2.10.2. Nanotechnologies
Due to their diminutive size, nanoparticles exhibit
properties that can differ substantially from those of matter in bulk or
organized in larger particles. There are two main reasons for this. First,
nanoparticles have, relatively, a larger surface area than the same mass of
material produced in a larger bulk form. This can make materials more
chemically reactive. Second, below 50 nm, the laws of classical physics give way
to quantum effects, causing optical, electrical and magnetic behaviours
different from those of the same material at a larger scale. These effects can
give materials very useful physical properties such as exceptional electrical
conduction or resistance, a high capacity for storing or transferring heat or
different solubility properties.
Nanoparticles, whose dimensions range between 1 and 100 nm
(0.001-0.1 μm), are characterized by specific properties. At the current
stage of rapid evolution of nanoscience and nanotechnology it is not possible
to be scientifically precise over inclusion and exclusion criteria for defining
a substance as a nanomaterial. But some aspects are known to be of utmost
importance for the classification (e.g. natural occurring vs. manufactured
nanoparticles, the status of micelles/capsule and the number of dimensions in
the Nan orange). Engineered nanoparticles are increasingly produced and used in
industrial fields as electronics, sporting products, clothes, sunscreens,
cosmetics, computer, aerospace and other fields such as food packaging, food
supplements, food and feed additives, animal health, veterinary drugs,
pesticides and plant health.
The existing and/or foreseen nanoparticles applications in
the medical field include molecular diagnostic, imaging, drug discovery and
drug delivery and therapy, for biomarker discovery, and uses in oncology and
cardiovascular medicine. Currently, there is a considerable effort at
international level for the evaluation and prevention of the possible health
and environmental risks (The Royal Society, 2004; NIOSH, 2006; Schulte
et al, 2007; Nel et al, 2006; Medina et al, 2007).
The nanoparticles categories of main interest for
biomedical and other uses include (Nel et al, 2006); (Medina et al, 2007).
- Carbon
nanoparticles: Fullerenes, with polygonal structure formed by 60 carbon atoms and
surfaces with tissue-binding capacity. Carbon nanotubes, of large use, with a
cylinder structure, a high electrical conductivity and a remarkable mechanical
strength. They may be also used in biomedicine as drug carriers;
- Ceramic
nanoparticles: Inorganic particles, with porous surface that can act as a drug
vehicle;
- Liposomes: lipid-based
nanoparticles, largely used in pharmaceutical and cosmetic industries for drug
delivery;
- Emulsions: oil-water mixtures,
with droplet diameters in the nanoscale; surfactants maintain their shape. Used
for skincare;
- Quantum dots: Nanosized
semiconductors (also named nanocrystals), which under stimulation can emit
light of various colours. Used for cell imaging, in particular in cancer
imaging:
- Nanorods: nanoparticles with 1-
100 nm length, used in medicine as imaging and contrast agents;
- Polymer
nanoparticles: Water-soluble polymer-protein and polymer-drug conjugates.
Polymer-drug conjugates may allow some tumour targeting; and
- Metallic and
supermagnetic nanoparticles: Iron-oxide nanoparticles (5-100 nm range) are used for
selective magnetic bioseparations and as vectors of drugs, bioactive molecules
and DNA, with an external magnetic field directing their progress towards the
target tissue.
For Europe, data on the actual use and market presence of
these products are very limited. Only the UK maintains a voluntary reporting
scheme for engineered nanomaterials in general and only nine products have been
reported so far (September 2007) 4. In the US, the Woodrow Wilson
International Centre for Scholars has compiled an inventory of products which
claim to contain nanotechnology products or be based on
nanotechnology5.
