The state of nano-sized titanium dioxide (TiO2) may affect sunscreen performance

Predicting environmental concentrations of nanomaterials for exposure assessment - a review

There have been major advances in the science to predict the likely environmental concentrations of nanomaterials, which is a key component of exposure and subsequent risk assessment. Considerable progress has been since the first Material Flow Analyses (MFAs) in 2008, which were based on very limited information, to more refined current tools that take into account engineered nanoparticle (ENP) size distribution, form, dynamic release, and better-informed release factors. These MFAs provide input for all environmental fate models (EFMs), that generate estimates of particle flows and concentrations in various environmental compartments. While MFA models provide valuable information on the magnitude of ENP release, they do not account for fate processes, such as homo- and heteroaggregation, transformations, dissolution, or corona formation. EFMs account for these processes in differing degrees. EFMs can be divided into multimedia compartment models (e.g., atmosphere, waterbodies and their sediments, soils in various landuses), of which there are currently a handful with varying degrees of complexity and process representation, and spatially-resolved watershed models which focus on the water and sediment compartments. Multimedia models have particular applications for considering predicted environmental concentrations (PECs) in particular regions, or for developing generic "fate factors" (i.e., overall persistence in a given compartment) for life-cycle assessment. Watershed models can track transport and eventual fate of emissions into a flowing river, from multiple sources along the waterway course, providing spatially and temporally resolved PECs. Both types of EFMs can be run with either continuous sources of emissions and environmental conditions, or with dynamic emissions (e.g., temporally varying for example as a new nanomaterial is introduced to the market, or with seasonal applications), to better understand the situations that may lead to peak PECs that are more likely to result in exceedance of a toxicological threshold. In addition, bioaccumulation models have been developed to predict the internal concentrations that may accumulate in exposed organisms, based on the PECs from EFMs. The main challenge for MFA and EFMs is a full validation against observed data. To date there have been no field studies that can provide the kind of dataset(s) needed for a true validation of the PECs. While EFMs have been evaluated against a few observations in a small number of locations, with results that indicate they are in the right order of magnitude, there is a great need for field data. Another major challenge is the input data for the MFAs, which depend on market data to estimate the production of ENPs. The current information has major gaps and large uncertainties. There is also a lack of robust analytical techniques for quantifying ENP properties in complex matrices; machine learning may be able to fill this gap. Nevertheless, there has been major progress in the tools for generating PECs. With the emergence of nano- and microplastics as a leading environmental concern, some EFMs have been adapted to these materials. However, caution is needed, since most nano- and microplastics are not engineered, therefore their characteristics are difficult to generalize, and there are new fate and transport processes to consider.

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.

Investigating the use of titanium dioxide (TiO2) nanoparticles on the amount of protection against UV irradiation

In this study, three samples of commercial titanium dioxide nanoparticles (TiO₂) in different sizes were used to investigate their effect on the formulation of sunscreen creams. The aim was to evaluate their role in the performance of sunscreens (i.e. SPF, UVAPF, and critical wavelength). Then the particle size of these samples was determined by photon correlation spectroscopy methods. As a result, the size of primary particles was reduced by using milling and homogenization methods at different times. The results showed that the particle size of samples TA, TB, and TC in the ultrasonic homogenizer decreased from 966.4, 2745.8, and 2471.6 nm to 142.6, 254.8, and 262.8 nm, respectively. These particles were used in the pristine formulation. Then the functional characteristics of each formulation were determined by standard methods. TA had the best dispersion in cream compared to other samples due to its smaller size (i.e. 142.6 nm). For each formulation, two important parameters, including pH and TiO₂ dosage, were investigated in different states. The results showed that the formulations prepared with TA had the lowest viscosity compared to formulations containing TB and TC. SPSS 17 statistical software analysis of variance showed that the performance of SPF, UVAPF and λc in formulations containing TA had the highest levels. Also, the sample containing TAU with the lowest particle size values had the highest protection against UV rays (SPF). According to the photocatalytic functionality of TiO₂, the photodegradation of methylene blue in the presence of each nanoparticle of TiO₂ was studied. The results showed that smaller nanoparticles (i.e. TA) had more photocatalytic activity under UV-Vis irradiation during 4 h (TA (22%) > TB (16%) > TC (15%)). The results showed that titanium dioxide can be used as a suitable filter against all types of UVA and UVB rays.

