DEPTH PROFILING OF MAMMALIAN-CELLS BY PHOTOACOUSTIC-SPECTROSCOPY - LOCALIZATION OF LIGANDS

Phase-resolved monitoring of photoacoustic signals can provide informa tion about the depth profile of a sample, We describe an application o f this principle to determine the depth profiles of ligands and antitu mor agents in mammalian cells, Measurements of the in-phase and quadra ture components of the photoacoustic spectra (which yield information from the surface and the interior, respectively) of a tumor cell line, AK-5, treated with the antitumor agent coralyne chloride have been ma de, They clearly show that the drug accumulates in the cell interior a nd is not seen on the cell surface, providing in situ evidence for the localization of this drug, Histochemical dyes which stain cells unifo rmly give identical in-phase and quadrature spectra; spectra of cells incubated with nuclear stains demonstrate a differential staining of t he nucleus and the cytoplasm, These results demonstrate the usefulness of phase-resolved photoacoustic spectroscopy in monitoring differenti al interactions of drugs and other ligands with cells.