable production foundation to produce such active elements. In this study, the effect of various concentrations of titanium dioxide nanoparticles (TiO₂ NPs) (0, 10, 20, 30, 50 mg L^-1) with two treatments (24 and 48 h) was examined on the growth level, antioxidant capacity, total phenol and flavonoid contents, antioxidant enzyme activities, certain polyphenol compounds and SO6 protein in hairy roots of S. officinalis. According to the results, the maximum (3.09 g) and minimum (0.96 g) fresh weight (FW) of hairy roots were observed in treated culture media with 10 and 20 mg L^-1 of TiO₂ NPs after 24 and 48 h of exposure times, respectively. The highest rate of total phenol (9.79 mg GLA g^-1 FW) and total flavonoid contents (1.06 mg QE g^-1 FW) were obtained in the treated hairy roots with 50 and 30 mg L^-1 of nano elicitor in 24 and 48 h of treatments, respectively. The maximum level of most polyphenols, such as rosmarinic acid, cinnamic acid, and rutin, was produced in 24 h of treatment. The use of TiO₂ NP for 48 h with 50 mg L^-1 concentration showed the highest production level of SO6 protein.

Ammonia in the presence of nano titanium dioxide (nano-TiO2) induces greater oxidative damage in the gill and liver of female zebrafish

Water pollution caused by a highly hazardous chemical ammonia and a widespread application nanomaterials-nano titanium dioxide (n-TiO₂) in nature water has attracted extensive concern of the world. However, the potential joint effects of the two factors are unknown. Aim to investigate the potential interactive effects of ammonia and n-TiO₂ and the behind mechanisms, adult female zebrafish (Danio rerio) were co-exposed for 8 weeks by total ammonia nitrogen (TAN; 0, 3, 30 mg/L) and n-TiO₂ (0, 0.1, 1 mg/L) in different combination conditions based on a full-factorial design. The analysis of absorption kinetics confirmed that n-TiO₂ could absorb free ammonia (NH₃) in aqueous solution and the loss rate of free NH₃ increased with the rise of n-TiO₂ concentration. Consistent with this, free NH₃ concentrations in the gill and liver were higher in the presence of n-TiO₂ compared to TAN exposure alone. The increases of MDA and PC concentrations in the gill and liver of fish indicated that TAN and n-TiO₂ alone or in combination caused oxidative stress. Simultaneously, the activity and transcription of antioxidant enzymes (T-SOD, CuZn-SOD, Mn-SOD, CAT, GPx and GST) as well as antioxidant GSH contents were extensively inhibited by TAN and n-TiO₂ via Nrf2-Keap1 signaling. The significant interactive effects of TAN and n-TiO₂ were detected on levels of GSH, GST and gstr1 mRNA in the gill, and on levels of GSH, T-SOD, Mn-SOD, CAT levels as well as gpx1a and keap1 mRNAs in the liver, implying synergistic toxic risk of TAN and n-TiO₂. The more severe histopathological alterations and higher IBR analysis in co-treatment groups further proved that the existence of n-TiO₂ excavated ammonia-induced toxicity in the gill and liver, especially in liver. In conclusion, ammonia and n-TiO₂ have a synergistic toxic risk of fish health because ammonia and n-TiO₂ cause oxidative-antioxidative imbalance by inducing ROS overproduction.

Reactive oxygen species-inducing titanium peroxide nanoparticles as promising radiosensitizers for eliminating pancreatic cancer stem cells

BACKGROUND

Despite recent advances in radiotherapy, radioresistance in patients with pancreatic cancer remains a crucial dilemma for clinical treatment. Cancer stem cells (CSCs) represent a major factor in radioresistance. Developing a potent radiosensitizer may be a novel candidate for the eradication of pancreatic CSCs.

METHODS

CSCs were isolated from MIA PaCa-2 and PANC1 human pancreatic cancer cell lines. Titanium peroxide nanoparticles (TiOxNPs) were synthesized from titanium dioxide nanoparticles (TiO2NPs) and utilized as radiosensitizers when added one hour prior to radiation exposure. The antitumor activity of this novel therapeutic strategy was evaluated against well-established pancreatic CSCs model both in vitro and in vivo.

RESULTS

It is shown that TiOxNPs combined with ionizing radiation exhibit anti-cancer effects on radioresistant CSCs both in vitro and in vivo. TiOxNPs exhibited a synergistic effect with radiation on pancreatic CSC-enriched spheres by downregulating self-renewal regulatory factors and CSC surface markers. Moreover, combined treatment suppressed epithelial-mesenchymal transition, migration, and invasion properties in primary and aggressive pancreatic cancer cells by reducing the expression of proteins relevant to these processes. Notably, radiosensitizing TiOxNPs suppressed the growth of pancreatic xenografts following primary or dissociating sphere MIA PaCa-2 cell implantation. It is inferred that synergy is formed by generating intolerable levels of reactive oxygen species (ROS) and inactivating the AKT signaling pathway.

CONCLUSIONS

Our data suggested the use of TiOxNPs in combination with radiation may be considered an attractive therapeutic strategy to eliminate pancreatic CSCs.

