​Place of Nanotoxicology in Modern Science

Nanotechnology, the manipulation of matter at the atomic and molecular scale, has rapidly evolved from the realm of science fiction to a cornerstone of contemporary scientific and industrial advances. But alongside its impressive applications, from improving drug delivery in medicine to increasing the strength and durability of materials, there is another area that demands our close attention: nanotoxicology.

By examining the unique properties of nanoparticles, the mechanisms by which they may cause harm, and the methods used to assess their safety, the article underscores the importance of this discipline in ensuring the responsible development and use of nanomaterials. Discover Nanografi's safe materials used in nanotechnology.

Introduction

In recent decades, nanotechnology has transitioned from a concept of science fiction to a transformative force in modern industry and research. Its applications are far-reaching, enabling innovations in drug delivery, materials engineering, and consumer products. However, the same properties that make nanoparticles so versatile—such as their minuscule size and high reactivity—also pose potential risks to human health and the environment. This has given rise to nanotoxicology, a specialized branch of toxicology dedicated to studying the safety and potential hazards of nanoparticles.

Understanding Nanotoxicology

Definition and Scope

Nanotoxicology is the sub-discipline of toxicology that addresses safety concerns associated with nanoparticles. As the field of nanotechnology rapidly expands and nanoparticles are used in various industries, the need to understand the potential health risks associated with these materials has become increasingly important. Nanotoxicology studies how the unique properties of nanoparticles, such as their small size and large surface area, affect their interactions with biological systems and lead to potentially toxic effects.

The scope of nanotoxicology extends to numerous sectors, including medicine, environmental science and industrial applications. Its importance lies not only in its potential to protect public health, but also in shaping the regulations and standards governing the use of nanomaterials.

Historical Background

The official beginnings of nanotoxicology date back to the early 2000s, but concerns about the potential health effects of nanoscale particles go back much further. The term "nanotoxicology" was first coined in 2004 by Günter Oberdörster, a leading toxicologist. Oberdörster's pioneering work led to the need to investigate the toxicological effects of nanoparticles, particularly in relation to their inhalation and ongoing effects on respiratory health. His work laid the foundation for this new discipline, which is rapidly gaining traction as nanotechnology applications become widespread.

However, the historical roots of nanotoxicology can also be traced to earlier studies on ultrafine particles and air pollution. Research on the health effects of fine and ultrafine particles in the 1990s, especially in the context of industrial pollution and respiratory diseases, indirectly paved the way for the understanding of nanoparticle toxicity. As nanomaterials began to be designed for specific applications, the need for a specialised field to address their unique toxicological profile became apparent, leading to the establishment of nanotoxicology as a separate scientific discipline.

Properties of Nanoparticles Affecting Toxicity

Nanoparticles are materials with at least one dimension on the nanometre scale (1-100 nanometres). At this scale, they exhibit unique properties different from their bulk counterparts. These different properties can significantly affect their interactions with biological systems and, consequently, their potential toxicity. Here are the key properties of nanoparticles that influence their toxicity:

Size: Their small size causes them to cross biological barriers and potentially reach sensitive areas such as the brain.

Surface Area and Chemistry: Nanoparticles have a high surface area relative to their volume, which increases their reactivity and potential to cause oxidative stress. Surface chemistry, including charge and coatings, affects how they interact with cells.

Figure 1. The relationship between size, surface area, and volume (number) of nanoparticles.

Shape: Nanoparticles can be of various shapes such as spheres, rods, tubes and sheets. Different shapes can interact with cells and tissues in unique ways. For example, long, needle-like nanoparticles are more likely to puncture cell membranes and cause physical damage, while spherical nanoparticles can be more easily taken up by cells. Shape can also influence how nanoparticles are distributed and cleared within the body, potentially affecting their toxicity.

Solubility and Dissolution Rate: The solubility and dissolution rate of nanoparticles in biological fluids are important factors in determining their toxicity. Some nanoparticles can dissolve into ions that can be toxic on their own. For example, silver nanoparticles can release silver ions, which are known to have antimicrobial properties but can also be toxic to human cells.

Aggregation: Nanoparticles can aggregate together to form larger particles. This behaviour can change their effective size, shape and surface area, which in turn affects their biological interactions and toxicity. Aggregation can reduce the ability of individual nanoparticles to penetrate cells, but it can also lead to the formation of larger, potentially more harmful aggregates that can clog blood vessels or accumulate in organs.

