Aptamers are oligonucleotides displaying specific binding properties for a predetermined target. They can be easily immobilized on various surfaces such as nanoparticles. Functionalized particles can then be used to various aims. We took advantage of the AlphaScreen(®) technology for monitoring aptamer-mediated interactions. A particle bearing an aptamer contains a photosensitizer whereas another type of particle contains a chemiluminescer. Irradiation causes the formation of singlet oxygen species in the photosensitizer-containing bead that in turn activates the chemiluminescer. Luminescence emission can be observed if the two types of beads are in close proximity (<200 nm). This is achieved when the cognate ligand of the aptamer is grafted onto the chemiluminescer-containing bead. Using this technology we have screened oligonucleotide libraries and monitored aptamer-protein interactions. This constitutes the basis for aptamer-based analytical assays.