Potential Application of Oleylamine-encapsulated AgInS2-ZnS Quantum Dots for Cancer Cell Labeling

This study improves a simple strategy for phase transfer process via ultrasonication approach. Water-soluble AgInS2-ZnS quantum dots (QDs) encapsulated with oleylamine have been successfully prepared without the presence of surfactant or polymer. During the propagation process, ultrasonication creates harmonic pressure (relative to the equilibrium hydrostatic pressure of the liquid), which was helpful for the dispersion of nanomaterials in two immiscible phases. The highly photoluminescent ZnS coated AgInS2 QDs (up to 55.3% QY) was synthesized with a one-pot two-step process with narrow particle distribution and successfully transferred to water phase without significant effect on optical properties. Beside QDs characterization, some factors such as pH stability, ionic strength, and bonding properties were investigated to reach a good condition of water soluble AgInS2-ZnS QDs. These nanoparticles also showed potential application for cancer cell staining. To demonstrate the targeting capability, folic acid was further conjugated with oleylamine encapsulated AgInS2-ZnS QDs for HeLa and MCF7 cancer cell staining. This study also reveals that the water-soluble QDs still gave lower fluorescence intensity on confocal imaging, even without folic acid conjugation. Moreover, folic acid is efficiently internalized into cells through folate receptor-mediated endocytosis. Confocal imaging characterization further informs folic acid-conjugated AgInS2-ZnS QDs that could specifically be targeted to the human cervical (HeLa) cells.