Uptake and intracellular distribution of various metal ions in human monocyte-derived dendritic cells detected by Newport Green™ DCF diacetate ester

Background: The attempt to visualise intracellular protein metal complexes has currently been difficult due to the unavailability of probes for such molecular structures. Newport Green (TM) DCF diacetate ester is a cell permeant acetate ester, which becomes fluorescent after hydrolysis. This molecule is initially uncharged, allowing it to pass through cell membranes. Once in the cell, it is hydrolysed and becomes charged, hindering its escape from the cell and allowing it to bind charged protein metal complexes, which then become fluorescent. Methods: In this study, we exposed cultured human monocyte-derived dendritic cells (mDC) to a variety of metal ions with the aim of having the cells take up and process protein metal complexes. Newport Green (TM) DCF diacetate ester was used to fluorescently label intracellular protein metal complexes. Results: Flow cytometry analysis and confocal imaging showed specific staining for mDC exposed to aluminium, chromium, nickel, titanium and zirconium ions. The intensity of staining varied between ion types, whereby Ti(III) resulted in the brightest fluorescence signal. Aluminium, Cr(III), Ni, Ti(IV) and Zr(IV) were also clearly detectable. Conclusion: For the first time, intracellular metal ion protein complexes undergoing cellular processing were successfully visualised in human mDC using flow cytometry and confocal microscopy. (C) 2008 Elsevier B.V. All rights reserved.