Abstract: Lipid vesicle particles capable of being targeted to a cell type of interest, said particle incorporating a peptide which is responsive to a predetermined metabolic signal from the targeted cell so as to modulate the permeability of the particle, said particle further incorporating a species to be targeted to the cell which is activated on said modulation of permeability. The particles may be used in methods for detecting cells, methods of treating cells and also therapeutically.

Abstract: A process for detecting an analyte which process comprises (a) contacting a sample suspected of containing said analyte with a containment means comprising a barrier which separates signal generating reagents from said sample, in the presence of an element which interacts specifically with said analyte, under conditions whereby interaction between the analyte and the said element results in activation of the signal generating reagents within the containment means on the side of the barrier opposite to the sample, and (b) detecting any signal generated and retained within the containment means from the sample side of the barrier. The process of the invention provides for sensitive detection of very small numbers of analyte materials using measurement techniques which include counting methods such as flow cytometry.