Recently, much attention has been given to the development of biofunctionalized nanoparticles with magnetic properties for novel biomedical imaging. Guided, smart, targeting nanoparticulate magnetic resonance imaging (MRI) contrast agents inducing high MRI signal will be valuable tools for future tissue specific imaging and investigation of molecular and cellular events. In this study, we report a new design of functionalized ultrasmall rare earth based nanoparticles to be used as a positive contrast agent in MRI. The relaxivity is compared to commercially available Gd based chelates. The synthesis, PEGylation, and dialysis of small (3-5 nm) gadolinium oxide (DEG-Gd(2)O(3)) nanoparticles are presented. The chemical and physical properties of the nanomaterial were investigated with Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and dynamic light scattering. Neutrophil activation after exposure to this nanomaterial was studied by means of fluorescence microscopy. The proton relaxation times as a function of dialysis time and functionalization were measured at 1.5 T. A capping procedure introducing stabilizing properties was designed and verified, and the dialysis effects were evaluated. A higher proton relaxivity was obtained for as-synthesized diethylene glycol (DEG)-Gd(2)O(3) nanoparticles compared to commercial Gd-DTPA. A slight decrease of the relaxivity for as-synthesized DEG-Gd(2)O(3) nanoparticles as a function of dialysis time was observed. The results for functionalized nanoparticles showed a considerable relaxivity increase for particles dialyzed extensively with r(1) and r(2) values approximately 4 times the corresponding values for Gd-DTPA. The microscopy study showed that PEGylated nanoparticles do not activate neutrophils in contrast to uncapped Gd(2)O(3). Finally, the nanoparticles are equipped with Rhodamine to show that our PEGylated nanoparticles are available for further coupling chemistry, and thus prepared for targeting purposes. The long term goal is to design a powerful, directed contrast agent for MRI examinations with specific targeting possibilities and with properties inducing local contrast, that is, an extremely high MR signal at the cellular and molecular level.

There is a demand for more efficient and tissue-specific MRI contrast agents and recent developments involve the design of substances useful as molecular markers and magnetic tracers. In this study, nanoparticles of gadolinium oxide (Gd2O3) have been investigated for cell labeling and capacity to generate a positive contrast. THP-1, a monocytic cell line that is phagocytic, was used and results were compared with relaxivity of particles in cell culture medium (RPMI 1640). The results showed that Gd2O3-labeled cells have shorter T1 and T2 relaxation times compared with untreated cells. A prominent difference in signal intensity was observed, indicating that Gd2O3 nanoparticles can be used as a positive contrast agent for cell labeling. The r1 for cell samples was 4.1 and 3.6 s(-1) mm(-1) for cell culture medium. The r2 was 17.4 and 12.9 s(-1) mm(-1), respectively. For r1, there was no significant difference in relaxivity between particles in cells compared to particles in cell culture medium, (p(r1) = 0.36), but r2 was significantly different for the two different series (p(r2) = 0.02). Viability results indicate that THP-1 cells endure treatment with Gd2O3 nanoparticles for an extended period of time and it is therefore concluded that results in this study are based on viable cells.