Toxicity of TiO2 nanoparticles to the marine microalga Chaetoceros muelleri Lemmermann, 1898 under long-term exposure

Titanium dioxide nanoparticles (TiO₂NPs) have been extensively used in industry, raising many concerns about their release into the aquatic environments. In marine ecosystems, microalgae are major primary producers; among them, Chaetoceros muelleri is an important microalga in the aquaculture industry as live feed. The impacts of TiO₂NPs on the growth, photosynthetic pigments, protein and lipid contents, and the interaction of TiO₂NPs with the cell wall of C. muelleri were investigated in the present study. Algal cells were exposed to concentrations of 5, 10, 50, 100, 200, and 400 mg/L TiO₂NPs for 10 days. There was a significant difference in the growth between the control and TiO₂NPs treatments on each day. The half-maximal inhibitory concentration (IC₅₀) of TiO₂NPs on algal cells was found to be 10.08 and 5.01 mg/L on the 3rd and 10th days, respectively. The contents of chlorophyll a and c reduced significantly in the TiO₂NPs-treated microalgae. TiO₂NPs also reduced the protein and lipid contents in the treated microalgae, up to 13.02% and 47.6% respectively, at the highest concentration. The interaction of TiO₂NPs with the C. muelleri cells was obvious based on Fourier transform infrared spectroscopy, microscopic images, EDS, and Mapping analyses. Toxic effects of the released TiO₂NPs can damage the stocks of C. muelleri as an important live feed in mariculture.

Nanotopography Sequentially Mediates Human Mesenchymal Stem Cell-Derived Small Extracellular Vesicles for Enhancing Osteogenesis

Engineered small extracellular vesicles (sEVs) are used as tools to enhance therapeutic efficacy. However, such application of sEVs is associated with several issues, including high costs and a high risk of tumorigenesis. Nanotopography has a greater influence on bone-related cell behaviors. However, whether nanotopography specifically mediate sEV content to perform particular biological functions remains unclear. Here, we demonstrate that selective nanotopography may be used to sequentially mediate human bone mesenchymal stem cell (hBMSC) sEVs to enhance the therapeutic efficacy of hBMSCs-EVs for osteogenesis. We subjected sEVs harvested from hBMSCs cultured on polished titanium plates (Ti) or nanotopographical titanium plates (Ti4) after 7, 14, and 21 d for RNA sequencing, and we found that there was no significant difference in sEV-miRNA expression after 7 d. Differentially expressed osteogenic-related microRNAs were founded after 14 days, and KEGG analysis indicated that the main microRNAs were associated with osteogenesis-related pathways, such as TGF-beta, AMPK, and FoxO. A significant difference was found in sEV-miRNAs expression after 21 d. We loaded sEV secreted from hBMSCs cultured on Ti4 after 21 d on 3D-printed porous PEEK scaffolds with poly dopamine (PDA) and found that such scaffolds showed superior osteogenic ability after 6- and 12-weeks. Here, we demonstrate the alkali- and heat-treated nanotopography with the ability of stimulating osteogenic differentiation of hBMSC can induce the secretion of pro-osteogenesis sEV, and we also found that sEVs meditate osteogenesis through miRNA. Thus, whether nanotopography has the ability to regulate other contents of sEVs such as proteins for enhancing osteogenesis needs further research. These findings may help us use nanotopography to extract sEVs for other biomedical applications, including cancer therapy.

Trans-generational response of TiO2 nanoparticles in inducing variability and changes in biochemical pool of lentil F2 progenies

Investigations were carried out to analyze the role of anatase nanoparticles in inducing genetic variability in lentils (Lens culinaris Medik.) for yield improvement and subsequent involvement in development, quality, and biochemical response of second-generation seedlings through their lifecycle. Trans-generational alterations in the morphological and biochemical pool of the plant system were evaluated over a range of concentrations (25-200 µg/mL). Analysis of F₂ seedlings showed an increase in yield parameters at the lowest concentration (25 µg/mL). Biochemical studies revealed that the F₂ plants experienced lower oxidative stress as compared with previous generation plants. Quality analysis of seeds revealed a slight positive shift in the mean values of seed protein content at the lowest concentration. The effect of nanoparticles on the growth parameters was antagonistic except at the lowest concentration, where the growth parameters were found to be slightly higher than in the controls. The variability present in different traits in the F₂ populations was quantified as phenotypic variability and its components, which is a measure of the transmissibility of variations of the so-called mutated populations as a result of nanoparticle application.

TiO2 NPs induce the reproductive toxicity in mice with gestational diabetes mellitus through the effects on the endoplasmic reticulum stress signaling pathway

The effect of one of the most widely studied nanomaterials at present, TiO₂ nanoparticles (NPs), on pregnancy-related diseases is not clear. In this study, the adverse effects of TiO₂ NPs on mice with gestational diabetes mellitus (GDM) and their possible mechanism were investigated. GDM mice were orally administered 0, 10, 50 and 250 mg/kg TiO₂ NPs for 14 days. GDM reduced the weight of pregnant mice, destroyed the placental structure and caused abnormal fetal development. After exposure to increasing doses of TiO₂ NPs, blood glucose levels increased significantly and body weight further decreased in GDM mice. The accumulation of the Ti content was detected in the placenta and fetus, which may further damage the placental structure in GDM mice, thereby exacerbating abnormal fetal development. In addition, the MDA and SOD activities were obviously increased, and the expression of genes associated with endoplasmic reticulum stress (ERS) (PERK, eIF2α, AFT4, IRE1α, and XBP1s) and apoptosis (CHOP, JNK, Bax/Bcl-2, Caspase-12, Caspase-9, and Caspase-3) were also obviously increased in the placenta, which reflected the possible activation of apoptosis. It could be speculated that the reproductive toxicity of TiO₂ NPs in GDM mice triggered oxidative stress that subsequently activated ERS pathways to induce cell apoptosis.

