Fluorescence turn-on chemodosimeter-functionalized mesoporous silicananoparticles and their application in cell imaging

Abstract

The monitoring of Cu²⁺ levels in living cells has attracted increasing interest, however, the techniques used often suffer from interference from Hg²⁺. In the present study, we synthesized mesoporous silica nanospheres modified with a rhodamine B derivative containing a thiourea group to be used as a chemodosimeter-functionalized nanoprobe for the detection of Cu²⁺. This system is expected to offer selective detection of Cu²⁺ over Hg²⁺, as these ions react differently with the rhodamine derivative. This chemodosimeter-functionalized nanoprobe was characterized by transmission electron microscopy, small-angle X-ray diffraction, and N₂ adsorption–desorption isotherms. The nanoprobe's response to metal cations was investigated using absorption and fluorescence spectroscopies. Addition of Hg²⁺ or Cu²⁺ induced a significant solution color change (colorless to purple) and an enhancement in fluorescence of the nanoprobe, even in the presence of other cations in aqueous media. Cu²⁺-promoted ring-opening and hydrolysis of rhodamine led to the release of rhodamine from the mesoporous nanospheres, while this reaction is not observed in the presence of Hg²⁺, allowing effective discrimination of these ions through a simple centrifugation treatment. The living cell imaging experiments further demonstrate its value in bioimaging intracellular Cu²⁺ by virtue of its water solubility, membrane permeability, and nontoxic nature.