Biomedical Engineering Reference
In-Depth Information
leukocytes to both bind naturally occurring anionic and cationic
polymers. Such properties of ligand recognition by the receptors are
also of direct relevance for the interaction between leukocytes and
nanomaterials, which are often functionalized with charged groups,
e.g., carboxyl and amine groups.
10.3
Nanomaterials and the Immune System
With the introduction above to functions of the immune system,
it is possible to outline a number of important principles that
regulate the immune response to nanomaterials. Below, emphasis
is given to how the chemical composition of materials may trigger
or avert the immune response. Many composites of nanomaterials
are biopolymers, meaning that these materials are equivalent to or
derived from biological materials. However, while such properties
often ensure that materials are chemically compatible with the
body through low or no toxicity and by permitting degradation,
their composition resembles that of many microbial biopolymers. In
consequence, the immune system produces a strong response to the
introduction of these materials in the body, which may cause a number
of undesirable eff ects ranging from neutralization of the function to
shock in the host receiving treatment with nanomaterials. Emerging
literature suggests that ultrastructural properties of materials also
may play a significant role in regulating the immune response.
Specifically, it appears that materials with relevant dimensions on
the nanometer scale may interfere with molecular functions of the
immune system by manipulating the ultrastructure of proteins.
10.3.1
Biopolymers and the Immune Response
While many biopolymers were chosen as coatings for nanomaterials
due to their low metabolic toxicity and degradability, it is now clear
that at least some of these represent a special challenge with regard
to the immune response they elicit.
One example is the application of dextran to cover or embed
ultrasmall superparamagnetic iron oxide (USPIO) particles used
clinically as contrast agent in magnetic resonance imaging. Dextran,
a branched high-oligomer of glucose, is well tolerated in most
patients when administered in formulations of plasma volume
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