FluoSpheres and TransFluoSpheres polystyrene microspheres
satisfy several prerequisites of ideal long-term biological
tracers. Because the dyes in our microspheres are incorporated
throughout the microsphere rather than just on its surface, the
fluorescence output per microsphere is significantly greater
than that obtained from protein or dextran conjugates
(Fluorescein equivalents in Molecular Probes yellow-green-
fluorescent FluoSpheres beads—Table 6.6) and is relatively
immune to photobleaching and other environment-dependent
effects. FluoSpheres and TransFluoSpheres microspheres are also
biologically inert and physically durable, and they are
available with a large number of uniform sizes and surface
properties. Furthermore, their spectral properties can be freely
manipulated during manufacture without altering their surface
properties. See Microspheres—Section 6.5 for an extensive
discussion of the properties of our FluoSpheres and
TransFluoSpheres polystyrene beads. Measuring the effect of
various interv