  Nanoparticles functionalized with multiple ligands can be programmed to bind
biological targets depending on the receptors they express, providing a general
mechanism exploited in various technologies, from selective drug-delivery to
biosensing. For binding to be highly selective, ligands should exclusively
interact with specific targeted receptors, because formation of bonds with
other, untargeted ones would lead to non-specific binding and potentially
harmful behaviour. This poses a particular problem for multivalent
nanoparticles, because even very weak bonds can collectively lead to strong
binding. A statistical mechanical model is used here to describe how
competition between different receptors together with multivalent effects can
be harnessed to design ligand-functionalized nanoparticles insensitive to the
presence of untargeted receptors, are insensitive to these problems, preventing
non-specific binding.
