Nano-TiO2 Inhibits Development of the Central Nervous System and Its Mechanism in Offspring Mice

Nervous system exposure of different classes of nanoparticles: A review on potential toxicity and mechanistic studies

Nanoparticles (NPs) are generally defined as very small particles in the size range of 1-100 nm. Due to the rapid development of modern society, many new materials have been developed. The widespread use of NPs in medical applications, the food industry and the textile industry has led to an increase in NPs in the environment and the possibility of human contact, which poses a serious threat to human health. The nervous system plays a leading role in maintaining the integrity and unity of the body and maintaining a harmonious balance with the external environment. Therefore, based on two categories of organic and inorganic NPs, this paper systematically summarizes the toxic effects and mechanisms of NPs released into the nervous system. The results showed that exposure to NPs may damage the nervous system, decrease learning and cognitive ability, and affect embryonic development. Finally, a remediation scheme for NPs entering the body via the environment is also introduced. This scheme aims to reduce the neurotoxicity caused by NPs by supplementing NPs with a combination of antioxidant and anti-inflammatory compounds. The results provide a valuable reference for future research in this field.

Titanium Dioxide Nanoparticles Induce Maternal Preeclampsia-like Syndrome and Adverse Birth Outcomes via Disrupting Placental Function in SD Rats

The escalating utilization of titanium dioxide nanoparticles (TiO2 NPs) in everyday products has sparked concerns regarding their potential hazards to pregnant females and their offspring. To address these concerns and shed light on their undetermined adverse effects and mechanisms, we established a pregnant rat model to investigate the impacts of TiO2 NPs on both maternal and offspring health and to explore the underlying mechanisms of those impacts. Pregnant rats were orally administered TiO2 NPs at a dose of 5 mg/kg body weight per day from GD5 to GD18 during pregnancy. Maternal body weight, organ weight, and birth outcomes were monitored and recorded. Maternal pathological changes were examined by HE staining and TEM observation. Maternal blood pressure was assessed using a non-invasive blood analyzer, and the urinary protein level was determined using spot urine samples. Our findings revealed that TiO2 NPs triggered various pathological alterations in maternal liver, kidney, and spleen, and induced maternal preeclampsia-like syndrome, as well as leading to growth restriction in the offspring. Further examination unveiled that TiO2 NPs hindered trophoblastic cell invasion into the endometrium via the promotion of autophagy. Consistent hypertension and proteinuria resulted from the destroyed the kidney GBM. In total, an exposure to TiO2 NPs during pregnancy might increase the risk of human preeclampsia through increased maternal arterial pressure and urinary albumin levels, as well as causing fetal growth restriction in the offspring.

Neurotoxicity of Titanium Dioxide Nanoparticles: A Comprehensive Review

The increasing use of titanium dioxide nanoparticles (TiO2 NPs) across various fields has led to a growing concern regarding their environmental contamination and inevitable human exposure. Consequently, significant research efforts have been directed toward understanding the effects of TiO2 NPs on both humans and the environment. Notably, TiO2 NPs exposure has been associated with multiple impairments of the nervous system. This review aims to provide an overview of the documented neurotoxic effects of TiO2 NPs in different species and in vitro models. Following exposure, TiO2 NPs can reach the brain, although the specific mechanism and quantity of particles that cross the blood-brain barrier (BBB) remain unclear. Exposure to TiO2 NPs has been shown to induce oxidative stress, promote neuroinflammation, disrupt brain biochemistry, and ultimately impair neuronal function and structure. Subsequent neuronal damage may contribute to various behavioral disorders and play a significant role in the onset and progression of neurodevelopmental or neurodegenerative diseases. Moreover, the neurotoxic potential of TiO2 NPs can be influenced by various factors, including exposure characteristics and the physicochemical properties of the TiO2 NPs. However, a systematic comparison of the neurotoxic effects of TiO2 NPs with different characteristics under various exposure conditions is still lacking. Additionally, our understanding of the underlying neurotoxic mechanisms exerted by TiO2 NPs remains incomplete and fragmented. Given these knowledge gaps, it is imperative to further investigate the neurotoxic hazards and risks associated with exposure to TiO2 NPs.

