As discussed in Chapter 1, unique features of nanomaterials such as size-dependent optical and magnetic properties, and high surface-to-volume ratio make them particularly interesting for applications in electronics and biomedicine. Biomedical applications are a powerful driver of the development of bionano hybrids, and novel preparation strategies have already enabled manufacturing of high-quality nanomaterials such as carbon nanotubes at scales that can satisfy market demands. Although the size of nanomaterials brings numerous advantages, working with them can be challenging. Due to their high surface energy, nanoparticles can form random aggregates, or non-selectively bind various molecular species, which impacts their physiochemical properties. This can be prevented by the functionalisation of nanomaterials’ surface with known molecules in a controllable way. Surface modification not only improves the stability of nanomaterials, but enables introduction of various functional groups that can change their properties and make them more adaptable to a broad range of applications.

Bionanotechnology has the potential not only to improve existing medical processes but also to introduce entirely new tools and materials. Advances have already been made, in particular, in design of probes and biosensors for advanced diagnostics, targeted drug nanocarriers and environment-responsive materials for tissue engineering. We need to keep in mind that at the core of all of these applications is the fundamental question of the nature of the interaction of nanomaterials and nanostructured surfaces with biological systems. The exploration of these interactions is strongly embedded within the field of nanomedicine, but it is also a part of nanotoxicology, a field that studies the environmental impact of new materials. Some strategies, findings and policy actions concerning the regulation of use of nanomaterials will be covered in the last chapter.

Despite the relative youth of the term nanotechnology, as far as we know nanomaterials have been around for centuries. Hundreds of years ago, dispersions of gold and silver nanoparticles were used by master glassblowers to produce coloured decorative glass for church windows (Figure 2.1a) or luxury glassware such as the Lycurgus Cup from fourth century CE Rome (Figure 2.1b). In the late nineteenth and early twentieth centuries, industrialists used carbon black to reinforce rubber and thus improve its strength, tensile properties and tear. We know now that carbon black is made of carbon particles that can vary in size, and some of them are nanosized spheres. But practical uses of early nanotechnology were not constrained only to Europe. A corrosion resistant azure pigment known as Mayan blue, first produced in 800 CE, was discovered in the pre-Columbian Mayan city of Chichen Itza (Figure 2.1c). It is a complex material made of nanoporous clay used to stablise the blue indigo dye. Damascus steel swords made in the Middle East between 300 CE and 1700 CE were known for their impressive strength and exceptionally sharp cutting edge, and studies have shown that the steel contains nanotubes and nanowire structures (Reibold, 2008). Swords were produced in a process of forging and forming that employs coal, iron powder, high temperatures and high pressures applied during hammering, a protocol that is in many ways similar to how the nanotubes are made today (see Section 2.4.2).

The understanding of double helix structure has brought revolution to the fields of molecular biology and genetics. The structural properties of DNA such as specific base pairing, a combination of stiffness and flexibility as well as remarkable stability (see Chapter 3) have made a huge impact in fields ranging from drug delivery to sensor design. With increased availability of chemically synthesised DNA strands and developments of super-resolution microscopy, DNA nanotechnology established itself as an independent area of research within bionanotechnology. DNA nanotechnology uses DNA as a versatile building block rather than a genetic code carrier. Although the genetic information of DNA was recognised soon after the discovery of the double helix in the 1950s, the potential of DNA assembly for the design of programmable structures was for the first time hinted in a theoretical paper written by Ned Seeman in 1982 (Seeman, 1982). His early theoretical work was followed by experimental studies that demonstrated the programmability of short DNA strands and their use for self-assembly of larger ordered structures.

Before we start looking into modification of nanomaterials and nanostructuring of biomolecular elements for various applications in biomedicine and material design, we need to get a glimpse into the structure of biomolecular building blocks and the way they interact and assemble.

In Chapter 6 we explored the field of DNA nanotechnology, and the use of nucleic acids to create programmable architectures on a nanoscale. In this chapter, we will look at other biomolecules and biological structures, which inspired the design of novel materials and devices. Although they can operate on a wide range of scales, going from nano to macro, all biosystems have one thing in common: they are the product of millions of years of evolution. They have been adapted to address a particular environmental challenge, such as the emergence of a new predator or the abundance of a particular nutrient or building block. For example, without an increase in the concentration of silicate and carbonate ions in water during the Cambrian period some 500 million years ago, there would have not been a dramatic increase in the number of marine creatures with silica and carbonate hard shells (Peters, 2012).

Nanomedicine, like conventional medicine, has two aims: to diagnose the disease, as accurately and as early as possible, and to deliver the most efficient treatment possible. Unlike conventional medicine, it uses nanomaterials and nanotools to achieve this. We saw in Chapter 8 the way in which nanotechnology advanced the field of biosensors, and we now look at some of the concepts behind the design of drug nanocarriers and nanocomposites for tissue engineering, as well as some challenges that still need to be overcome. In the core of bionanotechnology is the exploration of interactions between engineered nanomaterials with biomolecules and cells. Such studies are not only important to help the design of biocompatible materials, but also to assess the environmental impact of man-made nanosized structures. Nanotoxicology has emerged as an independent research discipline that studies the toxicology of nanostructures, which as we have seen in previous chapters have a unique set of properties due to their small size. Some of the protocols to assess the toxicological profile of new nanomaterials, as well as existing regulations and risk assessments, will be briefly covered in the last part of the chapter.

Characterisation of nanomaterials, whether this refers to their physicochemical properties or their interactions with biomolecules and cells, requires a combination of analytical strategies. Before we explore some of the main instrumental methodologies for analysis of bionano constructs and devices, it is important to define the main questions we are trying to answer using analytical techniques (Figure 5.1).