In all kinds of gadolinium based contrast agents, the presence of free gadolinium ions have to be avoided due to the cytotoxicity. The conventional way of producing a gadolinium based contrast agent is to form a chelate, i.e. stabilizing the metal ion using a chelating agent (for example DTPA or DOTA) but recently nanoparticles is an initial step towards biocompatible and directed nanoparticles.The main focus is on a material that in the nearby future will be the core of an The experimental results are supported by theoretical modeling studies.Theoretical IR spectra of three different Gd acetate complexes are presented as well as calculated NEXAFS spectra of one of the Gd acetate complexes and an isolated acetate group. These calculations were performed to elucidate the molecular capping of the synthesized particles. 5 EXPERIMENTAL DETAILS ChemicalsAll chemicals were used as received. Gadolinium(III) acetate hydrate (SigmaAldrich, 99.9 %), tetramethylammonium hydroxide (Sigma-Aldrich, >97 % ), ethyl acetate (Fisher Scientific, 99.99 %), dimethyl sulfoxide (Merck, 99.9 %), ammonium acetate (Merck, >96%), ethanol (Kemetyl, 99.5 %). For preparation of water based solutions, Milli-Q water (ρ > 18.2 MΩ) was used. A commercial gadolinium oxide nanopowder (Aldrich, < 100 nm, 99.8 %) was used as a reference. Preparation of Gd 2 O 3 nanoparticlesThe preparation of Gd 2 O 3 nanoparticles was based on a method previously used for producing nanocrystalline ZnO (Schwartz et al. 2003). As Zn 2+ is divalent and Ethyl acetate was added and the mixture was centrifuge washed (3500 rpm) at least three times with ethyl acetate before it was diluted in deionized water. A total amount of 0.28 g ammonium acetate was added to one whole batch to increase the water solubility. Powder samples were air dried. The yield of the sample is dependent on the washing procedure. The gadolinium content after three times of centrifuge washing with ethyl acetate is roughly 60-65 % of the initial amount added in the synthesis.6 Instrumentation X-ray diffraction XRD measurements were carried out with a Philips XRD powder diffractometer using Cu Kα radiation (λ = 1.5418 Å, 40kV, 40 mA). The 2θ step-size was 0.025° and the time per step 4 s. Air dried powder samples were used in the preparation.High-resolution transmission electron microscopy TEM measurements were performed on a FEI Tecnai G 2 electron microscope operated at 200 kV. Sample preparation was done by letting 1-2 drops of Gd 2 O 3 in water dry on an amorphous carbon-covered copper grid.Dynamic light scattering DLS measurements were carried out on an ALV/DLS/SLS-5022F system from ALV-GmbH, Langen Germany, using a HeNe laser at 632.8 nm with 22 mW output power. Prior to the measurements, the samples were temperature stabilized in a thermostat bath at 22.1 °C for at least 10 minutes. The scattering angle was 90°. 15 Gd 2 O 3 samples dispersed in MilliQ water were studied in DLS, and the long term stability of the suspensions were studied by repeated measurements during a period of 6 weeks.ζ Pot...

We report the self-assembly of stable nanoscale coordination polymers (NCPs), which exhibit temperature-controlled guest encapsulation and release, as well as an efficient light-harvesting property. NCPs are obtained by coordination-directed organization of pi-conjugated dicarboxylate (L1) and lanthanide metal ions Gd(III), Eu(III), and Yb(III) in a DMF system. Guest molecules trans-4-styryl-1-methylpyridiniumiodide (D1) and methylene blue (D2) can be encapsulated into NCPs, and the loading amounts can be controlled by changing reaction temperatures. Small angle X-ray diffraction (SAXRD) results reveal that the self-assembled discus-like NCPs exhibit long-range ordered structures, which remain unchanged after guest encapsulations. Experimental results reveal that the negatively charged local environment around the metal connector is the driving force for the encapsulation of cationic guests. The D1 molecules encapsulated in NCPs at 140 degrees C can be released gradually at room temperature in DMF. Guest-loaded NCPs exhibit efficient light harvesting with energy transfer from the framework to the guest D1 molecule, which is studied by photoluminescence and fluorescence lifetime decays. This coordination-directed encapsulation approach is general and should be extended to the fabrication of a wide range of multifunctional nanomaterials.

This study reports ZnO nanoparticles and thin film surface modification using a two-step functionalization strategy. A small silane molecule was used to build up a stabilizing layer and for conjugation of biotin (vitamin B7), as a specific tag. Biotin was chosen because it is a well-studied bioactive molecule with high affinity for avidin. ZnO nanoparticles were synthesized by electrochemical deposition under oxidizing condition, and ZnO films were prepared by plasma-enhanced metal-organic chemical vapor deposition. Both ZnO nanoparticles and ZnO thin films were surface modified by forming a (3-mercaptopropyl)trimethoxysilane (MPTS) layer followed by attachment of a biotin derivate. Iodoacetyl-PEG2-biotin molecule was coupled to the thiol unit in MPTS through a substitution reaction. Powder X-ray diffraction, transmission electron microscopy, X-ray photoemission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy were used to investigate the as-synthesized and functionalized ZnO materials. The measurements showed highly crystalline materials in both cases with a ZnO nanoparticle diameter of about 5 nm and a grain size of about 45 nm for the as-grown ZnO thin films. The surface modification process resulted in coupling of silanes and biotin to both the ZnO nanoparticles and ZnO thin films. The two-step functionalization strategy has a high potential for specific targeting in bioimaging probes and for recognition studies in biosensing applications.