Interaction of copper with titanium dioxide nanoparticles induced hematological and biochemical effects in Clarias gariepinus

The increasing demand for engineered nanomaterials induces potential harmful impact into aquatic ecosystems and is a great concern for freshwater biodiversity. The present study showed that enhancing toxic property of titanium dioxide nanoparticles (TiO₂ NPs) with copper (Cu) was responsible for the disruption of hormonal, hematological, and biochemical activities, in Clarias gariepinus. The study revealed that C. gariepinus intravenously injected with safe concentrations of TiO₂ NPs (3μg g) and Cu (2.5 μg g) alone and binary mixtures (TiO₂ NPs (3μg g) + Cu (2.5μg g)) for a period of 96h remarkably changed hormonal activities and hematological and biochemical indices of the fish. Our findings indicated that both chemicals accumulated in vital organs (the brain, serum, heart, gonad, liver, gills, serum, and kidney) and the presence of TiO₂ NPs enhanced the bioavailability of copper. Fish exposed to TiO₂ NPs alone significantly increased thyroxine (T₄) and further decreased triidothyronine (T₃). In addition, the binary mixtures showed antagonistic effects on both hormones. The hematological indices (WBC, RBC, HGt, MCV, MCH, MCHC, and Hct) were altered in all treatment groups. Decrease in WBC, RBC, HGt, Hct, and MCV were observed. Furthermore, the co-exposure further decreased WBC (60.28%), RBC (47.10%), HGt (75.99%), Hct (25.34%), and MCV (16.18%), in contrast, MCH and MCHC increased by of 2 folds, respectively. Metabolic enzymes alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) showed significant (p<0.05) increase, with additive effect in co-exposure. However, the alkaline phosphatase (ALP) activity decreased significantly in co-exposure. Significant (p<0.05) decrease of antioxidants, superoxide dismutase (SOD), glutathione transferase (GST), catalase (CAT), and metallothionein (Met) was observed in all the treatments with additive effect of 64.9%, 30.77%, and 91.31% in SOD, GST, and CAT, respectively. However, there was an increase in lipid peroxidation (MDA) in all treated fish. The results indicate that combined mixture influences the accumulation, hormonal, hematological, and biochemical factors which could affect the health of the fish.

Acute titanium dioxide nanoparticles exposure impaired spatial cognitive performance through neurotoxic and oxidative mechanisms in Wistar rats

CONTEXT

Titanium dioxide nanoparticles (TiO2-NPs) are used in many commercial products. However, their effects on human and animal organism remained to be clarified.

OBJECTIVE

The present study aimed to investigate the effects of TiO2-NPs on the behavioural performance, monoamine neurotransmitters and oxidative stress in the rat brain.

MATERIAL AND METHODS

Rats were injected intravenously with a single dose of TiO2-NPs (20 mg/kg body weight) and were subjected to cognitive and emotional tests using Morris water maze and elevated plus maze.

RESULTS

Cognitive capacity as well as the emotional reactivity were significantly disrupted, in TiO2-NPs-administered rats compared to control group. These behavioural effects were correlated with changes in brain neurotransmitter contents reflected by a significant increase in dopamine and a decrease in serotonin levels. TiO2-NPs also induced oxidative stress in the brain manifested by increased levels of H2O2 and malondialdehyde, associated with antioxidant enzymes activities disturbance, in particular, superoxide dismutase and catalase activities. Moreover, TiO2-NPs administration caused histological damages in the brain tissue with abundant lymphocytic clusters, capillary dilations, vascular congestion and oedema.

CONCLUSIONS

Acute intravenous injection of TiO2-NPs impaired behaviour performances through brain biochemical and structural changes and precautions should be taken to their usage in food additive and medical applications.

Long-Term Exposure to Nanosized TiO2 Triggers Stress Responses and Cell Death Pathways in Pulmonary Epithelial Cells

There is little in vitro data available on long-term effects of TiO₂ exposure. Such data are important for improving the understanding of underlying mechanisms of adverse health effects of TiO₂. Here, we exposed pulmonary epithelial cells to two doses (0.96 and 1.92 µg/cm²) of TiO₂ for 13 weeks and effects on cell cycle and cell death mechanisms, i.e., apoptosis and autophagy were determined after 4, 8 and 13 weeks of exposure. Changes in telomere length, cellular protein levels and lipid classes were also analyzed at 13 weeks of exposure. We observed that the TiO₂ exposure increased the fraction of cells in G1-phase and reduced the fraction of cells in G2-phase, which was accompanied by an increase in the fraction of late apoptotic/necrotic cells. This corresponded with an induced expression of key apoptotic proteins i.e., BAD and BAX, and an accumulation of several lipid classes involved in cellular stress and apoptosis. These findings were further supported by quantitative proteome profiling data showing an increase in proteins involved in cell stress and genomic maintenance pathways following TiO₂ exposure. Altogether, we suggest that cell stress response and cell death pathways may be important molecular events in long-term health effects of TiO₂.

Comparison of Different Surgical Systems for Treatment of Early-onset Scoliosis in the Context of Release of Titanium Ions

STUDY DESIGN

Case-control study.

OBJECTIVE

The aim of the study was to compare growth-friendly systems: traditional growing rod, guided growth systems (GGS), and vertical expandable prosthetic titanium rib in the context of titanium release.

