Wensheng Lu

Effects of aggregation and the surface properties of gold nanoparticles on cytotoxicity and cell growth

UNLABELLED The effect of gold nanoparticles (Au NPs) on cells remains open for investigation. Here we show that small Au NPs can be endocytosed by cells and form aggregates inside the cell, resulting in cytotoxicity. When the aggregates become too large to enter the cell and instead adhere onto the cell surface, however, the growth rate of HeLa cells increases. Printed patterns of Au NPs fabricated through inkjet printing technology were used to study the effects of Au NP aggregation on human cervical carcinoma (HeLa) cell activity. The growth of the HeLa cells was inhibited on the polymer-coated Au NPs but increased on the silicon substrate. On the uncoated Au NP surface, however, the HeLa cell growth rate was higher than that on the silicon substrate. Experiments with Escherichia coli cells showed a similar effect of the Au NPs. This phenomenon provides a new perspective for research on toxicity in nanoparticle biology. FROM THE CLINICAL EDITOR Printed patterns of Au NPs fabricated through inkjet printing technology were used to study the effects of Au NP aggregation on human cervical carcinoma (HeLa) cell activity. Small Au NPs can be endocytosed by cells resulting in cytotoxicity; in contrast, large aggregates adhere onto the cell surface and increase the growth rate of HeLa cells.

Influence of pH on the aggregation morphology of a novel surfactant with single hydrocarbon chain and multi-amine headgroups.

A novel single-chain surfactant with multi-amine headgroups, bis(amidoethyl-carbamoylethyl) octadecylamine (C18N3), was synthesized. Electronmicrographic study showed that in aqueous solution C18N3 formed small micelles (10-20 nm in diameter) at pH 2.0 and changed into much larger globule vesicles sized about 0.6-2.0 microm in diameter at pH 6.8. At pH 12.0 vesicles changed to a much larger continued lyotropic lamella structure. At pH = 2, the surface tension (gamma)-concentration (C) curve at pH 2 was an ordinary one, having one critical micelle concentration at 2.9 x 10(-3) mol L(-1) at relatively high surface tension (52 mN m(-1)). However, two unique transition points were observed in the gamma-C plot at pH = 6.8 and 10.5, showing higher surface activity that is believed to be associated with the micelle-bilayer structure transition. The protonation degree pKas of the three amine headgroups were found to be 6.6, 10.6, and 10.9, respectively, indicating that a complete protonation state of the headgroups occurred at pH 2.0, which is consistent with the apparent surface areas of headgroup calculated according to Gibbs adsorption isotherm. Variation of sizes and morphologies of C18N3 in aqueous solution at different pH values suggest that our synthetic surfactant may have great potential applications as a template in fabricating drug delivery, biosensors, and biomolecular devices.

Sensitive electrochemical immunosensor for α-fetoprotein based on graphene/SnO2/Au nanocomposite.

A label-free electrochemical immunosensor for sensitive detection of α-fetoprotein (AFP) was developed based on graphene/SnO2/Au nanocomposite. The graphene/SnO2/Au nanocomposite modified glassy carbon electrode was used to immobilize α-fetoprotein antibody (anti-AFP) and to construct the immunosensor. Results demonstrated that the peak currents of [Ru(NH3)6](3+) decreased due to the interaction between antibody and antigen on the modified electrode. Thus, a label-free immunosensor for the detection of AFP was realized by monitoring the peak current change of [Ru(NH3)6](3+). The factors influencing the performance of the immunosensor were investigated in details. Under optimal conditions, the peak currents obtained by DPV decreased linearly with the increasing AFP concentrations in the range from 0.02 to 50 ng mL(-1) with a linear coefficient of 0.9959. This electrochemical immunoassay has a low detection limit of 0.01 ng mL(-1) (S/N=3) and was successfully applied to the determination of AFP in serum samples.

The fabrication of photosensitive self-assembly Au nanoparticles embedded in silica nanofibers by electrospinning

In this study, we demonstrated a simple, efficient, and low-cost method to fabricate large-area self-assembly Au nanoparticles (AuNPs) encapsulated within silica nanofibers (Au/SiO(2)). The method is based on electrospinning and thermal decomposition of hybrid nanofibers prepared from the solution of tetraethylorthosilicate (TEOS), polyvinylpyrrolidone (PVP) and AuNPs. This study employed the electrospinning technique for the first time as a successful method for preparing a self-organized AuNP peapod chain in a silica nanofiber matrix, under mild conditions. It has the advantage of easily controlling the diameters of the silica nanofibers as well as the concentration of the AuNPs in the spinning solution. The Au/SiO(2) hybrid nanofibers fabricated by this method exhibited an obvious photoelectric response under the illumination wavelength around the Au/SiO(2) nanofibers surface plasmon resonance (SPR) absorption band, whereas no photoelectric response was observed for the pure silica fibers. The excellent characteristics of photoelectric response suggest that the electrospinning technique has a great potential for large-scale fabrication of functional nanofiber devices. The ability of coupling light responses into the nanosystems dependent on metallic nanoparticle SPR opens up new prospects for the construction of nanoscale waveguiding devices, sensors and optoelectronics.

