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Polyglutaraldehyde micro spheres can be prepared under alkaline conditions. Addition of fluorescin isothiocyanate (FITC) during the synthesis of micro spheres results in the formation of fluorescent micro spheres. The abundance of the aldehyde groups in the micro bead's gel matrix makes it probable for them, in addition to pure adsorption, to form covalent bonds with bioplymers like antibodies. It was possible to bind rabbit anti - human IgG to the e flurescent beads at physiological pH. These conjugate microsphere - IgGs were then used as a means of specific labeling of human RBCs by observing their attachment to RBO surface receptors under fluorescent microscope.