Synthesis of Planar-Type ZnO Powder in Non-Nano Scale Dimension and Its Application in Ultraviolet Protection Cosmetics

ZnO is one of the most widely used inorganic sunscreens, owing to its fine particle size and UV light shielding capability. However, powders at nanosizes can be toxic and cause adverse effects. The development of non-nanosized particles has been slow. The present work investigated synthesis methods of non-nanosized ZnO particles for ultraviolet protection application. By altering the starting material, KOH concentration, and input speed, the ZnO particles can be obtained in different forms, including needle type, planar type, and vertical wall type. Cosmetic samples were made by mixing different ratios of synthesized powders. The physical properties and the UV blockage efficacy of different samples were evaluated using scanning electron microscopy (SEM), X-ray diffraction (XRD), particle size analyzer (PSA), and ultraviolet/visible (UV/Vis) spectrometer. The samples with 1:1 ratio of needle-type ZnO and vertical wall-type ZnO exhibited superior light blocking effect owing to improved dispersibility and prevention of particle agglomeration. The 1:1 mixed sample also complied with the European nanomaterials regulation due to the absence of nanosized particles. With superior UV protection in the UVA and UVB regions, the 1:1 mixed powder showed potential to be used as a main ingredient in UV protection cosmetics.

Nanoparticle Impact on the Bacterial Adaptation: Focus on Nano-Titania

Titanium dioxide nanoparticles (nano-titania/TiO₂ NPs) are used in different fields and applications. However, the release of TiO₂ NPs into the environment has raised concerns about their biosafety and biosecurity. In light of the evidence that TiO₂ NPs could be used to counteract antibiotic resistance, they have been investigated for their antibacterial activity. Studies reported so far indicate a good performance of TiO₂ NPs against bacteria, alone or in combination with antibiotics. However, bacteria are able to invoke multiple response mechanisms in an attempt to adapt to TiO₂ NPs. Bacterial adaption arises from global changes in metabolic pathways via the modulation of regulatory networks and can be related to single-cell or multicellular communities. This review describes how the impact of TiO₂ NPs on bacteria leads to several changes in microorganisms, mainly during long-term exposure, that can evolve towards adaptation and/or increased virulence. Strategies employed by bacteria to cope with TiO₂ NPs suggest that their use as an antibacterial agent has still to be extensively investigated from the point of view of the risk of adaptation, to prevent the development of resistance. At the same time, possible effects on increased virulence following bacterial target modifications by TiO₂ NPs on cells or tissues have to be considered.

Damaging effects of TiO2 nanoparticles on the ovarian cells of Bombyx mori

As a new type of biologically compatible material, TiO₂ NPs are widely used in the industry as additives, drug carriers, and components of skin care products. Due to their wide use, residual TiO₂ NPs in the environment are a safety concern that has attracted extensive attention. In this study, the ovarian cell line BmN of the model organism Bombyx mori was used to reveal the damaging effects of TiO₂ NPs exposure. The results demonstrated that TiO₂ NPs exhibited a dose-dependent effect on the relative cell viability, with significant toxic effects being observed above 20 mg/L. Oxidative damage analysis showed that ROS accumulated significantly in BmN cells after exposure to TiO₂ NPs (P ≤ 0.05) and induced DNA damage. Further analysis revealed that the transcriptional levels of key superoxide dismutase genes (SOD) decreased significantly, while the transcriptions of key genes of the MAPK/NF-κB signaling pathway (P38, MEK, ERK and REL) and the downstream inflammatory factor genes (IL6 and TNFSF5) were all significantly up-regulated (P ≤ 0.05). Overall, our results indicate that exposure to TiO₂ NPs leads to reduced transcription of antioxidant genes, accumulation of peroxides, and inflammation. These findings provide valuable data for the safety evaluation of environmental residues of TiO₂ NPs.

