Functionalized nanoparticles for endotoxin binding in aqueous solutions

Nanoparticles consisting of a polystyrene core and a polyglycidyl methacrylate shell were prepared by a two-step emulsion polymerization. The size and surface properties of the particles were characterized by scanning electron microscopy, dynamic light scattering and polyelectrolyte titration techniques. Particles were found to be monodisperse with a mean diameter of about 85 nm. Parent particles were modified with a number of different ligands including diamines of increasing chain length, amino acids and corresponding amines and higher molecular weight ligands like polymyxin B. The modified particles were tested for their endotoxin (ET) binding capacity in water and physiological sodium chloride solution with the Limulus amebocyte lysate (LAL) assay. It was found that the ET binding properties of the different ligands depend both on the ability of the ligand to form Coulomb- and van der Waals-interactions with the ET molecule influenced by the nature of the suspension medium. Therefore, the choice of ligands for particle modification has to consider minutely the conditions under which ET has to be removed, e.g. removal from pure water, dialysis fluids, plasma or blood.