Magnetic and in vitro heating properties of implants formed in situ from injectable formulations and containing superparamagnetic iron oxide nanoparticles (SPIONs) embedded in silica microparticles for magnetically induced local hyperthermia

The biological and therapeutic responses to hyperthermia, when it is envisaged as an anti-tumor treatment modality, are complex and variable. Heat delivery plays a critical role and is counteracted by more or less efficient body cooling, which is largely mediated by blood flow. In the case of magnetically mediated modality, the delivery of the magnetic particles, most often superparamagnetic iron oxide nanoparticles (SPIONs), is also critically involved. We focus here on the magnetic characterization of two injectable formulations able to gel in situ and entrap silica microparticles embedding SPIONs. These formulations have previously shown suitable syringeability and intratumoral distribution in vivo. The first formulation is based on alginate, and the second on a poly(ethylene-co-vinyl alcohol) (EVAL). Here we investigated the magnetic properties and heating capacities in an alternating magnetic field (141 kHz, 12 mT) for implants with increasing concentrations of magnetic microparticles. We found that the magnetic properties of the magnetic microparticles were preserved using the formulation and in the wet implant at 37 °C, as in vivo. Using two orthogonal methods, a common SLP (20 W g⁻¹) was found after weighting by magnetic microparticle fraction, suggesting that both formulations are able to properly carry the magnetic microparticles in situ while preserving their magnetic properties and heating capacities.     

‘One‐Touch’ Voltammetry of Microparticles for the Identification of Corrosion Products in Archaeological Lead

Voltammetry of microparticles is applied to the identification of lead corrosion products by means of an essentially non‐invasive ‘one‐touch’ technique based on the use of graphite pencil. This methodology permits the mechanical attachment of few nanograms of sample from the surface of lead archaeological artefacts to a paraffin‐impregnated graphite electrode, which, upon immersion in aqueous electrolytes, provides distinctive voltammetric responses for litharge and cotunnite‐ anglesite‐, cerusite‐based corrosion products. The reported method is applied to the identification of corrosion products in archaeological lead pieces from different Iberian sites in Valencia (Spain).     

Mathematical modelling and simulation of adsorption processes at spherical microparticles.

A model for the adsorption process at spherical microparticles under transient diffusion conditions has been developed and solved using numerical simulation. This model allowed us to demonstrate that the system is controlled by two main dimensionless parameters: the adsorption rate constant ka' and the saturation parameter beta. Analytical models for the adsorption process at spherical microparticles under steady-state mass transport conditions have been derived. These models use previously developed empirical relationships for the calculation of the mass transfer coefficient (kc). The properties of the system were studied for both the case where mass transport is described by diffusion only and the case where it is the result of a coupled diffusion/convection process. These mathematical tools were then used to analyse the results obtained for the uptake of CuII by glassy carbon powder modified with the monomer L-cysteine methyl ester and to extract a minimum value for the adsorption rate constant which was found to be of the order of 10(-4) cm s(-1).     

Multicompartmental Microcylinders

Colorful columns : A simple yet scalable method that yields multicompartmental microcylinders with controllable internal architectures, aspect ratios, and controlled surface modification uses electrohydrodynamic co‐spinning followed by microsectioning. Compartments are discriminated by different colored dyes (see CLSM images; scale bars=10.0 μm).

     

Preparation, characterization and surface study of poly-epsilon caprolactone magnetic microparticles

Magnetic microparticles (MMP) have shown to be applied in increasing applications in various fields of biotechnology and medicine. One of their most promising utilization is the magnetic resonance imaging (MRI) in which superparamagnetic substances as magnetite are used in a nanometric size (less than 30 nm) and encapsulated within locally injected biodegradable microparticles. In this paper, magnetite has been encapsulated in polymer-based microparticles. The MMP have been prepared by an emulsion evaporation method. The different parameters influencing the particles size were investigated. The size was found to decrease as the stirring speed or the stabilizer amount (to certain limit) increases. The encapsulation efficacy was more than 90% yielding a magnetite loading of up to 30%, w/w. The X-ray photoelectron spectroscopy (XPS) showed less than 2% of iron atoms at the microparticles surface. The zeta potential response of MMP towards pH variation was very similar to that of magnetite-free microparticles confirming the encapsulation of magnetite within the microparticles. X-ray diffraction assays showed that magnetite crystalline structure was conserved after emulsification and MMP formation. Vibration simple magnetometer (VSM) showed a superparamagnetic profile of the MMP with a magnetic saturation increasing with the increased magnetite amount in the microparticles. These magnetic microparticles can enable clinicians to control microparticles distribution after a local administration in tumors by MRI. They can also be administered to target a defined tumor area by focusing a magnetic field on the surfaces covering the cancerous tissue.     

