Optimizing the Selectivity of Surface-Adsorbing Multivalent Polymers

Multivalent polymers are macromolecules containing multiple chemical moieties designed to bind to complementary moieties on a target; for example, a protein with multiple ligands that have affinity for receptors on a cell surface. Though the individual ligand-receptor bonds are often weak, the combinatorial entropy associated with the different possible ligand-receptor pairs leads to a binding transition that can be very sharp with respect to control parameters, such as temperature or surface receptor concentration. We use mean-field self-consistent field theory to study the binding selectivity of multivalent polymers to receptor-coated surfaces. Polymers that have their ligands clustered into a contiguous domain, either located at the chain end or chain midsection, exhibit cooperative surface adsorption and superselectivity when the polymer concentration is low. On the other hand, when the ligands are uniformly spaced along the chain backbone, selectivity is substantially reduced due to the lack of binding cooperativity and due to crowding of the surface by the inert polymer segments in the chain backbone.