Approach to using mechanism-based structure activity relationship (SAR) analysis to assess human health hazard potential of nanomaterials

With the increasing use and development of engineered nanoparticles in electronics, consumer products, pesticides, food and pharmaceutical industries, there is a growing concern about potential human health hazards of these materials. A number of studies have demonstrated that nanoparticle toxicity is extremely complex, and that the biological activity of nanoparticles will depend on a variety of physicochemical properties such as particle size, shape, agglomeration state, crystal structure, chemical composition, surface area and surface properties. Nanoparticle toxicity can be attributed to nonspecific interaction with biological structures due to their physical properties (e.g., size and shape) and biopersistence, or to specific interaction with biomolecules through their surface properties (e.g., surface chemistry and reactivity) or release of toxic ions. The toxic effects of most nanomaterials have not been adequately characterized and currently, there are many issues and challenges in toxicity testing and risk assessment of nanoparticles. Based on the possible mechanisms of action and available in vitro and in vivo toxicity database, this paper proposes an approach to using mechanism-based SAR analysis to assess the relative human health hazard/risk potential of various types of nanomaterials.     

In vitro evaluation of cellular response induced by manufactured nanoparticles

"Nanoparticle" is defined as the particles whose diameter in at least one dimension is less than 100 nm. Compared with fine-particles, nanoparticles have large specific surface area. There is a dramatic increase over fine-particles in chemical and physical activities, such as ion release, adsorption ability, and ROS production. These properties are important for industrial use, and many nanoparticles are already used in products familiar to consumers as sunscreens and cosmetics. However, nanoparticle properties beneficial to the industry may also induce biological influences, including toxic activities. Recently, many investigations about the toxicology of nanoparticles have been reported. In the evaluation of nanoparticles toxicity, in vitro studies give us important information, especially in terms of toxic mechanisms. In vitro studies showed that some nanoparticles induce oxidative stress, apoptosis, production of cytokines, and cell death. There are reports that cellular influences of other nanoparticles are small. There are also reports of different results, some with low and some with high influences, for the same nanoparticle. One of the causes of this inconsistency might be a diremption of the living body influence study and the characterization study. Characterization of individual nanoparticles and their dispersions are essential for in vitro evaluation of their biological effects since each nanoparticle shows unique chemical and physical properties. Particularly, the aggregation state and metal ion release ability of nanoparticles affect its cellular influences. Reports concerning the characterization in the in vitro toxicity assessment are increasing. For an accurate risk assessment of nanoparticles, in this review, we outline recent studies of in vitro evaluation of cellular influences induced by nanoparticles. Moreover, we also introduce current studies about the characterization methods of nanoparticles and their dispersions for toxicological evaluation.     

Effects of nanomaterial physicochemical properties on in vivo toxicity

It is well recognized that physical and chemical properties of materials can alter dramatically at nanoscopic scale, and the growing use of nanotechnologies requires careful assessment of unexpected toxicities and biological interactions. However, most in vivo toxicity concerns focus primarily on pulmonary, oral, and dermal exposures to ultrafine particles. As nanomaterials expand as therapeutics and as diagnostic tools, parenteral administration of engineered nanomaterials should also be recognized as a critical aspect for toxicity consideration. Due to the complex nature of nanomaterials, conflicting studies have led to different views of their safety. Here, the physicochemical properties of four representative nanomaterials (dendrimers, carbon nanotubes, quantum dots, and gold nanoparticles) as it relates to their toxicity after systemic exposure is discussed.     

Physical and chemical stability of drug nanoparticles

As nano-sizing is becoming a more common approach for pharmaceutical product development, researchers are taking advantage of the unique inherent properties of nanoparticles for a wide variety of applications. This article reviews the physical and chemical stability of drug nanoparticles, including their mechanisms and corresponding characterization techniques. A few common strategies to overcome stability issues are also discussed.     

