Biomedical Engineering Reference
In-Depth Information
Fig. 5 Cell adhesion to a material surface, including the adsorption of serum proteins
nonspecific adsorption; thus, they effectively prevented cell adhesion. Several studies
have described surfaces that prevent nonspecific protein adsorption [
59
,
72
,
73
]; those
surfaces are also likely to prevent cell adhesion.
We examined protein adsorption to SAMs that carried four different functional
groups [
42
] and mixed SAMs with different wettabilities [
21
]. Large amounts of
serum proteins adsorbed to all these SAMs, but the different surface functional
groups greatly affected cell adhesion behavior (Figs.
2
and
3
). Thus, the amount of
adsorbed proteins did not correlate with the degree of cell adhesion to SAMs.
2.3.2 Protein Composition on a Surface
Serum glycoproteins like Fn and Vn play a crucial role in cell adhesion to artificial
materials. These proteins carry peptide motifs, including arginine-glycine-aspartic
acid (RGD) [
74
] and proline-histidine-serine-arginine-asparagine (PHSRN) [
75
],
that specifically interact with integrin receptors on cell membranes. Adsorption of
Fn and Vn onto a material surface is required to support cell adhesion. However, the
concentrations of Fn and Vn in serum are much lower than that of albumin and
IgG (Fig.
4d
). The composition of proteins initially adsorbed to a surface reflects
the concentrations of each protein in the medium; thus, most proteins on the surface
will be albumin and IgG, which cannot support cell adhesion. Controlling the
composition of proteins in a solution is important for controlling cell adhesion on
artificial materials.
Various methods have been used to examine the composition of proteins
adsorbed to SAMs. Overall adsorption patterns can be examined with sodium
dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) [
50
,
76
,
77
].
Absorbed proteins are eluted from the surface with surfactant (SDS), and then
separated by electrophoresis. The proteins of interest are examined by western
blotting [
50
,
76
,
77
]. Protein-specific antibodies can be used to detect proteins of