Design and development of topical liposomal formulations in a regulatory perspective

The skin is the absorption site for drug substances intended to treat loco-regional diseases, although its barrier properties limit the permeation of drug molecules. The growing knowledge of the skin structure and its physiology have supported the design of innovative nanosystems (e.g. liposomal systems) to improve the absorption of poorly skin-permeable drugs. However, despite the dozens of clinical trials started, few topically applied liposomal systems have been authorized both in the EU and the USA. Indeed, the intrinsic complexity of the topically applied liposomal systems, the higher production costs, the lack of standardized methods and the more stringent guidelines for assessing their benefit/risk balance can be seen as causes of such inefficient translation. The present work aimed to provide an overview of the physicochemical and biopharmaceutical characterization methods that can be applied to topical liposomal systems intended to be marketed as medicinal products, and the current regulatory provisions. The discussion highlights how such methodologies can be relevant for defining the critical quality attributes of the final product, and they can be usefully applied based on the phase of the life cycle of a liposomal product: to guide the formulation studies in the early stages of development, to rationally design preclinical and clinical trials, to support the pharmaceutical quality control system and to sustain post-marketing variations. The provided information can help define harmonized quality standards able to overcome the case-by-case approach currently applied by regulatory agencies in assessing the benefit/risk of the topically applied liposomal systems.

Exposure to ZnO/TiO2 Nanoparticles Affects Health Outcomes in Cosmetics Salesclerks

Concerns about the effects of nanoparticles (NPs) on human health are being raised by researchers because the risks of nanocosmetics like sunscreen are unknown. We explored the association between urinary oxidative stress markers and exposure of cosmetics salesclerks to 20 cosmetics that might contain titanium dioxide (TiO₂)/zinc oxide (ZnO) NPs. We then recruited 40 cosmetics salesclerks and 24 clothing salesclerks and categorized them based on their exposure to ZnO and TiO₂ NPs. Nineteen and 15 samples met the EU definition for TiO₂ and ZnO nanomaterials, respectively. Participants with a higher co-exposure index of ZnO and TiO₂ NPs had a significantly higher base level of urinary 8-hydroxy-2′-deoxyguanosin (8-OHdG) concentrations than the lower co-exposure group (5.82 vs. 2.85 ng/mL, p < 0.001). After potential confounding factors had been adjusted for, the TiO₂ and ZnO NP co-exposure index was significantly positively associated with the urinary 8-OHdG base concentration (β = 0.308, 95% CI = 0.106 to 0.510) and the creatinine-adjusted concentration (β = 0.486, 95% CI = 0.017 to 0.954). Current evidence suggests that the likelihood of harm from using sunscreens containing nanoparticles might result in higher urinary 8-OHdG. However, our limited number and types of sample cosmetics might underestimate the risk.

Interactions of TiO2 Nanoparticles with Ingredients from Modern Lifestyle Products and Their Effects on Human Skin Cells