Development of a PIXE analysis method for the determination of the biopersistence of SiC and TiC nanoparticles in rat lungs

With the advent of nanoparticles produced in high quantities and employed in products or processes, the need to evaluate their potential toxicological effects is necessary. For this purpose, biopersistence studies are needed to assess the possible effects of nanoparticles in parallel with a proper characterization. The insoluble character of many nanomaterials makes traditional chemical analytical methods unapplicable for the ex-vivo measurements of their concentration in organs. Ion beam-based techniques such as Particle-Induced X-ray Emission (PIXE) can solve this difficulty. We illustrate that by the measurement of biopersistence of SiC and TiC nanoparticles instilled in rats lungs and investigated over a 60-day time span. The results can be obtained within minutes and the limits of detection are within ppm levels.     

Inorganic hollow nanoparticles and nanotubes in nanomedicine Part 1. Drug/gene delivery applications

Recent cytotoxicity studies on carbon nanotubes have shown that the biocompatibility of nanomaterial might be determined mainly by surface functionalization, rather than by size, shape, and material. Although the cytotoxicity for individual inorganic hollow nanomaterials should be extensively tested in vitro and in vivo, potential safety concerns about the use of inorganic nanomaterials in biomedical applications could be alleviated with proper surface treatment. Inorganic hollow nanoparticles and nanotubes have attracted great interest in nanomedicine because of the generic transporting ability of porous material and a wide range of functionality that arises from their unique optical, electrical, and physical properties. In this review, we describe recent developments of hollow and porous inorganic nanomaterials in nanomedicine, especially for drug/gene delivery.     

Biopharmaceutics and therapeutic potential of engineered nanomaterials

Engineered nanomaterials are at the leading edge of the rapidly developing nanosciences and are founding an important class of new materials with specific physicochemical properties different from bulk materials with the same compositions. The potential for nanomaterials is rapidly expanding with novel applications constantly being explored in different areas. The unique size-dependent properties of nanomaterials make them very attractive for pharmaceutical applications. Investigations of physical, chemical and biological properties of engineered nanomaterials have yielded valuable information. Cytotoxic effects of certain engineered nanomaterials towards malignant cells form the basis for one aspect of nanomedicine. It is inferred that size, three dimensional shape, hydrophobicity and electronic configurations make them an appealing subject in medicinal chemistry. Their unique structure coupled with immense scope for derivatization forms a base for exciting developments in therapeutics. This review article addresses the fate of absorption, distribution, metabolism and excretion (ADME) of engineered nanoparticles in vitro and in vivo. It updates the distinctive methodology used for studying the biopharmaceutics of nanoparticles. This review addresses the future potential and safety concerns and genotoxicity of nanoparticle formulations in general. It particularly emphasizes the effects of nanoparticles on metabolic enzymes as well as the parenteral or inhalation administration routes of nanoparticle formulations. This paper illustrates the potential of nanomedicine by discussing biopharmaceutics of fullerene derivatives and their suitability for diagnostic and therapeutic purposes. Future direction is discussed as well.     

Comparative study of cytotoxicity, oxidative stress and genotoxicity induced by four typical nanomaterials: the role of particle size, shape and composition

Although the biological effects of some nanomaterials have already been assessed, information on toxicity and possible mechanisms of various particle types are insufficient. Moreover, the role of particle properties in the toxic reaction remains to be fully understood. In this paper, we aimed to explore the interrelationship between particle size, shape, chemical composition and toxicological effects of four typical nanomaterials with comparable properties: carbon black (CB), single wall carbon nanotube, silicon dioxide (SiO(2)) and zinc dioxide (ZnO) nanoparticles. We investigated the cytotoxicity, genotoxicity and oxidative effects of particles on primary mouse embryo fibroblast cells. As observed in the methyl thiazolyl tetrazolium (MTT) and water-soluble tetrazolium (WST) assays, ZnO induced much greater cytotoxicity than non-metal nanoparticles. This was significantly in accordance with intracellular oxidative stress levels measured by glutathione depletion, malondialdehyde production, superoxide dismutase inhibition as well as reactive oxygen species generation. The results indicated that oxidative stress may be a key route in inducing the cytotoxicity of nanoparticles. Compared with ZnO nanoparticles, carbon nanotubes were moderately cytotoxic but induced more DNA damage determined by the comet assay. CB and SiO(2) seemed to be less effective. The comparative analysis demonstrated that particle composition probably played a primary role in the cytotoxic effects of different nanoparticles. However, the potential genotoxicity might be mostly attributed to particle shape.     