Effects of ultra-processed foods on the microbiota-gut-brain axis: The bread-and-butter issue

The topic of gut microbiota and the microbiota-gut-brain (MGB) axis has become the forefront of research and reports in the past few years. The gut microbiota is a dynamic interface between the environment, food, and the host, reflecting the health status as well as maintaining normal physiological metabolism. Modern ultra-processed foods (UPF) contain large quantities of saturated and trans fat, added sugar, salt, and food additives that seriously affect the gut and physical health. In addition, these unhealthy components directly cause changes in gut microbiota functions and microbial metabolism, subsequently having the potential to impact the neural network. This paper reviews an overview of the link between UPF ingredients and the MGB axis. Considerable studies have examined that high intake of trans fat, added sugar and salt have deleterious effects on gut and brain functions, but relatively less focus has been placed on the impact of food additives on the MGB axis. Data from several studies suggest that food additives might be linked to metabolic diseases and inflammation. They may also alter the gut microbiota composition and microbial metabolites, which potentially affect cognition and behavior. Therefore, we emphasize that food additives including emulsifiers, artificial sweeteners, colorants, and preservatives interact with the gut microbiota and their possible effects on altering the brain and behavior based on the latest research. Future studies should further investigate whether gut dysbiosis mediates the effect of UPF on brain diseases and behavior. This thesis here sheds new light on future research pointing to the potentially detrimental effects of processed food consumption on brain health.

Exploring the Physicochemical, Electroactive, and Biodelivery Properties of Metal Nanoparticles on Peripheral Nerve Regeneration

Despite the advances in the regeneration/rehabilitation field of damaged tissues, the functional recovery of peripheral nerves (PNs), especially in a long gap injury, is considered a great medical challenge. Recent progress in nanomedicine has provided great hope for PN regeneration through the strategy of controlling cell behavior by metal nanoparticles individually or loaded on scaffolds/conduits. Despite the confirmed toxicity of metal nanoparticles due to long-term accumulation in nontarget tissues, they play a role in the damaged PN regeneration based on the topography modification of scaffolds/conduits, enhancing neurotrophic factor secretion, the ion flow improvement, and the regulation of electrical signals. Determining the fate of neural progenitor cells would be a major achievement in PN regeneration, which seems to be achievable by metal nanoparticles through altering cell vital approaches and controlling their functions. Therefore, in this literature, an attempt was made to provide an overview of the effective activities of metal nanoparticles on the PN regeneration, until the vital clues of the PN regeneration and how they are changed by metal nanoparticles are revealed to the researcher.

Prenatal titanium exposure and child neurodevelopment at 1 year of age: A longitudinal prospective birth cohort study

Previous animal studies provided the evidence that prenatal titanium exposure can cause neurotoxicity in their offspring, while human data is vacant. Our aim was to identify the associations of prenatal titanium exposure with the child neurodevelopment. Participants in present study were recruited during early pregnancy between 2014 and 2017. Urinary concentrations of titanium at first trimester were determined. We assessed child neurodevelopment using the Chinese version of Gesell Developmental Schedules at first year follow-up. The multivariable linear regressions and the robust modified Poisson regressions were used to estimate the associations of specific gravity corrected urinary titanium concentrations with the child neurodevelopment. In adjusted models, children's developmental quotient scores in the language domain were 2.03 points (95% CI: -3.66, -0.40) lower in the highest tertile of prenatal urinary titanium than in the lowest tertile. Also, children with prenatal urinary titanium in the highest tertile had 1.42 times (95% CI: 1.17, 1.72) increased risk of language development delay compared to those in the lowest tertile. No statistically significant associations were observed between titanium exposure and child development delay in motor, adaptive and social areas. The findings indicated that prenatal higher titanium exposure was associated with impaired language development, suggesting that titanium might act as developmental neurotoxicants.

A review on the impacts of nanomaterials on neuromodulation and neurological dysfunction using a zebrafish animal model

Nanomaterials have been widely employed from industrial to medical fields due to their small sizes and versatile characteristics. However, nanomaterials can also induce unexpected adverse effects on health. In particular, exposure of the nervous system to nanomaterials can cause serious neurological dysfunctions and neurodegenerative diseases. A number of studies have adopted various animal models to evaluate the neurotoxic effects of nanomaterials. Among them, zebrafish has become an attractive animal model for neurotoxicological studies due to several advantages, including the well-characterized nervous system, efficient genome editing, convenient generation of transgenic lines, high-resolution in vivo imaging, and an array of behavioral assays. In this review, we summarize recent studies on the neurotoxicological effects of nanomaterials, particularly engineered nanomaterials and nanoplastics, using zebrafish and discuss key findings with advantages and limitations of the zebrafish model in neurotoxicological studies.

