Nanomedicine

Technologies and Applications

Thomas J. Webster, Thomas J Webster

• Publisher: Woodhead Publishing
• Year: 2012
• Print ISBN: 9780857092335
• eBook ISBN: 9780857096449
• Topic: Tecnologia e ingegneria
• Subtopic: Scienza dei materiali

Nanotechnology is at the forefront of advances in medicine. Nanomedicine: Technologies and applications provides an important review of this exciting technology and its growing range of applications.After an introduction to nanomedicine, part one discusses key materials and their properties, including nanocrystalline metals and alloys, nanoporous gold and hydroxyapatite coatings. Part two goes on to review nanomedicine for therapeutics and imaging, before nanomedicine for soft tissue engineering is discussed in part three, including organ regeneration, skin grafts, nanotubes and self-assembled nanomaterials. Finally, nanomedicine for bone and cartilage tissue engineering is the focus of part four, with electrically active biocomposites as smart scaffolds investigated, as is cartilage and bone tissue engineering, regeneration and replacement.With its distinguished editor and international team of expert contributors, Nanomedicine: Technologies and applications is an indispensable guide for all those involved in the research, development and application of this exciting technology, whilst providing a comprehensive introduction for students and academics interested in this field.

• Provides an important review of nanomedicine technology and its growing range of applications
• Discusses key nanomedicine materials and their properties, including nanocrystalline metals and alloys, nanoporous gold and hydroxyapatite coatings
• Reviews nanomedicine for therapeutics and imaging and nanomedicine for soft tissue engineering

Part I

Materials, properties and considerations

1

Introduction to nanomedicine

C. Yao, Nanovis LLC, USA

J. Lu, Purdue University, USA

Abstract:

This chapter reviews current research being undertaken in this rapidly progressing field. Clinical applications for passive and active nanomedicines are investigated, including issues such as drug carrying, imaging and diagnostics and tissue regeneration and antimicrobial products. Challenges from public perception, toxicity concerns, regulations and the commericalization process of nanomedicine are also described in this chapter. Finally, some directions to remedy the obstacles are discussed.

Key words

nanomedicine

passive nanostructures

active nanostructures

toxicity

nanorobot

1.1 Introduction: basic concepts of nanomedicine

In 1959 the concept of nanomachines was first hypothesized by the Nobel-winning physicist, Richard Feynman, during his classic talk named ‘There is Plenty of Room at the Bottom’. As he claimed the marvellous biological system as an example of doing things small, he was clearly aware of the potential medical applications of nanotechnology: a programmable nano-robot which exhibits and works in the same scale as proteins and cells and could be fabricated and introduced to human biological systems.

It is no wonder that one can see imaginations of nanorobots in books during the past 20 years (Drexler, 1992). Perhaps, a tube of smart drugs comprised of thousands of nanorobots is injected into patients. They are protected from the immune system, targeted to a specific organ, initiated by external signal, and then start stimulating surrounding biological entities. They can be programmed to release bioactive agents, ignited to kill unfavoured cells and tissue, or incorporated to reconstruct new tissues. In a word, their key ability to direct events in a controlled fashion at the molecular and cellular level is a must-have for doctors in order to conquer various obstacles in human health.

So, as we are in the second decade of twenty-first century now, has this ultimate dream about intelligent nanorobots for medicine come true? The answer is not yet. However, continuous and fruitful research activities on nanomedicine in the past decade and some successful clinical practices are moving us towards the goal. Nanomedicine has become such a fast-developing area that it is believed that the time has come to summarize some of the milestones and project its future development. This book is, thus, dedicated to those who are interested in this area and eager to take a broad view of the field. Particularly, this chapter will give an overview of nanomedicine.

First of all, let’s define the following terminologies: nanomaterial, nanotechnology and nanomedicine. Nanomaterial is material with at least one dimension less than 100 nm, exhibiting unique properties due to its nanoscale size and shape. Nanotechnology is defined as the ‘intentional design, characterization, production, and applications of materials, structures, devices, and systems by controlling their size and shape in the nanoscale range (1 to 100 nm)’ (COMA, 2007). Nanomedicine, a subset of nanotechnology, is defined as the ‘monitoring, repair, construction and control of human biological systems at the molecular level, using engineered nanodevices and nanostructures’ (Freitas, 1999).

Nanotechnology has been applied to various fields, such as medical, optics, electronics, fabrics, cosmetics, etc. There has been considerable hype in nonhealth nanotechnology in the past which might lead to a certain degree of bias among the public. Thus, it is important to note that the difference between nanomedicine and nanotechnology is profound. Nanomedicine is serious for safety issues such as toxicity, and it is highly regulated by regulatory authorities such as the Food and Drug Administration (FDA) in the USA.

1.2 Public perception of nanomedicine

The tremendous controversies triggered by some biotechnologies – cloning is an example – indicated that for any emerging technology a correctly informed benefit–risk perception by the public is critical for its acceptability and further development.