Enzyme-responsive nanoparticles for drug release and diagnostics

Enzymes are key components of the bionanotechnology toolbox that possess exceptional biorecognition capabilities and outstanding catalytic properties. When combined with the unique physical properties of nanomaterials, the resulting enzyme-responsive nanoparticles can be designed to perform functions efficiently and with high specificity for the triggering stimulus. This powerful concept has been successfully applied to the fabrication of drug delivery schemes where the tissue of interest is targeted via release of cargo triggered by the biocatalytic action of an enzyme. Moreover, the chemical transformation of the carrier by the enzyme can also generate therapeutic molecules, therefore paving the way to design multimodal nanomedicines with synergistic effects. Dysregulation of enzymatic activity has been observed in a number of severe pathological conditions, and this observation is useful not only to program drug delivery in vivo but also to fabricate ultrasensitive sensors for diagnosing these diseases. In this review, several enzyme-responsive nanomaterials such as polymer-based nanoparticles, liposomes, gold nanoparticles and quantum dots are introduced, and the modulation of their physicochemical properties by enzymatic activity emphasized. When known, toxicological issues related to the utilization nanomaterials are highlighted. Key examples of enzyme-responsive nanomaterials for drug delivery and diagnostics are presented, classified by the type of effector biomolecule, including hydrolases such as proteases, lipases and glycosidases, and oxidoreductases.     

纳米氧化铈在医药领域中的应用研究进展

纳米氧化铈作为金属氧化物纳米颗粒中重要的一员,通过与氧原子的可逆结合以及氧空位的存在,在Ce³⁺和Ce⁴⁺之间不断循环转换,使其具有氧化还原的双重特性。由于其特殊的物理化学性质,纳米氧化铈作为一种用途广泛的纳米材料得到广泛的关注,尤其是在医药领域方面。越来越多研究表明纳米氧化铈具有抗氧化、抗肿瘤、抗菌及神经保护等作用,这些作用通过模拟天然酶活性、诱导肿瘤细胞凋亡、抑制异常血管生长、破坏细菌细胞壁、清除活性氧等作用机制来实现。本文综述了纳米氧化铈在医药领域方面的应用,以期为纳米氧化铈生物医学研究和临床应用提供参考。     

纳米材料诱导肺部疾病及其机制研究进展

随着纳米科技的飞速发展, 纳米材料凭借其独特的理化性能在材料、 工业、 环保、 军事、 医药等多个领域扮 演着重要的角色。纳米材料的生产和使用, 使其不可避免地进入生态系统, 人们可通过环境暴露、 职业暴露和医源 性暴露接触到纳米材料。呼吸系统是纳米材料进入人体的最主要途径。大量研究证实, 吸入的纳米材料主要通过 氧化应激、 炎症反应和离子紊乱等毒性机制对肺造成损伤, 诱导肉芽肿病变、 肺纤维化、 哮喘、 慢性阻塞性肺疾病, 甚 至肺癌等肺部疾病的发生。本文对纳米材料暴露与肺部疾病的关系及其肺毒性作用机制进行简要综述。     

Alumina nanoparticles alter rhythmic activities of local interneurons in the antennal lobe of Drosophila