Chronic maternal exposure to titanium dioxide nanoparticles alters breathing in newborn offspring

Background

Over the last two decades, nanotechnologies and the use of nanoparticles represent one of the greatest technological advances in many fields of human activity. Particles of titanium dioxide (TiO₂) are one of the nanomaterials most frequently found in everyday consumer products. But, due in particular to their extremely small size, TiO₂ nanoparticles (NPs) are prone to cross biological barriers and potentially lead to adverse health effects. The presence of TiO₂ NPs found in human placentae and in the infant meconium has indicated unequivocally the capacity for a materno-fetal transfer of this nanomaterial. Although chronic exposure to TiO₂ NPs during pregnancy is known to induce offspring cognitive deficits associated with neurotoxicity, the impact of a gestational exposure on a vital motor function such as respiration, whose functional emergence occurs during fetal development, remains unknown.

Results

Using in vivo whole-body plethysmographic recordings from neonatal mice, we show that a chronic exposure to TiO₂ NPs during pregnancy alters the respiratory activity of offspring, characterized by an abnormally elevated rate of breathing. Correspondingly, using ex vivo electrophysiological recordings performed on isolated brainstem-spinal cord preparations of newborn mice and medullary slice preparations containing specific nuclei controlling breathing frequency, we show that the spontaneously generated respiratory-related rhythm is significantly and abnormally accelerated in animals prenatally exposed to TiO₂ NPs. Moreover, such a chronic prenatal exposure was found to impair the capacity of respiratory neural circuitry to effectively adjust breathing rates in response to excitatory environmental stimuli such as an increase in ambient temperature.

Conclusions

Our findings thus demonstrate that a maternal exposure to TiO₂ NPs during pregnancy affects the normal development and operation of the respiratory centers in progeny.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00497-4.

Relationship between maternal exposure to heavy metal titanium and offspring congenital heart defects in Lanzhou, China: A nested case-control study

Background

Previous studies have found that exposure to heavy metals increased the incidence of congenital heart defects (CHDs). However, there is a paucity of information about the connection between exposure to titanium and CHDs. This study sought to examine the relationship between prenatal titanium exposure and the risk of CHDs in offspring.

Methods

We looked back on a birth cohort study that was carried out in our hospital between 2010 and 2012. The associations between titanium exposure and the risk of CHDs were analyzed by using logistic regression analysis to investigate titanium concentrations in maternal whole blood and fetal umbilical cord blood.

Results

A total of 97 case groups and 194 control groups were included for a nested case-control study. The [P₅₀ (P₂₅, P₇₅)] of titanium were 371.91 (188.85, 659.15) μg/L and 370.43 (264.86, 459.76) μg/L in serum titanium levels in pregnant women and in umbilical cord serum titanium content in the CHDs group, respectively. There was a moderate positive correlation between the concentration of titanium in pregnant women's blood and that in umbilical cord blood. A higher concentrations of maternal blood titanium level was associated with a greater risk of CHDs (OR 2.706, 95% CI 1.547–4.734), the multiple CHDs (OR 2.382, 95% CI 1.219–4.655), atrial septal defects (OR 2.367, 95% CI 1.215–4.609), and patent ductus arteriosus (OR 2.412, 95% CI 1.336–4.357). Dramatically higher concentrations of umbilical cord blood levels had an increased risk of CHDs and different heart defects.

Conclusion

Titanium can cross the placental barrier and the occurrence of CHDs may be related to titanium exposure.

Influence of heavy metals in Parkinson's disease: an overview

Parkinson's disease (PD) is an ageing disorder with deterioration of dopamine neurons which leads to motor complications like tremor, stiffness, slow movement and postural disturbances. In PD, both genetics as well as environmental factors both play a major role in causing the pathogenesis. Though there are surfeit of risk factors involved in PD occurrence, till now there is lack of an exact causative agent as a risk for PD with confirmative findings. The role of heavy metals reported to be a significant factor in PD pathogenesis. Heavy metal functions in cell maintenance but growing pieces of evidences reported to cause dyshomeostasis with increased PD rate. Metals disturb the molecular processes and results in oxidative stress, DNA damage, mitochondrial dysfunction, and apoptosis. The present review elucidates the role of cobalt, nickel, mercury, chromium, thallium metals in α-synuclein aggregation and its involvement in blood brain barrier flux. Also, the review explains the plausible role of aforementioned metals with a mechanistic approach and therapeutic recommendations in PD.

Chronic consumption of food-additives lead to changes via microbiota gut-brain axis

Some food additives have demonstrated to induce dysbiosis leading to the development gut and gastrointestinal diseases. In order to clarify how this dysbiosis affects the microbiota gut-brain axis, a systematic interpretative literature review is carried out in this work. This review was made in seven academic search engines using the keywords shown below. The main finding of this work is a clear link between the changes in the gut microbiota promoted by food additives and the causes that lead to many reported diseases related to chronic food additives consumption. Despite the findings, studies on the effects of food additives on microbiota are still insufficient. Therefore, this work should serve as a motivation for future research on this subject.