AgCl and Ag/AgCl hollow spheres based on self-assemblies of a multi-amine head surfactant

A simple method for fabricating Ag/AgCl hollow spheres was developed by using a multi-amine head surfactant C18N3 as a soft template. After adding AgNO(3) to micelles of C18N3 dispersed in HCl solution, Ag/AgCl hollow spheres were formed with diameters ranging from 100 nm to 1200 nm which were a function of aging time. The mechanical strength of the formed spheres was found to be very good, probably due to the uniquely structured C18N3 surfactant as well as the reinforcement effect of Ag/AgCl on the NH(2) terminal groups. The active species on the surfaces of hollow spheres, Ag(+) and Cl(-), remained almost unchanged when exposed to natural daylight for more than 1 year, showing a very good stability against light and environmental reduction. However, the obtained Ag+ species on the surface could be transformed into Ag(0) quickly with high yield (ca. 90%) under UV light irradiation. The transfer process was studied by EDX spectra at different irradiation times. Thus the Ag/AgCl hollow spheres may serve as useful precursors for many other noble metallic hollow spheres because Ag could be replaced by other noble metals such as Au and Pt with the aid of the galvanic replacement reaction.

Formation of polydiacetylene–NH2–gold hollow spheres and their ability in DNA immobilization

A simple and effective means for fabricating gold hollow spheres with controllable gold particle size is presented, where polydiacetylene vesicles terminated with??NH2 were synthesized and used as templates for the fast combination of gold nanoparticles. The combination process of gold to the hollow ball and the subsequent particle reductive growth have been investigated using a quartz crystal microbalance, and the morphology and stability of these hollow spheres are characterized using transmission electron microscopy and ultraviolet?visible spectroscopy. This shows that different sizes of gold particles and a variety of coverage of gold nanoparticles on??NH2-terminated spheres could be easily controlled. The as-prepared gold hollow ball has an excellent ability against mechanical disturbance and the nanogolds on it have very high stability against aggregation and ageing. The immobilization effect of a single-strand DNA probe shows that gold nanoparticles on the surface of this kind of sphere have a great advantage over their counterparts on a planar substrate surface.

Copper hydroxide nano and microcrystal: facile synthesis, shape evolution and their catalytic properties.

In this paper, the morphology of copper hydroxide nano/microcrystals is finely controlled by adjusting the concentration of surfactant and NH(4)Cl as well as the reaction temperature, to provide plates, belts, wires, rods and urchin-like spheres, among others. A tree-type multiple head surfactant, bis (amidoethyl-carbamoylethyl) octadecylamine (C18N3), was used to prepare the copper hydroxide nano/microcrystals and it acted as a face-selective additive in the reaction system. The morphology of the Cu(OH)(2) microcrystals could be transformed from elliptical plates into truncated square plates as the NH(4)Cl concentration was increased. The results showed that the Cu(OH)(2) crystals were better than the amorphous type of Cu(OH)(2) in catalyzing the oxidation of resorcinol with H(2)O(2). Additionally, an investigation of the formation process of the nano/microcrystals was performed, which we believe is valuable for a precise understanding of the formation and fabrication of other metal hydroxides and metal oxides.

Facile preparation of gold nanocages and hollow gold nanospheres via solvent thermal treatment and their surface plasmon resonance and photothermal properties

Although template etching method is one of the most common ways of preparation of hollow gold nanostructures, this approach still requires further improvements to avoid the collapse of gold shells after the cores were removed. In this work, an improved template etching method, with which hollow gold nanostructure is fabricated by etching Polystyrene (PS) cores from PS@Au core-shell nanospheres with solvent thermal treatment in N,N-Dimethylformamide (DMF), is demonstrated. When PS cores were removed by a thermal treatment process, gold nanoshells reconstruct and the collapse of the nanoshells is avoided. Gold nanocages and hollow gold nanospheres are easily obtained from the various structures of PS@Au core-shell nanospheres. These hollow nanostructures represent special near infrared (NIR) optical property and photothermal property. Compared with hollow gold nanospheres, the gold nanocages show higher temperature increase at the same particle concentration.

New Dendritic Polydiacetylene Sensor with Good Reversible Thermochromic Ability in Aqueous Solution and Solid Film

Thermal responsive polydiacetylene derived from PAMAM dendrimer (PDA-G0) was synthesized. Unlike the ethylenediamine substituted PDA (PDA-NH2) solution, the prepared PDA-G0 vesicle solution showed reversible thermochromism property when temperature varied from 20 to 90 °C, which is due to the formation of an internal hydrogen bond in amide groups. Furthermore, PDA-G0/PMMA film with excellent stability was obtained by a mixed-drying method, which could be stored for a long time without denaturation. After polymerization by UV irradiation, it displayed much better reversible thermochromic ability and the responded temperature range became wider, from 20 to 110 °C.

Shape Homogenization and Long-Range Arrangement of Gold Nanorods Using a pH-Responsive Multiamine Surfactant

A relatively new and efficient method is reported here for the purification and arrangement of high-aspect-ratio gold nanorods (AuNRs) using a multiamine surfactant, bis[[(amidoethyl)carbamoyl]ethyl]octadecylamine (C18N3), which strongly adsorbs to the surface of AuNRs. The adsorbed layers of the multiamine surfactant on AuNRs exhibit the ability to deaggregate gold nanoparticles at low pH in an aqueous medium and to promote their aggregation at high pH. Through regulation of the pH of the dispersion medium, a well-ordered arrangement of 99% monodisperse AuNRs was obtained, having dimensions of approximately 18 nm diameter and 353 nm length and an area of several dozens of square micrometers, which is much larger than what has been reported in the literature. A very strong optical absorption in the near-infrared region of as-prepared AuNRs was shown. This strategy of using pH-responsive multiamine surfactant to mediate both the homogenization in shape and the arrangement of nanoparticles provides a new methodology for the formation of nanoparticle assemblies.