Magnetic nanoparticles (MNP) with a diameter of 8 nm were modified with different generations of polyamidoamine (PAMAM) dendrimers and mixed with antisense survivin oligodeoxynucleotide (asODN). The MNP then formed asODNdendrimer-MNP composites, which we incubated with human tumor cell lines such as human breast cancer MCF-7, MDA-MB-435, and liver cancer HepG2 and then analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, quantitative reverse transcription-PCR, Western blotting, laser confocal microscopy, and high-resolution transmission electron microscopy. Results showed that the asODN-dendrimer-MNP composites were successfully synthesized, can enter into tumor cells within 15 min, caused marked down-regulation of the survivin gene and protein, and inhibited cell growth in dose-and time-dependent means. No.5 generation of asODN-dendrimer-MNP composites exhibits the highest efficiency for cellular transfection and inhibition. These results show that PAMAM dendrimer-modified MNPs may be a good gene delivery system and have potential applications in cancer therapy and molecular imaging diagnosis.

With the aim of improving the amount and delivery efficiency of genes taken by carbon nanotubes into human cancer cells, different generations of polyamidoamine dendrimer modified multi-walled carbon nanotubes (dMNTs) were fabricated, and characterized by high-resolution transmission electron microscopy, atomic force microscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis, revealing the presence of dendrimer capped on the surface of carbon nanotubes. The dMNTs fully conjugated with FITC-labeled antisense c-myc oligonucleotides (asODN), those resultant asODN-dMNTs composites were incubated with human breast cancer cell line MCF-7 cells and MDA-MB-435 cells, and liver cancer cell line HepG2 cells, and confirmed to enter into tumor cells within 15 min by laser confocal microscopy. These composites inhibited the cell growth in time- and dose-dependent means, and down-regulated the expression of the c-myc gene and C-Myc protein. Compared with the composites of CNT-NH(2)-asODN and dendrimer-asODN, no. 5 generation of dendrimer-modified MNT-asODN composites exhibit maximal transfection efficiencies and inhibition effects on tumor cells. The intracellular gene transport and uptake via dMNTs should be generic for the mammalian cell lines. The dMNTs have potentials in applications such as gene or drug delivery for cancer therapy and molecular imaging.

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The effects of carbon nanotubes (CNT) with different surface groups on the luminescence properties of mercaptoacetic acid-capped CdSe quantum dots (QD) are reported. Carboxyl-, hydroxyl-, and amine-modified CNTs are used to interact with water-soluble luminescent mercaptoacetic acid-capped CdSe QDs. TEM and ζ-potential analysis results show that CNT and QDs can be assembled into complex nanostructure by electrostatic interaction. The photoluminescence (PL) quenching of QDs caused by CNTs can be described by a Stern-Volmer-type equation as well as by a double-logarithmic equation. Significant differences in the values of binding constants K SV and K b were found in these experiments. The binding constant for amineterminated CNT is much higher compared to that of carboxyl-and hydroxyl-terminated CNTs. Dynamic quenching and photoluminescence resonance energy transfer between QDs and CNTs should be responsible for the quenching of photoluminescence emissions of QDs caused by CNTs with different groups. The strategy shown in this paper may be useful for creating a novel methodology for investigating intermolecular interaction, and the quenching phenomena may be used as selective molecular probes and developed as fluorescence sensors.

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