Polystyrene microplastics disturb maternal-fetal immune balance and cause reproductive toxicity in pregnant mice

Microplastics (MPs), which are emerging as a new type of environmental pollutants, have raised great concerns regarding their threats to human health. A successful pregnancy depends on the sophisticated regulation of the maternal-fetal immune balance, but the risks of polystyrene MP (PS-MP) exposure in early pregnancy remain unclear. In this study, we exposed the C57BL/6-mated BALB/c mice to PS-MP particles and used the flow cytometry to explore threats towards the immune system. Herein, the allogeneic mating murine model showed an elevated embryo resorption rate with a 10 μm PS-MP particle exposure during the peri-implantation period. Both the number and diameter of uterine arterioles decreased, which might reduce the uterine blood supply. Moreover, the percentage of decidual natural killer cells was reduced, whereas the helper T cells in the placenta increased. In addition, the M1/M2 ratio in macrophages reversed significantly to a dominant M2-subtype. Lastly, the cytokine secretion shifted towards an immunosuppressive state. Overall, our results demonstrated that PS-MPs have the potential to cause adverse effects on pregnancy outcomes via immune disturbance, providing new insights into the study of reproductive toxicity of MP particles in the human body.

Pregnancy exposure of titanium dioxide nanoparticles causes intestinal dysbiosis and neurobehavioral impairments that are not significant postnatally but emerge in adulthood of offspring

BACKGROUND

Pregnancy exposure to titanium dioxide nanoparticles (TiO2NPs) is a vital consideration due to their inadvertent ingestion from environmental contamination. The potential health effects of TiO2NPs on the neurodevelopmental process should be seriously concerned in health risk assessment, especially for the pregnant women who are susceptible to the neurodevelopmental toxicity of nano-sized particles. However, the available evidence of neurodevelopmental toxicity of TiO2NPs remains very limited.

METHODS

In the present study, the pregnant mice were intragastric administered with 150 mg/kg TiO2NPs from gestational day (GD) 8 to 21, the maternal behaviors and neurodevelopment-related indicators in offspring were all assessed at different time points after delivery. The gut microbial community in both dams and their offspring were detected by using 16S ribosomal RNA (rRNA) gene sequencing. The gut-brain axis related indicators were also determined in the offspring.

RESULTS

The results clearly demonstrated that exposure to TiO2NPs did not affect the maternal behaviors of pregnant mice, or cause the deficits on the developmental milestones and perturbations in the early postnatal development of offspring. Intriguingly, our data revealed that pregnancy exposure of TiO2NPs did not affect locomotor function, learning and memory ability and anxiety-like behavior in offspring at postnatal day (PD) 21, but resulted in obvious impairments on these neurobehaviors at PD49. Similar phenomena were obtained in the composition of gut microbial community, intestinal and brain pathological damage in offspring in adulthood. Moreover, the intestinal dysbiosis induced by TiO2NPs might be highly associated with the delayed appearance of neurobehavioral impairments in offspring, possibly occurring through disruption of gut-brain axis.

CONCLUSIONS

This is the first report elucidated that pregnancy exposure to TiO2NPs caused delayed appearance of neurobehavioral impairments in offspring when they reached adulthood, although these perturbations did not happen at early life after delivery. These findings will provide valuable insights about neurodevelopmental toxicity of TiO2NPs, and call for comprehensive health risk assessment of TiO2NPs on the susceptible population, such as pregnant women.

Damage to the Blood Brain Barrier Structure and Function from Nano Titanium Dioxide Exposure Involves the Destruction of Key Tight Junction Proteins in the Mouse Brain

Numerous studies have proven that nano titanium dioxide (nano TiO₂) can accumulate in animal brains, where it damages the blood brain barrier (BBB); however, whether this process involves destruction of tight junction proteins in the mouse brain has not been adequately investigated. In this study, mice were exposed to nano TiO₂ for 30 consecutive days, and then we used transmission electron microscopy to observe the BBB ultrastructure and the Evans blue assay to evaluate the permeability of the BBB. Our data suggested that nano TiO₂ damaged the BBB ultrastructure and increased BBB permeability. Furthermore, we used immunofluorescence and Western blotting to examine the expression of key tight junction proteins, including Occludin, ZO-1, and Claudin-5 in the mouse brain. Our data showed that nano TiO₂ reduced Occludin, ZO-1 and Claudin-5 expression. Taken together, nano TiO₂-induced damage to the BBB structure and function may involve the destruction of key tight junction proteins.

