Polymer beads as nano-sensors

In order to measure local concentrations of ions in cells, we develop injectable fluorescent nana-sensors. We have chosen 100-nm nano-particles of polystyrene beads doped with fluorescent dyes. We propose to separate the molecular 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 be used to detect non-fluorescent molecules if a better sensitivity of the quenching effect could be achieved. (C) 1999 Elsevier Science S.A. All rights reserved.