Manganese displacement from Zinpyr-1 allows zinc detection by fluorescence microscopy and magnetic resonance imaging

Abstract

A paramagnetic manganese complex of a fluorescein-based probe affords a dual-modality zinc sensor featuring an improved fluorescence dynamic range and an MRI readout.

Fig. 1

Zinc-induced (0 to 3 equiv) fluorescence enhancement of (a) ZP1 and (b) [ZP1Mn₂] at pH 7.0 (10 µM). (c) Fluorescence dynamic range (Φ_Zn/Φ_free) of ZP1 (black) and [ZP1Mn₂] (red) at pH 6.0 (50 mM MES, 100 mM KCl), 7.0 (50 mM PIPES, 100 mM KCl) and 8.0 (25 mM HEPES, 100 mM KCl).

Fig. 2

Fluorescence microscopy images of HeLa cells incubated with ZP1 or [ZP1Mn₂]. Left: DIC images (scale bar = 25 µm), middle: background fluorescence images, right: zinc-induced response fluorescence images. Micrographs are shown relative to the same intensity scale for direct comparison.

Fig. 3

T₂-weighted MRI (TR = 2000 ms, TE = 80 ms, field strength = 200 MHz. Scale bars represent acquired MRI signal intensity (/10⁵)) and transverse relaxivity (r₂) of [ZP1Mn₂] (0.1 mM) before and after addition of ZnCl₂ or Zn(ClO₄)₂ (2 mM) in 50 mM PIPES buffer containing either KCl or KClO₄ (100 mM), respectively, pH 7.0.

Scheme 1

Complex [ZP1Mn₂] and displacement reaction