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A facile one-step Cu(i)-catalyzed "click" reaction, between a dansyl-azide and a propargyl-substituted rhodamine B hydrazide, is employed to fabricate a novel FRET ratiometric "off-on" fluorescent probe. The sensitive emission of the donor, a dansyl group, overlaps perfectly with the absorption of the acceptor, xanthene in the open-ring rhodamine. The proposed probe shows high selectivity towards Cu 2+ . The ratio of emission intensities at 568 and 540 nm (I 568 /I 540 ) exhibits a drastic 28-fold enhancement upon addition of Cu 2+ . The probe shows an excellent linear relationship between emission ratios and the concentrations of Cu 2+ from 10 to 50 μM, with a detection limit (S/N = 3) of 0.12 μM. The preliminary cellular studies demonstrated that the probe is cell membrane permeable and could be applied for ratiometric fluorescence imaging of intracellular Cu 2+ with almost no cytotoxicity. The ingenuity of the probe design is to construct a FRET donor-acceptor interconnector and a selective receptor simultaneously by "click" reaction. The strategy was verified to have great potential for developing novel FRET probes for Cu 2+ .

Water-dispersible and luminescent gadolinium oxide (GO) nanoparticles (NPs) were designed and synthesized for potential dual-modal biological imaging. They were obtained by capping gadolinium oxide nanoparticles with a fluorescent glycol-based conjugated carboxylate (HL). The obtained nanoparticles (GO-L) show long-term colloidal stability and intense blue fluorescence. In addition, L can sensitize the luminescence of europium(III) through the so-called antenna effect. Thus, to extend the spectral ranges of emission, europium was introduced into L-modified gadolinium oxide nanoparticles. The obtained EuIII-doped particles (Eu:GO-L) can provide visible red emission, which is more intensive than that without L capping. The average diameter of the monodisperse modified oxide cores is about 4 nm. The average hydrodynamic diameter of the L-modified nanoparticles was estimated to be about 13 nm. The nanoparticles show effective longitudinal water proton relaxivity. The relaxivity values obtained for GO-L and Eu:GO-L were r1=6.4 and 6.3 s−1 mM−1 with r2/r1 ratios close to unity at 1.4 T. Longitudinal proton relaxivities of these nanoparticles are higher than those of positive contrast agents based on gadolinium complexes such as Gd-DOTA, which are commonly used for clinical magnetic resonance imaging. Moreover, these particles are suitable for cellular imaging and show good biocompatibility.

A method to prepare amyloid-like fibrils functionalized with magnetic nanoparticles has been developed. The amyloid-like fibrils are prepared in a two step procedure, where insulin and magnetic nanoparticles are mixed simply by grinding in the solid state, resulting in a water soluble hybrid material. When the hybrid material is heated in aqueous acid, the insulin/nanoparticle hybrid material self assembles to form amyloid-like fibrils incorporating the magnetic nanoparticles. This results in magnetically labeled amyloid-like fibrils which has been characterized by Transmission Electron Microscopy (TEM) and electron tomography. The influence of the aggregation process on proton relaxivity is investigated. The prepared materials have potential uses in a range of bio-imaging applications., (Copyright © 2012 Elsevier Inc. All rights reserved.)

ZnO nanostructured materials, such as films and nanoparticles, could provide a suitable platform for development of high performance biosensors due to their unique fundamental material properties. This paper reviews different preparation techniques of ZnO nanocrystals and material issues like wettability, biocompatibility and toxicity, which have an important relevance to biosensor functionality. Efforts are made to summarize and analyze existing results regarding surface modification and molecular attachments for successful biofunctionalization and understanding of the mechanisms involved. A section is devoted to implementations of tailored surfaces in biosensors. We end with conclusions on the feasibility of using ZnO nanocrystals for biosensing.

