Polymer beads as nano-sensors

In order to measure local concentrations of ions in cells, we develop injec table fluorescent nana-sensors. We have chosen 100-nm nano-particles of pol ystyrene beads doped with fluorescent dyes. We propose to separate the mole cular recognition and the detection functions. The connection between them is mediated by Forster energy transfer. In the present work we demonstrate that methylene blue (MB) can be adsorbed on the signalling beads. Besides, MB quenches latex fluorescence till a plateau value of 50%. This plateau is reached before surface saturation suggesting a specific interaction of the dye with surface located fluorophores. The device we have designed could b e used to detect non-fluorescent molecules if a better sensitivity of the q uenching effect could be achieved. (C) 1999 Elsevier Science S.A. All right s reserved.