An improved method for separating materials is provided, using colloidal,
magnetizable aggregates, optionally silanized, and coated with a one or
more layers of novel polysaccharide derivatives. Materials separated by
the aggregates of the invention include inorganic and organic molecules,
viruses, organelles, and cells. The invention also relates to a kit for
separating such materials. The separated materials are useful in
analytical and preparative or in diagnostic and therapeutic techniques.