Abstract

The special physical and chemical properties of nanomaterials open up new capabilities and functions. However, concerns have been raised about the risks produced by nanoparticles, their potential to cause undesirable effects, such as contamination of the environment and other adverse effects. In this study, we used Drosophila as a model organism to explore the effects of nano-alumina on the central nervous system. We focused on the rhythmic activities in the antennal lobe of Drosophila using patch clamps to record the electrophysiological activities. We found that 15 min after application of alumina nanoparticles, the average frequencies of spontaneous activities were significantly decreased compared with control groups (0.65 ± 0.13 Hz, 0.34 ± 0.07 Hz, *p < 0.05). These results indicated that nano-alumina might have adverse effects on the central nervous system in Drosophila.     

Noble metal nanomaterial-based aptasensors for microbial toxin detection

Microbial toxins generated by bacteria, fungi and algae cause serious food-safety problems due to the frequent contamination of foodstuffs and their poisonous nature. Becoming acquainted with the contamination condition of foodstuffs is highly dependent on developing sensitive, specific, and accurate methods for targeting microbial toxins. Aptamers, obtained from systematic evolution of ligands by exponential enrichment (SELEX), have significant advantages for microbial toxin analysis, such as small size, reproducible chemical synthesis, and modification, as well as high binding affinity, specificity, and stability. Besides, aptamers have a predictable structure and can be tailored using biomolecular tools (e.g., ligase, endonuclease, exonuclease, polymerase, and so on), which is conducive to the development of flexible and variable amplification methods. Recent studies revealed that the combination of aptamers and noble metal nanomaterials offers unprecedented opportunities for microbial toxin detection. Noble metal nanomaterials with outstanding physical and chemical properties facilitate the detection process and improve the sensitivity and specificity. In this review, we discuss current progress in the development of various noble metal nanomaterial-based aptasensors for microbial toxin detection. These noble metal nanomaterials include gold nanoparticles, gold nanorods, gold nanoclusters, silver nanoparticles, silver nanoclusters, and bimetallic nanomaterials. Aptasensors based on noble metal nanomaterials exhibiting high selectivity and sensitivity represent a promising tool for microbial toxin detection.     

Green synthesis of zinc oxide nanoparticles: A review of the synthesis methodology and mechanism of formation

Zinc oxide is of significant importance for many industries due to its versatile properties, which have been enhanced with the production of this material in the nanoscale. Nonetheless, the increase in concerns related to environmental impact has led to the development of eco-friendly processes for its production. Recent interest in obtaining metal and metal oxide nanoparticles using biological approaches has been reported in the literature. This method was termed ‘green synthesis’ as it is a less hazardous process than chemical and physical synthesis methods currently used in the industry to obtain these nanomaterials. Zinc oxide nanoparticles have been successfully obtained by green synthesis using different biological substrates. However, large scale production using green synthesis approaches remains a challenge due to the complexity of the biological extracts that poses a barrier onto the elucidation of the reactions and mechanism of formation that occur during the synthesis. Hence, the current review includes a summary of the different sources of biological substrates and methodologies applied to the green synthesis of zinc oxide nanoparticles and the impact on their properties. This work also describes the advances on the understanding of the mechanism routes reported in the literature.     

Nanomedicine and nanotoxicology: two sides of the same coin

Current advances in nanotechnology have led to the development of the new field of nanomedicine, which includes many applications of nanomaterials and nanodevices for diagnostic and therapeutic purposes. The same unique physical and chemical properties that make nanomaterials so attractive may be associated with their potentially calamitous effects on cells and tissues. Our recent study demonstrated that aspiration of single-walled carbon nanotubes elicited an unusual inflammatory response in the lungs of exposed mice with a very early switch from the acute inflammatory phase to fibrogenic events resulting in pulmonary deposition of collagen and elastin. This was accompanied by a characteristic change in the production and release of proinflammatory to anti-inflammatory profibrogenic cytokines, decline in pulmonary function, and enhanced susceptibility to infection. Chemically unmodified (nonfunctionalized) carbon nanotubes are not effectively recognized by macrophages. Functionalization of nanotubes results in their increased recognition by macrophages and is thus used for the delivery of nanoparticles to macrophages and other immune cells to improve the quality of diagnostic and imaging techniques as well as for enhancement of the therapeutic effectiveness of drugs. These observations on differences in recognition of nanoparticles by macrophages have important implications in the relationship between the potentially toxic health effects of nanomaterials and their applications in the field of nanomedicine.     

