Toxicological aspects of long-term treatment of keratinocytes with ZnO and TiO2 nanoparticles

Assessment of myco-fabricated Al2O3 NPs toxicity on cancer cells and pathogenic microbes by suppression of bacterial metabolic key enzymes

There has been a recent change in global attention towards addressing antimicrobial resistance (AMR) as a result of the concerning increase in mortality rates. Nanomaterials have become highly favorable options for a wide range of industrial and biological uses. The objective of this study was to produce aluminum oxide nanoparticles (Al2O3 NPs) using a crude extract from the fungus Aspergillus sp. WAH23, and then analyze the nanoparticles using UV-analysis, electron microscopy (TEM and SEM), and (FT-IR) and X-ray diffraction (XRD). Results revealed that formed nanoparticles are spherical with an average size of 8.5 nm. XRD analysis confirmed the crystalline nature of the synthesized Al2O3 NPs. The Al2O3 nanoparticles exhibited antibacterial properties against a wide range of pathogenic microbes. The antibacterial efficacy of these nanoparticles on the examined bacterial strains was exhibited through their ability to hinder several metabolic processes, including phosphofructokinase (PFK), enolase, and glutamine synthetase. Additionally, the nanoparticles increased the activity of NADH-oxidase, the content of MDA, and the formation of H2O2. The study also examined the anticancer properties of Al2O3 nanoparticles on various types of cancer cells.

Anti-dengue potential and mosquitocidal effect of marine green algae-stabilized Mn-doped superparamagnetic iron oxide nanoparticles (Mn-SPIONs): an eco-friendly approach

Vector-borne diseases pose a significant public health challenge in economically disadvantaged nations. Malaria, dengue fever, chikungunya, Zika, yellow fever, Japanese encephalitis, and lymphatic filariasis are spread by mosquitoes. Consequently, the most effective method of preventing these diseases is to eliminate the mosquito population. Historically, the majority of control programs have depended on chemical pesticides, including organochlorines, organophosphates, carbamates, and pyrethroids. Synthetic insecticides used to eradicate pests have the potential to contaminate groundwater, surface water, beneficial soil organisms, and non-target species. Nanotechnology is an innovative technology that has the potential to be used in insect control with great precision. The goal of this study was to test the in vitro anti-dengue potential and mosquitocidal activity of Chaetomorpha aerea and C. aerea-synthesized Mn-doped superparamagnetic iron oxide nanoparticles (CA-Mn-SPIONs). The synthesis of CA-Mn-SPIONs using C. aerea extract was verified by the observable alteration in the colour of the reaction mixture, transitioning from a pale green colour to a brown. The study of UV-Vis spectra revealed absorbance peaks at approximately 290 nm, which can be attributed to the surface Plasmon resonance of the CA-Mn-SPIONs. The SEM, TEM, EDX, FTIR, vibrating sample magnetometry, and XRD analyses provided evidence that confirmed the presence of CA-Mn-SPIONs. In the present study, results revealed that C. aerea aqueous extract LC50 values against Ae. aegypti ranged from 222.942 (first instar larvae) to 349.877 ppm in bioassays (pupae). CA-Mn-SPIONs had LC50 ranging from 20.199 (first instar larvae) to 26.918 ppm (pupae). After treatment with 40 ppm CA-Mn-SPIONs and 500 ppm C. aerea extract in ovicidal tests, egg hatchability was lowered by 100%. Oviposition deterrence experiments showed that in Ae. aegypti, oviposition rates were lowered by more than 66% by 100 ppm of green algal extract and by more than 71% by 10 ppm of CA-Mn-SPIONs (oviposition activity index values were 0.50 and 0.55, respectively). Moreover, in vitro anti-dengue activity of CA-Mn-SPIONs has good anti-viral property against dengue viral cell lines. In addition, GC-MS analysis showed that 21 intriguing chemicals were discovered. Two significant phytoconstituents in the methanol extract of C. aerea include butanoic acid and palmitic acid. These two substances were examined using an in silico methodology against the NS5 methyltransferase protein and demonstrated good glide scores and binding affinities. Finally, we looked into the morphological damage and fluorescent emission of third instar Ae. aegypti larvae treated with CA-Mn-SPIONs. Fluorescent emission is consistent with ROS formation of CA-Mn-SPIONs against Ae. aegypti larvae. The present study determines that the key variables for the successful development of new insecticidal agents are rooted in the eco-compatibility and the provision of alternative tool for the pesticide manufacturing sector.

Doxorubicin and folic acid-loaded zinc oxide nanoparticles-based combined anti-tumor and anti-inflammatory approach for enhanced anti-cancer therapy

BACKGROUND

Zinc oxide nanoparticles (ZnONPs) have impressively shown their efficacy in targeting and therapy of cancer. The present research was designated to investigate the potential of ZnONP nanocomposites as a cancer chemotherapeutic-based drug delivery system and to assess the anti-tumor and anti-inflammatory effectiveness of ZnONP nanocomposites combination with systemic chemotherapeutic drugs doxorubicin (DOX) and folic acid (FA) in Ehrlich ascites carcinoma (EAC) tumor cell line both in vitro and in vivo.

METHODS

Anti-tumor potential of ZnONP nanocomposites: ZnONPs, ZnONPs/FA, ZnONPs/DOX and ZnONPs/DOX/FA against EAC tumor cell line was evaluated in vitro by MTT assay. Anti-tumor and anti-inflammatory efficacy of ZnONP nanocomposites were analyzed in vivo by examination of the proliferation rate and apoptosis rate of EAC tumor cells by flow cytometry, splenocytes count, level of inflammatory markers interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α), as well as liver and kidney function in EAC-challenged mice.

RESULTS

In vitro results showed that ZnONP nanocomposites showed a high anti-proliferative potency against EAC tumor cells. Furthermore, the in vivo study revealed that the treatment EAC-challenged mice with ZnONPs, ZnONPs/DOX, ZnONPs/FA and ZnONPs/DOX/FA hindered the proliferation rate of implanted EAC tumor cells through lowering their number and increasing their apoptosis rate. Moreover, the treatment of EAC-challenged mice with ZnONPs/DOX/FA markedly decreased the level of IL-6 and TNF-α and remarkably ameliorated the liver and kidney damages that were elevated by implantation of EAC tumor cells, restoring the liver and kidney functions to be close to the naïve mice control.

CONCLUSION

ZnONP nanocomposites may be useful as a cancer chemotherapeutic-based drug delivery system. ZnONP nanocomposites: ZnONPs/DOX, ZnONPs/FA and ZnONPs/DOX/FA regimen may have anti-inflammatory approaches and a great potential to increase anti-tumor effect of conventional chemotherapy, overcoming resistance to cancer systemic chemotherapeutics and reducing their side effects, offering a promising regimen for cancer therapy.

