Nanotoxicology

Toxicity Evaluation of Nanomedicine Applications

Hemant Kumar Daima, S. L. Kothari, Bhargava Suresh Kumar, Hemant Kumar Daima, Shanker Lal Kothari, Bhargava Suresh Kumar

• Publisher: CRC Press
• Year: 2021
• ISBN:
  9781000399974
• Edition: 1
• Topic: Medicine
• Subtopic: Toxicology

The field of nanomedicine has risen quickly due to the increasing number of designer-made nanomaterials. These nanomaterials have the potential to manage diseases and change the way medicine is currently studied. However, the increased practice of using nanomaterials has shed light on how many concepts of nanomedicine and nanotoxicity have been overlooked. Nanotoxicology: Toxicity Evaluation of Nanomedicine Applications addresses the existing gaps between nanomedicine and nanotoxicity. This book also brings together up-to-date knowledge on advances toward safe-by-design nanomaterials and existing toxicity challenges.

This book delivers a comprehensive coverage in the field with fundamental understanding, serving as a platform to convey essential concepts of nanotoxicology and how these concepts can be employed to develop advanced nanomaterials for a range of biomedical applications. This book is an effort to answer some of the thoughtful nanotoxicological complications and their auspicious probable solutions with new approaches and careful toxicity assessment.

Key Features:

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• Reveals novel nanoscale approaches, toxicity assessment, and biomedical applications

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• Includes importance of nanotoxicity concepts in developing smart nanomaterials

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• Highlights unique contributions and "A to Z" aspects on the state-of-the-art from global leaders

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• Offers a complete package to learn fundamentals with recommendations on nanomaterials toxicity and safe-by-design nanomedicines

Nanotoxicology: Toxicity Evaluation of Nanomedicine Applications illuminates the high potential of many innovative nanomaterials, ultimately demonstrating them to be promising substitutes for available therapies that can be effectively used in fighting a myriad of biomedical complications. Further, this book reports legal, ethical, safety, and regulatory issues associated with nanomaterials, which have often been neglected, if not overlooked in literature and limiting clinical translation at nanoscale level. It will equip readers with cutting-edge knowledge of promising developments in nanomedicine and nanotoxicology, along with potential future prospects.

1 Nanomaterials

Types of Nanomaterials and Their Fundamental Physicochemical Properties

A. Shubha and S. R. Manohara

Siddaganga Institute of Technology

S. S. Subhranshu

International Advanced Research Centre for
Powder Metallurgy & New Materials (ARCI)

Contents

1.1 Introduction to Nanomaterials

1.1.1 Nanoscale Size Effect

1.1.1.1 Surface Area and Surface Area to Volume Ratio

1.1.1.2 Quantum Confinement Effect

1.1.2 Classification of Nanomaterials

1.1.2.1 Zero-Dimensional (0-D) Nanostructured Materials

1.1.2.2 One-Dimensional (1-D) Nanostructured Materials

1.1.2.3 Two-Dimensional (2-D) Nanostructured Materials

1.1.2.4 Three-Dimensional (3-D) Nanostructured Materials

1.1.3 Special Nanomaterials

1.1.4 Properties of Nanomaterials

1.2 Bottom-Up and Top-Down Approaches

1.2.1 Bottom-Up Approach

1.2.2 Top-Down Approach

1.3 Synthesis of Nanomaterials by Chemical Methods

1.3.1 Solvothermal Synthesis

1.3.2 Photochemical Synthesis

1.3.3 Sonochemical Synthesis

1.3.4 Chemical Vapour Deposition (CVD)

1.3.5 Sol–Gel Process

1.4 Physicochemical Properties of Nanoparticles with Reference to Biological Systems

1.4.1 Size and Dispersion Ability

1.4.2 Shapes

1.4.3 Surface Charges

1.4.4 Targeting Mechanism

References

1.1 Introduction to Nanomaterials

Nanomaterials are the materials having at least one of the dimensions in nanometer scale, i.e. in the range of 1–100 nm. The word “nano” originates from the Greek word “nanos” (or Latin “nanus”) which means “dwarf,” i.e. an abnormally short person. However, scientifically, the word “nano” is a prefix which is equal to 10⁻⁹ or one billionth. Hence, one nanometer is equal to one billionth of a meter (1 nm = 10⁻⁹ m). The following examples help to understand a sense of nanoscaled objects: (i) diameter of a hydrogen atom is about 0.1 nm (if ten hydrogen atoms are aligned in a line, then the resulting length would be approximately 1 nm), (ii) diameter of single strand of human hair is about 20,000 nm, and (iii) size of a DNA molecule is about 2.5 nm.

