Rong He

Synthesis and characterization of polyamidoamine dendrimer-coated multi-walled carbon nanotubes and their application in gene delivery systems

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.

Self-Assembly of Quantum Dots and Carbon Nanotubes for Ultrasensitive DNA and Antigen Detection

A highly selective, ultrasensitive, fluorescence detection method for DNA and antigen based on self-assembly of multiwalled carbon nanotubes (CNTs) and CdSe quantum dots (QDs) via oligonucleotide hybridization is reported. Mercaptoalkyloligonucleotide molecules bind to the quantum dots, while amineoalkyloligonucleotides bind to CNTs with -COCl surface groups. QDs and CNTs further assemble into nanohybrids through DNA hybridization in the presence of target complementary oligonucleotides. The method is achieved with good repeatability with the detection limit of 0.2 pM DNA molecules and 0.01 nM antigen molecules. This novel detection system can also be used for multicomponent detection and antigen-antibody immunoreaction. The novel system has great potential in applications such as ultrasensitive pathogen DNA or antigen or antibody detection, molecular imaging, and photoelectrical biosensors.

End-to-end self-assembly and colorimetric characterization of gold nanorods and nanospheres via oligonucleotide hybridization

We report end-to-end assembly for tuning the optical properties of a gold nanorod/sphere based on oligonucleotide hybridization. The rationale behind the selection of the mercaptoalkyloligonucleotide molecule is based on the fact that the thiol group binds to the ends of the nanorods, which further assemble in an end-to-end fashion through hybridization with the target oligonucleotide. A highly selective, colorimetric polynucleotide detection method based on mercaptoalkyloligonucleotide-modified gold nanorod/sphere probes is also reported.

Hydrophilic high-luminescent magnetic nanocomposites

In this study, hydrophilic high-luminescent magnetic nanocomposites (LMNCs) composed of both fluorescent clusters (quantum dots, QDs) and magnetic nanoparticles were synthesized. The nanocomposites exhibited high luminescence and were easily separated in an external magnetic field. The LMNCs were capped with streptavidin (SA), and the SA on the surface of LMNC-SA composites was confirmed to be bioactive by competitive inhibition analytic methods. The fabricated LMNC-SA composites have potential application in biolabelling, bioseparation, immunoassay and pathogenic diagnosis.

Growth kinetics of CdSe nanoparticles in lauric acid

A safe, common, and low-cost method was proven to be effective for the synthesis of high quality CdSe nanocrystals. Cd(Ac)2 and Lauric acid were found to be the excellent cadmium precursor and solvent/ligand, respectively. The size and shape of CdSe nanocrystals synthesized by this route can be varied in a controllable manner in a broad size range, from about 2.0 nm to 4 nm. The growth kinetics of CdSe nanocrystals nucleated from TOPSe and cadmium acetate was also investigated in Lauric Acid. The rate constant for steady-state CdSe growth was found to be 4.15×10─8 m s─1 at 260°C.