With the goal of identifying an improved delivery scheme for intracellular tracking and anticancer therapy, we explored a novel double functionalization of a carbon nanotube delivery system containing antisense oligodeoxynucleotides (ASODNs) as a therapeutic gene and CdTe quantum dots as fluorescent labeling probes via electrostatically layer-by-layer assembling. This is the first time that we used mercaptoacetic acid-capped CdTe quantum dots as fluorescent labeling probes for clearly tracking the intracellular transport and evaluating delivery efficiency of ASODNs by functionalized multiwalled carbon nanotubes (MWNTs).

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A novel functionaliztion of gold nanorods (GNRs) intracellular delivery system was prepared via electrostatically layer-by-layer assemblying, in which multilayer polyelectrolyte-coated GNRs were used as vector and antisense oligodeoxynucleotides (ASODNs) as therapeutic gene. The as-prepared positively charged GNRs were firstly modified with two successive polyelectrolyte layers of the negatively charged poly(sodium-4-styrenesulfonate) (PSS) and positively charged polyenthylenimine (PEI) in order to greatly improve the biocompatibility of these cetyltrimethylammonium bromide(CTAB)-coated GNRs and facilitate further biofunctionalization. The multilayered polyelectrolyte functionalized GNRs were characterized by UV-vis spectroscopy, transmission electron microscopy (TEM) and MTT assay. The polyelectrolytes-coated GNRs were then used as vector for ASODNs. Electrochemical impedance spectroscopy(EIS) was employed to confirm the formation of the GNRs-ASODNs conjugates through electrostatic interaction. Furthermore, cellular uptake and delivery efficiency of the GNRs-ASODNs conjugates as well as cellular apoptosis induced by the ASODNs transfected with gold nanorods were investigated by confocal microscopy and flow cytometry, exhibiting efficient intracellular delivery and improved antitumor activity of ASODNs by the polyelectrolytes-coated GNRs carriers.

Novel multi-color fluorescent nanoprobes were prepared by electrostatically assembling differently sized CdTe quantum dots on polyethylenimine (PEI) functionalized multi-walled carbon nanotubes (MWNTs). The structural and optical properties of the nano-assemblies (MWNTs-PEI-CdTe) were characterized by transmission electron microscopy (TEM), electron diffraction spectra (EDS), Raman spectroscopy, confocal microscopy and photoluminescence spectroscopy (PL), respectively. Electrochemical impedance spectroscopy (EIS) was also applied to investigate the electrostatic assembling among oxidized MWNTs, PEI and CdTe. Furthermore, confocal fluorescence microscopy was used to monitor the nano-assemblies' delivery into tumor cells. It was found that the nano-assemblies exhibit efficient intracellular transporting and strong intracellular tracking. These properties would make this luminescent nano-assembly an excellent building block for the construction of intracellular nanoprobes, which could hold great promise for biomedical applications.

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