Inorganic nanoparticles in dermopharmaceutical and cosmetic products: Properties, formulation development, toxicity, and regulatory issues

The use of nanotechnology strategies is a current hot topic, and research in this field has been growing significantly in the cosmetics industry. Inorganic nanoparticles stand out in this context for their distinctive physicochemical properties, leading in particular to an increased refractive index and absorption capacity giving them a broad potential for cutaneous applications and making them of special interest in research for dermopharmaceutical and cosmetic purposes. This performance is responsible for its heavy inclusion in the manufacture of skin health products such as sunscreens, lotions, beauty creams, skin ointments, makeup, and others. In particular, their suitable bandgap energy characteristics allow them to be used as photocatalytic semiconductors. They provide excellent UV absorption, commonly known as UV filters, and are responsible for their wide worldwide use in sunscreen formulations without the undesirable white residue after consumer application. In addition, cosmetics based on inorganic nanoparticles have several additional characteristics relevant to formulation development, such as being less expensive compared to other nanomaterials, having greater stability, and ensuring less irritation, itching, and propensity for skin allergies. This review will address in detail the main inorganic nanoparticles used in dermopharmaceutical and cosmetic products, such as titanium dioxide, zinc oxide, silicon dioxide, silver, gold, copper, and aluminum nanoparticles, nanocrystals, and quantum dots, reporting their physicochemical characteristics, but also their additional intrinsic properties that contribute to their use in this type of formulations. Safety issues regarding inorganic nanoparticles, based on toxicity studies, both to humans and the environment, as well as regulatory affairs associated with their use in dermopharmaceuticals and cosmetics, will be addressed.

Nanomaterials in sunscreens: Potential human and ecological health implications

Inorganic nanomaterials such as TiO2 and ZnO provide significant benefits in terms of UV protection, and their use generally has increased in commercial sunscreens. However, more recently there have been concerns about their potential human and ecological health implications, mostly driven by perception rather than by formal assessments. The large and increasing body of literature on these nanomaterials indicates that in most circumstances their risk are minimal. Penetration of the human epidermis is minimal for these nanomaterials, significantly reducing the potential effects that these nanomaterials may pose to internal organs. The excess Zn ion dose is very small compared to normal dietary consumption of Zn, which is a necessary element. The levels of residual nanomaterials or released ions in public swimming pools is also low, with minimal effect in case this water is ingested during swimming or bathing. In natural environments with significant water flow due to wind and water currents, the concentrations of nanomaterials and released ions are generally well below levels that would cause effects in aquatic organisms. However, sensitive habitats with slow currents, such as coral reefs, may accumulate these nanomaterials. The number of studies of the levels and effects of nanomaterials in these sensitive habitats is very small; more research is needed to determine if there is an elevated risk to these ecosystems from the use of sunscreens with these nanomaterials.

Determination of biological activities of nanoparticles containing silver and copper in water disinfection with/without ultrasound technique

The final and most crucial step in obtaining clean water is disinfection. More innovative methods of water disinfection have recently been sought. Water disinfection is a promising application for nanoparticles as disinfectants. As a contribution to the literature, biofilm and metal-containing nanoparticles as antiadhesion inhibitors were used in conjunction with ultrasound in this study. The microbroth dilution test was used to reveal the microbiological antibacterial activities of different concentrations of AgNO3 and CuCl2 containing nanoparticles against the Escherichia coli ATCC 25,922 strain, which is an indicator bacterium in water systems. Antibiofilm activities were then investigated using biofilm attachment and biofilm inhibition tests. The inhibitory effect of nanoparticle ultrasonic waves on biofilm contamination was determined using a novel approach. Human keratinocyte cells (HaCaT cell line) were used in cell culture studies after water disinfection, and their cytotoxic effects were demonstrated using the MTT assay. The findings suggest that the nanoparticles utilized might be a viable choice for water disinfection applications. Furthermore, employing ultrasound at low doses with nanoparticles resulted in greater results. One feasible option is to employ nanoparticles to cleanse water without producing cytotoxicity.

Effect of Titanium Dioxide Nanoparticles on Mammalian Cell Cycle In Vitro: A Systematic Review and Meta-Analysis

Although most studies that explore the cytotoxicity of titanium dioxide nanoparticles (nano-TiO₂) have focused on cell viability and oxidative stress, the cell cycle, a basic process of cell life, can also be affected. However, the results on the effects of nano-TiO₂ on mammalian cell cycle are still inconsistent. A systematic review and meta-analysis were therefore performed in this research based on the effects of nano-TiO₂ on the mammalian cell cycle in vitro to explore whether nano-TiO₂ can induce cell cycle arrest. Meanwhile, the impact of physicochemical properties of nano-TiO₂ on the cell cycle in vitro was investigated, and the response of normal cells and cancer cells was compared. A total of 33 articles met the eligibility criteria after screening. We used Review Manager 5.4 and Stata 15.1 for analysis. The results showed an increased percentage of cells in the sub-G1 phase and an upregulation of the p53 gene after being exposed to nano-TiO₂. Nevertheless, nano-TiO₂ had no effect on cell percentage in other phases of the cell cycle. Furthermore, subgroup analysis revealed that the cell percentage in both the sub-G1 phase of normal cells and S phase of cancer cells were significantly increased under anatase-form nano-TiO₂ treatment. Moreover, nano-TiO₂ with a particle size <25 nm or exposure duration of nano-TiO₂ more than 24 h induced an increased percentage of normal cells in the sub-G1 phase. In addition, the cell cycle of cancer cells was arrested in the S phase no matter if the exposure duration of nano-TiO₂ was more than 24 h or the exposure concentration was over 50 μg/mL. In conclusion, this study demonstrated that nano-TiO₂ disrupted the cell cycle in vitro. The cell cycle arrest induced by nano-TiO₂ varies with cell status and physicochemical properties of nano-TiO₂.

Antagonistic Skin Toxicity of Co-Exposure to Physical Sunscreen Ingredients Zinc Oxide and Titanium Dioxide Nanoparticles

Being the main components of physical sunscreens, zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO₂ NPs) are often used together in different brands of sunscreen products with different proportions. With the broad use of cosmetics containing these nanoparticles (NPs), concerns regarding their joint skin toxicity are becoming more and more prominent. In this study, the co-exposure of these two NPs in human-derived keratinocytes (HaCaT) and the in vitro reconstructed human epidermis (RHE) model EpiSkin was performed to verify their joint skin effect. The results showed that ZnO NPs significantly inhibited cell proliferation and caused deoxyribonucleic acid (DNA) damage in a dose-dependent manner to HaCaT cells, which could be rescued with co-exposure to TiO₂ NPs. Further mechanism studies revealed that TiO₂ NPs restricted the cellular uptake of both aggregated ZnO NPs and non-aggregated ZnO NPs and meanwhile decreased the dissociation of Zn²⁺ from ZnO NPs. The reduced intracellular Zn²⁺ ultimately made TiO₂ NPs perform an antagonistic effect on the cytotoxicity caused by ZnO NPs. Furthermore, these joint skin effects induced by NP mixtures were validated on the epidermal model EpiSkin. Taken together, the results of the current research contribute new insights for understanding the dermal toxicity produced by co-exposure of different NPs and provide a valuable reference for the development of formulas for the secure application of ZnO NPs and TiO₂ NPs in sunscreen products.

Phytochemicals and Nano-Phytopharmaceuticals Use in Skin, Urogenital and Locomotor Disorders: Are We There?

Nanomedicines emerged from nanotechnology and have been introduced to bring advancements in treating multiple diseases. Nano-phytomedicines are synthesized from active phytoconstituents or plant extracts. Advancements in nanotechnology also help in the diagnosis, monitoring, control, and prevention of various diseases. The field of nanomedicine and the improvements of nanoparticles has been of keen interest in multiple industries, including pharmaceutics, diagnostics, electronics, communications, and cosmetics. In herbal medicines, these nanoparticles have several attractive properties that have brought them to the forefront in searching for novel drug delivery systems by enhancing efficacy, bioavailability, and target specificity. The current review investigated various therapeutic applications of different nano-phytopharmaceuticals in locomotor, dermal, reproductive, and urinary tract disorders to enhance bioavailability and efficacy of phytochemicals and herbal extracts in preclinical and in vitro studies. There is a lack of clinical and extensive preclinical studies. The research in this field is expanding but strong evidence on the efficacy of these nano-phytopharmaceuticals for human use is still limited. The long-term efficacy and safety of nano-phytopharmaceuticals must be ensured with priority before these materials emerge as common human therapeutics. Overall, this review provides up-to-date information on related contemporary research on nano-phytopharmaceuticals and nano-extracts in the fields of dermatological, urogenital, and locomotor disorders.