The number of consumer products containing nanoparticles (NPs) experienced a rapid increase during the past decades. However, most studies of nanosafety have been conducted using only pure NPs produced in the laboratory, while the interactions with other ingredients in consumer products have rarely been considered so far. In the present study, we investigated such interactions—with a special focus on modern lifestyle products (MLPs) used by adolescents. An extensive survey was undertaken at different high schools all over Austria to identify MLPs that either contain NPs or that could come easily in contact with NPs from other consumer products (such as TiO₂ from sunscreens). Based on the results from a survey among secondary schools students, we focused on ingredients from Henna tattoos (2-hydroxy-1,4-naphtoquinone, HNQ, and p-phenylenediamine, PPD), fragrances (butylphenyl methylpropional, known as Lilial), cosmetics and skin-care products (four different parabens). As a cellular model, we decided to use neonatal normal human dermal fibroblasts (nNHDF), since skin contact is the main route of exposure for these compounds. TiO₂ NPs interacted with these compounds as evidenced by alterations in their hydrodynamic diameter observed by nanoparticle tracking analysis. Combinations of TiO₂ NPs with the different MLP components did not show altered cytotoxicity profiles compared to MLP components without TiO₂ NPs. Nevertheless, altered cellular glutathione contents were detected after incubation of the cells with Lilial. This effect was independent of the presence of TiO₂ NPs. Testing mixtures of NPs with other compounds from consumer products is an important approach to achieve a more reliable safety assessment.

Assessing UV filter inputs into beach waters during recreational activity: A field study of three French Mediterranean beaches from consumer survey to water analysis

In order to assess the release of UV filters from the sunscreen used by beachgoers into seawater within the bathing zone, a field campaign was carried out during the summer of 2017 at three beaches in Marseille, along the French Mediterranean coast. A social survey analyzed beachgoer attendance, the quantities and types of suncare products used and the bathing frequencies, while the bathing water was analyzed spatially and temporally so as to quantify both mineral and organic UV filters directly released and recovered. During the peak recreational time at the three beaches, both mineral and organic UV filters were detected in higher concentrations in the bathing area than offshore. In general, higher concentrations were recovered in the water top surface layer than in the water column, giving respectively 100-900 and 20-50 μg/L for TiO₂, 10-15 and 1-3 μg/L for ZnO, 40-420 and 30-150 ng/L for octocrylene, and 10-15 and 10-350 ng/L for avobenzone. More than 75% of the 471 interviewees reported bathing every time they go to the beach, with 68% using a suncare product 2.6 times on average. From these data we estimated that an average mass of 52 kg/day or 1.4 t/month of suncare products are possibly released into bathing water for a beach attended by 3000 people daily. The mass ratio of UV filters in such products typically ranges from 0.03 to 0.1, allowing us to propose theoretical maximum concentrations in the beach water. Our recovery of measured UV filter concentrations in seawater compared to the theoretical concentrations revealed two distinct scenarios for the mineral and organic filters. While up to 49% of the mineral filters used by beachgoers may be released into the seawater, the organic filters were minimally recovered in the environment, most likely due to internalization through the skin barrier or partial photodegradation.

Synthesis of Silicon Quantum Dots with Highly Efficient Full-Band UV Absorption and Their Applications in Antiyellowing and Resistance of Photodegradation

UV absorbers are very effective in the fields of antiyellowing, resistance of photocatalytic degradation, and sunscreen cosmetics. However, commercialized UV absorbers have the drawbacks of toxicity, low absorption efficiency, transparency, etc. Here, we report for the first time silicon quantum dots as full-band UV absorbers. The NH-refunctionalized silicon quantum dots with high-performance UV absorption were successfully synthesized under the synergistic effect of sodium citrate and ethanediamine, and the (NH, OH)-functionalized silicon quantum dots (SiQDs) with full-band UV absorption can be achieved by reregulating -NH₂ and -OH groups on the surface. The as-prepared (NH, OH)-functionalized SiQDs exhibited good stability and underwent treatment of varying pH and temperature. Furthermore, experimental results demonstrated that compared to commercial water-soluble organic UV absorbers, the (NH, OH)-functionalized SiQDs showed better antiyellowing performance for polyurethane and resistance of photocatalytic degradation for rhodamine B, and presented huge application potential in sunscreen cosmetics. Finally, the UV absorption mechanism of SiQDs was explained to be mainly related to Γ → Γ direct band gap transition, which absorb UV light and release it as thermal radiation.