Biochemical assessment of the neurotoxicity of gold nanoparticles functionalized with colorectal cancer-targeting peptides in a rat model

The application of gold nanoparticle-peptide conjugates as theranostic agents for colorectal cancer shows much promise. This study aimed at determining the neurotoxic impact of 14 nm gold nanoparticles (AuNPs) functionalized with colorectal cancer-targeting peptides (namely p.C, p.L or p.14) in a rat model. Brain tissue samples, obtained from Wistar rats that received a single injection of citrate-capped AuNPs, polyethylene glycol-coated (PEG) AuNPs, p.C-PEG-AuNPs, p.L-PEG-AuNPs or p.14-PEG-AuNPs, and sacrificed after 2- and 12-weeks, respectively, were analysed. Inflammation marker (tumour necrosis factor-α, interleukin-6, interleukin-1β), oxidative stress (superoxide dismutase, catalase, glutathione peroxidase) and apoptotic biomarker (cytochrome c, caspase-3) levels were measured. Gold nanoparticle-treated groups sacrificed after 2-weeks did not exhibit any significant inflammatory, oxidative stress or apoptotic effects in brain tissue compared to the untreated control group. In brain tissue from rats that were exposed to citrate-capped AuNPs for 12-weeks, tumour necrosis factor-α and interleukin-6 levels were significantly increased compared to the untreated control. Exposure to PEG-AuNP, p.C-PEG-AuNP, p.L-PEG-AuNP and p.14-PEG-AuNP did not elicit significant toxic effects compared to the control after 12-weeks, as evidenced by the absence of inflammatory, oxidative stress and apoptotic effects in brain tissue. We thus report on the safety of PEG-coated AuNP-peptide conjugates for potential application in the diagnosis of colorectal cancer; however, exposure to citrate-capped AuNPs could induce delayed neuro-inflammation, and as such, warrants further investigation.

Fetotoxicity of Nanoparticles: Causes and Mechanisms

The application of nanoparticles in consumer products and nanomedicines has increased dramatically in the last decade. Concerns for the nano-safety of susceptible populations are growing. Due to the small size, nanoparticles have the potential to cross the placental barrier and cause toxicity in the fetus. This review aims to identify factors associated with nanoparticle-induced fetotoxicity and the mechanisms involved, providing a better understanding of nanotoxicity at the maternal–fetal interface. The contribution of the physicochemical properties of nanoparticles (NPs), maternal physiological, and pathological conditions to the fetotoxicity is highlighted. The underlying molecular mechanisms, including oxidative stress, DNA damage, apoptosis, and autophagy are summarized. Finally, perspectives and challenges related to nanoparticle-induced fetotoxicity are also discussed.

Developmental Toxicity of the Neural Tube Induced by Titanium Dioxide Nanoparticles in Mouse Embryos

Background:

This study investigated the potential effects of Titanium dioxide nanoparticles (Tio2NPs) followed by maternal gavage on fetal development and neural tube formation during pregnancy in mice.

Methods:

Thirty pregnant mice were randomly divided into five main study groups including the untreated control and 4 experimental groups (n=6 per group). The control group was treated with normal saline and the experimental groups were orally treated with doses of 30, 150, 300, and 500 mg/kg Body Weight (BW) of Tio2NPs during pregnancy. On gestational day 16 and 19 (n=3 per group), pregnant mice were euthanized and then examined for neural tube defects and compared with control. Serial transverse sections were prepared in both cranial region and in lumbar region of spinal cord.

Results:

Treatment with Tio2NPs resulted in low fetal weight and short length, dilation of lateral ventricle, thinning of cerebral cortex and spinal cord, spina bifida occulta and an increase in the number of apoptotic neurons in exposed embryos at doses of 300 and 500 mg/kg (p<0.05).

Conclusion:

It seems that exposure to nanoparticles of Tio2 during pregnancy induces growth retardation and for the first time, teratogenicity of this nanomaterial in neural tube development and induction of defects such as spinal bifida, reduction in cortical thickness and dilatation of lateral ventricles were verified which can be related to incidence of apoptosis in central nervous system.

