Quantum-Dots-Doped ORMOSIL Nanoparticles as Optical Probes for Total Internal Reflection Fluorescence Imaging of Cancer Cells

We report the novel use of organically modified silica (ORMOSIL) nanoparticles to encapsulate hydrophobic quantum dots (QDs), thus making them hydrophilic and yet maintaining stable optical properties. QDs are resistant to photobleaching, and the cationic charge on the surfaces of the ORMOSIL nanoparticles can facilitate them being uptaken at the cell substrate regions. An objective-lens-based total internal reflection fluorescence (TIRF) microscope is used to observe the staining and dynamics of HeLa cancer cells, which have been targeted by the synthesized QD-doped ORMOSIL nanoparticles. Since the same microscope objective is used for launching the incident light beam and the collection lens, the observation and manipulation of live samples under a TIRF microscope is therefore much easier than that in the case of using the conventional prism-based TIRF setup. The present nanoparticle-assisted approach has made TIRF imaging a much more powerful tool for real-time monitoring of intracellular biological metabolic activities.