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The throughput of spontaneous Raman spectroscopy for cell identification applications is limited to the range of one cell per second because of the relatively low sensitivity. Surface-enhanced Raman scattering (SERS) is a widespread way to amplify the intensity of Raman signals by several orders of magnitude and, consequently, to improve the sensitivity and throughput. SERS protocols using immuno-functionalized nanoparticles turned out to be challenging for cell identification because they require complex preparation procedures. Here, a new SERS strategy is presented for cell classification using non-functionalized silver nanoparticles and potassium chloride to induce aggregation. To demonstrate the principle, cell lysates were prepared by ultrasonication that disrupts the cell membrane and enables interaction of released cellular biomolecules to nanoparticles. This approach was applied to distinguish four cell lines – Capan-1, HepG2, Sk-Hep1 and MCF-7 – using SERS at 785 nm excitation. Six independent batches were prepared per cell line to check the reproducibility. Principal component analysis was applied for data reduction and assessment of spectral variations that were assigned to proteins, nucleotides and carbohydrates. Four principal components were selected as input for classification models based on support vector machines. Leave-three-batches-out cross validation recognized four cell lines with sensitivities, specificities and accuracies above 96%. We conclude that this reproducible and specific SERS approach offers prospects for cell identification using easily preparable silver nanoparticles.

Since ancient times, noble gold has continuously contributed to several aspects of life from medicine to electronics. It perpetually reveals its new features. We report the finding of a unique form of gold, reticular nanostructured gold (RNG), as an aqueous black colloid, for which we present a one-step synthesis. The reticules consist of gold crystals that interconnect to form compact strands. RNG exhibits high conductivity and low reflection, and these features, coupled with the high specific surface area of the material, could prove valuable for applications in electronics and catalysis. Due to high absorption throughout the visible and infrared domain, RNG has the potential to be applied in the construction of sensitive solar cells or as a substrate for Raman spectroscopy.

We report the assembly and structural characterization of a Y-shaped DNA template incorporating a central biotin moiety. We also report that this template may be used to assemble nanoscale architectures, which demonstrate the potential of this and related approaches to the fabrication of next-generation electronic devices. Of particular significance is the finding that it is possible to selectively metallize the above DNA template to obtain a three-electrode configuration. Also of particular significance is the finding that a biotin modified nanoparticle will recognize and bind selectively the central biotin moiety of the same template, once functionalized by the protein streptavidin.

The assembly and detailed structural characterization of a Y-shaped DNA template incorporating a central biotin moiety is reported. Also reported is the use of this template to assemble a model protein-functionalized three-electrode architecture. Of particular significance is the finding that a biotin-modified nanoparticle will recognize and selectively bind the central biotin moiety, once functionalized by the protein streptavidin. Potential applications of the above and related DNA templates in the emerging field of nanoelectronics are considered.

Fluorescent ion indicators are widely used to measure ion concentrations in living cells. However, despite considerable efforts in synthesizing new compounds, no ratiometric sodium indicator is available that can be excited at visible wavelengths. Ratiometric indicators have an advantage in that measured fluorescence intensities can be corrected for fluctuations of the indicator concentration and the illumination intensity, which is not possible when non-ratiometric indicators are used. One way to circumvent this problem is to measure fluorescence lifetimes, which are independent of these factors. Another way to overcome the disadvantages of a non-ratiometric indicator dye is to embed it, together with a reference dye, into nanoparticles. By relating the indicator fluorescence to the fluorescence of the reference dye, inhomogeneities in the nanosensor concentration or the illumination intensity can be cancelled out reliably. In this study we compare the benefits and drawbacks of these approaches. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Several linear and branched DNA structures from 80-200 nm with a biotine molecule in the middle have been prepared. These structures have been decorated by addition of positively charged gold nanoparticles carrying 4-(dimethylamino)pyridine ligands. Streptavidin binds to the central biotine molecule introducing a 20 nm gap in the structure in which a biotinylated nanoparticle can be introduced. The simplest structure (80 nm, linear) is formed by 4 oligonucleotides. By changing some of these components changes on length, shape, and recognition system easily can be introduced., Project financed by E.E.C.C., IST-1999-11974, BIOAND and STRP 014006 Nano3D and Spanish Ministry of Education BFU2005-23719-E, NAN2004-09415-C05-03 and BFU2004-02048.

The iron oxide-hydroxyapatite (FeOxHA) nanoparticles reported here differ from those reported before by their advantage of homogeneity and simple preparation; moreover, the presence of carboxymethyldextran (CMD), together with hydroxyapatite (HA), allows access to the cellular membrane, which makes our magnetic apatite unique. These nanoparticles combine magnetic behavior, Raman label ability and the property of interaction with the cellular membrane; they therefore represent an interesting material for structural differentiation of the cell membrane. It was observed by Raman spectroscopy, scanning electron microscopy (SEM) and fluorescence microscopy that FeOxHA adheres to the plasma membrane and does not penetrate the membrane. These insights make the nanoparticles a promising material for magnetic cell sorting, e.g. in microfluidic device applications.

Reported is the use of DNA to template the assembly of nanowires and protein-functionalized nanogap electrodes. Specifically, the use of DNA to template the assembly of gold nanowires between conventionally patterned gold contacts on a silicon wafer substrate. Also the use of DNA to template the assembly of protein-functionalized gold nanogap electrodes on a silicon wafer substrate. Of particular significance is the finding that suitably modified gold nanoparticles recognize and bind selectively the protein-functionalized nanogap between the above electrodes and are localized there. This and related work forms part of a broader effort directed toward the development of the alternative bottom-up fabrication technologies that will be needed to extend Moore's Law beyond 2012.

In this study, we describe the design of new ratiometric fluorescent nanosensors, whose architecture is based on a gold core surrounded by a poly(vinylalcohol)-polyacetal shell. To the gold core, indicator dyes and reference dyes are attached via a cysteine linker. This nanosensor architecture is flexible with regards to the number and types of fluorophore linkages possible. The robust poly(vinylalcohol)-polyacetal shell protects the fluorophores linked to the core from non-specific interactions with intracellular proteins. The nanosensors developed in this way are biocompatible and can be easily incorporated into mammalian cells without the use of transfection agents. Here, we show the application of these nanosensors for intracellular pH and sodium ion measurements. © 2010 IOP Publishing Ltd.