Harnessing rat derived model cells to assess the toxicity of TiO2 nanoparticles

Until now, a few studies have been conducted on the destructive effects of TiO2 NPs in living organisms, and studies on the toxicity of TiO2 NPs are still in the beginning phases. Because of the widespread use of TiO2 NPs in all areas of human life, it is essential to study their profound and fundamental toxic effects on each organ and body cell. Herein, we evaluate the effect of exposure to TiO2 NPs on in vitro models derived from the rat bone marrow and adipose tissues. Exposure to TiO2 NPs at 100 and 200 μg/ml exhibited cytotoxicity for the rat bone marrow mesenchymal stem cells (rBMSCs) and rat adipose mesenchymal stem cells (rATSC), respectively. Additionally, reduced rBMSCs and rATSCs frequencies in the S phase of the cell cycle. Moreover, TiO2 NPs enhanced the activity of cellular senescence-associated β-galactosidase in both model cells. Significantly higher relative expression of aging-related genes P53 and NF-kB (p < 0.05) and lower expression levels of anti-aging-related genes Nanog and SIRT1 were found in the treated cells (p < 0.05). Colony-forming and DAPI staining showed the reduction of cell growth and DNA damage in both rBMSCs and rATSCs. Our findings along with other similar findings showed that TiO2 NPs probably have negative effects on the cell growth, prompt the cells for entry into proliferation stop, DNA damage, and trigger the aging process. Graphical abstract.

Continuous ZnO nanoparticle exposure induces melanoma-like skin lesions in epidermal barrier dysfunction model mice through anti-apoptotic effects mediated by the oxidative stress–activated NF-κB pathway

Background

Increasing interest in the hazardous properties of zinc oxide nanoparticles (ZnO NPs), commonly used as ultraviolet filters in sunscreen, has driven efforts to study the percutaneous application of ZnO NPs to diseased skin; however, in-depth studies of toxic effects on melanocytes under conditions of epidermal barrier dysfunction remain lacking.

Methods

Epidermal barrier dysfunction model mice were continuously exposed to a ZnO NP-containing suspension for 14 and 49 consecutive days in vivo. Melanoma-like change and molecular mechanisms were also verified in human epidermal melanocytes treated with 5.0 µg/ml ZnO NPs for 72 h in vitro.

Results

ZnO NP application for 14 and 49 consecutive days induced melanoma-like skin lesions, supported by pigmented appearance, markedly increased number of melanocytes in the epidermis and dermis, increased cells with irregular nuclei in the epidermis, recruited dendritic cells in the dermis and dysregulated expression of melanoma-associated gene Fkbp51, Trim63 and Tsp 1. ZnO NPs increased oxidative injury, inhibited apoptosis, and increased nuclear factor kappa B (NF-κB) p65 and Bcl-2 expression in melanocytes of skin with epidermal barrier dysfunction after continuously treated for 14 and 49 days. Exposure to 5.0 µg/ml ZnO NPs for 72 h increased cell viability, decreased apoptosis, and increased Fkbp51 expression in melanocytes, consistent with histological observations in vivo. The oxidative stress–mediated mechanism underlying the induction of anti-apoptotic effects was verified using the reactive oxygen species scavenger N-acetylcysteine.

Conclusions

The entry of ZnO NPs into the stratum basale of skin with epidermal barrier dysfunction resulted in melanoma-like skin lesions and an anti-apoptotic effect induced by oxidative stress, activating the NF-κB pathway in melanocytes.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01308-w.

Analysis of cytotoxicity and genotoxicity in a short-term dependent manner induced by a new titanium dioxide nanoparticle in murine fibroblast cells

The extensive use of titanium dioxide nanoparticles (TiO₂ NPs) in cosmetics, food, personal care products, and industries brought concerns about their possible harmful effects. Nowadays it has become important to assess TiO₂ NPs toxic effects as a way to understand their primary risks. In the cellular environment, after cell uptake, TiO₂ NPs were described to induce reactive oxygen species (ROS) production, unbalance oxidative state, and activate apoptosis in several cell lines. Therefore, we aimed to evaluate the cytotoxicity and genotoxicity of a new TiO₂ NP surface-functionalized with sodium carboxylic ligands in a murine fibroblast cell line (LA-9). TEM and DLS analyses were performed to define nanoparticle physicochemical characteristics. We evaluated the metabolic activity and LDH released after 24 h exposition to determine cytotoxic effects. Also, we evaluated DNA damage, intracellular reactive oxygen species (ROS) production, and apoptosis induction after 24 h exposure. The TiO₂ NP impaired the cell membrane integrity at 1000 μg/mL, induced intracellular ROS production and late apoptosis at 24 h. The genotoxic effects were observed at all conditions tested at 24 h. Indeed, in fibroblasts exposed at 100 μg/mL was observed early apoptosis cells. The intracellular ROS content was increased in a dose-dependent manner. Thus, short-term exposure to TiO₂ NP promoted cytotoxicity, genotoxicity and activated apoptosis pathways based on the potential role of oxygen species in the fibroblasts cell line.

NRF2 deficiency sensitizes human keratinocytes to zinc oxide nanoparticles-induced autophagy and cytotoxicity

Zinc oxide nanoparticles (ZnO NPs) are one of the most commonly used metal oxide particles in many industrial fields. Many studies have shown that ZnO NPs induce harmful effects to human skin, but the mechanisms remain poorly understood. Our results showed that ZnO NPs concentration-dependently induced cytotoxicity, ROS accumulation, and mitochondrial dysfunction in HaCaT cells. The expressions of adaptive antioxidant response transcriptional factor NRF2 and autophagy-related proteins P62 and LC3 II/I were increased by ZnO NPs. Knock-down of NRF2 (NRF2-KD) sensitized the cells to ZnO NPs-induced autophagy and cytotoxicity while an autophagy inhibitor, 3-methyladenine, protected the cells from ZnO NPs-induced cell death. These results demonstrated that NRF2 deficiency sensitizes human keratinocytes to ZnO NPs induced autophagy and cytotoxicity, and proposed a key role of NRF2 in protecting skin cells against ZnO NPs through regulation of antioxidants and autophagy.

Influence of Titanium Dioxide Nanoparticles on Human Health and the Environment

Nanotechnology has enabled tremendous breakthroughs in the development of materials and, nowadays, is well established in various economic fields. Among the various nanomaterials, TiO₂ nanoparticles (NPs) occupy a special position, as they are distinguished by their high availability, high photocatalytic activity, and favorable price, which make them useful in the production of paints, plastics, paper, cosmetics, food, furniture, etc. In textiles, TiO₂ NPs are widely used in chemical finishing processes to impart various protective functional properties to the fibers for the production of high-tech textile products with high added value. Such applications contribute to the overall consumption of TiO₂ NPs, which gives rise to reasonable considerations about the impact of TiO₂ NPs on human health and the environment, and debates regarding whether the extent of the benefits gained from the use of TiO₂ NPs justifies the potential risks. In this study, different TiO₂ NPs exposure modes are discussed, and their toxicity mechanisms—evaluated in various in vitro and in vivo studies—are briefly described, considering the molecular interactions with human health and the environment. In addition, in the conclusion of this study, the toxicity and biocompatibility of TiO₂ NPs are discussed, along with relevant risk management strategies.