SUMMARY OF BACKGROUND DATA

The problem of scoliosis affects even up to 3% of the population, and ca. 0.1% of patients need surgical treatment. Surgical treatment carries the risk of a long-term presence of implants in the organism, which may result in release of metal ions into the tissues and bloodstream.

METHODS

Seventy-one patients (13.5 ± 3.54 years' old) were treated for spinal deformity using various surgical systems and the samples of paraspinal tissue, blood, nails, and hair were collected before and after treatment. The quantification of titanium was performed using inductively coupled plasma optical emission spectrometry.

RESULTS

The metallic particles were released into the peri-implant tissue, and the greatest amounts of titanium were detected in patients with GGS. The concentration of soluble titanium forms in subcutaneous tissue (ST) was low and do not statistically differ from control. The average titanium content in the paraspinal tissue in patients with GGS was two- to three-fold higher than the average value in the other investigated groups. A slightly increased level of titanium compared with the control was noted in all studied groups of patients. The highest content of titanium in blood was observed in patients with the GGS system.

CONCLUSION

Neverless the system used, the concentration of soluble titanium forms in both ST and blood was only slightly higher than in the control and did not exceed the allowable levels. The increased level of titanium with GGS system is probably associated with the friction between implant components, whereas the components in the other systems are immobile relative to each other.Level of Evidence: 3.

TiO2 nanoparticles dose, application method and phosphorous levels influence genotoxicity in Rice (Oryza sativa L.), soil enzymatic activities and plant growth

The present study focused on investigating the effect of titanium dioxide nanoparticles (TiO₂NPs) on rice (Oryza sativa L.) growth and changes in soil health in two contrasting soil textures (silt-loam and clay). Moreover, response of rice to different methods of TiO₂NPs application and phosphorous fertilizer levels were also evaluated. For toxicity assessment, pot experiment was carried out. TiO₂NPs (0, 500, 750 mg kg^-1) were applied and plants were grown till vegetative stage. After harvesting, physiological parameters, stress assay, soil microbial and enzymatic activities were determined. Based on the results of toxicity study, impact of three methods of TiO₂NPs application (foliar, irrigation, soil) and four phosphorous fertilizer levels (0, 10, 20, 40 mg kg^-1) on rice growth were assessed. During the 1st phase, results showed an adverse effect of TiO₂NPs on plant growth and soil microorganisms in both soil textures at 750 mg kg^-1. The H₂O₂ production, lipid peroxidation and leaf membrane injury index were increased by 4.3-, 2.4-, and 1.9-folds in clay soil upon 750 mg kg^-1 TiO₂NPs application. Likewise, at the same level of TiO₂NPs; microbial biomass, dehydrogenase, and respiration were decreased by 0.91-, 0.79-, and 0.78- folds respectively. In 2nd phase, maximum shoot length, biomass, phosphorous uptake and rice grain protein content were observed under application of TiO₂NPs (500 mg kg^-1) through irrigation method in combination with 40 mg P kg^-1. However, 20 and 40 mg P kg^-1 performed equally well upon TiO₂NPs application and the results were not statistically significant. The results suggest that 750 mg kg^-1 of TiO₂NPs negatively affect plant growth and soil enzymatic activities. Moreover, combined application of TiO₂NPs (500 mg kg^-1) through irrigation and 20 mg P kg^-1 is recommended to be the optimum for growth of rice plant.

Uptake, excretion and toxicity of titanate nanotubes in three stains of free-living ciliates of the genus Tetrahymena

The potential exposure of titanate nanotubes (TNTs) to wildlife and humans may occur as a result of increased use and application as functional nanomaterials. However, there is a dearth of knowledge regarding the pathways of uptake and excretion of TNTs and their toxicity in cells. In this study, three strains of the Tetrahymena genus of free-living ciliates, including a wild type strain (SB210) and two mutant strains (SB255: mucocyst-deficient; NP1: temperature-sensitive "mouthless''), were used to study the pathways of uptake and excretion and evaluate the cytotoxicity of TNTs. The three Tetrahymena strains were separately exposed to 0, 0.01, 0.1, 1 or 10 mg/L of TNTs, and cells were collected at different time points for quantification of intracellular TNTs (e.g., 5, 10, 20, 40, 60, 90 and 120 min) and evaluation of cytotoxicity (12 and 24 h). TNT contents in NP1 and SB255 were greater or comparable to the contents in SB210 while exposure to 10 mg/L TNTs in 120 min. Furthermore, exposure to 10 mg/L TNTs for 24 h caused greater decreases in cell density of NP1 (38.2 %) and SB255 (36.8 %) compared with SB210 (26.5 %) and upregulated the expression of caspase 15 in SB210. Taken together, our results suggested that TNT uptake by pinocytosis and excretion by exocytosis in Tetrahymena, and the exposure could cause cytotoxicity which can offer novel insights into the accumulation kinetics of nanotubes and even nanomaterials in single cell.

Food-Grade Titanium Dioxide Particles Decreased the Bioaccessibility of Vitamin D3 in the Simulated Human Gastrointestinal Tract

Food-grade titanium dioxide (E171) particles, as a "whiteness" additive, are often co-ingested with lipid-rich foods. Therefore, we explored the impact of E171 on lipid digestion and vitamin D₃ (VD₃) bioaccessibility encapsulated within oil-in-water emulsions in a simulated human gastrointestinal tract (GIT) model. VD₃ bioaccessibility significantly decreased from 80 to 74% when raising E171 from 0 to 0.5 wt %. The extent of lipid digestion was reduced by E171 addition in a dose-dependent manner. VD₃ bioaccessibility was positively correlated with the final amount of free fatty acids (FFAs) produced by lipid digestion (R² = 0.95), suggesting that the reduction in VD₃ bioaccessibility was due to the inhibition of lipid digestion by E171. Further experiments showed that E171 interacted with lipase and calcium ions, thereby interfering with lipid digestion. The findings of this study enhance our understanding toward the potential impact of E171 on the nutritional attributes of foods for human digestion health.