Thermosensitive Microparticles Based on Unsaturated Esters of some Poly- and Oligosaccharides: Preparation,Characterization, Drug Inclusion and Release

Summary: The paper concerns the preparation and characterization of hydrogel microparticles based on exopolysaccharide (Gellan, Xanthan) unsaturated derivatives and respectively on cyclodextrin as well as their application for some hydrosoluble and liposoluble drugs inclusion. In the first step the polysaccharide and cyclodextrin unsaturated esters (maleate, acrylate) were synthesized and their hydrogel forming capacity was tested using a grafting-crosslinking free-radical reaction with N-isopropyl acrylamide (NIPAm), at room temperature. For a better control of the crosslinking degree N,N' methylene-bis-acrylamide (BIS), replaced by cyclodextrin tri-acrylate (A-CD) in a few experiments, was used. The microparticles were obtained by using the method in w/o emulsion, in which the dispersed aqueous phase is the reaction mixture and the oil phase is hexane. The particles containing polysaccharide esters showed an average diameter around 100 µm when crosslinking was achieved with BIS. They were smaller than those crosslinked with A-CD, which are in the range of 200-300 µm; the particles based on Xanthan maleate were smaller than Gellan maleate based ones. Even much smaller particles (2-2.5 µm in diameter) were obtained by starting from A-CD grafted-crosslinked systems. The synthesized microparticles are able to include chloramphenicol, as well as progesterone; the drug is slowly released according to diffusion controlled kinetics. The application of these microparticles in emergency ophthalmic treatments is possible as a result of their thermal sensitivity; they can collapse and release the drug instantly when placed in contact with the human eye, at 37 °C.     

聚苯乙烯微球表面的链段堆积状态

聚苯乙烯微球表面的链段堆积状态徐伟，陈殿勇，华中一，吕绪良，胡建华，府寿宽（复旦大学材料科学系，上海，２００４３３）（复旦大学高分子科学系）关键词聚苯乙烯微球，聚合物链段，聚集态，扫描隧道显微镜用微乳液聚合法制备的聚苯乙烯微球与常规聚苯乙烯相比有许多...     

H‐Point Standard Addition Method Applied to Voltammetry of Microparticles. Quantitation of Dyes in Pictorial Samples

A solid‐state electrochemical application of the H‐point standard addition method (HPSAM) for quantifying two electroactive compounds, A, B, that produce strongly overlapped voltammetric peaks is described. It is based on peak current measurement in square‐wave voltammograms recorded for solid samples containing a reference compound R, upon additions of a A‐ (or B‐) containing standard compound. The method allows to the determination of the mass fraction of A and B by applying the H‐point standard addition method to solid state voltammetry. The quotients between the currents measured at two selected potentials and the peak current of R vary linearly with the mass ratio of the added standard and the reference compound, thus providing an electrochemical method for determining the content of A and B in the sample avoiding matrix effects. The method is applied to the simultaneous determination of alizarin and purpurin in madder pigments and pictorial specimens using morin as a reference material.     

Development of an Amperometric Enzymatic Biosensor Based on Gold Modified Magnetic Nanoporous Microparticles

Gold modified nanoporous silica based magnetic microparticles have been prepared as support for the immobilization of the enzyme horseradish peroxidase (HRP). The enzyme modified gold microparticles were retained onto the surface of a solid carbon paste electrode with the help of a permanent magnet. The analytical performances of the resulting biosensor were characterized by studying hydroquinone (HQ) and hydrogen peroxide. The former was monitored by the direct electroreduction of the biocatalytically generated quinone. Several experimental parameters influencing the biosensor response were investigated. A linear response to HQ was obtained in the concentration range comprised between 5×10^?7 and 4.5×10^?6 M with a detection limit of 4×10^?7 M. The enzyme electrode provided a linear response to hydrogen peroxide over a concentration range comprised between 5×10^?7?1.3×10^?4 M with a detection limit of 4×10^?7 M. The inhibition of the biosensor response in the presence of thiols e.g. cysteine, captopril, glutathione and Nacystelyn (NAL) has been pointed out.