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Biomedical subjects

Liming Dai

Publications and source records attributed to Liming Dai.

14 recordsLinked to original sources
PubMed2007

Are diamond nanoparticles cytotoxic?

Finely divided carbon particles, including charcoal, lampblack, and diamond particles, have been used for ornamental and official tattoos since ancient times. With the recent development in nanoscience and nanotechnology, carbon-based nanomaterials (e.g., fullerenes, nanotubes, nanodiamonds) attract a great deal of interest. Owing to their low chemical reactivity and unique physical properties, nanodiamonds could be useful in a variety of biological applications such as carriers for drugs, genes, or proteins; novel imaging techniques; coatings for implantable materials; and biosensors and biomedical nanorobots. Therefore, it is essential to ascertain the possible hazards of nanodiamonds to humans and other biological systems. We have, for the first time, assessed the cytotoxicity of nanodiamonds ranging in size from 2 to 10 nm. Assays of cell viability such as mitochondrial function (MTT) and luminescent ATP production showed that nanodiamonds were not toxic to a variety of cell types. Furthermore, nanodiamonds did not produce significant reactive oxygen species. Cells can grow on nanodiamond-coated substrates without morphological changes compared to controls. These results suggest that nanodiamonds could be ideal for many biological applications in a diverse range of cell types.

Carbon↗
PubMed2006

Direct measurements of interactions between polypeptides and carbon nanotubes.

The interactions of various polypeptides with individual carbon nanotubes (CNTs), both multiwall (MW) and single wall (SW), were investigated by atomic force microscopy (AFM). While adhesion forces arising from electrostatic attraction interactions between the protonated amine groups of polylysine and carboxylic groups on the acid-oxidized multi-wall carbon nanotubes (Ox-MWCNTs) dominate the interaction at a low pH, weaker adhesion forces via the hydrogen bonding between the neutral -NH2 groups of polylysine and -COO- groups of the Ox-MWCNTs were detected at a high pH. The adhesion force was further found to increase with the oxidation time for Ox-MWCNTs and to be negligible for oxidized single-wall carbon nanotubes (Ox-SWCNTs) because carboxylate groups were only attached onto the nanotube tips in the latter whereas onto both the nanotube tips and sidewall in the former. Furthermore, it was demonstrated that proteins containing aromatic moieties, such as polytryptophan, showed a stronger adhesion force with Ox-MWCNTs than that of polylysine because of the additional pi-pi stacking interaction between the polytryptophan chains and CNTs.

Amino Acid Sequence↗
PubMed2006

Shape/size-controlled syntheses of metal nanoparticles for site-selective modification of carbon nanotubes.

Shape- and size-controlled syntheses of metal nanoparticles have been achieved by galvanic displacement reaction between an aqueous solution of metal salt and Cu foil substrate. In particular, cubic and spheric nanoparticles of Pt (Au) with a fairly narrow size distribution were produced by reacting K(2)PtCl(4) (HAuCl(4)) with a Cu foil in an aqueous medium with and without CuCl(2) under different reaction conditions (e.g., different concentrations and reaction times). In conjunction with the substrate-enhanced electroless deposition (SEED) technique (Qu, L.; Dai, L. J. Am. Chem. Soc. 2005, 127, 10806), the shape/size-controlled syntheses have been successfully exploited to site-selectively deposit these metal nanoparticles onto the outerwall, innerwall, or end-tip of carbon nanotubes (CNTs). Asymmetric sidewall modification by attaching the innerwall and outerwall of CNTs with metal nanoparticles of different shapes was also achieved. Furthermore, it was demonstrated that the nanotube-supported Pt nanoparticles could be converted into hollow Au nanoboxes by galvanic displacement of Pt with Au. These CNT-supported metal nanoparticles were shown to possess interesting optical and electrocatalytic properties.

Journal Article↗
PubMed2006

Multifunctional chemical vapor sensors of aligned carbon nanotube and polymer composites.

Partially coating perpendicularly aligned carbon nanotube arrays with an appropriate polymer thin film along their tube length provides a novel concept for developing new sensors of high sensitivity, good selectivity, and excellent environmental stability for the detection of a broad class of chemical vapors with low power consumption. The absorption and desorption of chemical vapors by the polymer matrix cause changes in the inter-tube distance and, hence, the surface resistance across the nanotube film. Simple measurements of the resistance change, therefore, constitute the nanotube-polymer chemical vapor sensors. These rationally designed, aligned carbon nanotube-polymer composite films are flexible and can be effectively integrated into many systems for a wide range of potential applications, including their use as multifunctional sensors for sensing chemical vapors, mechanical deformations, thermal and optical exposures.

Journal Article↗
PubMed2006

Carbon microfibers sheathed with aligned carbon nanotubes: towards multidimensional, multicomponent, and multifunctional nanomaterials.

Multicomponent and multifunctional hybrid structures based on microsized carbon fibers sheathed with aligned carbon nanotubes and their derivatives have been successfully prepared, and have been demonstrated to be an effective means for connecting nanoscale entities to the outside world and to possess interesting electrochemical properties attractive for a wide range of potential applications, including in methanol direct fuel cells and highly sensitive biological and chemical sensors. Judicious modification of the carbon-fiber-supported aligned carbon nanotubes with various functional moieties could lead to a class of novel multidimensional, multicomponent, and multifunctional materials of practical significance.