Characterization of titanium dioxide and zinc oxide nanoparticles in sunscreen powder by comparing different measurement methods

Numerous consumer products, such as cosmetics, contain nanoparticles (NPs) of titanium dioxide (TiO₂) or zinc oxide (ZnO); however, this raises questions concerning the safety of such additives. Most of these products do not indicate whether the product includes NPs. In this study, we characterized metal oxide NPs according to size, shape, and composition as well as their aggregation/agglomeration characteristics. In order to comprehend quickly the characterization of metal oxide NPs, we employed single particle inductively coupled plasma (SP-ICPMS) to help quantify the size of metal oxide NPs; then, we use transmission electron microscopy (TEM) to corroborate the results. The crystal size and structure was measured by X-ray diffraction (XRD), there are two crystal phase of TiO₂ NPs in sunscreen powder showed in XRD. However, SP-ICPMS proved highly effective in determining the size of NPs, the results of which remarkably good agreement with the TEM measurements. Pretreatment included a conventional copper grid (requiring sample dilution) to evaluate the size, shape and composition of primary particles or plastic embedding (without the need for sample dilution) to evaluate the aggregate/aggregation of native NOAAs. The proposed method is an effective and fast approach to the characterization of oxide NPs in cosmetic sunscreen powder. These findings outline an alternative approach to the analysis of NPs in powder-form matrix.

How Has CDER Prepared for the Nano Revolution? A Review of Risk Assessment, Regulatory Research, and Guidance Activities

The Nanotechnology Risk Assessment Working Group in the Center for Drug Evaluation and Research (CDER) within the United States Food and Drug Administration (FDA) was established to assess the potential impact of nanotechnology on drug products. One of the working group's major initiatives has been to conduct a comprehensive risk management exercise regarding the potential impact of nanomaterial pharmaceutical ingredients and excipients on drug product quality, safety, and efficacy. This exercise concluded that current review practices and regulatory guidance are capable of detecting and managing the potential risks to quality, safety, and efficacy when a drug product incorporates a nanomaterial. However, three risk management areas were identified for continued focus during the review of drug products containing nanomaterials: (1) the understanding of how to perform the characterization of nanomaterial properties and the analytical methods used for this characterization, (2) the adequacy of in vitro tests to evaluate drug product performance for drug products containing nanomaterials, and (3) the understanding of properties arising from nanomaterials that may result in different toxicity and biodistribution profiles for drug products containing nanomaterials. CDER continues to actively track the incorporation of nanomaterials in drug products and the methodologies used to characterize them, in order to continuously improve the readiness of our science- and risk-based review approaches. In parallel to the risk management exercise, CDER has also been supporting regulatory research in the area of nanotechnology, specifically focused on characterization, safety, and equivalence (between reference and new product) considerations. This article provides a comprehensive summary of regulatory and research efforts supported by CDER in the area of drug products containing nanomaterials and other activities supporting the development of this emerging technology.

Nanodiamonds protect skin from ultraviolet B-induced damage in mice

BACKGROUND

Solar ultraviolet (UV) radiation causes various deleterious effects, and UV blockage is recommended for avoiding sunburn. Nanosized titanium dioxide and zinc oxide offer effective protection and enhance cosmetic appearance but entail health concerns regarding their photocatalytic activity, which generates reactive oxygen species. These concerns are absent in nanodiamonds (NDs). Among the UV wavelengths in sunlight, UVB irradiation primarily threatens human health.

RESULTS

The efficacy and safety of NDs in UVB protection were evaluated using cell cultures and mouse models. We determined that 2 mg/cm(2) of NDs efficiently reduced over 95% of UVB radiation. Direct UVB exposure caused cell death of cultured keratinocyte, fibroblasts and skin damage in mice. By contrast, ND-shielding significantly protected the aforementioned pathogenic alterations in both cell cultures and mouse models.

CONCLUSIONS

NDs are feasible and safe materials for preventing UVB-induced skin damage.

