Nanomaterials: A Danger or a Promise?

Among the chemical, physical, or electrochemical processes generally used in particles production, the polyol-mediated synthesis of inorganic nanoparticles appears as an easy to carry out and versatile route. In this chapter, properties of polyols (α-diols and etherglycols) are first recalled in order to explain the versatility of this process. Guidelines which allow controlling the nucleation and growth steps in such media are then given in order to obtain particles with well-defined characteristics namely, a uniform shape, a mean size in the micron, submicron or nanometer range with a narrow size distribution, and a low degree of agglomeration. Examples of size tuning of ferromagnetic metals (Fe, Co, Ni, and their alloys) and noble metals are given as well as examples of shape control leading to 1D nanostructures with a particulate emphasis on the growth mechanism of silver nanorods or nanowires. Examples of polyol-mediated synthesis of oxide (spinel ferrites, Cu₂O, ZnO) nanoparticles through hydrolysis reaction are also given. Throughout this chapter it is pointed out how the polyol process allows tuning the size and shape-dependent magnetic properties of ferromagnetic metal or spinel ferrite particles which may be used as advanced functional materials in various fields: high permeability composite materials, high density recording media, high temperature permanent magnets, and in biomedical applications such as magnetic resonance imaging, cancer treatment by hyperthermia, or targeted drug delivery

Since the emergence of Nanotechnology in the past decades, the development and design of organic and bioorganic nanomaterials has become an important field of research. Such materials find many applications in a wide range of domains such as electronic, photonic, or biotechnology, which contribute to impact our society and our way of life. The improvement of properties and the discovery of new functionalities are key goals that cannot be obtained without a well controlled and a better understanding of the preparation methods which constitute the starting point of the design of a specific organic material. In this context, this chapter gives a general but non-exhaustive overview of the methods of preparation of organic and bioorganic nanoparticles. Some general definitions about organic nanoparticles and description of organic compounds are given before describing the most common methods used divided into two families, the two-step and one-step procedures. The major part of the two-step procedures is based on an emulsification step followed by generation of nanoparticles through different mechanisms such as precipitation, gelation, or polymerization. The one-step procedures are founded on generation of nanoparticles through different techniques such as nanoprecipitation, desolvation, or drying processes without preliminary emulsification step. For each method, the description is supported by several examples and focused on the explanation of the general mechanisms and of the major key parameters involved in the control of the nanoparticles formation. In addition, since emergence and improvement of syntheses are often associated to development of experimental setups, technological aspects are also mentioned.

Quantum dots (QDs) are semiconductor nanocrystals with unique optical and electronic properties. They have distinct advantages over traditional fluorescent organic dyes in chemical and biological studies in terms of tunable emission spectra, signal brightness, photostability, and can be conjugated to a wide range of biological targets, including proteins, antibodies, and nucleic acid probes. Currently, the major type of QDs is the heavy metal containing II-VI, IV–IV, or III-V QDs. The new generations of QDs, have far-reaching potential for the study of intracellular processes at the single-molecule level, high resolution cellular imaging, long-term in vivo observation of cell trafficking, tumor targeting, and diagnostics. However, with respect to medical applications, caution must be exercised with QDs due to their toxic components. Development of suitable health and safety regulations is necessary for commercialization. Despite of these difficulties, QDs appear to be too valuable to nanomedecine to dismiss, and will eventually come essential into practical use.

Medicine provides an increasing interest for magnetic nanoparticles, thanks not only to the growing control of their chemical and morphological design and colloidal stabilization, but also to the increasing tendency to use magnetic fields in diverse medical areas such as radiology, neurosurgery, or oncology. This contribution focuses on their potential usefulness as contrast agents for magnetic resonance imaging (MRI) and colloidal mediators for magnetic fluid hyperthermia (MFH). A physical background of these nanoparticles magnetism is first considered discussing their behavior either under static magnetic field or an alternating one. The design and preparation of magnetic fluids is then described from the synthesis of nanoparticles up to their colloidal stabilization in physiological media. Requirements with regard to in vivo administration are subsequently presented, i.e., the factors affecting their biocompatibility, their biodistribution, the solutions envisaged for enhancing their half-life in the blood compartment, and the active targeting of tumor cells. Finally, magnetic nanoparticles are considered as contrast agents for MRI and mediators for MFH, highlighting the involved problems and the current and future possibilities for solving them.