The Beneficial Role of Filipendula ulmaria Extract in Prevention of Prodepressant Effect and Cognitive Impairment Induced by Nanoparticles of Calcium Phosphates in Rats

Mineral components of dental composites are used in many medical and dental applications, including preventive, restorative, and regenerative dentistry. To evaluate the behavioural alterations induced by nanosized particles of novel dental composites, by means of depressive level and cognitive functions, experimental groups of rats were chronically administered with nanosized hydroxyapatite (HA), tricalcium phosphate (TCP), and amorphous calcium phosphate (ACP) with or without simultaneous application of Filipendula ulmaria L. (FU) methanolic extract. The significant prodepressant action was observed in groups solely treated with HA and ACP. Besides, prolonged treatment with ACP also resulted in a significant decline in cognitive functions estimated in the novel object recognition test. The adverse impact of calcium phosphates on estimated behavioural functions was accompanied by increased oxidative damage and apoptotic markers in the prefrontal cortex, as well as diminished specific neurotrophin (BDNF) and gabaergic expression. The results of our investigation showed that simultaneous antioxidant supplementation with FU extract prevented calcium phosphate-induced behavioural disturbances, as well as prooxidative and apoptotic actions, with the simultaneous restoration of BDNF and GABA-A receptors in the prefrontal cortex. These findings suggest that FU may be useful in the prevention of prodepressant impact and cognitive decline as early as the manifestation of calcium phosphate-induced neurotoxicity.

Nanopolystyrene translocation and fetal deposition after acute lung exposure during late-stage pregnancy

BACKGROUND

Plastic is everywhere. It is used in food packaging, storage containers, electronics, furniture, clothing, and common single-use disposable items. Microplastic and nanoplastic particulates are formed from bulk fragmentation and disintegration of plastic pollution. Plastic particulates have recently been detected in indoor air and remote atmospheric fallout. Due to their small size, microplastic and nanoplastic particulate in the atmosphere can be inhaled and may pose a risk for human health, specifically in susceptible populations. When inhaled, nanosized particles have been shown to translocate across pulmonary cell barriers to secondary organs, including the placenta. However, the potential for maternal-to-fetal translocation of nanosized-plastic particles and the impact of nanoplastic deposition or accumulation on fetal health remain unknown. In this study we investigated whether nanopolystyrene particles can cross the placental barrier and deposit in fetal tissues after maternal pulmonary exposure.

RESULTS

Pregnant Sprague Dawley rats were exposed to 20 nm rhodamine-labeled nanopolystyrene beads (2.64 × 10¹⁴ particles) via intratracheal instillation on gestational day (GD) 19. Twenty-four hours later on GD 20, maternal and fetal tissues were evaluated using fluorescent optical imaging. Fetal tissues were fixed for particle visualization with hyperspectral microscopy. Using isolated placental perfusion, a known concentration of nanopolystyrene was injected into the uterine artery. Maternal and fetal effluents were collected for 180 min and assessed for polystyrene particle concentration. Twenty-four hours after maternal exposure, fetal and placental weights were significantly lower (7 and 8%, respectively) compared with controls. Nanopolystyrene particles were detected in the maternal lung, heart, and spleen. Polystyrene nanoparticles were also observed in the placenta, fetal liver, lungs, heart, kidney, and brain suggesting maternal lung-to-fetal tissue nanoparticle translocation in late stage pregnancy.

CONCLUSION

These studies confirm that maternal pulmonary exposure to nanopolystyrene results in the translocation of plastic particles to placental and fetal tissues and renders the fetoplacental unit vulnerable to adverse effects. These data are vital to the understanding of plastic particulate toxicology and the developmental origins of health and disease.

A key moment for TiO2: Prenatal exposure to TiO2 nanoparticles may inhibit the development of offspring

Applications of TiO₂ nanoparticles (NPs) in food, personal care products and industries pose risks on human health, particularly on vulnerable populations including pregnant women and infants. Fetus, deficient in mature defense system, is more susceptible to NPs. Publications on the developmental toxicity of TiO₂ NPs on the maternal-exposed progeny have emerged. This review presents the main exposure routes of TiO₂ NPs during pregnancy, including skin penetration, ingestion and inhalation, followed by transport of TiO₂ NPs to the placenta. Accumulation of TiO₂ NPs in placenta may cause dysfunction in nutrient transfer. TiO₂ NPs can be even transported to the fetus and generate toxicities, such as impairments of nervous and reproductive system, and failure in lung and cardiovascular development. The toxicities rely on the crystalline phase and concentrations, and the main mechanisms include the accumulation of excessive reactive oxygen species, DNA damage, and over-activation of signaling pathways such as MAPK which impairs neurotransmission. Finally, this review remarks on the significance for identifying TiO₂ NPs dosage safe for both mother and fetus, and particular attention should be paid at TiO₂ NPs concentrations safe for mother but toxic to fetus. Importantly, research on the epigenetic trans-generational inheritance of TiO₂ NPs is urgently needed to provide insights for deciding the prospects of TiO₂ NPs applications.