Product quality for nanomaterials: current U.S. experience and perspective

In recent years, there has been an increased focus on developing novel drug delivery systems and targeted therapies through the use of nanotechnology and nanomaterials. Such focus is translating to an increasing number of investigational new drug (IND) applications, new drug applications (NDAs), and abbreviated new drug applications (ANDAs) for drug products containing nanomaterials to the United States Food and Drug Administration (FDA). Although subject to the same rigorous regulatory standards and regulatory pathways as any drug product, unique properties that arise from the small size, large surface area, and polydispersity of nanomaterials may lead to additional scientific considerations when following current FDA guidelines and practices for drug evaluation. This review article will discuss these scientific considerations based on the experience with FDA-approved drug products containing nanomaterials.

Nanosafety research--are we on the right track?

The number of studies that have been published on the topic of nanosafety speaks for itself. We have seen an almost exponential rise over the past 15 years or so in the number of articles on nanotoxicology. Although only a couple of hundred papers had appeared on the topic of "Nanomaterials: environmental and health effects" before 2000, this number has exploded to over 10 000 since 2001. Most of these studies, however, do not offer any kind of clear statement on the safety of nanomaterials. On the contrary, most of them are either self-contradictory or arrive at completely erroneous conclusions. Three years ago in this Journal we underscored the deficiencies in the way these studies were designed and pointed out the sources of error in the methods used. Now, on the basis of a comprehensive review of the literature and with the help of selected toxicological end points, we attempt to indicate where the significant weaknesses of these studies lie and what we must improve in the future.

Understanding engineered nanomaterial skin interactions and the modulatory effects of ultraviolet radiation skin exposure

The study of engineered nanomaterials for the development of technological applications, nanomedicine, and nano-enabled consumer products is an ever-expanding discipline as is the concern over the impact of nanotechnology on human environmental health and safety. In this review, we discuss the current state of understanding of nanomaterial skin interactions with a specific emphasis on the effects of ultraviolet radiation (UVR) skin exposure. Skin is the largest organ of the body and is typically exposed to UVR on a daily basis. This necessitates the need to understand how UVR skin exposure can influence nanomaterial skin penetration, alter nanomaterial systemic trafficking, toxicity, and skin immune function. We explore the unique dichotomy that UVR has on inducing both deleterious and therapeutic effects in skin. The subject matter covered in this review is broadly informative and will raise awareness of potential increased risks from nanomaterial skin exposure associated with specific occupational and life style choices. The UVR-induced immunosuppressive response in skin raises intriguing questions that motivate future research directions in the nanotoxicology and nanomedicine fields.

Dispersion and surface functionalization of oxide nanoparticles for transparent photocatalytic and UV-protecting coatings and sunscreens

This review describes recent efforts on the synthesis, dispersion and surface functionalization of the three dominating oxide nanoparticles used for photocatalytic, UV-blocking and sunscreen applications: titania, zinc oxide, and ceria. The gas phase and liquid phase synthesis is described briefly and examples are given of how weakly aggregated photocatalytic or UV-absorbing oxide nanoparticles with different composition, morphology and size can be generated. The principles of deagglomeration are reviewed and the specific challenges for nanoparticles highlighted. The stabilization of oxide nanoparticles in both aqueous and non-aqueous media requires a good understanding of the magnitude of the interparticle forces and the surface chemistry of the materials. Quantitative estimates of the Hamaker constants in various media and measurements of the isoelectric points for the different oxide nanoparticles are presented together with an overview of different additives used to prepare stable dispersions. The structural and chemical requirements and the various routes to produce transparent photocatalytic and nanoparticle-based UV-protecting coatings, and UV-blocking sunscreens are described and discussed.

Characterization of physicochemical properties of ivy nanoparticles for cosmetic application

Background

Naturally occurring nanoparticles isolated from English ivy (Hedera helix) have previously been proposed as an alternative to metallic nanoparticles as sunscreen fillers due to their effective UV extinction property, low toxicity and potential biodegradability.