Biosensing Techniques↗
PubMed2005

Substrate-enhanced electroless deposition of metal nanoparticles on carbon nanotubes.

By simply supporting carbon nanotubes with a metal substrate of a redox potential lower than that of the metal ions to be reduced into nanoparticles, we have developed a facile yet versatile and effective substrate-enhanced electroless deposition (SEED) method for functionalizing nanotubes with a large variety of metal nanoparticles, including those otherwise impossible by more conventional electroless deposition methods, in the absence of any additional reducing agent. The nanotube-supported metal nanoparticles thus produced are electrochemically active, and the newly developed SEED process represents a significant advance in functionalization of carbon nanotubes with metal nanoparticles for a wide range of potential applications, including in advanced sensing and catalytic systems.

Journal Article↗
PubMed2005

Novel silver nanostructures from silver mirror reaction on reactive substrates.

Novel silver clusters have been prepared by simply carrying out the silver mirror reaction on certain reactive substrates. Leaflike fractal silver microstructures and perpendicularly aligned silver nanosheets were produced on a commercially available copper foil and sandpaper-rubbed copper foil, respectively. The surface features of copper foils and the chemical state of Cu atoms play important roles in regulating the morphological structures of the resulting silver clusters. Silver nanoclusters with various morphologies ranging from the leaflike to flowerlike hierarchical structures can be produced from the silver mirror reaction on commercially available copper foils after being treated with a dilute aqueous HCl solution under different conditions. The aqueous solution of silver nanosheets shows an optical absorption spectrum with a broad light-scattering peak at about 350 nm, compared to a corresponding surface plasmon absorption band around 430 nm for silver nanoparticles from the conventional silver mirror reaction on glass.

Journal Article↗
PubMed2005

Multiwalled carbon nanotubes with chemically grafted polyetherimides.

Covalent attachment of a non-fluorinated polyetherimide onto the surface of carboxylic acid-functionalized multiwalled carbon nanotubes (MWNTs) has been achieved via grafting reactions. This confirms for the first time that the grafting reaction occurs at the nanotube surface when the carboxylic acid-functionalized MWNTs react with the polyetherimide with amine-terminated groups, through both amide and imide linkages formed at the interface between the carbon nanotubes and the polyetherimide. Additionally, an increase in the average molecular weight is detected in gel permeation chromatography when the polyetherimide is chemically attached onto the nanotubes. More interestingly, the chemical bonding at the interface provides much better interfacial adhesion and mechanical stress transfer, evidenced by a significant improvement in mechanical properties. As a result of the chemical attachment, the carbon nanotube-reinforced polyetherimide composite films have enhanced electrical conductivity, thermal deformation temperatures, and mechanical properties.

Journal Article↗
PubMed2005

Asymmetric end-functionalization of multi-walled carbon nanotubes.

Asymmetric end-functionalization of carbon nanotubes was achieved by sequentially floating a substrate-free aligned carbon nanotube film on two different photoreactive solutions with only one side of the nanotube film being contacted with the photoreactive solution and exposed to UV light each time. The resultant nanotubes with different chemical reagents attached onto their opposite tube-ends should be very useful for site-selective self-assembling of carbon nanotubes into many novel functional structures for various potential applications.

Journal Article↗
PubMed2005

DNA-directed self-assembling of carbon nanotubes.

Multicomponent structures were constructed by DNA-directed self-assembling of multiple carbon nanotubes and gold nanoparticles. The work presented here represents an important advance in constructing many multicomponent nanotube structures for multifunctional material and device applications.

DNA, Single-Stranded↗
PubMed2004

Large-scale synthesis of perpendicularly aligned helical carbon nanotubes.

Large-scale perpendicularly aligned helical carbon nanotube arrays were prepared by co-pyrolysis of Fe(CO)5 and pyridine onto the pristine quartz glass plates in a tube furnace at 900-1100 degrees C under a mixture flow of Ar and H2. The resultant aligned helical carbon nanotubes could not only facilitate the structure-property characterization for helical carbon nanotubes but also allow them to be effectively incorporated into devices for practical applications.

Journal Article↗
PubMed2004

Aligned carbon nanotube-DNA electrochemical sensors.

Single-strand DNA chains were chemically grafted onto aligned carbon nanotube electrodes, leading to novel aligned carbon nanotube-DNA sensors of a high sensitivity and selectivity for probing complementary DNA and target DNA chains of specific sequences.

DNA↗
PubMed2003

Aligned nanotubes.

Since the discovery of carbon nanotubes by lijima in 1991, various carbon nanotubes with either a single- or multilayered graphene cylinder(s) have been produced, along with their noncarbon counterparts (for example, inorganic and polymer nanotubes). These nanostructured materials often possess size-dependent properties and show new phenomena related to the nanosize confinement of the charge carriers inside, which leads to the possibility of developing new materials with useful properties and advanced devices with desirable features for a wide range of applications. In particular, carbon nanotubes have been shown to exhibit superior properties attractive for various potential applications, ranging from their use as novel electron emitters in flat-panel displays to electrodes in electrochemical sensors. For many of the applications, it is highly desirable to have aligned/patterned forms of carbon nanotubes so that their structure/property can be easily assessed and so that they can be effectively incorporated into devices. In this Review, we present an overview on the development of aligned and micropatterned nanotubes, with an emphasis on carbon nanotubes.

Journal Article↗