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Atomic force microscopy is an emerging tool for investigating the biomolecular aspects of cellular interactions; however, cell and tissue analyses must frequently be performed in aqueous environment, over rough surfaces, and on complex adhesive samples that complicate the imaging process and readily facilitate the blunting or fouling of the AFM probe. In addition, the shape and surface chemistry of the probe determine the quality and types of data that can be acquired from biological materials, with certain information becoming available only within a specific range of tip lengths or diameters, or through the assistance of specific chemical or biological functionalization procedures. Consequently, a broad range of probe modification techniques has been developed to extend the capabilities and overcome the limitations of biological AFM measurements, including the fabrication of AFM tips with specialized morphologies, surface coating with biologically affine molecules, and the attachment of proteins, nucleic acids and cells to AFM probes. In this review, we underline the importance of probe choice and modification for the AFM analysis of biomaterials, discuss the recent literature on the use of non-standard AFM tips in life sciences research, and consider the future utility of tip functionalization methods for the investigation of fundamental cell and tissue interactions.

The present review details the methods used for the measurement of cells and their exudates using atomic force microscopy (AFM) and outlines the general conclusions drawn by the mechanical characterization of biological materials through this method. AFM is a material characterization technique that can be operated in liquid conditions, allowing its use for the investigation of the mechanical properties of biological materials in their native environments. AFM has been used for the mechanical investigation of proteins, nucleic acids, biofilms, secretions, membrane bilayers, tissues and bacterial or eukaryotic cells; however, comparison between studies is difficult due to variances between tip sizes and morphologies, sample fixation and immobilization strategies, conditions of measurement and the mechanical parameters used for the quantification of biomaterial response. Although standard protocols for the AFM investigation of biological materials are limited and minor differences in measurement conditions may create large discrepancies, the method is nonetheless highly effective for comparatively evaluating the mechanical integrity of biomaterials and can be used for the real-time acquisition of elasticity data following the introduction of a chemical or mechanical stimulus. While it is currently of limited diagnostic value, the technique is also useful for basic research in cancer biology and the characterization of disease progression and wound healing processes.

We report the preparation of silver-coated magnetic polymethacrylate core–shell nanoparticles for use in surface-enhanced Raman scattering based drug detection. Monodisperse porous poly (mono-2-(methacryloyloxy)ethyl succinate-co-glycerol dimethacrylate), poly (MMES-co-GDMA) microbeads of ca. 5 μm diameter were first synthesized through a multistage microsuspension polymerization technique to serve as a carboxyl-bearing core region. Microspheres were subsequently magnetized by the co-precipitation of ferric ions, aminated through the surface hydroxyl groups and decorated with Au nanoparticles via electrostatic attraction. An Ag shell was then formed on top of the Au layer through a seed-mediated growth process, resulting in micron-sized monodisperse microbeads that exhibit Raman enhancement effects due to the roughness of the Ag surface layer. The core–shell microspheres were used as a new substrate for the detection of amoxicillin at trace concentrations up to 10−8 M by SERS. The proposed SERS platform can be evaluated as a useful tool for the follow-up amoxicillin pollution and low-level detection of amoxicillin in aqueous media.

Plasmon resonances are widely used in biomolecular sensing and continue to be an active research field due to the rich variety of surface and measurement configurations, some of which exhibit down to single molecule level sensitivity. The resonance wavelength shift of the plasmonic structure upon binding of molecules, strongly depends, among other parameters, on how well the field of the resonant mode is confined to the binding site. Here it is shown that, by using properly designed metal-insulator-metal type resonators, improved wavelength response can be achieved with localized surface plasmon resonators (LSPRs) compared to that of the commonly used Kretschmann geometry. Using computational tools we investigate theoretically the refractive index response of several LSPR structures to a 2 nm thin film of binding molecules. LSPR resonators are shown to feature improved sensitivity over conventional Kretschmann geometry in the wavelength interrogation scheme for such a thin film. Moreover, some of the LSPR modes are quasi-omnidirectional and such angular independence (up to 30 angle of incidence) allows higher numerical apertures to be used in colorimetric imaging. Results highlight the potential of LSPRs for biomolecular sensing with high sensitivity and high spatial resolution. (C) 2013 Elsevier B.V. All rights reserved.

Mechanical properties of differentiating stem cells on peptide nanofibers Here we investigate changes in Young's moduli of mesenchymal stem cells while they are differentiating to osteogenic lineage on bioactive peptide nanofiber. We measured the elasticity of cells on hydrogels made of peptide amphiphiles that can be used to manipulate the cells through bioactive peptide sequences. Peptide nanofibers can mimic the extracellular matrix both in physical shape and biochemical activity. In this study, the peptide nanofibers presented osteoinductive Glu-Glu-Glu (EEE) sequence and Lys-Lys-Lys (KKK) sequence. Cells were analyzed on peptide-coated glass coverslips at days 1, 3, 5, 7, 14, 21 and 28 of osteogenic differentiation by measuring 50 μm x 50 μm and 16 x 16 points and lines force maps on cells. 5.2 μm diameter gold colloidal microsphere probes were used for AFM measurements and the force maps were converted to Young's modulus maps by applying JKR model. Peptide nanofibers provide a three-dimensional environment to cells and reduce the stiff glass substrate effect on Young's moduli value. Osteogenic differentiation of stem cells cultured in normal growth medium and in osteogenic growth medium was also compared. Differentiation of mesenchymal stem cells to osteoblasts was detected by analyzing mechanical properties during osteogenic differentiation.

N-doped TiO2 nanoparticles were prepared by using 1° and 2° alkyl and alcohol amines [n-propylamine (nPRYL), ethanolamine (ETOH), propanolamine (PROH), diethylamine (DETYL), dipropylamine (DPRYL), diethanolamine (DETOH), and ammonium hydroxide (NH4OH)] as nitrogen sources through microwave and hydrothermal growth (HT) methods. Characterization of the nanoparticles was done by X-ray diffraction, scanning electron microscopy, ultraviolet–visible absorption spectra, X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy and BET analysis techniques. Nitrogen species in TiO2 lattice were interstitial impurities. Nitrogen content of the particles depended on the preparation conditions and structural differences of nitrogen sources. Photocatalytic degradation of methylene blue was carried out under Xenon lamp irradiation. N-doped TiO2 nanoparticles exhibited higher photocatalytic activity, compared to undoped ones. Acidity differences of amine sources and irradiation differences of synthetic conditions had an effect on photocatalytic activity. Although N doping into TiO2 lattice was the least effective in the particle prepared by the use of nPRYL as the amine source and HT as the synthetic condition, its photocatalytic activity was slightly better compared to others.

Symposium on Germanium-Based Semiconductors from Materials to Devices held at the 2006 EMRS Spring Meeting -- MAY 29-JUN 02, 2006 -- Nice, FRANCE WOS: 000243574100080 Formation of Ge nanocrystals in SiNx matrices has been studied using plasma enhanced chemical vapor deposition in both as deposited samples as well as in post-vacuum annealed samples. Low temperature and short duration anneals in vacuum resulted in Ge nanocrystals whereas prolonged anneals at higher temperatures resulted in Ge nanocrystals accompanied with SiGe formation at the SiNx/Si interface. Raman Scattering Spectroscopy was extensively used to track the formation of various phonon modes during the diffusion of Ge through SiNx and into the Si substrate. (C) 2006 Published by Elsevier Ltd. European Mat Res Soc