Characterization of nanomaterial dispersion in solution prior to in vitro exposure using dynamic light scattering technique.

The need to characterize nanoparticles in solution before assessing the in vitro toxicity is a high priority. Particle size, size distribution, particle morphology, particle composition, surface area, surface chemistry, and particle reactivity in solution are important factors which need to be defined to accurately assess nanoparticle toxicity. Currently, there are no well-defined techniques for characterization of wet nanomaterials in aqueous or biological solutions. Previously reported nanoparticle characterization techniques in aqueous or biological solutions have consisted of the use of ultra-high illumination light microscopy and disc centrifuge sedimentation; however, these techniques are limited by the measurement size range. The current study focuses on characterizing a wide range of nanomaterials using dynamic light scattering (DLS) and transmission electron microscopy, including metals, metal oxides, and carbon-based materials, in water and cell culture media, with and without serum. Cell viability and cell morphology studies were conducted in conjunction with DLS experiments to evaluate toxicological effects from observed agglomeration changes in the presence or absence of serum in cell culture media. Observations of material-specific surface properties were also recorded. It was also necessary to characterize the impact of sonication, which is implemented to aid in particle dispersion and solution mixture. Additionally, a stock solution of nanomaterials used for toxicology studies was analyzed for changes in agglomeration and zeta potential of the material over time. In summary, our results demonstrate that many metal and metal oxide nanomaterials agglomerate in solution and that depending upon the solution particle agglomeration is either agitated or mitigated. Corresponding toxicity data revealed that the addition of serum to cell culture media can, in some cases, have a significant effect on particle toxicity possibly due to changes in agglomeration or surface chemistry. It was also observed that sonication slightly reduces agglomeration and has minimal effect on particle surface charge. Finally, the stock solution experienced significant changes in particle agglomeration and surface charge over time.     

Research strategies for safety evaluation of nanomaterials. Part VI. Characterization of nanoscale particles for toxicological evaluation.

To properly assign mechanisms or causes for toxic effects of nanoscale materials, their properties and characteristics both outside and within the biological environment must be well understood. Scientists have many tools for studying the size, shape, and surface properties of particulates outside of the physiological environment; however, it is difficult to measure many of these same properties in situ without perturbing the environment, leading to spurious findings. Characterizing nanoparticle systems in situ can be further complicated by an organism's active clearance, defense, and/or immune responses. As toxicologists begin to examine nanomaterials in a systematic fashion, there is consensus that a series of guidelines or recommended practices is necessary for basic characterization of nanomaterials. These recommended practices should be developed jointly by physical scientists skilled in nano characterization and biological scientists experienced in toxicology research. In this article, basic nanoparticle characterization techniques are discussed, along with the some of the issues and implications associated with measuring nanoparticle properties and their interactions with biological systems. Recommendations regarding how best to approach nanomaterial characterization include using proper sampling and measurement techniques, forming multidisciplinary teams, and making measurements as close to the biological action point as possible.     

