[Pathogenic viruses in activated sludge: problems and quantification].

The number of repeat in the microsatellite region (AATG)(5-14) of the human thyroid peroxidase gene (TOPX) was determined using an automated DNA analysis system with nano-scale engineered biomagnetite. Thermal melting curve analysis of DNA duplexes on biomagnetite indicated that shorter repeat sequences (less than 9 repeats) were easily discriminated. However, it was difficult to determine the number of repeats at more than nine. In order to improve the selectivity of this method for the longer repeats, a "double probe hybridization assay" was performed in which an intermediate probe was used to replace a target repeat sequence having more than 9 repeats with a shorter sequence possessing less than 9 repeats. Thermal probe melting curve analyses and Tm determination confirmed that the target with 10 repeats was converted to 5 repeats, 11 repeats converted to 4 and 12 to 3, respectively. Furthermore, rapid determination of repeat numbers was possible by measuring fluorescence intensities obtained by probe dissociation at 56 and 66 degrees C, and 40, 60 and 80 degrees C for signal normalization.

Ferrosoferric Oxide↗

PubMed2006

Oriented assembly of Fe3O4 nanoparticles into monodisperse hollow single-crystal microspheres.

Magnetite nanoparticles of Fe3O4 were found to assemble into monodisperse hollow Fe3O4 microspheres with tunable diameters ranging from 200 to 400 nm and open pores on the shells in ethylene glycol in the presence of dodecylamine (DDA). The oriented assembly of nanoparticles conferred the individual hollow Fe3O4 microspheres a remarkable feature of single crystals. The morphologies of the products could be easily manipulated by varying the synthesis parameters. Increasing the concentration of DDA led to an obvious shape evolution of the products from rhombic nanoparticles to hollow microspheres, solid microspheres, and finally irregular nanoparticles, which were mainly attributed to the special self-assembly phenomenon of Fe3O4 nanoparticles in the solvothermal process.

Ferrosoferric Oxide↗

PubMed2006

Delivery of nanogram payloads using magnetic porous silicon microcarriers.

A transport and delivery system for nanogram quantities of molecular species that does not use microfluidic channels, pumps, or valves is described. Microparticles consisting of magnetic porous silicon are prepared, and loading and delivery of an enzymatic payload are demonstrated. The high porosity (60%) porous Si host particles are made magnetic by infusion of superparamagnetic iron oxide nanoparticles (30 nm-diameter magnetite, Fe(3)O(4)) under oxidative conditions. After magnetite incorporation, the porous microparticle is still empty enough to accommodate nanogram quantities of a molecular payload; the enzymes horseradish peroxidase or pronase E are used in the present work. The assembly can be transported to a microliter water droplet containing the enzyme substrate with the aid of an external magnetic field. The enzyme is released into the droplet upon contact. The particles can be transported through air or a hydrocarbon liquid without loss in enzymatic activity of the payload.

Ferrosoferric Oxide↗