As the utility of magnetic resonance imaging (MRI) broadens, the importance of having specific and efficient contrast agents increases and in recent time there has been a huge development in the fields of molecular imaging and intracellular markers. Previous studies have shown that gadolinium oxide (Gd(2)O(3)) nanoparticles generate higher relaxivity than currently available Gd chelates: In addition, the Gd(2)O(3) nanoparticles have promising properties for MRI cell tracking. The aim of the present work was to study cell labeling with Gd(2)O(3) nanoparticles in hematopoietic cells and to improve techniques for monitoring hematopoietic stem cell migration by MRI. Particle uptake was studied in two cell lines: the hematopoietic progenitor cell line Ba/F3 and the monocytic cell line THP-1. Cells were incubated with Gd(2)O(3) nanoparticles and it was investigated whether the transfection agent protamine sulfate increased the particle uptake. Treated cells were examined by electron microscopy and MRI, and analyzed for particle content by inductively coupled plasma sector field mass spectrometry. Results showed that particles were intracellular, however, sparsely in Ba/F3. The relaxation times were shortened with increasing particle concentration. Relaxivities, r(1) and r(2) at 1.5 T and 21°C, for Gd(2)O(3) nanoparticles in different cell samples were 3.6-5.3 s(-1) mM(-1) and 9.6-17.2 s(-1) mM(-1), respectively. Protamine sulfate treatment increased the uptake in both Ba/F3 cells and THP-1 cells. However, the increased uptake did not increase the relaxation rate for THP-1 as for Ba/F3, probably due to aggregation and/or saturation effects. Viability of treated cells was not significantly decreased and thus, it was concluded that the use of Gd(2)O(3) nanoparticles is suitable for this type of cell labeling by means of detecting and monitoring hematopoietic cells. In conclusion, Gd(2)O(3) nanoparticles are a promising material to achieve positive intracellular MRI contrast; however, further particle development needs to be performed.

Pure and mixed monolayers of a synthetic peptide, GPR-i3n, derived from the third intracellular loop of the alpha2 adrenergic receptor and a shorter inactive oligopeptide, N-formyl-(Gly)3-(Cys) (called 3GC), were prepared on gold surfaces. The mixing ratio of the GPR-i3n and 3GC was used to control G-protein binding capability. The GPR-i3n peptide is specially designed for bovine G-protein selectivity and has been proven to have high affinity to G-proteins [Vahlberg, C.; Petoral, R. M., Jr.; Lindell, C.; Broo, K.; Uvdal, K. Langmuir 2006, 22 (17), 7260-7264]. Pure 3GC monolayers show very low protein adsorption capability. In this study, 3GC is chosen as a coadsorbent, with the aim to induce molecular conformational changes during monolayer formation to enhance G-protein adsorption. A full characterization of the mixed monolayers was done. The monolayer thickness and the mass-related surface coverage for both GPR-i3n and 3GC were investigated using radio labeling. The GPR-i3n was labeled by 125I-targeting tyrosine, and the activity was measured by using radioimmunoassay (RIA). The formation and chemical composition of GPR-i3n and 3GC monolayers were investigated using X-ray photoelectron spectroscopy, and it is shown that both GPR-i3n and 3GC bind chemically to the gold surface. The interaction between the mixed monolayers and G-proteins was investigated by means of real-time surface plasmon resonance. There is a higher protein binding capacity to the monolayer when the GPR-i3n peptide is intermixed with the 3GC coadsorbent, despite the fact that the 3GC itself has a very low G-protein binding capability. This supports a molecular reorientation at the surface, while 3GC is intermixed with GPR-i3n.

The affinity of alpha(2A)-adrenergic receptor (alpha(2A)-AR) derived peptide adsorbates for the functional bovine brain G-protein is studied in the search for the minimum sequence recognition. Three short peptides (GPR-i2c, GPR-i3n, and GPR-i3c) are designed to mimic the second and third intracellular loops of the receptor. X-ray photoelectron spectroscopy is used to study the chemical composition of the peptides and the binding strength to the surfaces. Chemisorption of the peptides to the gold substrates is observed. Infrared spectroscopy is used to study the characteristic absorption bands of the peptides. The presence of peptides on the surfaces is verified by prominent amide I and amide II bands. The interaction between the peptides and the G-protein is studied with surface plasmon resonance. It is shown that GPR-i3n has the highest affinity for the G-protein. Equilibrium analysis of the binding shows that the G-protein keeps its native conformation when interacting with GPR-i3c, but during the interaction with GPR-i2c and GPR-i3n the conformation of G-protein is changed, leading to the formation of aggregates and/or multilayers.