highly fluorescent , stable and biocompatible microspheres are obtained by copolymerizing an acrylic monomer containing a covalent bonding group such as hydroxyl , amine or carboxyl , for example , hydroxyethylmethacrylate , with an addition polymerizable fluorescent comonomer such as dansyl allyl amine . a lectin or antibody is bound to the covalent site to provide cell specificity . when the microspheres are added to a cell suspension the marked microspheres will specifically label a cell membrane by binding to a specific receptor site thereon . the labeled membrane can then be detected by fluorescence of the fluorescent monomer .