What will be the biggest benefit from nanomedicine for human society? Optimistically, nanomedicine will help in finding a solution to most diseases and allow the extension of human capabilities. That is why most of today’s public is supporting scientific research and government funding for nanomedicine. Some studies revealed optimistic and enthusiastic public attitudes towards nanomedicine in Italy (Bottini et al, 2011) and the USA (Burri and Bellucci, 2008), respectively.

On the other hand, our understanding of nanomaterials and nanomedicine is incomplete. There are potential health, environmental and social risks that need to be assessed seriously and thoroughly (Handy and Shaw, 2007). In this light, people in European countries, such as Switzerland (Burri and Bellucci, 2008) and the UK (Rogers-Hayden and Pidgeon, 2006), show a more pragmatic attitude or balanced approach towards nanomedicine. They are neither reluctant towards nanomedicine nor highly enthusiastic, facing the potential risks associated with nanomedicine. They support further research in the field, emphasizing the importance of acquiring information on potential risks as well. They require sound science and better information on both research activities and future products. It, thus, obligates material scientists, nanotechnologists, toxicologists and regulators to establish a more responsible dialogue with the public regarding the nature and implications of nanomedicine.

While public bias and concerns may exist today, the development of nanomedicine is likely to foster a renewed and strong interest and trust in the field (Berube, 2009). First, there is a high likelihood that near-term successful uses of nanomedicine in the diagnosis and treatment of diseases will ease the way for more nanomedicine applications and improve the public perception. Second, in contrast to the infinite applications of nanotechnology, nanomedicine is a highly regulated field. Any drug or medical device must be approved by the regulatory authorities to ensure their safety and efficacy before going to market. Moreover, the regulatory requirements for nanomedicine are being raised as our understanding of the field and our technical capabilities advance. This also will increase public confidence.

1.3 Scientific principles and applications of nanomedicine

Today’s biology and pathology demonstrate that many diseases originate from malfunctioned cells (Kim et al., 2010). The fate of these micron-size cells is further determined by nanosize molecules such as genes and proteins contained within the cells. Thus, for novel medicine targeting to specific locations within the cells, passing through some biological barriers is a prerequisite. Some of these important barriers for nanomedicine delivery are listed in Table 1.1. Conventional medicine, due to its micron-scale size, does not have such ability. In comparison, the development of nanomedicine has a significant impact on drug delivery in terms of the ability to pass through various biologic barriers and get access to molecules within specific cell compartments.

Table 1.1

Examples of nanobarriers that require the use of nanomedicine

Where the barrier locates	Size	Application
Vasculature of immature tumor	Pores < 200 nm	Tumor therapy
Blood–brain barrier	~ 35 nm	Drug to central nerve system
Cell membrane	Endocytosis up to ~ 100 nm	Cell/gene therapy
Nuclear membrane	Pores < 40 nm	Cell/gene therapy

Nanomaterials used in medicine have many unique characteristics compared to conventional micron-size materials. First, they have a high ratio of surface area to volume, which enables high loading of drugs on nanomaterial carriers. Hollow polymeric nanomaterials can even encapsulate hundreds of drug molecules inside a single vehicle and control the release of drugs. In addition, size-dependent properties such as quantum confinement in semiconductor particles (e.g., quantum dots) and superparamagnetism in magnetic materials (e.g., iron oxide nanoparticles) lead to important improvements in medical imaging techniques. Nanomaterials can be engineered to have different sizes, shapes, chemistries and surface characteristics so that they exhibit tunable optical, electronic, magnetic and biologic properties. Common nanostructured materials used in medicine are summarized in Table 1.2.

Table 1.2

Categories of nanostructured materials for medical applications

Categories	Select characteristics
Nanoparticles, quantum dots, nanorods	Size, shape, charge, magnetization, crystallininity
Nanotubes, fullerene, nanofibres, nanowires	Single/multiwalled, aspect ratio, chemistry, orientation
Nanostructured surfaces and scaffolds	Thickness, porosity, chemistry, degradability, bioactivity
Nanocomposites and supra-molecular scaffolds (liposomes, dendrimers, etc.)	Self-assembly, dimension, composition, surface functional groups

Mike Roco (2008) of the US National Nanotechnology Initiative has described four generations of nanoproducts: passive nanostructures, active nanostructures, systems of nanosystems and molecular nanosystems. Most of today’s nanomedicines are passive nanostructures, which are designed to perform one task and not to change their forms and functionality during life. The second phase, which we are shifting to, is a...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributor contact details
• Woodhead Publishing Series in Biomaterials
• Dedication
• Part I: Materials, properties and considerations
• Part II: Nanomedicine for therapeutics and imaging
• Part III: Nanomedicine for soft tissue engineering
• Part IV: Nanomedicine for bone and cartilage tissue engineering
• Index