Assessment Methods in Nanotoxicology

In Vitro Tests

In vitro testing using cell culture models offers a controlled environment to study the effects of nanoparticles. Common tests include cytotoxicity assays and oxidative stress measurements. While in vitro studies provide valuable insights, they may not fully mimic the complexity of living organisms.

In Vivo Tests

In vivo testing involves the use of animal models to assess nanoparticle toxicity. These studies can provide comprehensive data on how nanoparticles affect whole organisms, but raise ethical considerations and face increasing scrutiny from regulatory agencies. Alternatives and improvements to animal testing, such as the use of lower organisms or improved imaging techniques, are being actively explored.

Computational Models

Computational models and simulations represent an emerging frontier in nanotoxicology. By integrating experimental data, these models can predict toxicological outcomes and guide the design of safer nanomaterials. Such predictive approaches are becoming increasingly sophisticated and offer a promising complement to traditional testing methods.

Example: The Case of Nanosilver in Consumer Products

In the early 2000s, nanosilver was increasingly used in consumer products like antimicrobial coatings, clothing, and even food packaging due to its ability to kill bacteria. However, concerns arose regarding the potential health and environmental impacts of nanosilver. Studies revealed that nanosilver could release silver ions, which are toxic to both bacteria and human cells.

One notable incident involved a nanosilver-based dietary supplement marketed for its supposed health benefits. The product was withdrawn from the market after it was found to cause argyria, a condition where silver accumulates in the skin, giving it a blue-gray color. This incident highlighted the risks of using nanomaterials in consumer products without fully understanding their potential toxic effects.

This case underscored the importance of nanotoxicology in assessing the safety of nanoparticles before they are widely used in consumer products, as well as the need for regulation to protect public health.

Figure 2. Possible transport pathway for nanoparticles in the lung

Future Directions and Challenges

As nanotechnology continues to advance, the field of nanotoxicology faces several challenges. One of the biggest challenges is the lack of standardised test methods and the complexity of assessing the long-term effects of nanoparticles. Furthermore, more comprehensive studies that consider the life cycle of nanomaterials from production to disposal are needed to fully understand their environmental impact. Future research will likely focus on developing more accurate models to predict nanoparticle behaviour in biological systems and exploring strategies to mitigate their potential toxic effects.

Conclusion

Nanoparticles are used in a wide range of applications from medicine (e.g. drug delivery, imaging) to consumer products (e.g. cosmetics, food packaging). While these applications provide significant benefits, they also raise concerns about potential human and environmental health risks. Nanotoxicology plays a crucial role in assessing these risks and ensuring that nanomaterials are safe to use. Regulatory agencies are increasingly considering nanotoxicology data in their guidelines to ensure the responsible development and use of nanotechnologies.

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References:

Collins, A. R., et al. (2016). High throughput toxicity screening and intracellular detection of nanomaterials. WIREs Nanomedicine and Nanobiotechnology, 9(1), e1413. https://doi.org/10.1002/wnan.1413

Donaldson, K., Stone, V., & Tran, C. L. (2004). Nanotoxicology. Occupational and Environmental Medicine, 61(9), 727-728. https://doi.org/10.1136/oem.2004.013243

Fadeel, B., & Garcia-Bennett, A. E. (2010). Better safe than sorry: Understanding the toxicological properties of inorganic nanoparticles manufactured for biomedical applications. Advanced Drug Delivery Reviews, 62(3), 362-374. https://doi.org/10.1016/j.addr.2009.11.008

Maynard, A. D., & Kuempel, E. D. (2005). Airborne nanostructured particles and occupational health. Journal of Nanoparticle Research, 7(6), 587-614. https://doi.org/10.1007/s11051-005-6770-9

Oberdörster, G., Oberdörster, E., & Oberdörster, J. (2005). Nanotoxicology: An emerging discipline evolving from studies of ultrafine particles. Environmental Health Perspectives, 113(7), 823-839. https://doi.org/10.1289/ehp.7339

Krug, H. F., & Wick, P. (2011). Nanotoxicology: An interdisciplinary challenge. Angewandte Chemie International Edition, 50(6), 1260-1278. https://doi.org/10.1002/anie.201001037

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