Showing papers by "Xiaoming Sun published in 2007"

In vivo biodistribution and highly efficient tumour targeting of carbon nanotubes in mice

Abstract: Single-walled carbon nanotubes (SWNTs) exhibit unique size, shape and physical properties1,2,3 that make them promising candidates for biological applications. Here, we investigate the biodistribution of radio-labelled SWNTs in mice by in vivo positron emission tomography (PET), ex vivo biodistribution and Raman spectroscopy. It is found that SWNTs that are functionalized with phospholipids bearing polyethylene-glycol (PEG) are surprisingly stable in vivo. The effect of PEG chain length on the biodistribution and circulation of the SWNTs is studied. Effectively PEGylated SWNTs exhibit relatively long blood circulation times and low uptake by the reticuloendothelial system (RES). Efficient targeting of integrin positive tumour in mice is achieved with SWNTs coated with PEG chains linked to an arginine–glycine–aspartic acid (RGD) peptide. A high tumour accumulation is attributed to the multivalent effect of the SWNTs. The Raman signatures of SWNTs are used to directly probe the presence of nanotubes in mice tissues and confirm the radio-label-based results.

Supramolecular chemistry on water-soluble carbon nanotubes for drug loading and delivery.

Abstract: We show that large surface areas exist for supramolecular chemistry on single-walled carbon nanotubes (SWNTs) prefunctionalized noncovalently or covalently by common surfactant or acid-oxidation routes. Water-soluble SWNTs with poly(ethylene glycol) (PEG) functionalization via these routes allow for surprisingly high degrees of π-stacking of aromatic molecules, including a cancer drug (doxorubicin) with ultrahigh loading capacity, a widely used fluorescence molecule (fluorescein), and combinations of molecules. Binding of molecules to nanotubes and their release can be controlled by varying the pH. The strength of π-stacking of aromatic molecules is dependent on nanotube diameter, leading to a method for controlling the release rate of molecules from SWNTs by using nanotube materials with suitable diameter. This work introduces the concept of “functionalization partitioning” of SWNTs, i.e., imparting multiple chemical species, such as PEG, drugs, and fluorescent tags, with different functionalities onto t...

Langmuir-blodgett assembly of densely aligned single-walled carbon nanotubes from bulk materials.

Abstract: Single-walled carbon nanotubes (SWNTs) exhibit advanced electrical and surface properties useful for high performance nanoelectronics. Important to future manufacturing of nanotube circuits is a large-scale assembly of SWNTs into aligned forms. Despite progress in assembly and oriented synthesis, pristine SWNTs in aligned and close-packed form remain elusive and needed for high-current, -speed, and -density devices through collective operations of parallel SWNTs. Here, we develop a Langmuir−Blodgett (LB) method achieving monolayers of aligned SWNTs with dense packing, central to which is a noncovalent polymer functionalization by poly(m-phenylenevinylene-co-2,5-dioctoxy-p-phenylenevinylene) (PmPV) imparting high solubility and stability of SWNTs in an organic solvent 1,2-dichloroethane (DCE). Pressure cycling or “annealing” during LB film compression reduces hysteresis and facilitates high-degree alignment and packing of SWNTs characterized by microscopy and polarized Raman spectroscopy. The monolayer SWN...

Langmuir blodgett assembly of densely aligned single walled carbon nanotubes from bulk materials

Abstract: Single walled carbon nanotubes exhibit advanced electrical and surface properties useful for high performance nanoelectronics. Important to future manufacturing of nanotube circuits is large scale assembly of SWNTs into aligned forms. Despite progress in assembly and oriented synthesis, pristine SWNTs in aligned and close-packed form remain elusive and needed for high current, speed and density devices through collective operations of parallel SWNTs. Here, we develop a Langmuir Blodgett method achieving monolayers of aligned SWNTs with dense packing, central to which is a non covalent polymer functionalization by PmPV imparting high solubility and stability of SWNTs in an organic solvent DCE. Pressure cycling or annealing during LB film compression reduces hysteresis and facilitates high degree alignment and packing of SWNTs characterized by microscopy and polarized Raman spectroscopy. The monolayer SWNTs are readily patterned for device integration by microfabrication, enabling the highest currents 3mA through the narrowest regions packed with aligned SWNTs thus far.

Noncovalent functionalization of carbon nanotubes by fluorescein-polyethylene glycol: supramolecular conjugates with pH-dependent absorbance and fluorescence.

Abstract: We report the use of fluorescein−polyethylene glycol (Fluor-PEG) to noncovalently functionalize single-walled carbon nanotubes (SWNTs) for obtaining water-soluble nanotube conjugates (Fluor-PEG/SWNT) and simultaneously affording fluorescence labels to nanotubes. We find serendipitously that fluorescein, a widely used fluorophore, can strongly adsorb onto the sidewall of the SWNTs, likely via π-stacking, and the hydrophilic PEG chain imparts high aqueous solubility. Interaction between fluorescein and SWNT is pH dependent; it weakens as the pH is increased, causing the Fluor-PEG/SWNT conjugate to be less stable at high pHs. Fluorescein molecules bound to SWNTs exhibit interesting pH-dependent optical absorbance and fluorescence properties that are distinct from free molecules, as a result of pH-dependent interactions with SWNT sidewalls. Fluorescence emission from fluorescein adsorbed on SWNT is quenched by ∼67%, but remains sufficient and useful as a fluorescent label. The utility of Fluor-PEG/SWNT as a s...