Many functions of the extracellular matrix can be mimicked by small peptide
fragments (e.g., arginine–glycine–aspartic acid (RGD) sequence) of the entire
molecule, but the presentation of the peptides is critical to their effects on cells. It
is likely that some effects of peptide presentation from biomaterials simply relate
to the number of bonds formed between cell receptors and the adhesion ligands,
but a lack of tools to quantify bond number limits direct investigation of this
assumption. The impact of different ligand presentations (density, affinity, and
nanoscale distribution) on the proliferation of C2C12 and human primary
myoblasts was first examined in this study. Increasing the ligand density or
binding affinity led to a similar enhancement in proliferation of C2C12 cells and
human primary myoblasts. The nanoscale distribution of clustered RGD ligands
also influenced C2C12 cells and human primary myoblast proliferation, but in an
opposing manner. A rheological technique and a FRET technique were then
utilized to quantify the number of receptor–ligand interactions as a function of
peptide presentation. Higher numbers of bonds were formed when the RGD
density and affinity were increased, as measured with both techniques, and bond
number correlated with cell growth rates. However, the influence of the nanoscale
peptide distribution did not appear to be solely a function of bond number.
Altogether, these findings provide significant insight to the role of peptide
presentation in the regulation of cell proliferation, and the approaches developed
in this work may have significant utility in probing how adhesion regulates
a variety of other cellular functions and aid in developing design criterion for
cell-interactive materials.