Although the role of extracellular Caconcentrations differ greatly depending on the compartment. Typically, the Ca 2+ concentration is ~100 nanomolar (nM) in intracellular cytosol, ~100 micromolar (μM) in the endoplasmic reticulum and mitochondria and ~1 millimolar (mM) in extracellular fluid and blood (Fig. 1a,b 2+ imaging, one has to create a mechanism to avoid the outflow of indicators from an observation area through molecular diffusion. Obviously, this issue is intractable with existing molecular-based indicators.

Self-assembled microspherical aggregates that work as whispering gallery mode (WGM) optical resonators are synthesized from a novel hygroscopic polymer covalently appended with an aggregation-induced emission luminogen. The resultant microspheres can...