Nanoparticle imaging and diagnostic of Caenorhabditis elegans intracellular pH

A novel diagnostic tool has been developed for the characterization of intracellular pH (pHi) in the model organism Caenorhabditis elegans. This tool exploits the chemical stability of colloidal silica and the pH sensitivity of certain fluorescent dyes. Once ingested, the fluorescent colloidal dispersion yields a reliable visual indication of pH without the use of chemical fixatives or damaging the nematode. The pH-sensitive silica nanoparticles were visualized by confocal microscopy, and the fluorescence spectra from the internally referenced colloidal particulates were measured. By comparing the fluorescence profile of colloids in wild-type (N2) and mutant (eat-3) C. elegans against a calibration series, the intestinal pHi could be established in each population. The rapid characterization of pHi using this inexpensive nonintrusive technique has significant implications for disease research where C. elegans is used as a model organism.