The functional quantum dots (QDs) were specifically designed to overcome barriers in siRNA delivery such as siRNA protection, cellular penetration, endosomal release, carrier unpacking, intracellular transport and gene silencing. In this paper, two l-arginine-functional-modified CdSe/ZnSe QDs were synthesized as siRNA carriers to silence HPV18 E6 gene in HeLa cells. Using such constructs, these QDs showed significantly low cellular cytotoxicity and good siRNA protection. Flow cytometric and confocal microscopic analyses confirmed that the QDs delivered siRNA into HeLa cells efficiently. Importantly, superior gene silencing efficiency was achieved as evaluated by Reverse Transcription-PCR (RT-PCR) and Western blotting and HeLa cells growth was inhibited in xCELLigence installation analysis and MTT assay when treated with QD-siRNA complexes. Interestingly, the QDs coated with β-CD-l-Arg showed optimized property compared with those coated with l-Arg. Furthermore, these QDs complexes could also be used as nanocrystal probing agents, allowing real-time tracking and localization of QDs during delivery and transfection. The properties and capabilities of these QDs showed that amino acid-modified QDs could be used as useful siRNA carriers to effectively silence a target gene as well as fluorescence probes to analyze intracellular imaging in vivo.
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