Methods

This study focused on analyzing the physicochemical properties of the ivy nanoparticles, specifically, those parameters which are crucial for use as sunscreen fillers, such as pH, temperature, and UV irradiation. The visual transparency and cytotoxicity of ivy nanoparticles were also investigated comparing them with other metal oxide nanoparticles.

Results

Results from this study demonstrated that, after treatment at 100°C, there was a clear increase in the UV extinction spectra of the ivy nanoparticles caused by the partial decomposition. In addition, the UVA extinction spectra of the ivy nanoparticles gradually reduced slightly with the decrease of pH values in solvents. Prolonged UV irradiation indicated that the influence of UV light on the stability of the ivy nanoparticle was limited and time-independent. Compared to TiO₂ and ZnO nanoparticles, ivy nanoparticles showed better visual transparency. Methylthiazol tetrazolium assay demonstrated that ivy nanoparticles exhibited lower cytotoxicity than the other two types of nanoparticles. Results also suggested that protein played an important role in modulating the three-dimensional structure of the ivy nanoparticles.

Conclusions

Based on the results from this study it can be concluded that the ivy nanoparticles are able to maintain their UV protective capability at wide range of temperature and pH values, further demonstrating their potential as an alternative to replace currently available metal oxide nanoparticles in sunscreen applications.

Tissue and cellular distribution of gold nanoparticles varies based on aggregation/agglomeration status

AIM

The ability of nanoparticles to form larger superstructures of aggregates and agglomerates has been extensively noted in the literature. The in vivo biological impact of these structures, however, has not been assessed. This knowledge gap is especially critical in the safety assessment of nanoparticles to be used for therapeutic purposes.

METHOD/RESULTS

Here we show that when administered intravenously into a mouse model, gold nanoparticle superstructures of reversible agglomerates and irreversible aggregates demonstrate significant differences in organ and cellular distribution compared with the primary particle building blocks. In addition, different structures produced different blood serum chemistry data.

CONCLUSION

These findings raise the possibility for different mechanisms of toxicity between the structures. Such a possibility necessitates complete characterization and stability assessment of nanomaterials prior to their in vivo administration.

Titanium dioxide in our everyday life; is it safe?

BACKGROUND

Titanium dioxide (TiO(2)) is considered as an inert and safe material and has been used in many applications for decades. However, with the development of nanotechnologies TiO(2) nanoparticles, with numerous novel and useful properties, are increasingly manufactured and used. Therefore increased human and environmental exposure can be expected, which has put TiO(2) nanoparticles under toxicological scrutiny. Mechanistic toxicological studies show that TiO(2) nanoparticles predominantly cause adverse effects via induction of oxidative stress resulting in cell damage, genotoxicity, inflammation, immune response etc. The extent and type of damage strongly depends on physical and chemical characteristics of TiO(2) nanoparticles, which govern their bioavailability and reactivity. Based on the experimental evidence from animal inhalation studies TiO(2) nanoparticles are classified as "possible carcinogenic to humans" by the International Agency for Research on Cancer and as occupational carcinogen by the National Institute for Occupational Safety and Health. The studies on dermal exposure to TiO(2) nanoparticles, which is in humans substantial through the use of sunscreens, generally indicate negligible transdermal penetration; however data are needed on long-term exposure and potential adverse effects of photo-oxidation products. Although TiO(2) is permitted as an additive (E171) in food and pharmaceutical products we do not have reliable data on its absorption, distribution, excretion and toxicity on oral exposure. TiO(2) may also enter environment, and while it exerts low acute toxicity to aquatic organisms, upon long-term exposure it induces a range of sub-lethal effects.

CONCLUSIONS

Until relevant toxicological and human exposure data that would enable reliable risk assessment are obtained, TiO(2) nanoparticles should be used with great care.