Aerobic sludge digestion is distinguishingly affected by the different entering pathways of zinc oxide nanoparticles

Zinc oxide nanoparticles (ZnO NPs) are widespread emerging pollutants raising global concerns about their influences on biological wastewater treatment processes. However, the impacts of ZnO NPs on aerobic sludge digestion that is a major sludge treatment process remain unknown. Herein, this study comprehensively investigated the key influences of ZnO NPs on aerobic digestion of waste activated sludge (WAS) and the potential mechanisms involved. Two different entering pathways, i.e., ZnO NPs directly entered into aerobic sludge digester and ZnO NPs initially entered into wastewater bio-treatment reactor, were tested to evaluate the different impacts. Compared to the control, ZnO NPs initially entering into wastewater bioreactor inhibited WAS degradation by 18.2 ± 0.1%, whereas ZnO NPs immediately entered into digester inhibited it by 29.7 ± 0.1%. This was accompanied by a similar decrease in inorganic nitrogen production and oxygen consumption. ZnO NPs exposure in wastewater bioreactor changed WAS characteristics in favor of solubilization in aerobic digestion. Modelling analysis indicated that ZnO NPs inhibited WAS hydrolysis, especially for their direct entering into aerobic digester. Correspondingly, microbial community was shifted in the direction against aerobic digestion by the ZnO NPs. Excessive oxidative stress and Zn²⁺ release represented the primary toxicity factors for the inhibition.

Assessing the Toxicological Relevance of Nanomaterial Agglomerates and Aggregates Using Realistic Exposure In Vitro

Low dose repeated exposures are considered more relevant/realistic in assessing the health risks of nanomaterials (NM), as human exposure such as in workplace occurs in low doses and in a repeated manner. Thus, in a three-week study, we assessed the biological effects (cell viability, cell proliferation, oxidative stress, pro-inflammatory response, and DNA damage) of titanium-di-oxide nanoparticle (TiO₂ NP) agglomerates and synthetic amorphous silica (SAS) aggregates of different sizes in human bronchial epithelial (HBE), colon epithelial (Caco2), and human monocytic (THP-1) cell lines repeatedly exposed to a non-cytotoxic dose (0.76 µg/cm²). We noticed that neither of the two TiO₂ NPs nor their agglomeration states induced any effects (compared to control) in any of the cell lines tested while SAS aggregates induced some significant effects only in HBE cell cultures. In a second set of experiments, HBE cell cultures were exposed repeatedly to different SAS suspensions for two weeks (first and second exposure cycle) and allowed to recover (without SAS exposure, recovery period) for a week. We observed that SAS aggregates of larger sizes (size ~2.5 µm) significantly affected the cell proliferation, IL-6, IL-8, and total glutathione at the end of both exposure cycle while their nanosized counterparts (size less than 100 nm) induced more pronounced effects only at the end of the first exposure cycle. As noticed in our previous short-term (24 h) exposure study, large aggregates of SAS did appear to be similarly potent as nano sized aggregates. This study also suggests that aggregates of SAS of size greater than 100 nm are toxicologically relevant and should be considered in risk assessment.

The emerging role of nanotechnology in skincare

The role of cosmetic products is rapidly evolving in our society, with their use increasingly seen as an essential contribution to personal wellness. This suggests the necessity of a detailed elucidation of the use of nanoparticles (NPs) in cosmetics. The aim of the present work is to offer a critical and comprehensive review discussing the impact of exploiting nanomaterials in advanced cosmetic formulations, emphasizing the beneficial effects of their extensive use in next-generation products despite a persisting prejudice around the application of nanotechnology in cosmetics. The discussion here includes an interpretation of the data underlying generic information reported on the product labels of formulations already available in the marketplace, information that often lacks details identifying specific components of the product, especially when nanomaterials are employed. The emphasis of this review is mainly focused on skincare because it is believed to be the cosmetics market sector in which the impact of nanotechnology is being seen most significantly. To date, nanotechnology has been demonstrated to improve the performance of cosmetics in a number of different ways: 1) increasing both the entrapment efficiency and dermal penetration of the active ingredient, 2) controlling drug release, 3) enhancing physical stability, 4) improving moisturizing power, and 5) providing better UV protection. Specific attention is paid to the effect of nanoparticles contained in semisolid formulations on skin penetration issues. In light of the emerging concerns about nanoparticle toxicity, an entire section has been devoted to listing detailed examples of nanocosmetic products for which safety has been investigated.

ZnO NPs delay the recovery of psoriasis-like skin lesions through promoting nuclear translocation of p-NFκB p65 and cysteine deficiency in keratinocytes

BACKGROUND

This study aimed to evaluate the safety of applying zinc oxide nanoparticles (ZnO NPs) to pathological skin. The majority of previous studies confirmed the safety of applying ZnO NPs to normal skin. However, we know very little about the risks of using sunscreen, cosmetics and topical drugs containing ZnO NPs for individuals with skin diseases.

RESULTS

ZnO NPs passed through gaps between keratinocytes and entered stratum basale of epidermis and dermis in imiquimod-induced psoriasis-like skin lesions. Application of a ZnO NP-containing suspension for 3 connective days delayed the healing of the epidermal barrier; increased the expression levels of inflammatory cytokines; promoted keratinocyte apoptosis and disturbed redox homeostasis. In TNF-α-stimulated HaCaT cells, QNZ and JSH-23 (NFκB inhibitors) blocked ZnO NP-induced inflammation. JSH-23 and NAC (a precursor of cysteine) inhibited ZnO NP-induced nuclear translocation of p-NFκB p65, cysteine deficiency and apoptosis. Additionally, ZnO NPs decreased CD98 level in main pathway and failed to activate transsulfuration pathway in cysteine biosynthesis.

CONCLUSIONS

ZnO NPs can enter psoriasis-like skin lesions and promote inflammation and keratinocyte apoptosis through nuclear translocation of p-NFκB p65 and cysteine deficiency. This work reminds the public that ZnO NPs have harmful effects on the recovery of inflammatory skin diseases.

Nanotechnology in cosmetics pros and cons

The field of nanotechnology is being greatly explored by cosmetic industries in order to improve the efficacy of cosmetic products. The increased use of nanomaterials in the field of cosmetics can have two sides as health-related benefits and detrimental effects. This review mainly seeks the pros and cons of the use of nanomaterials in cosmetics along with some examples of nanomaterials that are widely used in cosmetic industries along with different types of nanotechnology-based cosmetic products. The benefits of nanomaterials in cosmetic formulations are huge. Moreover the study regarding the toxic effects on the health also equally matters. This review gives a brief outline of the advantages as well as disadvantages of nanotechnology in cosmetics.

