Magnetic nanobeads as potential contrast agents for magnetic resonance imaging.

Metal-oxo clusters have been used as building blocks to form hybrid nanomaterials and evaluated as potential MRI contrast agents. We have synthesized a biocompatible copolymer based on a water stable, nontoxic, mixed-metal-oxo cluster, Mn8Fe4O12(L)16(H2O)4, where L is acetate or vinyl benzoic acid, and styrene. The cluster alone was screened by NMR for relaxivity and was found to be a promising T2 contrast agent, with r1 = 2.3 mM(-1) s(-1) and r2 = 29.5 mM(-1) s(-1). Initial cell studies on two human prostate cancer cell lines, DU-145 and LNCap, reveal that the cluster has low cytotoxicity and may be potentially used in vivo. The metal-oxo cluster Mn8Fe4(VBA)16 (VBA = vinyl benzoic acid) can be copolymerized with styrene under miniemulsion conditions. Miniemulsion allows for the formation of nanometer-sized paramagnetic beads (~80 nm diameter), which were also evaluated as a contrast agent for MRI. These highly monodispersed, hybrid nanoparticles have enhanced properties, with the option for surface functionalization, making them a promising tool for biomedicine. Interestingly, both relaxivity measurements and MRI studies show that embedding the Mn8Fe4 core within a polymer matrix decreases r2 effects with little effect on r1, resulting in a positive T1 contrast enhancement.

Comparative study of the pheromone-manufacturing femoral glands in two sympatric species of lacertid lizards (Acanthodactylus).

Femoral glands are holocrine structures that produce compounds used by lizards as pheromones. Few studies have investigated the morphology and ultrastructure of these glands. We chose a closely related species pair from a lizard family having femoral glands in male and female of both species to illustrate comparative morphology and ultrastructure and their implications for the mechanism of secretion dispersal to the environment. We also aimed to test whether the structure and mechanism of secretion production differ between related species. In addition, we sought to gain a better understanding of the holocrine mechanism of secretion. Femoral glands of selected sympatric lacertid species, Acanthodactylus boskianus and A. scutellatus were studied comparatively using light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). SEM revealed both interspecific and sexual variation in the morphology of the glandular pores. The external morphology suggests the mechanism of the secretion deposition where the convex part of pore-carrying scale is probably used to partition the secretory plug. Histology shows the epithelial cells of the gland duct as an extension of the epidermis with its covering keratin. The glandular acini are composed of germinal and secretory cells. The latter undergo four different stages of differentiation, from the beginning of the formation of secretory granules, through the accumulation of these granules, disintegration and formation of the secretory plug, which protrudes externally. The study considers the sequence of holocrine secretion development, and explains in part how such secretions are deposited on the substrate. Sexual differences at the external morphology level were more evident than interspecific differences.

Characterization of Salmonella type III secretion hyper-activity which results in biofilm-like cell aggregation.

We have previously reported the cloning of the Salmonella enterica serovar Typhimurium SPI-1 secretion system and the use of this clone to functionally complement a ΔSPI-1 strain for type III secretion activity. In the current study, we discovered that S. Typhimurium cultures containing cloned SPI-1 display an adherent biofilm and cell clumps in the media. This phenotype was associated with hyper-expression of SPI-1 type III secretion functions. The biofilm and cell clumps were associated with copious amounts of secreted SPI-1 protein substrates SipA, SipB, SipC, SopB, SopE, and SptP. We used a C-terminally FLAG-tagged SipA protein to further demonstrate SPI-1 substrate association with the cell aggregates using fluorescence microscopy and immunogold electron microscopy. Different S. Typhimurium backgrounds and both flagellated and nonflagellated strains displayed the biofilm phenotype. Mutations in genes essential for known bacterial biofilm pathways (bcsA, csgBA, bapA) did not affect the biofilms formed here indicating that this phenomenon is independent of established biofilm mechanisms. The SPI-1-mediated biofilm was able to massively recruit heterologous non-biofilm forming bacteria into the adherent cell community. The results indicate a bacterial aggregation phenotype mediated by elevated SPI-1 type III secretion activity with applications for engineered biofilm formation, protein purification strategies, and antigen display.

