Wrong Resemblance? Role of the Immune System in the Biocompatibility of Nanostructured Materials - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 300

binding sites for C1 [4, 71]. Comparison between the established
structure of IgM, specifically the conformation suggested to permit
binding of the C1 complex and hence activate complement, and the
dimensions of the particles suggested that binding of IgM only to the
∼ 100 nm to ∼ 250 nm particles, but not the 600 nm particles, would
support the “staple”-like conformation (Figure 10.1). The critical
feature was suggested to be the curvature of the particles [70],
which also in other cases appears as a topological feature that may
distort or change the ultrastructure of surface-bound proteins [72].
The report by Pedersen et al. may consequently be an example of
how nanostructured features can manipulate protein structure and
function. In the case of the immune response, such induced changes
in protein structure may be critical as an increasing number of
examples show how the function of proteins in the immune system
is regulated by their conformation.

10.3.3 Structural Decay of Adsorbed Proteins and the

Immune Response

All nanomaterials introduced into the human body are exposed
to proteins and other biomacromolecules that may potentially
coat solvent-exposed surfaces of the material. The physisorption
of the molecules is referred to as “biofouling” and will often
dramatically change the properties of nanoparticles with regard
to colloidal stability and in vivo circulation time. Non-colloidal
nanomaterials such as implants may also be aff ected with regard to
tissue integration or other functionality. Some of these changes are
attributable to simple alterations in the physico-chemical properties
of the nanomaterials, including changes in the surface electrostatic
potential and hydrophobicity, usually making such contributions as
the aggregation of the particles. However, the biofouling may also
contribute to unwanted immunological reactions. Many investigations
suggest that nanostructuring of surfaces acts to control properties
of cellular adhesion or cellular uptake by manipulating protein
structure of the adsorbed proteins, including membrane-bound
receptors. However, a contribution from the spontaneous adsorption
of proteins is difficult to prevent. It is a well-established property of
protein adsorption of protein onto materials such as polystyrene that
the adsorption may not only change the conformation of the protein