The nanomaterials are not new, but only the term “nanomaterial” used to name these materials is new. Human beings have used these materials for centuries without knowing that they are nanomaterials. The nanomaterials were in existence from the Roman period. Romans used colloidal metals to treat arthritis, to dye fabrics, and to color glasses.

The Purple of Cassius, a popular dye made up of tin oxide and gold nanoparticles, can be obtained by reacting stannic acid with chloroauric acid. Romans were experts in impregnating glasses with metal particles to produce dramatic effects. The Lycurgus cup is an outstanding example for this [1].^* The cup appears red for the transmitted light, if a light source is kept inside the cup, whereas the cup appears opaque-green for the reflected light, if the light source is kept outside the cup (Figure 1.1). These unique optical properties are due to small amounts of colloidal gold and silver present in the cup.

FIGURE 1.1 Lycurgus cup (An episode from the myth of Lycurgus, a king of the Thracians (around 800 BC), is the theme of the scene in the cup. Lycurgus attacked to kill Ambrosia, the follower of the god Dionysus. Ambrosia appealed Dionysus for help. Dionysus turned Ambrosia into vine and held Lycurgus by making Ambrosia coiling around the cruel king). (See the ebook for the color version of this figure.) (From https://www.britishmuseum.org/research/collection_online/collection_object_details/collection_image_gallery.aspx?partid=1&assetid=1066672&objectid=61219. With permission.)¹

Michael Faraday was the first to prepare nanoparticles in laboratory. Faraday called these particles as “divided state of gold” in his diary dated April 2, 1856 [2]. His gold colloidal samples are still at the British Museum, United Kingdom showing beautiful magenta-red color but not yellow color (Figure 1.2).

FIGURE 1.2 Michael Faraday’s colloidal gold. (See the ebook for the color version of this figure.) (From http://personal.bgsu.edu/~nberg/faraday/diary2.htm. With permission.)

The stained glass windows of medieval churches were made of gold and silver particles. Maya blue used by the Mayas consisted of silica, indigo, metal, and oxide nanocrystals. Over 5,000 years ago, the Egyptians used gold nanoparticles in dentistry. Alchemists in Alexandria had developed a powerful colloidal elixir known as “liquid gold” to restore youthfulness. The colloidal gold has been incorporated in vases and glasses for coloring them.

^* An episode from the myth of Lycurgus, a king of the Thracians (around 800 BC), is the theme of the scene in the cup. Lycurgus attacked to kill Ambrosia, the follower of the god Dionysus. Ambrosia appealed Dionysus for help. Dionysus turned Ambrosia into vine and held Lycurgus by making Ambrosia coiling around the cruel king.

1.1.1 Nanoscale Size Effect

The laws of physics operate somewhat differently at nanometer length scale dimensions. At nanoscale, laws of quantum mechanics take the place of classical mechanics which are applicable for macroscopic objects. For example, at nanoscale, the surface of a table spoon is not smooth; instead, it consists of discrete atoms and/or molecules.

In general, at micrometer scale, the physical properties of materials are the same as those of their bulk counterparts. However, at nanometer scale, the materials may display physical properties different from those of their bulk counterparts. The properties of nanomaterials are different from their bulk forms due to increased surface area to volume ratio and quantum confinement effect. These concepts will be discussed in the following sections.

1.1.1.1 Surface Area and Surface Area to Volume Ratio

The properties of a material depend partly on its size. In general, the physical, chemical, and biological properties of a material differ at the nanoscale, i.e. nanomaterials, when compared to its bulk counterpart. This is due to the fact that the nanomaterials have relatively larger surface area to volume ratio than the same quantity of materials produced in a bulk form. This will make materials more chemically reactive. In several cases, materials that are inert in their bulk form become reactive in their nanoscale form, and thus, the size of materials affects their strength or electrical properties.

Let us now understand how reduction in the size of a material increases its surface area and surface area to volume ratio. Consider a cube of salt. Let us assume that the cube has sides of 2 cm length. The cube has six squared faces each having a surface area of 4 cm² (=2 cm × 2 cm), and hence, the total surface area (S) of the cube is 24 cm² (=6 × 4 cm²). The volume of the cube is equal to length × breadth × height. So, the total volume (V) of the cube is 8 cm³ (=2 cm × 2 cm × 2 cm). Hence, the S/V ratio is 3 × 10² m⁻¹ (=24 cm²/8 cm³). Similarly, for a cube with a side length of 1 cm, the S/V ratio is 6 × 10² m⁻¹ (=6 cm²/1 cm³). Similarly, for a cube with a side length of 1 nm, the S/V ratio is 6 × 10⁹ m⁻¹ (=6 nm²/1 nm³). This illustration demonstrates that a smaller cube will have a greater surface area to volume ratio than a bigger cube.

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