Effect of morphology on larvicidal activity of chemically synthesized zinc oxide nanoparticles against mosquito vectors

We report the larvicidal effects of four different morphologies of zinc oxide nanoparticles (ZnO NPs) [star-shaped (S), needle-like (N), plate-like (P) and cubical (C)] on larvae of Aedes albopictus and Anopheles vagus; the mosquitoes causing dengue fever and malaria, respectively. The nanoparticles were characterized by several analytical techniques, and their sizes and shapes were determined. Second instar larvae of the two types of mosquitoes were exposed to several concentrations of nanoparticles (25 mg L-1, 50 mg L-1, 75 mg L-1, 100 mg L-1) at 25 ± 2 °C and 84 ± 5% R.H, separately, for each morphology. Larval mortality was reported at 24 h intervals up to 21 days. The resulting LC50 for Aedes albopictus were, respectively, 38.90 mg L-1, 47.53 mg L-1, 68.38 mg L-1, 50.24 mg L-1 for S-, N-, P- and C-shaped nanoparticles. The LC50 of Anopheles vagus is lower (LC50 4.78 mg L-1, 6.51 mg L-1, 13.64 mg L-1, 10.47 mg L -1 ), respectively, for S-, N-, P- and C-shaped nanoparticles indicating that the nanoparticles are more toxic to Anopheles vagus larvae. The highest larvicidal effect was obtained from star-shaped nanoparticles [Aedes albopictus (38.90 mg L-1) on Anopheles vagus (4.78 mg L-1)], and the lowest was shown by the plate-like nanoparticles [Aedes albopictus (68.38 mg L-1), Anopheles vagus (13.64 mg L-1)]. The rate of development of surviving mosquito larvae was retarded when exposed to ZnO nanoparticles suggesting the possibility for these nanoparticles to kill and delay the growth of Aedes albopictus and Anopheles vagus larvae.

Acute toxicity of Zinc Oxide nanoparticles to silkworm (Bombyx mori L.)

Zinc Oxide nanoparticles (ZnO NPs) has been heavily used in the industry, and increasing concerns on the ecotoxicity has arisen due to the risk of release into the environment. In this work, silkworm was used here as a model organism to study the toxicity of ZnO NPs, due to the presence of a conserved immune response as well as a pharmacokinetics similar to mammals. Zn accumulation, biodistribution and toxicity in silkworms were monitored at different time points after a subcutaneous injection. The highest cumulative content of ZnO NPs was detected in the midgut. The results of catalytic activity studies confirmed that the antioxidant enzymes (SOD, CAT, GSH-PX) in midgut cells were expressed in response to ZnO NPs. The expression of genes (Dronc and Caspase-1) related to apoptosis was increased, while the Trt gene was down-regulated. A possible mechanism was proposed for toxicity of ZnO NPs to silkworms.

Proposing Urothelial and Muscle In Vitro Cell Models as a Novel Approach for Assessment of Long-Term Toxicity of Nanoparticles

Many studies evaluated the short-term in vitro toxicity of nanoparticles (NPs); however, long-term effects are still not adequately understood. Here, we investigated the potential toxic effects of biomedical (polyacrylic acid and polyethylenimine coated magnetic NPs) and two industrial (SiO₂ and TiO₂) NPs following different short-term and long-term exposure protocols on two physiologically different in vitro models that are able to differentiate: L6 rat skeletal muscle cell line and biomimetic normal porcine urothelial (NPU) cells. We show that L6 cells are more sensitive to NP exposure then NPU cells. Transmission electron microscopy revealed an uptake of NPs into L6 cells but not NPU cells. In L6 cells, we obtained a dose-dependent reduction in cell viability and increased reactive oxygen species (ROS) formation after 24 h. Following continuous exposure, more stable TiO₂ and polyacrylic acid (PAA) NPs increased levels of nuclear factor Nrf2 mRNA, suggesting an oxidative damage-associated response. Furthermore, internalized magnetic PAA and TiO₂ NPs hindered the differentiation of L6 cells. We propose the use of L6 skeletal muscle cells and NPU cells as a novel approach for assessment of the potential long-term toxicity of relevant NPs that are found in the blood and/or can be secreted into the urine.

Interactions of Zinc Oxide Nanostructures with Mammalian Cells: Cytotoxicity and Photocatalytic Toxicity

This article presents a state-of-the-art review and analysis of literature studies on the morphological structure, fabrication, cytotoxicity, and photocatalytic toxicity of zinc oxide nanostructures (nZnO) of mammalian cells. nZnO with different morphologies, e.g., quantum dots, nanoparticles, nanorods, and nanotetrapods are toxic to a wide variety of mammalian cell lines due to in vitro cell-material interactions. Several mechanisms responsible for in vitro cytotoxicity have been proposed. These include the penetration of nZnO into the cytoplasm, generating reactive oxygen species (ROS) that degrade mitochondrial function, induce endoplasmic reticulum stress, and damage deoxyribonucleic acid (DNA), lipid, and protein molecules. Otherwise, nZnO dissolve extracellularly into zinc ions and the subsequent diffusion of ions into the cytoplasm can create ROS. Furthermore, internalization of nZnO and localization in acidic lysosomes result in their dissolution into zinc ions, producing ROS too in cytoplasm. These ROS-mediated responses induce caspase-dependent apoptosis via the activation of B-cell lymphoma 2 (Bcl2), Bcl2-associated X protein (Bax), CCAAT/enhancer-binding protein homologous protein (chop), and phosphoprotein p53 gene expressions. In vivo studies on a mouse model reveal the adverse impacts of nZnO on internal organs through different administration routes. The administration of ZnO nanoparticles into mice via intraperitoneal instillation and intravenous injection facilitates their accumulation in target organs, such as the liver, spleen, and lung. ZnO is a semiconductor with a large bandgap showing photocatalytic behavior under ultraviolet (UV) light irradiation. As such, photogenerated electron-hole pairs react with adsorbed oxygen and water molecules to produce ROS. So, the ROS-mediated selective killing for human tumor cells is beneficial for cancer treatment in photodynamic therapy. The photoinduced effects of noble metal doped nZnO for creating ROS under UV and visible light for killing cancer cells are also addressed.

Nanotechnology-based Drug Delivery, Metabolism and Toxicity

BACKGROUND

Nanoparticles (NPs) are being used extensively owing to their increased surface area, targeted delivery and enhanced retention. NPs have the potential to be used in many disease conditions. Despite widespread use, their toxicity and clinical safety still remain a major concern.

OBJECTIVE

The purpose of this study was to explore the metabolism and toxicological effects of nanotherapeutics.

METHODS

Comprehensive, time-bound literature search was done covering the period from 2010 till date. The primary focus was on the metabolism of NP including their adsorption, degradation, clearance, and bio-persistence. This review also focuses on updated investigations on NPs with respect to their toxic effects on various in vitro and in vivo experimental models.

RESULTS

Nanotechnology is a thriving field of biomedical research and an efficient drug delivery system. Further their applications are under investigation for diagnosis of disease and as medical devices.

CONCLUSION

The toxicity of NPs is a major concern in the application of NPs as therapeutics. Studies addressing metabolism, side-effects and safety of NPs are desirable to gain maximum benefits of nanotherapeutics.

Involvement of Bcl-2 Activation and G1 Cell Cycle Arrest in Colon Cancer Cells Induced by Titanium Dioxide Nanoparticles Synthesized by Microwave-Assisted Hybrid Approach

The toxic effect of TiO₂ nanoparticles (TNP) greatly varies with the variation in synthesis protocol followed. Any morphological alteration of TNPs affects their activity. In the present study, we report the detailed toxicological analysis of TNPs fabricated by a microwave irradiation–assisted hybrid chemical approach. The toxicological mechanism was studied in human colon cancer cell lines (HCT116). Results indicate that TNP induces oxidative stress on HCT116, which, in turn, causes mitochondrial membrane depolarization. We also observed activation of Bcl-2 and caspase-3 by Western blot analysis. This indicates TNPs induce mitochondrial-mediated apoptosis. Furthermore, G1 cell cycle arrest was observed by flow-cytometric analysis. This study provides an understanding of the mechanism of action for apoptosis induced by TNPs, which can be further used to design safe TNPs for various consumer products and also suggests that extensive research needs to be done on harmful effects of TNPs synthesized from different approaches before commercial application.

