We present preliminary results obtained in the development of multiple-controlled drug delivery vehicles using magnetic nanoparticle-polymer composites. Two types of magnetic nanoparticle-polymer composites were prepared and tested for their potential as drug delivery systems with multiple controls (magnetically and thermally induced controlled delivery). These studies focused on the release of fluorescein isothiocyanate (FITC) from poly(methylmethacrylate) (PMMA), containing either magnetite or cobalt nanoparticles, by changing the sample temperature or by exposing it to an oscillating magnetic field. The magnetite-PMMA and cobalt-PMMA composites were 250 µm or less in size and were superparamagnetic. The investigations reported here demonstrated that the release of FITC from magnetite-PMMA particles can be induced thermally but not magnetically. There was no release of FITC from cobalt-PMMA composites either through thermal or magnetic induction. Characterization of the composites included transmission electron microscopy and scanning electron microscopy for size and morphology and elemental analysis for iron and cobalt content. Synchrotron radiation-based X-ray absorption near edge spectroscopy analysis was carried out to determine chemical, electronic, and geometric properties, and a superconducting quantum interference device magnetometer was utilized for measuring the magnetic properties of the composites.

Monodisperse Co, Fe, and FeCo nanoparticles are prepared via thermal decomposition of metal carbonyls in the presence of aluminium alkyls, yielding air-stable magnetic metal nanoparticles after surface passivation. The particles are characterized by electron microscopy (SEM, TEM, ESI), electron spectroscopy (MIES, UPS, and XPS) and x-ray absorption spectroscopy (EXAFS). The particles are peptized by surfactants to form stable magnetic fluids in various organic media and water, exhibiting a high volume concentration and a high saturation magnetization. In view of potential biomedical applications of the particles, several procedures for surface modification are presented, including peptization by functional organic molecules, silanization, and in situ polymerization.

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KEYWORDS: clustersTransition-metal nanoclusters display novel physical and catalytic properties.1 Platinum clusters less than 1 nm in size have been prepared entrapped in zeolites via the so-called 'ship-in-a-bottle' method.2 -4 However, to our knowledge, no wet-chemical method has been reported for synthesizing free Pt 13 clusters with a uniform particle size distribution.Bönnemann and Richards 5 opened a novel synthetic pathway to mono-and bi-metallic nanoparticles via the 'reductive stabilization' of colloidal transition metals using aluminium trialkyls as reducing agents and colloid stabilizers. A nearly monodispersed platinum colloid with a mean diameter of 1.2 nm was obtained by reducing platinum acetylacetonate with trimethylaluminium. 6 Recently, a facile one-pot procedure was developed for dimethyl (1,5-cyclooctadiene)7 This communication describes the size-selective preparation of Pt 13 clusters by decomposing complex 1 in the presence of aluminium trialkyls.When excess Al(CH 3 ) 3 was added to a toluene solution of complex 1, no colour change was observed. However, upon addition of Al(C 8 H 17 ) 3 or Al(C 2 H 5 ) 3 , the initially colourless reaction mixture turned brown, and a black solution of colloidal platinum was obtained over the course of a few days. . Free 1,5-COD ethylene and were also detected in the NMR spectra and their presence was confirmed by gas chromatography-mass spectrometry (GC-MS) analyses. In the case of the reaction of complex 1 with Al(C 8 H 17 ) 3 , 13 C NMR is much better for analysing the reaction mixture than the proton spectra because of the number of signals from the longer alkyl chains. The platinum-octyl groups were identified unambiguously: the α-carbon signal is found at δ C = 28.0 [ 1 J( 195 Pt, 13 C) = 845 Hz]. Similarly, free 1,5-COD, octane and octenes were found by NMR and GC-MS to be present in the reaction mixture.The NMR investigations imply that the β-H elimination is the rate-determining step. When using 10 equivalents of Al(C 2 H 5 ) 3 at room temperature the decomposition is very slow, and it takes more than a month for complex 1 to decompose fully. Transmission electron microscopy (TEM) analyses show that the initial particle size is around 0.7 nm.

Nanoparticle networks can be synthesized by the self‐assembly of arrays of metal colloid particles linked by spacer molecules of different sizes. The particles are linked through reactive aluminum sites in a metal–organic shell around the metal particles. Rigid spacer molecules with functional groups at each end are used to bind at these reactive sites. The resulting networks have been characterized by various methods such as transmission electron microscopy (TEM), sorption analysis, X‐ray absorption spectroscopy (XAFS), anomalous small angle X‐ray scattering (ASAXS), metastable impact electron spectroscopy (MIES), and ultraviolet photoelectron spectroscopy (UPS). These investigations showed that the metal nanoparticles form aggregated networks with average distances between the metal particles that are determined by the sizes of the spacer molecules applied. In this way, porous as well as nonporous networks have been obtained. Whether accessible pores are formed depends on the type of spacer molecule. Furthermore, the properties of the metal particles have proved to be sensitive towards the reaction of the aluminum in the protective shells with the linker molecules. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)