Magnetite nanoparticles for biosensor model based on bacteria fluorescence

Fluorescence emission of pyoverdine – the siderophore synthesized by iron scavenger bacteria - was studied using in vitro cultures of Pseudomonas aeruginosa with the aim to design a biosensor system for liquid sample iron loading. Diluted suspensions of colloidal magnetite nanoparticles were supplied in the culture medium (10 microl/l and 100 microl/l) to simulate magnetic loading with iron oxides of either environmental waters or human body fluids. The electromagnetic exposure to radiofrequency waves of bacterial samples grown in the presence of magnetic nanoparticles was also carried out. Cell density diminution but fluorescence stimulation following 10 microl/l ferrofluid addition and simultaneous exposure to radiofrequency waves was evidenced. The inhibitory influence of 100 microl/l ferrofluid combined with RF exposure was evidenced by fluorescence data. Mathematical model was proposed to approach quantitatively the dynamics of cell density and fluorescence emission in relation with the consumption of magnetite nanoparticle supplied medium. The biosensor scheme was shaped based on the response to iron loading of bacterial sample fluorescence

Preparation and characterization of PbTiO 3-epoxy resin compositionally graded thick films

The preparation and properties of compositionally graded PbTiO3 (PT)-epoxy resin (EPR) composite thick films are reported in this study. Various graded specimens were prepared using gravity casting method by embedding PT powders into the EPR matrix. The existence of a graded structure with two distinct phases, a good intermixing, some air pores, and different morphologies, was confirmed by scanning electron microscopy micrographs. The dielectric constants of these composites have values in the range 5-12 at the frequency of 3c104 Hz and about 3-13 at 3c5 7 108Hz. The composites with permittivity gradient act as a natural impedance match system in the frequency range 2-4 GHz, resulting in very low reflections. Therefore, the compositionally graded PT-EPR composite thick films are suitable as adapting impedance materials for microwave applications