Biomedical Engineering Reference
In-Depth Information
9.1 Hierarchical structures from `micron' (a) to `nano' (f) in nacre showing at
least six structural levels. (Adapted and redrawn from Luz and Mano [3].)
micron level. While our tissues do have micron-structured features, recently,
researchers have emphasized the natural nanostructure of our tissue. Well-
organized supramolecules consist of a tiny, finely controlled, functional
materials organized at nanometer level (a nanometer is a tenth of a micrometer),
just like the nacre shell illustrated in Fig. 9.1. Even though our tissues and
organs have nanometer level structures and associated roughness, which are
important for various biological functions, nanotechnology has only recently
been emphasized in biomaterials. With the growing knowledge of `nano',
researchers have emphasized that nanomaterials, which correlate to materials
with at least one dimension less than 100 nm, have unique physical, chemical,
mechanical and biological properties, significantly different from corresponding
micron structured materials.
The US National Nanotechnology Initiative describes nanotechnology as
research and development aimed at understanding and working with (such as
observing, measuring and manipulating) matter at the atomic, molecular and
supramolecular levels [4]. With the continuous investment and growing demand
for innovation (especially in biomaterials), nanotechnology has become an
intense area for both industry and academic research. From 2000 to 2007, the US
invested around $8.5 billion in nanotechnology and the total sales of nano-
technology-related products reached $50 billion. It is estimated that by 2015 the
global market for nanotechnology-related products will be $2 trillion [5].
At the core of nanotechnology are nanomaterials and these have attracted
much attention. Due to their size, nanomaterials often exhibit unique properties,
such as improved magnetic, electrical, structural integrity and optical properties
[6]. Thus, they enhance properties of most engineering materials (Table 9.1).
Most importantly, previous studies have shown that nanomaterials have great
potential for improving tissue/organ implantation and regeneration. Because of
the larger surface to volume ratio of nanostructured biomaterials compared with