Toxic effects of TiO2 NPs in the blood-milk barrier of the maternal dams and growth of offspring

Titanium dioxide nanoparticles (TiO₂ NPs) are amongst the most frequently used nanomaterial in everyday consumer products, and their widespread applications have raised concerns of the consequent deleterious effects on human health, particularly to vulnerable populations, such as lactating females remains elusive. Therefore, this study was initiated to investigate the detrimental effects and toxic mechanisms induced by TiO₂ NPs in maternal dams and offspring during the lactation period. Dams were randomly divided into three groups. The water (Control; Group I) and TiO₂ NPs (100 mg/kg; Group II) were orally administered from postnatal day 1-20, respectively. The results indicated that TiO₂ NPs could cause toxicity in the dams, such as pathological damages to mammary gland tissues. The excessive accumulation of TiO₂ NPs could induce oxidative stress in the mammary gland, leading to the dysfunctional blood-milk barrier; besides, TiO₂ NPs could also be transferred to offspring via breastfeeding, causing abnormal development of infant. We further accessed the possible underlying molecular mechanism; for this, we orally administered TiO₂ NPs with vitamin E (100 mg/kg; Group III). The results revealed that toxicity induced by TiO₂ NPs was rescued. Collectively, this study presented the deleterious pathological effects of oral exposure to TiO₂ NPs in the mammary gland tissues and blood-milk barrier via the production of reactive oxygen species (ROS) in dams and developmental concerns in offspring. However, the administration of VE could mitigate the toxic effects induced by the TiO₂ NPs.

Restraining the TiO2 nanoparticles-induced intestinal inflammation mediated by gut microbiota in juvenile rats via ingestion of Lactobacillus rhamnosus GG

Human were given a lot of opportunities to ingest TiO₂ NPs in the environment. Children have low, sensitive intestinal tolerance, and they could be exposed to higher levels of TiO₂ NPs than adults. Few studies have been conducted on the interaction between TiO₂ NPs and juvenile intestine phase models. Thus, in this work, weaning rats were orally exposed to TiO₂ NPs for 7 and 14 days. Results indicate that Ti accumulated in the intestine, liver, and feces. Inflammatory infiltration damage was observed in the colonic epithelial tissue, and gut microbiota fluctuated with a decreased abundance of Lactobacilli in feces. Oral supplementation with Lactobacillus rhamnosus GG (LGG) lessened TiO₂ NPs-induced colonic inflammatory injury, which might due to downregulation of nuclear factor kappa-B (NF-κB). Meanwhile, LGG maintained normal intestinal microbiome homeostasis, thereby improving TiO₂ NPs-induced colon injury in juvenile rats. Moreover, fecal microbiota transplant (FMT) experiment indicated possible TiO₂ NPs-induced intestinal microbiota disorder led to colonic inflammation. Our works suggested the urgent need for additional studies on the risk safety assessment, mechanism, and prevention of juvenile health damage from exposure to TiO₂ NPs.

Urinary Oxidative Stress Biomarkers in Workers of a Titanium Dioxide Based Pigment Production Plant

Titanium dioxide is produced or imported into the EU for over one million tons/year. The International Agency for Research on Cancer (IARC) classification is 2B, a possible inhalation carcinogen for humans. This study evaluates urinary biomarkers of oxidative stress in workers of a plant producing TiO2 pigment powder, having 0.25 µm average particle size and an ultrafine fraction, compared to unexposed subjects. Urine samples were collected from forty workers before and after the shift, from six employees of the same company and eighteen volunteers from the same geographical area. Titanium and other metals concentrations were measured by ICP-MS, while DNA, RNA, and protein oxidation products by HPLC/MS-MS. A statistically significant increase was found for the urinary concentration of Al, Cd, Cr, Cu, Fe, Mn, Pb, Ti, and Zr, and for all biomarkers of oxidative stress in post-shift workers' urine samples. Urinary concentrations after the working shift were higher than for employees and volunteers pooled together for Cd, Mn, and Zr, and for the oxidative stress biomarkers 8-oxoGuo, 8-oxodGuo, and 3NO2Tyr. Biomonitoring studies on dose and effect biomarkers for TiO2 occupational exposure provide information useful for protecting workers' health even in conditions that comply with health and safety standards, highlighting reversible effects of chronic exposure at very low doses.

Influence of TiO2 on Mucosal Permeation of Aceclofenac: Analysis of Crystal Strain and Dislocation Density

Titanium dioxide can adhere with human epithelial cells and have good tolerability. Present work has been undertaken to explore the influence of TiO2 on mucosal permeation of aceclofenac. Mucosal permeation of aeclofenac solution containing TiO2 has been carried out. In fourier transform infrared spectrosopy (FTIR), the intensity of the peaks has decreased along with the increase of TiO2 content in the formulation indicating a possible binding between drug and TiO2. Melting enthalpy has been decreased with the increased content of TiO2 in the solid. The status of crystal strain and dislocation density of TiO2 and aceclofenac in the solid state formulation has also been evaluated from Xray Diffraction data using Debye-Scherrer's equation. Mucosal permeation of aceclofenac has shown sustained effect for more than 20 h in presence of titanium dioxide. Titanium dioxide could be used in designing formulation for sustaining mucosal aceclofenac delivery after performing risk assessment study.