Y2O3 decorated TiO2 nanoparticles: Enhanced UV attenuation and suppressed photocatalytic activity with promise for cosmetic and sunscreen applications

Nanoparticulate titanium dioxide (TiO₂) is widely used in cosmetic products and sunscreens. However, primarily due to their photocatalytic activity, some TiO₂ products have been shown to be cytotoxic. Thus, the aim of this study was to reduce the photoactivity and consequent cytotoxicity of TiO₂nanoparticles. As such, in this work, yttrium oxide (Y₂O₃) was deposited onto TiO₂, at 5% and 10% Y/Ti weight ratio, via a hydrothermal method. The nanocomposites produced, TiO₂@Y₂O₃ 5 and 10 wt%, were characterised to assess their physical, photochemical and toxicological properties. These materials exhibit a uniform yttria coating, enhanced UV attenuation in the 280-350 nm range and significantly reduced photoactivity compared with a pristine commercial TiO₂ sample (Degussa Aeroxide® P25). Furthermore, the comparative cytotoxicity and photo-cytotoxicity of these materials to a human keratinocyte cell line (HaCaT), was assessed using a colorimetric tetrazolium salt (MTS) assay. Following 24-hour incubation with cells, both Y₂O₃ loadings exhibited improved biocompatibility with HaCaT cells, compared to the pristine TiO₂ sample, under all subsequent test conditions. In conclusion, the results highlight the potential of these materials for use in products, applied topically, with sun protection in mind.

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

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

Effects of Four Kinds of Oxide Nanoparticles on Proteins in Extracellular Polymeric Substances of Sludge

Proteins are the most important component in sludge extracellular polymeric substances (EPS) and play a crucial role in the formation of sludge flocs, adsorption performance of sludge, and flocculation ability of sludge. This research is aimed at exploring the changes in proteins in EPS extracted from concentrated sludge after various nanoparticle (NP) treatments. The results showed that the protein content in EPS decreased by 40% after nanoalumina (Al₂O₃ NPs) treatment but increased at varying degrees after nanoferric oxide (Fe₃O₄ NPs), nanozinc oxide (ZnO NPs), and nanotitanium dioxide (TiO₂ NPs) treatments. The four kinds of nanoparticles not only affected the protein content in EPS but also influenced the types and structures of proteins. The results of three-dimensional fluorescence spectroscopy showed that the tyrosine-like protein content in soluble EPS (SEPS) decreased after treatments with four kinds of NPs. Infrared spectroscopy analysis revealed that the absorption intensity of amide I and amide II weakened after Al₂O₃ NP treatment, whereas that of amide I enhanced after Fe₃O₄ NP, ZnO NP, and TiO₂ NP treatments. Further analysis of the secondary structure of proteins in the infrared range of 1700–1600 cm⁻¹ demonstrated that the value of α-helix/(β-sheet+random coil) decreased from 0.513 to 0.383 in SEPS after TiO₂ NP treatment. For the samples treated by Fe₃O₄ NPs, the percentage of α-helix significantly increased and that of β-sheet slightly decreased in proteins from SEPS and loosely bound EPS.

Metagenomic analysis of the biotoxicity of titanium dioxide nanoparticles to microbial nitrogen transformation in constructed wetlands

Extensive use of titanium dioxide nanoparticles (TiO₂ NPs) in various products has increased the release of these particles into wastewater, posing potential environmental risks. As an ecological wastewater treatment facility, constructed wetland (CW) is an important sink of NPs. However, little is known about the effects of NPs on microbial nitrogen transformation and related genes in CWs. In this study, short-term (5 days) and long-term (60 days) exposure experiments were conducted to investigate the effect of TiO₂ NPs (0, 1, and 50 mg/L) on microbial nitrogen removal in CWs. The results showed that nitrogen removal efficiency was decreased by 35%-51% after long-term exposure to TiO₂ NPs. Metagenomic analysis further confirmed that TiO₂ NPs declined the relative abundance of functional genes and those enzyme encoding genes involved in the nitrogen metabolism pathway and glycolysis metabolism process. Furthermore, our data proved that the indigent glycolysis metabolism process resulted in the shortage of electron (NADH) and energy sources (ATP), causing inefficient nitrogen removal. Overall, these results revealed that the accumulation of TiO₂ NPs altered the genetic expression of biofilm in CWs, which had significant impacts on biological nitrogen transformation.

Zinc oxide nanoparticles synthesized from Allium cepa prevents UVB radiation mediated inflammation in human epidermal keratinocytes (HaCaT cells)

The extensive relevance of nanoparticles arouses the requirement for manufacturing although the predictable technique are frequently perilous and energy saving. In the current study, zinc oxide nanoparticles manufactured from Allium cepa avert UVB radiation interceded irritation in human epidermal keratinocytes (HaCaT cells). In the current study, the zinc oxide nanoparticles (ZnO-NPs) was synthesized from the extract of A. cepa. The optimized ZnO-NPs hence attained and was enumerated and exemplified by UV visible spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscope (SEM) and EDAX impending analysis. In addition, amalgamated ZnO-NPs were experienced for cell viability (MTT), formation of reactive oxygen species (ROS), apoptosis, and antioxidant and lipid peroxidation (TBARS) levels. Also, we explored the effect of A. cepa ZnO-NPs in molecular level by evaluating the inflammatory and apoptotic markers, in which ZnO-NPs reinstated the interleukins 6, 10 and related signaling molecules like iNOS, COX-2 levels. Ultimately, ZnO-NPs induce apoptotic markers (Bax, Bcl-2) and also recommended that ZnO-NPs might aggravate cancer cell apoptosis in HaCaT cells.

Disposition and measured toxicity of zinc oxide nanoparticles and zinc ions against keratinocytes in cell culture and viable human epidermis

Suspensions of the UV filter, zinc oxide nanoparticles (ZnO NP), are widely used in sunscreen products. This paper compared the relative disposition and local cytotoxicity of ZnO NP, and zinc ions formed on its dissolution, against keratinocyte cultures and in the human epidermis (ex vivo) after application of suspensions of ZnO NP. HaCaT keratinocyte cytotoxicities were found to be related to labile intra-cellular zinc but also total zinc and extra-cellular concentrations in cell culture media and to a degree ameliorated by the presence of a zinc chelating agent. Secondly, the zinc species were then dosed onto exposed ex vivo viable human epidermis and it was found that an increase in labile zinc level correlated with a shift in the metabolic state of the viable epidermis. This study highlights that excised viable skin acts as a more relevant model for determining cutaneous toxicity over keratinocyte monolayers in vitro.