Miniemulsion synthesis of metal-oxo cluster containing copolymer nanobeads.

Hybrid nanobeads containing either a manganese-oxo or manganese-iron-oxo cluster have been prepared via the miniemulsion polymerization technique. Two new ligand substituted oxo clusters, Mn(12)O(12)(VBA)(16)(H(2)O)(4) and Mn(8)Fe(4)O(12)(VBA)(16)(H(2)O)(4) (where VBA = 4-vinylbenzoate), have been prepared and characterized. Polymerization of the functionalized metal-oxo clusters with styrene under miniemulsion conditions produced monodispersed polymer nanoparticles as small as ~60 nm in diameter. The metal-oxo polymer nanobeads were fully characterized in terms of synthetic parameters, composition, structure, and magnetic properties.

TiO(2)/LiCl-based nanostructured thin film for humidity sensor applications.

A simple and straightforward method of depositing nanostructured thin films, based on LiCl-doped TiO(2), on glass and LiNbO(3) sensor substrates is demonstrated. A spin-coating technique is employed to transfer a polymer-assisted precursor solution onto substrate surfaces, followed by annealing at 520°C to remove organic components and drive nanostructure formation. The sensor material obtained consists of coin-shaped nanoparticles several hundred nanometers in diameter and less than 50 nm thick. The average thickness of the film was estimated by atomic force microscopy (AFM) to be 140 nm. Humidity sensing properties of the nanostructured material and sensor response times were studied using conductometric and surface acoustic wave (SAW) sensor techniques, revealing reversible signals with good reproducibility and fast response times of about 0.75 s. The applicability of this nanostructured film for construction of rapid humidity sensors was demonstrated. Compared with known complex and expensive methods of synthesizing sophisticated nanostructures for sensor applications, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), this work presents a relatively simple and inexpensive technique to produce SAW humidity sensor devices with competitive performance characteristics.

Gadolinium doped europium sulfide.

We have prepared gadolinium doped europium sulfides, Eu(1-x)Gd(x)S for a doping range of 0 ≤ x ≤ 0.1 by thermal decomposition of the precursors Eu(S(2)CNEt(2))(3)Phen/Gd(S(2)CNEt(2))(3)Phen with respective ratios. Electron doping provides indirect evidence for the magnetic coupling through carrier electrons in magnetic semiconductors. Based on the magnetic properties, we determined that the paramagnetic Curie temperature, Θp, varies with doping level, in a similar way to Eu(1-x)Gd(x)O exhibiting a significant increase at low doping levels. All materials have been characterized by X-ray powder diffraction, magnetic measurements, ICP-MS, and TEM.

A novel approach to examining compositional heterogeneity of detergent-resistant lipid rafts.

Lipid rafts play an important role in cell signalling, cell adhesion and other cellular functions. Compositional heterogeneity of lipid rafts provides one mechanism of how lipid rafts provide the spatial and temporal regulation of cell signalling and cell adhesion. The constitutive presence of some signalling receptors/molecules and accumulation of others in the lipid raft allows them to interact with each other and thereby facilitate relay of signals from the plasma membrane to the cell interior. Devising a method that can analyze these lipid microdomains for the presence of signalling receptors/molecules on an individual raft basis is required to address the issue of lipid raft heterogeneity. SDS-PAGE analysis, currently used for analyses of detergent-resistant lipid rafts, does not address this question. We have designed a cell-free assay that captures detergent-resistant lipid rafts with an antibody against a raft-resident molecule and detects the presence of another lipid raft molecule. Our results suggest that detergent-resistant lipid rafts, also known as detergent-resistant membranes, are heterogeneous populations on an immortalized mouse T-cell plasma membrane with respect to antigen receptor/signalling complex and other signalling/adhesion proteins. This cell-free assay provides a simple and quick way to examine the simultaneous presence of two proteins in the lipid rafts and has the potential to estimate trafficking of molecules in and out of the lipid microdomains during cell signalling on a single detergent-resistant lipid raft basis.