Effects of titanium dioxide nanoparticles on the intestine, liver, and kidney of Danio rerio

Titanium dioxide nanoparticles (Np-TiO₂) have become the common component of sunscreen cosmetic products. Np-TiO₂ can affect especially aquatic ecosystems health, including aquatic organisms such as fish. It is therefore necessary to acquire a better understanding of the effect of Np-TiO₂ on aquatic organisms. This study evaluated the biological effects of Np-TiO₂ on Danio rerio, such as survival rate and weight change and, in particular, the Ti content or retention in the intestine and liver, as well as the activities of catalase and superoxide dismutase enzymes. In addition, the structure of the intestine, kidney, and liver was investigated through histological analysis. Ninety zebrafish were used, randomly divided into three treatment-groups: a control group (fed with food without adding Np-TiO₂) and two groups of fish fed with food containing Np-TiO₂ exposed for 7 and 14 days. The amount of Ti in the liver and intestine was measured using atomic absorption spectrophotometry coupled to a graphite furnace (GFAAS). Morphological analysis and enzyme catalase and superoxide dismutase assays were likewise performed. Ti was detected in all fish even in control group; probably Ti must have been introduced during production by the fish food industry. Structural changes were detected in fish fed with Np-TiO₂ as vacuolization and disruption of the apical cytoplasm of epithelial cells that covered the intestinal villi. Although kidney morphology appeared intact, the lumen of the proximal tubule was enlarged, and the cells of the distal tubule were vacuolated. No morphological changes in the liver were detected; however, superoxide dismutase activity decreased, suggesting that liver changes occurred at the molecular level. Thus, Np-TiO₂ causes morphological changes in the intestine, kidney, and liver of zebrafish and biochemical changes in the liver exposed for 7 and 14 days. Although not highly lethal, Np-TiO₂ in the food chain can interfere with the morphophysiology of aquatic organisms. Neither mortalities nor body weight losses were recorded among fish in all groups over the duration of the experiment.

Environmental transformation of n-TiO2 in the aquatic systems and their ecotoxicity in bivalve mollusks: A systematic review

Over the past decades, titanium dioxide nanoparticles (n-TiO₂) have been extensively used in several industrial applications and the manufacture of novel consumer products. Although strict regulations have been put in place to limit their release into the aquatic environment, these nanoparticles can still be found at elevated levels within the environment, which can result in toxic effects on exposed organisms and has possible implications in term of public health. Bivalve mollusks are a unique and ideal group of shellfish for the study and monitoring the aquatic pollution by n-TiO₂ because of their filter-feeding behaviour and ability to accumulate toxicants in their tissues. In these animals, exposure to n-TiO₂ leads to oxidative stress, immunotoxicity, neurotoxicity, and genotoxicity, as well as behavioral and physiological changes. This review summarizes the uptake, accumulation, and fate of n-TiO₂ in aquatic environments and the possible interactions between n-TiO₂ and other contaminants such as heavy metals and organic pollutants. Moreover, the toxicological impacts and mechanisms of action are discussed for a wide range of bivalve mollusks. This data underlines the pressing need for additional knowledge and future research plans for the development of control strategies to mitigate the release of n-TiO₂ to the aquatic environment to prevent the toxicological impacts on bivalves and protect public health.

An in vivo study of nanorod, nanosphere, and nanowire forms of titanium dioxide using Drosophila melanogaster: toxicity, cellular uptake, oxidative stress, and DNA damage

The biological impact of nanomaterials (NMs) is determined by several factors such as size and shape, which need to be taken into consideration in any type of analysis. While investigators often prefer to conduct in vitro studies for detection of any possible adverse effects of NMs, in vivo approaches yield more relevant data for risk assessment. For this reason, Drosophila melanogaster was selected as a suitable in vivo model to characterize the potential risks associated with exposure nanorods (NRs), nanospheres (NSs), nanowires (NWs) forms of titanium dioxide (TiO₂), and their microparticulated (or bulk) form, as TiO₂. Third instar larvae (72 hr old larvae) were fed with TiO₂ (NRs, NSs, or NWs) and TiO₂ at concentrations ranging from 0.01 to 10 mM. Viability (toxicity), internalization (cellular uptake), intracellular reactive oxygen species (ROS) production, and genotoxicity (Comet assay) were the end-points evaluated in hemocyte D. melanogaster larvae. Significant intracellular oxidative stress and genotoxicity were noted at the highest exposure concentration (10 mM) of TiO₂ (NRs, NSs, or NWs), as determined by the Comet assay and ROS analysis, respectively. A concentration-effect relationship was observed in hemocytes exposed to the NMs. Data demonstrated that selected forms of TiO₂.-induced genotoxicity in D. melanogaster larvae hemocytes indicating this organism is susceptible for use as a model to examine in vivo NMs-mediated effects.