Survival Mechanisms and Xenobiotic Susceptibility of Keratinocytes Exposed to Metal-Derived Nanoparticles

Metal-derived nanoparticles (Mt-NPs) are increasingly used in cosmetology due to their ultraviolet shielding (titanium dioxide [TiO₂]), antioxidant (cerium dioxide [CeO₂]), and biocidal (silver [Ag]) properties. In the absence of overt toxicity (i.e., cell death), Mt-NPs are considered safe for cosmetic applications. However, there is little understanding about the mechanisms involved in the survival of keratinocytes exposed to subtoxic levels of Mt-NPs. Human keratinocytes (HaCaT) were exposed subacutely to subtoxic concentrations (≤30 μg/mL, 48-72 h) of rutile (r) TiO₂ (cylindrical), CeO₂ (cubic) and Ag (spherical) with a core/hydrodynamic size of <50/<100 nm and >98% purity. Mt-NP uptake was indirectly quantified by changes in the light side scatter, where the kinetics (time/dose-response) suggested that the three types of Mt-NPs were similarly uptaken by keratinocytes. rTiO₂ and CeO₂, but not Ag-NPs, increased autophagy, whose inhibition prompted cell death. No increase in the steady-state levels of reactive oxygen species (ROS) was induced by exposure to any of the Mt-NPs tested. Interestingly, intracellular Ag-NP aggregates observed an increased far-red autofluorescence (≥740 nm em), which has been ascribed to their binding to thiol molecules such as glutathione (GSH). Accordingly, inhibition of GSH synthesis, but not the impairment of oxidized GSH recycling, sensitized keratinocytes to Ag-NPs suggesting that GSH homeostasis, and its direct scavenging of Ag-NPs, but not ROS, is essential for keratinocyte survival upon exposure to Ag-NP. rTiO₂ and Ag, but not CeO₂-NPs, compromised metabolic flux (glycolysis and respiration), but ATP levels were unaltered. Finally, we also observed that exposure to Mt-NPs sensitized keratinocytes to non-UV xenobiotic exposure (arsenite and paraquat). Our results demonstrate the differential contribution of autophagy and GSH homeostasis to the survival of human keratinocytes exposed to subtoxic concentrations of Mt-NPs and highlight the increased susceptibility of keratinocytes exposed to Mt-NPs to a second xenobiotic insult.

Advances and controversies in studying sunscreen delivery and toxicity

This review critically evaluates the sunscreen delivery and toxicity field. We chose to focus on approved sunscreens in this review. Optimal sunscreen use prevents skin cancer and photoageing but there is an important knowledge gap in sunscreen/skin interactions. Sunscreen delivery is a key for efficacy, but studying sunscreen delivery is not straightforward. We review the strengths and weaknesses of in vitro, excised skin and clinical approaches. Understanding positive and negative sunscreen effects on skin homeostasis is also challenging. The results in this field, especially in vitro testing, are controversial and experimental design varies widely which further supports disparities between some findings. We hypothesize that bias towards showing sunscreen toxicity to increase impact could be problematic. We explore that perception through a detailed review of experimental design, especially in cell culture models. Our conclusion is that emerging, non- and minimally invasive technologies are enabling new approaches to volunteer studies that could significantly improve knowledge of sunscreen delivery and interactions.

Toxicity of ZnO/TiO2 -conjugated carbon-based nanohybrids on the coastal marine alga Thalassiosira pseudonana

Increasing consumption of metal-oxide nanoparticles (NPs) and carbon-based nanomaterials has caused significant concern about their potential hazards in aquatic environments. The release of NPs into aquatic environments could result in adsorption of NPs on microorganisms. While metal-oxide NP-conjugated carbon-based nanohybrids (NHs) may exhibit enhanced toxicity toward microorganisms due to their large surface area and the generation of reactive oxygen species (ROS), there is a lack of information regarding the ecotoxicological effects of NHs on marine diatom algae, which are an indicator of marine pollution. Moreover, there is scant information on toxicity mechanisms of NHs on aquatic organisms. In this study, four NHs (ie, ZnO-conjugated graphene oxide [GO], ZnO-conjugated carbon nanotubes [CNTs], TiO₂ -conjugated GO, and TiO₂ -conjugated CNT) that were synthesized by a hydrothermal method were investigated for their toxicity effects on a Thalassiosira pseudonana marine diatom. The in vitro cellular viability and ROS formation employed at the concentration ranges of 50 and 100 mg/L of NHs over 72 hours revealed that ZnO-GO had the most negative effect on T. pseudonana. The primary mechanism identified was the generation of ROS and GO-induced dispersion that caused electrostatic repulsion, preventing aggregation, and an increase in surface areas of NHs. In contrast to GO-induced dispersion, large aggregates were observed in ZnO/TiO₂ -conjugated CNT-based NHs. The scanning electron microscopy images suggest that NHs covered algae cells and interacted with them (shading effects); this reduced light availability for photosynthesis. Detailed in vitro toxicity effects and mechanisms that cause high adverse acute toxicity on T. pseudonana were unveiled; this implied concerns about potential hazards of these mechanisms in aquatic ecosystems.

Lamellar liquid crystals maintain keratinocytes' membrane fluidity: An AFM qualitative and quantitative study

Despite extensive investigations of lamellar liquid crystals for dermal application, the effects of these systems at the cellular level are still not well elucidated. The key aim of this study was to determine the elasticity and morphological features of keratinocytes after exposure to a lamellar liquid crystal system (LLCS) using atomic force microscopy (AFM) as the method of choice. Prior to AFM assessment, a cell proliferation test and light plus fluorescence imaging were applied to determine the sub-toxic concentration of LLCS. According to the AFM results, slightly altered morphology was observed in the case of fixed keratinocytes, while an intact morphology was visualized on live cells. From the quantitative study, decreased Young's moduli were determined for fixed cells (i.e., 8.6 vs. 15.2 MPa and 1.3 vs. 2.9 MPa for ethanol or PFA-fixed LLCS-treated vs. control cells, respectively) and live cells (i.e., ranging from 0.6 to 2.8 for LLCS-treated vs. 1.1-4.5 MPa for untreated cells), clearly demonstrating increased cell elasticity. This is related to improved membrane fluidity as a consequence of interactions between the acyl chains of cell membrane phosphatidylcholine and those of LLCS. What seems to be of major importance is that the study confirms the potential clinical relevance of such systems in treatment of aged skin with characteristically more rigid epithelial cells.

The Radiosensitizing Effect of Zinc Oxide Nanoparticles in Sub-Cytotoxic Dosing Is Associated with Oxidative Stress In Vitro

Radioresistance is an important cause of head and neck cancer therapy failure. Zinc oxide nanoparticles (ZnO-NP) mediate tumor-selective toxic effects. The aim of this study was to evaluate the potential for radiosensitization of ZnO-NP. The dose-dependent cytotoxicity of ZnO-NP_{20 nm} and ZnO-NP_{100 nm} was investigated in FaDu and primary fibroblasts (FB) by an MTT assay. The clonogenic survival assay was used to evaluate the effects of ZnO-NP alone and in combination with irradiation on FB and FaDu. A formamidopyrimidine-DNA glycosylase (FPG)-modified single-cell microgel electrophoresis (comet) assay was applied to detect oxidative DNA damage in FB as a function of ZnO-NP and irradiation exposure. A significantly increased cytotoxicity after FaDu exposure to ZnO-NP_{20 nm} or ZnO-NP_{100 nm} was observed in a concentration of 10 µg/mL or 1 µg/mL respectively in 30 µg/mL of ZnO-NP_{20 nm} or 20 µg/mL of ZnO-NP_{100 nm} in FB. The addition of 1, 5, or 10 µg/mL ZnO-NP_{20 nm} or ZnO-NP_{100 nm} significantly reduced the clonogenic survival of FaDu after irradiation. The sub-cytotoxic dosage of ZnO-NP_{100 nm} increased the oxidative DNA damage compared to the irradiated control. This effect was not significant for ZnO-NP_{20 nm}. ZnO-NP showed radiosensitizing properties in the sub-cytotoxic dosage. At least for the ZnO-NP_{100 nm}, an increased level of oxidative stress is a possible mechanism of the radiosensitizing effect.