Rethinking Nano-TiO2 Safety: Overview of Toxic Effects in Humans and Aquatic Animals

Titanium dioxide nanoparticles (nano-TiO₂ ) are widely used in consumer products, raising environmental and health concerns. An overview of the toxic effects of nano-TiO₂ on human and environmental health is provided. A meta-analysis is conducted to analyze the toxicity of nano-TiO₂ to the liver, circulatory system, and DNA in humans. To assess the environmental impacts of nano-TiO₂ , aquatic environments that receive high nano-TiO₂ inputs are focused on, and the toxicity of nano-TiO₂ to aquatic organisms is discussed with regard to the present and predicted environmental concentrations. Genotoxicity, damage to membranes, inflammation and oxidative stress emerge as the main mechanisms of nano-TiO₂ toxicity. Furthermore, nano-TiO₂ can bind with free radicals and signal molecules, and interfere with the biochemical reactions on plasmalemma. At the higher organizational level, nano-TiO₂ toxicity is manifested as the negative effects on fitness-related organismal traits including feeding, reproduction and immunity in aquatic organisms. Bibliometric analysis reveals two major research hot spots including the molecular mechanisms of toxicity of nano-TiO₂ and the combined effects of nano-TiO₂ and other environmental factors such as light and pH. The possible measures to reduce the harmful effects of nano-TiO₂ on humans and non-target organisms has emerged as an underexplored topic requiring further investigation.

Nanomaterial integration into the scaffolding materials for nerve tissue engineering: a review

The nervous system, which consists of a complex network of millions of neurons, is one of the most highly intricate systems in the body. This complex network is responsible for the physiological and cognitive functions of the human body. Following injuries or degenerative diseases, damage to the nervous system is overwhelming because of its complexity and its limited regeneration capacity. However, neural tissue engineering currently has some capacities for repairing nerve deficits and promoting neural regeneration, with more developments in the future. Nevertheless, controlling the guidance of stem cell proliferation and differentiation is a challenging step towards this goal. Nanomaterials have the potential for the guidance of the stem cells towards the neural lineage which can overcome the pitfalls of the classical methods since they provide a unique microenvironment that facilitates cell-matrix and cell-cell interaction, and they can manipulate the cell signaling mechanisms to control stem cells' fate. In this article, the suitable cell sources and microenvironment cues for neuronal tissue engineering were examined. Afterward, the nanomaterials that impact stem cell proliferation and differentiation towards neuronal lineage were reviewed.

Molecular mechanism of nanoparticulate TiO2 induction of axonal development inhibition in rat primary cultured hippocampal neurons

Numerous studies have demonstrated the in vitro and in vivo neurotoxicity of nanoparticulate titanium dioxide (nano-TiO₂ ), a mass-produced material for a large number of commercial and industrial applications. The mechanism of nano-TiO₂ -induced inhibition of axonal development, however, is still unclear. In our study, primary cultured hippocampal neurons of 24-hour-old fetal Sprague-Dawley rats were exposed to 5, 15, or 30 μg/mL nano-TiO₂ for 6, 12, and 24 hours, and the toxic effects of nano-TiO₂ exposure on the axons development were detected and its molecular mechanism investigated. Nano-TiO₂ accumulated in hippocampal neurons and inhibited the development of axons as nano-TiO₂ concentrations increased. Increasing time in culture resulted in decreasing axon length by 32.5%, 36.6%, and 53.8% at 6 hours, by 49.4%, 53.8%, and 69.5% at 12 hours, and by 44.5%, 58.2%, and 63.6% at 24 hours, for 5, 15, and 30 μg/mL nano-TiO₂ , respectively. Furthermore, nano-TiO₂ downregulated expression of Netrin-1, growth-associated protein-43, and Neuropilin-1, and promoted an increase of semaphorin type 3A and Nogo-A. These studies suggest that nano-TiO₂ inhibited axonal development in rat primary cultured hippocampal neurons and this phenomenon is related to changes in the expression of axon growth-related factors.