Total and subcellular Ti distribution and detoxification processes in Pontoporia blainvillei and Steno bredanensis dolphins from Southeastern Brazil

Titanium (Ti), used in many dailyuse products, such as shampoos and sunscreen filters, in the form of TiO₂ nanoparticles (NPs), may elicit adverse marine biota effects. Marine mammal Ti data is scarce, and subcellular distribution and detoxification information is non-existent. Ti concentrations and metalloprotein detoxification in Pontoporia blainvillei and Steno bredanensis dolphins from Southeastern Brazil were assessed. Metallothionein (MT) concentrations were determined spectrophotometrically, total and subcellular Ti, by ICP-MS and detoxification, by HPLC-ICP-MS. Ti detoxification occurred through MT complexation. Statistical Ti-MT associations were observed in S. bredanensis liver, indicating TiO₂ NPs contamination, as Ti binds to MT only as NPs. MT-Ti correlations were observed for both the coastal (P. blainvillei) and offshore (S. bredanensis) dolphins, evidencing oceanic TiO₂ diffusion. Ti detoxification through binding to reduced glutathione occurred in both species. Thermostable subcellular fractions are a valuable tool for cetacean Ti detoxification assessments and should be applied to conservation efforts.

The role of Fe oxyhydroxide coating, illite clay, and peat moss in nanoscale titanium dioxide (nTiO2) retention and transport in geochemically heterogeneous media

Natural media such as soil and sediment contain mineralogical and organic components with distinct chemical, surface, and electrostatic properties. To better understand the role of various soil and sediment components on particle transport, columns were packed with quartz sand and natural sediment with added Fe oxyhydroxide coating, illite clay, and peat moss to investigate how these added components influence nTiO₂ retention and transport in geochemically heterogeneous medium. Results showed that nTiO₂ transport was low at pH 5, attributable to the electrostatic attraction between positively-charged nTiO₂ and negatively-charged medium. While illite did not notably affect nTiO₂ transport at pH 5, Fe oxyhydroxide coating increased nTiO₂ transport due to electrostatic repulsion between Fe oxyhydroxide and nTiO₂. Peat moss also increased nTiO₂ transport at pH 5, attributable to the increased DOC concentration, which resulted in higher DOC adsorption to nTiO₂ and intensified electrostatic repulsion between nTiO₂ and the medium. At pH 9, nTiO₂ transport was high due to the electrostatic repulsion between negatively-charged nTiO₂ and medium surfaces. Fe oxyhydroxide coating at pH 9 slightly delayed nTiO₂ transport due to electrostatic attraction, while illite clay and peat moss substantially inhibited nTiO₂ transport via straining/entrapment or electrostatic attraction. Overall, this study demonstrated that pH has a considerable effect on how minerals and organic components of a medium influence nTiO₂ transport. At low pH, electrostatic attraction was the dominant mechanism, therefore, nTiO₂ mobility was low regardless of the differences in mineralogical and organic components. Conversely, nTiO₂ mobility was high at high pH and nTiO₂ retention was dominated by straining/entrapment and sensitive to the mineralogical and organic composition of the medium.

A novel method for biosynthesis of different polymorphs of TiO2 nanoparticles as a protector for Bacillus thuringiensis from Ultra Violet

Bacillus thuringiensis (Bt) were used for biosynthesis of amorphous TiO2 converted to distinct polymorphs (anatase, rutile, mix) under different temperature conditions. Characterizations of TiO2 nanoparticles were performed by using X-ray diffraction spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and, energy-dispersive X-ray spectroscopy (EDX) analysis. Stability of five formulations under ultraviolet (UV) radiation with spore viability and mortality test on Ephestia kuehniella Zeller larvae were investigated. TiO2(mix) showed the highest viabilities of 79.76% after exposure to ultraviolet (UVA385 nm), while viabilities of non-protected spores under these conditions were 41.32%. The mortality of TiO2(mix), TiO2(anatase), TiO2(rutile), TiO2(amorphous) and free spore formulations on second-instar larvae of Ephestia kuehniella were 73.76%, 71.24%, 57.12%, 51.32%, and 50.32%, respectively on the 10th day of the experiment. The obtained results suggest that TiO2(amorphous) does not increase Bt resistance, but both phases of TiO2 nanoparticles synthesized (anatase and rutile) through the Bacillus thuringiensis and phase mixture can increase the persistence of Bt to the UV light. Furthermore, the combination of both crystalline phases of TiO2(mix) has the highest performance in improving the Bt resistance.

Effects of statherin on the biological properties of titanium metals subjected to different surface modification

The failure of dental implants is usually caused by bacteria infection, poor bioactivity and biocompatibility. It is a common phenomenon clinically. Statherin, a salivary protein, plays a crucial role of mediator between materials and cells/bacteria. However, the conformation of statherin might be changed by the implants in vivo. In this study, we investigated the effects of statherin on the bioactivities, antibacterial abilities and biocompatibilities of the titanium metals and the reaction mechanism. We found that the conformation of statherin was mainly influenced by surface composition, surface structure, surface roughness, surface hydrophilia and Ti-OH groups of materials. Statherin could decrease the cell biocompatibility of the titanium metals including pure titanium (PT), anodic oxidation (AO), sandblasting and etching (SLA) and plasma spraying hydroxyapatite (HA) coating in HGF cell experiments, regulate the bio-mineralization ability of HA coating in SBF, and enhance the antibacterial properties of PT and HA coating. This study revealed that surface properties of materials could change the conformation of statherin, which influenced the bioactivities, antibacterial properties and biocompatibilities of the materials in return.

