Poly(methyl methacrylate) beads were hybridized with Y 3 Al 5 O 12 :Ce 3þ nanoparticles through electrostatic interactions using the layer-by-layer adsorption technique to prepare fluorescent beads for biological application. The subsequent sequential adsorption of poly(sodium 4-styrenesulfonate) and poly(allylamine hydrochloride) onto the composite beads prevented the detachment of the Y 3 Al 5 O 12 :Ce 3þ nanoparticles. The fluorescent beads were observed as tight dot plots by flowcytometry. Bovine serum albumin can be immobilized on the surface of the composite beads and tagged with a red dye through an antigen-antibody reaction. This result indicates that the composite beads are useful for bead assays such as flowcytometry.

Positively charged Y 3 Al 5 O 12 :Ce 3+ nanoparticles and negatively charged poly(sodium 4-styrenesulfonate) are sequentially adsorbed on the surface of negatively charged poly(methyl methacrylate) beads by the layer-by-layer adsorption method to obtain the composite beads, showing green emission under the blue light excitation. These fluorescent composite beads are detected as a dot group by flowcytometry (FCM). Bovine serum albumin (BSA) immomobilized on the composite beads with green emission are mixed with anti-BSA tagged with organic red dye. The antigen-antibody reaction is detected from both green and red emissions by FCM, showing that the fluorescent composite beads can be used for detecting biological reactions.