Neurotoxicology of Nanomaterials

The remarkable advances coming about through nanotechnology promise to revolutionize many aspects of modern life; however, these advances come with a responsibility for due diligence to ensure that they are not accompanied by adverse consequences for human health or the environment. Many novel nanomaterials (having at least one dimension <100 nm) could be highly mobile if released into the environment and are also very reactive, which has raised concerns for potential adverse impacts including, among others, the potential for neurotoxicity. Several lines of evidence led to concerns for neurotoxicity, but perhaps none more than observations that inhaled nanoparticles impinging on the mucosal surface of the nasal epithelium could be internalized into olfactory receptor neurons and transported by axoplasmic transport into the olfactory bulbs without crossing the blood-brain barrier. From the olfactory bulb, there is concern that nanomaterials may be transported deeper into the brain and affect other brain structures. Of course, people will not be exposed to only engineered nanomaterials, but rather such exposures will occur in a complex mixture of environmental materials, some of which are incidentally generated particles of a similar inhalable size range to engineered nanomaterials. To date, most experimental studies of potential neurotoxicity of nanomaterials have not considered the potential exposure sources and pathways that could lead to exposure, and most studies of nanomaterial exposure have not considered potential neurotoxicity. Here, we present a review of potential sources of exposures to nanoparticles, along with a review of the literature on potential neurotoxicity of nanomaterials. We employ the linked concepts of an aggregate exposure pathway (AEP) and an adverse outcome pathway (AOP) to organize and present the material. The AEP includes a sequence of key events progressing from material sources, release to environmental media, external exposure, internal exposure, and distribution to the target site. The AOP begins with toxicant at the target site causing a molecular initiating event and, like the AEP, progress sequentially to actions at the level of the cell, organ, individual, and population. Reports of nanomaterial actions are described at every key event along the AEP and AOP, except for changes in exposed populations that have not yet been observed. At this last stage, however, there is ample evidence of population level effects from exposure to ambient air particles that may act similarly to engineered nanomaterials. The data give an overall impression that current exposure levels may be considerably lower than those reported experimentally to be neurotoxic. This impression, however, is tempered by the absence of long-term exposure studies with realistic routes and levels of exposure to address concerns for chronic accumulation of materials or damage. Further, missing across the board are "key event relationships", which are quantitative expressions linking the key events of either the AEP or the AOP, making it impossible to quantitatively project the likelihood of adverse neurotoxic effects from exposure to nanomaterials or to estimate margins of exposure for such relationships.

Retardation of Axonal and Dendritic Outgrowth Is Associated with the MAPK Signaling Pathway in Offspring Mice Following Maternal Exposure to Nanosized Titanium Dioxide

Exposure to nanosized titanium oxide (nano-TiO₂) has been proven to suppress brain growth in mouse offspring; however, whether retardation of axonal or dendritic outgrowth is associated with activation of the mitogen-activated protein kinase (MAPK) pathway remains unclear. In the present study, pregnant mice were exposed to nano-TiO₂ at 1.25, 2.5, and 5 mg/kg body weight, and the molecular mechanism of axonal or dendritic outgrowth retardation was investigated. The results suggested that nano-TiO₂ crossed the blood-fetal barrier and blood-brain barrier and deposited in the brain of offspring, which retarded axonal and dendritic outgrowth, including the absence of axonal outgrowth, and decreased dendritic filament length, dendritic branching number, and dendritic spine density. Importantly, maternal exposure to nano-TiO₂ increased phosphorylated (p)-extracellular signal-regulated kinase1/2 (ERK1/2, +24.35% to +59.4%), p-p38 (+60.82% to 181.85%), and p-c-jun N-terminal kinase (JNK, +28.28% to 97.28%) expression in the hippocampus of the offspring. These findings suggested that retardation of axonal and dendritic outgrowth in mouse offspring caused by maternal exposure to nano-TiO₂ may be related to excessive activation of the ERK1/2/MAPK signaling pathway. Therefore, the potential toxicity of nano-TiO₂ is a concern, especially in pregnant woman or children who are exposed to nano-TiO₂.

Toxic Effects of TiO₂ NPs on Zebrafish

Titanium dioxide nanoparticles (TiO₂ NPs) have become a widely used nanomaterial due to the photocatalytic activity and absorption of ultraviolet light of specific wavelengths. This study investigated the toxic effects of rutile TiO₂ NPs on zebrafish by examining its embryos and adults. In the embryo acute toxicity test, exposure to 100 mg/L TiO₂ NPs didn’t affect the hatching rate of zebrafish embryos, and there was no sign of deformity. In the adult toxicity test, the effects of TiO₂ NPs on oxidative damage in liver, intestine and gill tissue were studied. Enzyme linked immunosorbent assay (ELISA) and fluorescence-based quantitative real-time reverse transcription PCR (qRT-PCR) were used to detect the three antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT) and glutathione S transferase (GSTs) in the above mentioned zebrafish organs at protein and gene levels. The results showed that long-term exposure to TiO₂ NPs can cause oxidative damage to organisms; and compared with the control group, the activity of the three kinds of enzyme declined somewhat at the protein level. In addition, long-term exposure to TiO₂ NPs could cause high expression of CAT, SOD and GSTs in three organs of adult zebrafish in order to counter the adverse reaction. The effects of long-term exposure to TiO₂ NPs to adult zebrafish were more obvious in the liver and gill.