Scattering/Fluorescence Dual-Mode Imaging in MnO₂-Coated Silicon Nanospheres for Cancer Cell Detection

A tumor microenvironment (TME)-responsive nanoprobe composed of a fluorescent dye-decorated silicon (Si) nanosphere core and a thin MnO₂ shell is proposed for simple and intelligent detection of cancer cells. The Si nanosphere core with diameters of 100-200 nm provides environment-independent Mie scattering imaging, while, simultaneously, the MnO₂ shell provides the capability to switch the on/off state of the dye fluorescence reacted to the glutathione (GSH) and/or H₂O₂ levels in a cancer cell. Si-MnO₂ core-shell nanosphere probes are fabricated in a solution-based process from crystalline Si nanosphere cores. The fluorescence switching under exposure to GSH is demonstrated, and the mechanism is discussed based on detailed optical characterizations including single-particle spectroscopy. Different types of human cells are incubated with the nanoprobes, and a proof of concept experiment is performed. From the combination of the robust scattering images and GSH- and H₂O₂-sensitive fluorescence images, the feasibility of cancer cell detection by the multimodal nanoprobes is demonstrated.