Photogeneration of reactive oxygen species over ultrafine TiO2 particles functionalized with rutin–ligand induced sensitization and crystallization effects

Interaction of amorphous and crystalline TiO2 ultrafine particles (2–6 nm) with rutin results in the formation of colored nanomaterials of an excellent dispersity and enhanced colloidal stability in aqueous media. The FTIR and Raman spectra confirmed attachment of the rutin ligand via vicinal hydroxyl groups in a catechol-like fashion. The binding of rutin to amorphous TiO2 gives rise to spontaneous crystallization of the parent nanoparticles into hydrogen titanates (H2Ti3O7 and H2Ti12O25). Such structural transformations result in photosensitization toward visible light with enhanced efficiency of the charge separation and interfacial charge transfer processes, confirmed by detailed photoelectrochemical studies of the examined nanomaterials. The effectiveness of the photocatalytic ROS generation reactions was also strongly influenced by hydrogen peroxide, which plays a double role of a reactant prone to reduction and generation of hydroxyl radicals or a redox agent destroying the intra-band gap electronic states, suppressing thereby charge recombination. The photoinduced charge transfer processes lead to generation of various reactive oxygen species, which were detected by EPR using DMPO spin trap (HOO· detection) and in the reaction with terephthalic acid acting as a chemical scavenger (HO· detection). Complexation of TiO2 particles with rutin shifts the photogeneration of hydroperoxyl (HOO·) and hydroxyl (HO·) radicals toward visible light (λ > 400 nm). A triple effect of rutin attachment to titania was established. It consists in pronounced photosensitization, promotion of crystallization and enhancement of the colloidal stability of ultrafine titania particles. Environmental implications of these assets on the photoinduced redox reactions with hydrogen peroxide in aqueous solutions upon UV or visible light irradiation were also discussed.

Enhanced Photocatalytic and Antibacterial Performance of ZnO Nanoparticles Prepared by an Efficient Thermolysis Method

ZnO nanoparticles (ZnO-NPs) were synthesized by a straightforward modified thermal method using only one chemical: zinc acetate dihydrate. The process is environmentally safer than other methods because it does not involve other chemicals or a catalyst, acid, or base source. X-ray diffraction analysis indicated that the ZnO-NPs crystallize in the hexagonal wurtzite structure. The UV–vis absorption spectra revealed a marked redshift, which is critical for enhanced photocatalytic activity. We used methylene blue for photocatalytic activity tests and found an excellent degradation percentage (99.7%) within a short time (80 min). The antibacterial activity of the synthesized ZnO-NPs was tested against Escherichia coli at different concentrations of ZnO-NPs. The analysis revealed that the minimum inhibitory concentration (MIC) of the ZnO-NPs against E. coli was 30–50 μg/mL. Our ZnO-NPs were found to be more effective than previously reported ZnO-NPs synthesized via other methods.

Rutile nano-bio-interactions mediate dissimilar intracellular destiny in human skin cells

The use of nanoparticles (NPs) in the healthcare market is growing exponentially, due to their unique physicochemical properties. Titanium dioxide nanoparticles (TiO₂ NPs) are used in the formulation of sunscreens, due to their photoprotective capacity, but interactions of these particles with skin cells on the nanoscale are still unexplored. In the present study we aimed to determine whether the initial nano-biological interactions, namely the formation of a nano-bio-complex (other than the protein corona), can predict rutile internalization and intracellular trafficking in primary human fibroblasts and keratinocytes. Results showed no significant effect of NPs on fibroblast and keratinocyte viability, but cell proliferation was possibly compromised due to nano-bio-interactions. The bio-complex formation is dependent upon the chemistry of the biological media and NPs' physicochemical properties, facilitating NP internalization and triggering autophagy in both cell types. For the first time, we observed that the intracellular traffic of NPs is different when comparing the two skin cell models, and we detected NPs within multivesicular bodies (MVBs) of keratinocytes. These structures grant selected input of molecules involved in the biogenesis of exosomes, responsible for cell communication and, potentially, structural equilibrium in human tissues. Nanoparticle-mediated alterations of exosome quality, quantity and function can be another major source of nanotoxicity.

Preferential Accumulation of Phospholipid-PEG and Cholesterol-PEG Decorated Gold Nanorods into Human Skin Layers and Their Photothermal-Based Antibacterial Activity

Herein, a library of gold nanorods (GNR) decorated with polyethylene glycol-thiol (PEG-SH) containing different functionalities were synthesized and characterized by optical absorption spectroscopy, zeta potential, dynamic light scattering (DLS), transmission electron microscope (TEM) and proton nuclear magnetic resonance (1H-NMR). The colloidal stability of GNR when exposed to skin, and their preferential accumulation into excised human skin layers were investigated. Confocal laser scanning microscopy, transmission electron microscope (TEM) and inductively coupled plasma-optical emission spectroscopy (ICP-OES) were utilized to track the penetration of GNR into different skin layers. The results demonstrated that cholesterol-PEG coated GNR were preferentially loaded up in the upper layers of skin (stratum corneum), while phospholipid-PEG coated counterparts were drastically deposited in skin dermis. Neutral methoxy-PEG-coated GNR were distributed in both SC and dermis skin layers, while charged GNR (anionic-carboxylic acid-PEG-GNR and cationic-amine-PEG-GNR) revealed a minimal accumulation into skin. DSPE-PEG-GNR and Chol-PEG-GNR demonstrated antibacterial activities against Staphylococcus aureus (S aureus) at MIC values of 0.011 nM and 0.75 nM, respectively. Photothermal treatment for S. aureus at sub-MIC concentrations resulted in a significant bactericidal effect when using Chol-PEG-GNR but not DSPE-PEG-GNR. Gold-based nanoscale systems have great value as a promising platform for skin diseases therapy.

ZnO Nanoparticles Modified with an Amphipathic Peptide Show Improved Photoprotection in Skin

ZnO nanoparticles of different sizes were functionalized with an amphipathic peptide, and its effect on nanoparticle stabilization and UV photoprotective activity was studied in this article. The peptide-modified nanoparticles exhibited lower aggregation, significant reduction in Zn²⁺ leaching in vitro and even inside the cells for smaller particle sizes, reduced photocatalytic activity, and reduced cellular toxicity under UV-B treated conditions. In addition, the peptide-modified 60 nm ZnO nanoparticles showed lower genotoxicity, lower oxidative stress induction levels, less DNA damage responses, and less immunogenic potential than the bare counterparts in the presence of UV-B rays. They localized more in the stratum corneum and epidermis ex vivo, indicating better retention in epidermis, and demonstrated improved UV-B protection and/or skin integrity in SKH-1 mice in vivo compared to unmodified nanoparticles and commercial UV-protective agents tested. To our knowledge, this is the first report on the application of peptide-modified ZnO nanoparticles for improved photoprotection.

Health hazards of nanoparticles: understanding the toxicity mechanism of nanosized ZnO in cosmetic products

In recent years, nanoparticles are being used extensively in personal healthcare products such as cosmetics, sunscreens, soaps, and shampoos. Particularly, metal oxide nanoparticles are gaining competence as key industrial constituents, progressing toward a remarkable rise in their applications. Zinc oxide and titanium oxide nanoparticles are the most commonly employed metal oxide nanoparticles in sunscreens, ointments, foot care, and over the counter topical products. Dermal exposure to these metal oxides predominantly occurs through explicit use of cosmetic products and airway exposure to nanoparticle dusts is primarily mediated via occupational exposure. There is a compelling need to understand the toxicity effects of nanoparticles which can easily enter the cells and induce oxidative stress. Consequently, these products have become a direct source of pollution in the environment and thereby greatly impact our ecosystem. A complete understanding of the toxicity mechanism of nano-ZnO is intended to resolve whether and to what extent such nanoparticles may pose a threat to the environment and to human beings. In this review article, we have discussed the characteristics of metal oxide nanoparticles and its applications in the cosmetic industry. We have also highlighted about their toxicity effects and their impact on human health.