Rhodamine-based chemosensor for Sn2+ detection and its application in nanofibrous film and bioimaging.

A simple rhodamine-based compound CK was designed and synthesized as a fluorescent chemosensor for Sn2+ based on Sn2+-mediated cyclization. The optical investigation indicated that the probe could quantitatively detect Sn2+ in a concentration range of 10-30 µM, with a detection limit of 118 nM. Moreover, probe CK, with low cytotoxicity, was successfully applied for imaging of Sn2+ in HeLa cells and mice, exhibiting excellent biocompatibility and cell membrane permeability. For on-site monitoring, CK-hybridized polymethyl methacrylate (PMMA) nanofibers were prepared by electrospinning and successfully employed for the visual detection of Sn2+ in actual samples. All the results demonstrated that the chemosensor could be a promising tool for the detection of Sn2+ in vitro and in vivo.

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

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.

Fabrication of color changeable polystyrene spheres decorated by gold nanoparticles and their label-free biosensing.

A novel and simple method for gold nanoshell synthesis with controllable core and shell sizes is reported here. A new 'tree-shape' surfactant bis(amidoethyl-carbamoylethyl) octadecylamine (C18N3) was synthesized and used as the glue for the fast combination of gold nanoparticles and the subsequent gold shell outside. The functionalized polystyrene (PS) cores were covered by a surfactant (PS@C18N3) bilayer. The presence of the surfactant double layer played the role of 'glue' in this method, so that upon controlling the amount of surfactant, it was possible to achieve: the manipulation of gold seed density on the PS@C18N3 spheres, the preparation of PS@Au hybrid structures, and a red-shift in the extinction absorption from 520 to 750 nm. Besides, the as-prepared PS@Au composites supported on a glass substrate exhibited excellent effectiveness in the molecular recognition of human-immunoglobulin G (h-IgG) and goat anti-human-immunoglobulin G (goat anti-h-IgG), showing a rapid response within 20 min with a low detection limit of 10 ng ml(-1). This demonstrates that PS@Au prepared and assembled using our method is potentially useful as a nanosensor platform for immunoassay.