Affinity Chromatography as a Tool to Analyze Polyanion–Polycation Complexes: the Case of Poly(Llysine Citramide)–Poly(L-lysine) Systems

Abstract

Artificial polymeric carriers for bioactive compounds, such as drugs and genes, are increasingly being reported in the literature. Most are polyelectrolytes aimed at being injected into body fluids that are composed of charged macromolecules (proteins, glycoproteins, poly(glycosamino glycane)s, polynucleotides, etc.). Many interactions can occur and lead to dramatic phenomena, such as polyelectrolyte complexation or substitution, cell aggregation and hemolysis. For the purpose of modeling and better understanding these interactions and their effects, a library of polyanions of the poly(L-lysine citramide)-type was interacted with the polycation poly(L-lysine) in aqueous media. Different fractions of complexes were generated by successive additions of aliquots of the polycation solution to the polyanion library solution by a titrating process. The two components, the polycation and the complex population of polyanions, were separated from the collected complex fractions by affinity chromatography and then analyzed by aqueous SEC. Molecular weight selectivity was shown, the high molecular weight polyanion macromolecules precipitated first, while complexes involving smaller molecules were found to remain in solution. The data show the potential of affinity chromatography for studying interpolyelectrolyte complexes and emphasizes the critical role that polydispersity can play when therapeutic charged macromolecules are injected into blood.