Nonendocytic Cell Delivery of Quantum Dot Using Arginine-Terminated Gold Nanoparticles.

Direct membrane translocation of quantum dot for straight access to cytosol is essential for subcellular targeting and intracellular imaging application. However, cellular entry of the quantum dot usually occurs via endocytosis that is associated with vesicular entrapment followed by trafficking to endosome/lysosome. Thus, quantum dots are not freely available in cytosol that restrict their subcellular targeting/labeling. Recent works show that arginine-terminated nanoparticle of <10 nm size (Au-arginine) can enter into cell via direct membrane translocation and delivers protein into subcellular compartments. Here we report Au-arginine as delivery carrier for direct membrane translocation of quantum dot with the straight access to cytosol. The approach involves simple mixing of the colloidal solutions of quantum dot and Au-arginine followed by incubation with cell. We found that quantum dot forms colloidal assembly after binding with Au-arginine, enter into cell with higher efficiency and faster kinetics, distribute homogeneously in cytosol. It has also been observed that the cell uptake mechanism of quantum dot shifts from energy dependent endocytosis to energy independent nonendocytic processes after the binding with Au-arginine. This approach is independent of cell type and can be adapted for direct cytosolic delivery of wide variety of nanoparticles.