Competitive binding inhibitors based on multivalent nanoparticles have shown
great potential for preventing virus infections. However, general design
principles of highly efficient inhibitors are lacking as the quantitative
impact of factors such as virus concentration, inhibitor size, steric
shielding, or multivalency effects in the inhibition process is not known.
Based on two complementary experimental inhibition assays we determined size-
dependent steric shielding and multivalency effects. This allowed us to adapt
the Cheng–Prusoff equation for its application to multivalent systems. Our
results show that the particle and volume normalized IC50 value of an
inhibitor at very low virus concentration predominantly depends on its
multivalent association constant, which itself exponentially increases with
the inhibitor/virus contact area and ligand density. Compared to multivalency
effects, the contribution of steric shielding to the IC50 values is only
minor, and its impact is only noticeable if the multivalent dissociation
constant is far below the virus concentration, which means if all inhibitors
are bound to the virus. The dependence of the predominant effect, either
steric shielding or multivalency, on the virus concentration has significant
implications on the in vitro testing of competitive binding inhibitors and
determines optimal inhibitor diameters for the efficient inhibition of
viruses