Gadolinium chelate coated gold nanoparticles as contrast agents for both X-ray computed tomography and magnetic resonance imaging

Functionalized gold nanoparticles were applied as contrast agents for both in vivo X-ray and magnetic resonance imaging. These particles were obtained by encapsulating gold cores within a multilayered organic shell which is composed of gadolinium chelates bound to each other through disulfide bonds. The contrast enhancement in MRI stems from the presence of gadolinium ions which are entrapped in the organic shell, whereas the gold core provides a strong X-ray absorption. This study revealed that these particles suited for dual modality imaging freely circulate in the blood vessels without undesirable accumulation in the lungs, spleen, and liver.     

'On-the-fly' hydrogen/deuterium exchange liquid chromatography/mass spectrometry using a dual-sprayer atmospheric pressure ionisation source

In-source 'on-the-fly' hydrogen/deuterium (H/D) exchange liquid chromatography mass spectrometry (LC/MS) has been investigated. The work was performed using a dual-sprayer source. The analyte was introduced through an electrospray ionisation sprayer and D2O was introduced through an atmospheric pressure chemical ionisation sprayer. To achieve H/D exchange sufficient to determine the number of exchangeable H atoms of a compound, a saturated 'steady-state' D2O atmosphere had to be created in the ion source by having a 2:1 or higher D2O-to-analyte flow rate ratio. Under these conditions H/D exchange levels of 32-90% were achieved. In most cases the H/D exchange was sufficient to measure the number of exchangeable H atoms in some antiulcerative and anthelmintic pharmaceuticals. The concept of in-source 'on-the-fly' H/D exchange by introducing the deuterating agent via a second sprayer has been shown. It allows the integrity of the chromatographic separation to be kept, since the H/D exchange takes place post-separation.     

Preparations and spectroscopic studies of organotin complexes of diclofenac

The reactions of the potent and widely used anti-inflammatory drug diclofenac, HL, with diorganotin(IV) oxides were studied. The dimeric tetraorganodistannoxane complexes [Me(2)LSnOSnLMe(2)](2), [Bu(2)LSnOSnLBu(2)](2), [Ph(2)LSnOSnLPh(2)](2) and the dibutyltin complex [Bu(2)SnL(2)], have been prepared and structurally characterized in the solid state by means of vibrational and 119Sn M?ssbauer spectroscopy. Determination of lattice dynamics by temperature-dependent 119Sn M?ssbauer spectroscopy. From the variable-temperature M?ssbauer effect, the Debye temperature was determined. The complexes have been characterized in solution by NMR (1H and 13C) spectroscopy. Vibrational, M?ssbauer, and NMR data are discussed in terms of the proposed structures.     

Mimicking biological cation-transport based on sphere-surface supramolecular chemistry: simultaneous interaction of porous capsules with molecular plugs and passing cations

Spherical capsules of the type [{(Mo)Mo(5)}(12){Mo(2)(ligand)}(30)](n-) exhibiting 20 {Mo(9)O(9)} pores with crown ether functions allowed us to perform a sophisticated study of the title phenomenon based on synthetic work as well as NMR spectroscopy. The pores of the host system interact in solution specifically with guests that can be noncovalently bonded, such as formamidinium and acetamidinium cations, while having different affinities to the pores. The exchange between the guest species present in solution and in the pores was investigated, including, besides the extreme scenarios of complete pore closing and complete opening, that of stepwise pore plugging. Because of this option it was possible to model for the first time passive transmembrane cation transport based on gated pores/channels. These have the appropriate dimensions and can even adopt different structure flexibilities in response to different cations. The present investigation is based on related syntheses as well as on numerous detailed (7)Li NMR studies of Li(+) transport/exchange equilibria in dependence of the pore environment/guest situations. One compound containing capsules with sulfate ligands (2) could be obtained in which all the pores are plugged with formamidinium cations and another corresponding one was obtained with additionally encapsulated Ca(2+) ions (3); these were taken up after temporary release of some of the formamidinium plugs/guests upon short heating of the related solution.     

Reversible activation of diblock copolymer monolayers at the interface by pH modulation, 2: Membrane interactions at the solid/liquid interface

A monolayer of the pH-responsive poly[2-(dimethylamino)ethyl methacrylate-block-methyl methacrylate] diblock copolymer [PDMAEMA-PMMA] was transferred from the air/water interface to a silicon substrate for evaluation as a tunable interlayer between biological material and solid substrates. Specular neutron reflectivity experiments revealed that the weak polyelectrolyte PDMAEMA chains at the solid/liquid interface can be reversibly activated by pH modulation. The thickness, scattering length density, and surface roughness of the polymer film can be systematically controlled by pH titration. As a simple model of plasma membranes, a lipid bilayer was deposited onto the polymer film. The membrane-substrate interaction was characterized by neutron reflectivity experiments, demonstrating that the membrane-substrate distance could be reversibly regulated by pH titration. These results confirm the potential of stimuli-responsive polymers for precise control of cell-surface interactions.