Soon after the discovery of liposomes by Bangham in 1966 (Bangham et al. 1969), nanomaterials were introduced in medicine and the development of the first polymer nanoparticles for oral administration was achieved by Speiser in the late 1960s (Khanna and Speiser 1969). In the early 1970s, these objects were considered as the possible “magic bullet” that was a concept proposed 60 years before by the Nobel Prize laureate in Medicine Paul Ehrlich. The aim of the magic bullet is to improve treatments by targeting drugs to diseased tissues cells and subcellular compartments (Kreuter 2007). The introduction of nanomaterials in drug formulation strategies became sources of major innovations in drug delivery over the last 40 years (Couvreur and Vauthier 2006; Kreuter 2007; Bosch and Rosich 2008).

TiO₂-based heterogeneous photocatalysis is a process that develops rapidly in environmental engineering and it is now employed in several industrial domains, including water treatment, air purification, and self-cleaning surfaces. Photocatalysis is a natural phenomenon in which the TiO₂ accelerates a chemical reaction through the action of light, without being altered. The illuminated TiO₂ induces the formation of reactive species, able to decompose by oxidation and/or reduction reactions organic or inorganic substances. The major part of the applications of photocatalysis corresponds to organic oxidation, and it is now considered as one of the Advanced Oxidation Technologies (AOTs), gathering the reactions mainly based on hydroxyl radical (HO^•) chemistry. The development of a system based on photocatalysis requires gathering knowledge of numerous and various scientific domains: physical-chemistry, materials science, catalysis, environmental chemistry, biology, and engineering science. This chapter is therefore designed to give a detailed survey of the different scientific fields concerning TiO₂-based photocatalysis. Various aspects are developed: materials (synthesis, crystal chemistry, electronic and optical properties of TiO₂), physical-chemistry (photon absorption, charge-carrier dynamics, surface adsorption, and photooxidation mechanisms), environmental chemistry (dyes, pesticides, bacteria, and antibiotic photodegradation, real industrial wastewater treatment), and engineering (photocatalytic reactor design and simulation).

In the last decade an intensive research effort has been performed in the field of biosensors design. These tools are very promising to detect chemical pollutants in the environment because they can provide rapid, sensitive, simple, and low-cost on-field detection. Nowadays the use of nanomaterials for the construction of biosensing devices constitutes one of the most exciting approaches. The extremely promising prospects of these devices accrue from the unique properties of nanomaterials. Different nanostructures can be employed and the assets of this new technology in biosensors design are reviewed in this chapter. The properties related to these nanomaterials used in the different transduction modes are presented at first, and then we discuss the interest of nanotechnologies to provide a stable immobilization of biomolecules in retaining their bioactivity. Enzymes-based biosensors, immunosensors, and cell-based biosensors are finally considered separately in their use for environmental monitoring application. The main advantages of the different nanosensing devices are discussed.

Carbon nanotubes (CNT) are emblematic nanomaterials, and have generated a highly competitive international scientific research activity. Since their initial description in 1991, the understanding of their unique physicochemical properties led to a large number of actual applications and uses, as well as future developments. Because of these promising applications, there is an increasing concern regarding the consequences that could result from human exposure to CNT. Analysis of the existing literature shows that respiratory exposure to CNT can lead to the occurrence of pulmonary inflammation, the formation of granuloma, and the development of pulmonary fibrosis. The exact determinants of these effects still remain to be clearly identified, although intrinsic physicochemical characteristics of CNT (i.e. length, dispersion status, and residual catalyst content) seem to be of importance. Several critical issues still remain to be solved, such as the translocation of CNT outside the lungs and the occurrence of their biotransformation, which should open a new understanding to the respiratory effects of CNT.

Inorganic nanoparticles (NPs) either based on metal oxides (iron oxide, cerium oxide, titanium dioxide, silicon dioxide, etc.) or metals (gold and silver) have now wide applications. Consequently it increases the probability of unintended exposure that could affect workers as well as the general population including susceptible people. Inhalation, ingestion, and dermal contact are the main routes of exposure. Before reaching the epithelial barrier lining the respiratory tract, the digestive tract, or the skin, NPs get in contact with biological fluids and become covered by molecules present in these fluids forming the so-called “corona”. The fate and the effects of NPs may be different according to the corona composition as the cell membrane does not interact directly with the NPs surface but with the NP surrounded by its corona. Endocytosis has been shown to be an important route of NPs uptake. However, the rate and mechanism of uptake seem to be cell-type dependent, cell density-dependent and vary for NPs of different size, charge, and other surface properties. Uptake is mostly an energy-dependent process, dependent on NPs size, shape, and charge. There is also some evidence of NPs exocytosis allowing NPs to cross epithelial barrier and enter systemic circulation. Different in vitro models have been proposed showing potential of different NPs to translocate. NPs biodistribution have been studied in different in vivo models after intravenous injection, oral ingestion, intratracheal instillation, or inhalation showing that smaller NPs can be better eliminated, but are also more widespread in secondary organs. Inhalation studies underline that NPs mainly remain at the site of exposure and only a low amount translocates. NPs health effects are widely studied. Toxicological studies performed on animals by intratracheal instillation have underlined that the most predominant effect of NPs is the induction of lung inflammation characterized by the increase of immune cells, frequently macrophages and neutrophils, in the bronchoalveolar lavage and the increased release of pro-inflammatory mediators (cytokines and chemokines), and all this effects are dependent on dose, size, surface reactivity, and NPs composition. There is also evidence of some cardiovascular and neurologic effects of NPs. NPs toxicity mainly results from their ability to induce an oxidative stress resulting from the ability of NPs to directly or indirectly generate reactive oxygen species (ROS). Some studies have shown the role of specific interactions between NPs and proteins in cell activation or cell metabolism suggesting potential additional pathways of toxicity independent of oxidative stress. A better knowledge about the NPs properties involved in their toxicity is expected in order to propose NPs safe by design.

