The first nanometer scale
anion sensing fluorescent spherical nanosensors, or PEBBLEs (probes encapsulated by biologically localized embedding) have been developed for the intracellular monitoring of
chloride. The general scheme for the polymerization and introduction of sensing components creates a matrix that allows for the utilization of the highly selective
ionophores used in poly(
vinyl chloride) and poly(decyl
methacrylate)
ion-selective electrodes. We have demonstrated that our previously developed scheme for
cation sensors can be utilized to tailoring selective submicron sensors for use in intracellular measurements of biologically relevant
anions for which selective enough
fluorescent probes do not exist. Three schemes were attempted for the development of
chloride sensitive PEBBLEs. The first two used the
Chloride ionophore indium(III) octaethylporphyrin chloride (In(OEP)Cl) (1) as an
ionophore working in tandem with a chromoionophore and (2) as a chromoionophore with a peak shift generated by
chloride mediated breaking of
hydroxide ion-bridged
porphyrin dimer. The third method used the optically silent
Chloride ionophore III (ETH 9033) working in tandem with chromoionophore III (ETH 5350) to indirectly monitor Cl- activity by reporting the H+ coextracted into the matrix. Method 3 gave the most promising results, at a pH of 7.2 these PEBBLEs have a limit of detection of 0.2 mM Cl- with a linear dynamic range of 0.4 mM-190 mM Cl-. These PEBBLEs were delivered into C6
glioma cells, utilizing a gene gun, and intracellular
chloride levels were monitored during
ion-channel stimulation by
kainic acid.