Mutagenic effects of gold nanoparticles induce aberrant phenotypes in Drosophila melanogaster

The peculiar physical/chemical characteristics of engineered nanomaterials have led to a rapid increase of nanotechnology-based applications in many fields. However, before exploiting their huge and wide potential, it is necessary to assess their effects upon interaction with living systems. In this context, the screening of nanomaterials to evaluate their possible toxicity and understand the underlying mechanisms currently represents a crucial opportunity to prevent severe harmful effects in the next future. In this work we show the in vivo toxicity of gold nanoparticles (Au NPs) in Drosophila melanogaster, highlighting significant genotoxic effects and, thus, revealing an unsettling aspect of the long-term outcome of the exposure to this nanomaterial. After the treatment with Au NPs, we observed dramatic phenotypic modifications in the subsequent generations of Drosophila, demonstrating their capability to induce mutagenic effects that may be transmitted to the descendants. Noteworthy, we were able to obtain the first nanomaterial-mutated organism, named NM-mut. Although these results sound alarming, they underline the importance of systematic and reliable toxicology characterizations of nanomaterials and the necessity of significant efforts by the nanoscience community in designing and testing suitable nanoscale surface engineering/coating to develop biocompatible nanomaterials with no hazardous effects for human health and environment. FROM THE CLINICAL EDITOR: While the clinical application of nanomedicine is still in its infancy, the rapid evolution of this field will undoubtedly result in a growing number of clinical trials and eventually in human applications. The interactions of nanoparticles with living organisms determine their toxicity and long-term safety, which must be properly understood prior to large-scale applications are considered. The paper by Dr. Pompa's team is the first ever demonstration of mutagenesis resulting in clearly observable phenotypic alterations and the generation of nano-mutants as a result of exposure to citrate-surfaced gold nanoparticles in drosophila. These groundbreaking results are alarming, but represent a true milestone in nanomedicine and serve as a a reminder and warning about the critical importance of "safety first" in biomedical science.     

Importance of researches on chronic effects by manufactured nanomaterials

Manufactured nanomaterials are the most important substances for the nanotechnology. The nanomaterials possess different physico-chemical properties from bulk materials. The new properties may lead to biologically beneficial effects and/or adverse effects. However, there are no standardized evaluation methods at present. Some domestic research projects and international OECD programs are ongoing, in order to share the health impact information of nanomaterials or to standardize the evaluation methods. From 2005, our institutes have been conducting the research on the establishment of health risk assessment methodology of manufactured nanomaterials. In the course of the research project, we revealed that the nanomaterials were competent to cause chronic effects, by analyzing the intraperitoneal administration studies and carcinogenic promotion studies. These studies suggested that even aggregated nanomaterials were crumbled into nanosized particles inside the body during the long-term, and the particles were transferred to other organs. Also investigations of the toxicokinetic properties of nanomaterials after exposure are important to predict the chronically targeted tissues. The long lasting particles/fibers in the particular tissues may cause chronic adverse effects. Therefore, focusing on the toxicological characterization of chronic effects was considered to be most appropriate approach for establishing the risk assessment methods of nanomaterials.     

Nanosafety studies of nanomaterials about biodistribution and immunotoxicity

A diverse array of nanomaterials such as nanosilicas and carbon nanotubes are in widespread use due to the development of nanotechnology. Nanomaterials are already being applied in universal fields such as electronics, sunscreens, cosmetics, and medicine, because they have unique physicochemical properties such as high conductivity, strength, durability, and chemical reactivity. The advent of nanomaterials has also provided extraordinary opportunities for biomedical applications. However, the increasing use of nanomaterials has raised public concern about their potential risks to human health. In particular, recent reports have indicated that carbon nanotubes induced exaggerated inflammation and mesothelioma-like lesions in mice. However, few studies have examined the immunotoxicity of nanomaterials and it is essential to progress studies on the immunotoxicity of nanomaterials to ensure their safety. In this regard, we have attempted to elucidate the pharmacodynamics and immunotoxicity of nanomaterials, in order to develop novel safe nanomaterials and to establish scientifically based regulations. In this review, we would like to introduce our data on the immunotoxicity of nanosilicas, especially the relationship between physical properties (primary grain size, configuration and surface charge), pharmacodynamics of these materials, and their immunotoxicity. We consider that our study will improve the quality of human life by safely using nanomaterials, which can benefit society in general.