TiO2 nanoparticles and multi-walled carbon nanotubes monitoring and bioremediation potential using ciliates Pseudocohnilembus persalinus

In recent years, the release of nanomaterials pollutants to water bodies, to a great extent, attributed to anthropogenic activities. Their impacts on aquatic organisms as well as nanomaterial monitoring and bioremediation using organism have drawn much attentions. However, studies on relationship of nano-contaminants and aquatic organisms are very scarce. Our results showed that titanium dioxide nanoparticles (TiO₂-NPs) and Multi-walled carbon nanotubes (MWCNTs) caused an obvious cell decreases on the whole, but a significant increase at 48 h TiO₂-NPs exposure, indicating a resistant mechanism in ciliates for nano-toxic. Besides, MWCNTs was more toxic to Pseudocohnilembus persalinus than that of TiO₂-NPs in terms of EC₅₀ value. It is firstly found that P. persalinus ingested and released TiO₂-NPs through cytostome and cytoproct, which might be the reason that TiO₂-NPs less toxic than MWCNTs. The significantly increased superoxide dismutase (SOD) and glutathione S-transferase (GST) enzyme activities and expression levels were evaluated by reactive oxygen species ROS generation, which demonstrated that P. persalinus antioxidant defense enzyme played roles on nano-toxic resistant in ciliates. Moreover, the integrated biomarker response (IBR) was also determined, which demonstrated that MWCNTs had comparatively higher values than those of TiO₂-NPs after higher concentration exposure to ciliates. In addition, it was confirmed by the present work that sod, gst and cat played different roles on immunity, and the sensitivity of cat gene expression to these two nanomaterials exposure was dissimilar. Damages of shrunk as well as losses of cilia on the cell surface caused by TiO₂-NPs and MWCNTs exposure in P. persalinus using SEM revealed possible physical hazards of aggregated nanomaterials. Our findings will be helpful to understand the effect mechanisms of NPs on ciliates, and also demonstrated the possibility of P. persalinus as bio-indicator of nanomaterials in aquatic and potentials on bioremediation.

Translocation of transition metal oxide nanoparticles to breast milk and offspring: The necessity of bridging mother-offspring-integration toxicological assessments

Although infant nanomaterial exposure is a worldwide concern, breastfeeding transfer of transition metal-oxide nanoparticles to as well as their toxicity to offspring are still unclear. Breastfeeding transmits nutrition and immunity from mothers to their offspring; it also provides a portal for maternal toxins to enter offspring. Thus, a toxicology assessment of both mothers and their offspring should be established to monitor nanomaterial exposure during lactation. Here, we determined the effects of the exposure route on the biodistribution, biopersistence, and toxicology of nanoparticles (titanium dioxide, zinc oxide, and zirconium dioxide) in both mouse dams and their offspring. Oral and airway exposure routes were tested using gavage and intranasal administration, respectively. Biodistribution in the main organs (breast, liver, spleen, lung, kidney, intestine, and brain) and biopersistence in the blood and milk were determined using inductively coupled plasma mass spectrometry. Hematology and histomorphology analyses were performed to determine the toxicology of the nanoparticles. A reduced offspring body weight was found with the reduced nanoparticle size. Furthermore, both oral and airway exposure increased the nanoparticle concentrations in the main tissues and milk. More nanoparticles were transferred into maternal tissues and milk via airway exposure than via oral exposure. During the transfer of the metal from the exposed nanoparticles to milk, the immune cell pathway played a more important role in the airway route than in the oral exposure route. Finally, maternal exposure via both the oral and airway routes reduced the body weight and survival rate of their breastfeeding offspring, which could possibly be attributed to the toxicity of nanoparticles to blood cells and organs. In conclusion, maternal exposure to nanoparticles led to a reduced body weight and survival rate in breastfed offspring, and nanoparticle exposure via the airway route led to a higher immune response and tissue injury than that via the oral exposure route. This study suggests that the use of products containing metal nanoparticles in breastfeeding mothers and their offspring should be reconsidered to maintain a safe breastfeeding system.

Diminishing bioavailability and toxicity of P25 TiO2 NPs during continuous exposure to marine algae Chlorella sp

Titanium dioxide nanoparticles (TiO₂ NPs) find applications in our day-to-day life because of unique physicochemical properties. Their release into the aquatic environment poses a possible risk to the organisms. However, the continuing exposure of NPs might reduce their bioavailability to marine organisms owing to aggregation and sedimentation in the aqueous systems thus significantly reducing their toxic impact. In this regard, the present study investigates the effect of continuous exposure of TiO₂ NPs to marine microalgae Chlorella sp. under UV-A irradiation through "tanks in series" mode of experiments. In a three-cycle experiment, concentration of TiO₂ NPs in the first cycle was fixed at 62.6 μM, and the interacted nanoparticles was subsequently exposed to fresh batches of algae in the next two cycles. After the interaction, the NPs underwent severe aggregation (mean hydrodynamic diameter 3000 ± 18.2 nm after cycle I) leading to gravitational settling in the medium and thus decreased bioavailability. The aggregation can be attributed to interactions between the particles themselves (homo-aggregation) further aggravated by the presence of the algal cells (hetero-aggregation). Cellular viability after cycle I was found to be only 24.2 ± 2.5%, and it was enhanced to 96.5 ± 2.8% after the cycle III in the course of continuous exposure. The results were validated with estimation of oxidative stress markers such as intracellular ROS (total ROS, superoxide and hydroxyl radicals) and LPO after each cycle of exposure. The continuing decrease in the EPS across the cycles further confirmed the diminishing toxicity of the NPs.