Intracellular distribution of fluorescent copper and zinc bis(thiosemicarbazonato) complexes measured with fluorescence lifetime spectroscopy

James L. Hickey, Janine L. James, Clare A. Henderson, Katherine A. Price, Alexandra I. Mot, Gojko Buncic, Peter J. Crouch, Jonathan M. White, Anthony R. White, Trevor A. Smith, Paul S. Donnelly

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The intracellular distribution of fluorescently labeled copper and zinc bis(thiosemicarbazonato) complexes was investigated in M17 neuroblastoma cells and primary cortical neurons with a view to providing insights into the neuroprotective activity of a copper bis(thiosemicarbazonato) complex known as CuII(atsm). Time-resolved fluorescence measurements allowed the identification of the CuII and ZnII complexes as well as the free ligand inside the cells by virtue of the distinct fluorescence lifetime of each species. Confocal fluorescent microscopy of cells treated with the fluorescent copper(II)bis(thiosemicarbazonato) complex revealed significant fluorescence associated with cytoplasmic puncta that were identified to be lysosomes in primary cortical neurons and both lipid droplets and lysosomes in M17 neuroblastoma cells. Fluorescence lifetime imaging microscopy confirmed that the fluorescence signal emanating from the lipid droplets could be attributed to the copper(II) complex but also that some degree of loss of the metal ion led to diffuse cytosolic fluorescence that could be attributed to the metal-free ligand. The accumulation of the copper(II) complex in lipid droplets could be relevant to the neuroprotective activity of CuII(atsm) in models of amyotrophic lateral sclerosis and Parkinson's disease.

Original languageEnglish
Pages (from-to)9556-9567
Number of pages12
JournalInorganic Chemistry
Issue number19
Publication statusPublished - 5 Oct 2015
Externally publishedYes

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