The specific properties of engineered nanoparticles have been used in many fields (e.g., medicine, cosmetic, electronics, catalysis, and environment). Their increased production and use come along with questions about their environmental and human health impacts. Rather than doing case-by-case studies, our vision is to extract general principles from environmental pertinent examples that determine nanoparticles behavior and biological effects. In this chapter, we will discuss the case of TiO₂ (used as additive in sunscreen) in terms of environmental degradation of nanoTiO₂-based formulations, reactive oxygen species generation, colloidal stability in the water column, transport in porous media, and also ecotoxicological impacts.

To produce unique products with novel properties, we need to manipulate materials at the nanoscale level. In the world, these nanomaterials are being rapidly produced in large scale, and it was shown, in the past 10 years, that the nanomaterials have different toxicity profiles compared with bulk particles because of their small size and consequently, their high reactivity. In this moment, the toxicological and environmental effects of direct or indirect exposure to these manufactured nanomaterials are not completely elucidated.

In this chapter, the physical, chemical, and ecotoxicological features of nanometric cerium oxide will be discussed on the basis of the recent research. In contrast with other oxides such as SiO₂, ZnO, ZrO₂, or TiO₂ with relevant industrial applications, ceria presents a unique redox chemistry that expanded its application to fields that take advantage of its chemical reactivity, as heterogeneous catalysis and detoxification of gaseous exhausts. In the past, several studies were strictly focused on the exploration of its eventual damage to environment and human health. CeO₂, as other rare earths oxides, is basically a low toxicity substance[1] and nowadays there is vast and increasing evidence pointing to its potential role as protective compound in terms of human health. The aim of this chapter is to offer a wide scope of description of the intrinsic physicochemical behavior of this unique compound, with deep emphasis in the inherent challenge that represents a definitive understanding of its surface chemistry. The apparent contradiction between toxicity and health benefits will be discussed according to the present evidence and the intrinsic limitations of these complex studies.

Among the 12 principles that define green chemistry, the use of renewable resources is of paramount importance in the perspective of building a sustainable society. The effort that has been put, in the past 25 years, into the research and development of new materials with controlled nanoscale structures and properties has not specifically taken into account the possibility of employing natural resources. This trend has, nevertheless, changed in the past 10 years. In this chapter, some examples of nanomaterials and nanoscale-related processes are overviewed through the prism of sustainability. In particular, it will be shown how natural resources, from proteins to carbohydrates and more complex organisms, can be employed as precursors in the synthesis of nanomaterials.

Nanotechnologies are a rapidly growing field of researches and applications. Their interdisciplinary scope, as well as the wide range of products they permit, qualified them, early, as enabling or general purpose technologies [1]. Almost all the fields of social life, from research, innovation, work safety, health, consumption, etc., to waste treatment, are, thus, affected by their development. These fields are already framed by legal norms. Thus, a rapid answer to the question we have raised might be, yes, there is plenty of law for the Nano [2].

How to deal with nanomaterials in democratic societies? Answering this question requires an understanding of the political qualities of nanomaterials. Rather than discussing “political impacts” that could be assessed once they are properly identified, this paper argues that nanomaterials are inherently political in so far as they are uncertain objects, connected to the future developments of nanotechnology, and tied to public concerns and the mobilization of various publics. It starts by discussing the political dimensions of nanomaterials through the examples of a European “network of excellence” and a carbon nanotube development project in a private company. The paper then describes three democratic formations enacted by the management of nanomaterials. These formations rely on the arrangement between the definition of nanomaterials, expectations about the future, the identification of public concerns, and the mobilization of various publics. I contrast an international “science-based” expertise, a European moral space, and French attempts for the responsible development of nanomaterials.