Process for immobilizing a chelator on silica, device containing immobilized chelator, and use thereof

In an improved process for immobilizing a chelator moiety on a silica substrate, the substrate is reacted in a liquid reaction medium with an alkyltrialkoxysilane compound having a functional group that provides an attachment site for covalently binding the chelator moiety to the substrate. The improvement comprises providing a particulate silica substrate having a surface area of less than about 50 m2/g. An improved extracorporeal device for removing metal ions from blood and other fluids includes a cartridge having an inlet and an outlet and containing a plurality of tubular fibers that extend from the inlet to the outlet. Each fiber has a lumen enclosed by an anisotropic membrane. The membrane is supported by a macroporous structure that contains a chelator moiety immobilized on a particulate silica substrate having a surface area of less than about 50 m2/g. The anisotropic membrane forms a diffusion barrier that is permeable to metal cations contained in the fluid but is substantially impermeable to high molecular weight components. A method of removing chelatable metal cations from blood fluid uses the described extracorporeal device. The blood fluid containing the chelatable cations is passed through the lumen of each tubular fiber and diffused through the anisotropic membrane enclosing each lumen. The cations are contacted with the immobilized chelator moieties in the macroporous structure supporting the membrane, which causes the cations to be immobilized in the macroporous structure. The metal cations are thereby effectively removed from the fluid.