Optochemical nanosensor PEBBLEs: photonic explorers for bioanalysis with biologically localized embedding

Nanosized photonic explorers for bioanalysis with biologically localized embedding (PEBBLEs) have been created for the intracellular monitoring of small analytes (e.g. H+, Ca2+, Mg2+, Zn2+, O-2, K+, Na+, Cl-, OH and glucose). The probes are based on the inclusion of fluorescent analyte-sensitive indicator dyes and analyte-insensitive reference dyes in a polymer (polyacrylamide, polydecylmethacrylate) or sol-gel (silica, ormosil) nanoparticle. The probes are ratiometric, reversible and protected from interaction with the cellular environment, a quality which is of benefit to the integrity of both the cell and the sensor functionalities. Herein we describe two types of PEBBLE sensors, direct measurement sensors and ion correlation sensors, as well as the use of these PEBBLEs in intracellular sensing.