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Biomedical subjects

Yuri Lvov

Publications and source records attributed to Yuri Lvov.

7 recordsLinked to original sources
PubMed2006

Organophosphorus hydrolase multilayer modified microcantilevers for organophosphorus detection.

We report a biosensor based on organophosphorus hydrolase (OPH) multilayer modified microcantilever (MCL) for detection of organophosphorus compounds (OPs). The assay is based on substrate-dependent bending of the OPH functionalized MCLs. The cantilever bending amplitude at equilibrium was a function of the concentration of paraoxon with the dynamic range extending from 10(-7) to 10(-3)M. The lower detection limit of approximately 10(-7)M for paraoxon was an order of magnitude better than the OPH-based potentiometric and optical biosensors based on pH modulation. There was a good intra-sensor and an acceptable inter-sensor reproducibility as evidenced by the standard errors of 5% and 15%, respectively. OPs measured using this technique included parathion and diisopropyl fluorophosphate (DFP) in the order of paraoxon>DFP>parathion. The conformational change of the OPH was most likely the main origin of MCL bending.

Aryldialkylphosphatase↗
PubMed2006

Composite phospholipid-calcium carbonate microparticles: influence of anionic phospholipids on the crystallization of calcium carbonate.

The synthesis and characterization of calcium carbonate microparticles by reaction of calcium chloride and ammonium bicarbonate in the presence of negatively charged phospholipid mixtures of negative and zwitterionic phospholipids has been reported. Negatively charged phospholipids influence the crystal morphology of calcium carbonate and induce the formation of thermodynamically less stable veterite polymorph as opposed to calcite polymorph. The phospholipids are entrapped in the calcium carbonate microparticles during the crystallization process, with a uniform distribution of phospholipids in the interior of the microparticles. This phenomenon was exploited to encapsulate a model hydrophobic fluorophore, the tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) dichloride complex, to simulate encapsulation of hydrophobic drug molecules. Thermogravimetric analysis reveals that, in these microparticles, the calcium carbonate and the phospholipid exhibit strong interactions.

Anions↗
PubMedDate not supplied

Microcapsule modification with peroxidase-catalyzed phenol polymerization.

A biocatalytic polymer synthesis on a surface of polyelectrolyte microcapsules was studied. Horseradish peroxidase assembled in nanoorganized capsule walls by alternate adsorption with linear polyions retains its activity in reactions of enzyme-catalyzed polymerization of 4-oxyphenols. It allowed controllable synthesis of a phenolic polymer layer on microcapsule walls using an outermost surface peroxidase layer as a template. By varying the phenol type, buffer pH, and reaction component concentrations, the phenolic polymer coating of the capsules with a thickness in the range 20-50 nm was formed. The polymeric products are fluorescent, which provided a good opportunity for confocal image analysis of the capsule wall structure and the attached layer. The influence of a phenolic polymer layer on the permeability of the capsule walls was investigated.

Catalysis↗
PubMedDate not supplied

Spatial patterning of colloidal nanoparticle-based thin film by a combinative technique of layer-by-layer self-assembly and lithography.

A novel approach to generating clear patterns of different types of nanoparticles is presented in this paper. Nanoassembly in the vertical direction was combined with planar micropatterning. This provides industrial applications of a popular layer-by-layer method to produce multilayers of polymers, nanoparticles, and proteins organized on the nanometer scale. A thin film of organic polystyrene spheres was first coated on the pretreated silicon wafer with layer-by-layer self-assembly. Then a layer of aluminium was deposited on the thin film. A layer of positive photoresist was spun on the surface of aluminum and then illuminated with UV light. The exposed parts of the resist were removed and windows were opened above the aluminum. The subsequent etching removed exposed aluminium and left a polystyrene thin film in the open windows. Oxygen plasma was employed to remove the polystyrene thin film on the bottom. Eventually, aluminum and photoresist were removed and only the desired pattern remained. This approach was also employed for the patterning of the silica nanoparticle thin film, a widely used material in various applications. In this case, wet etching was demonstrated to etch silica particles. A scanning electron microscope was used to produce the image of the pattern.

Aluminum↗
PubMedDate not supplied

Nanoparticle multilayers: surface modification of photosensitive drug microparticles for increased stability and in vitro bioavailability.

The results of this study report the novel use of electrostatic layer-by-layer nanoassembly of biocompatible nanoparticulate TiO2 multilayers to coat irregular nifedipine (NF) microcrystals to increase the photostability of the drug when exposed to simulated sunlight and to increase the dissolution rate and possibly the bioavailability of the drug after oral administration. The photostability of NF microcrystals (35 microm) coated with multiple bilayers of positively charged PDDA and negatively charged nanosized TiO2 particles (20-25 nm) was measured when exposed to an illuminance of 12 W/m2 corresponding to a light dose of 30 k lux or 25 W/m2 corresponding to light dose of 60 k lux. The dissolution rate of nifedipine from the coated microcrystals was measured in simulated gastric fluid containing 0.05% w/v polysorbate 80. Coating with one TiO2 layer increased the shelf life of nifedipine by 30 hours independent of the intensity of the light exposure. With an increase in the number of TiO2 layers; the photostability of the drug was enhanced even more. A TiO2 monolayer decreased the contact angle by 20 degrees for water and 33 degrees for the dissolution medium as compared with uncoated NF surfaces. This increase in wettability due to a decrease in contact angle increased the dissolution rate of nifedipine microcrystals coated with 1 PDDA/TiO2 bilayer 13-fold after 10 minutes, 5-fold after 1 hour, and 2-fold after 12 hours when compared to uncoated microcrystals. It is assumed that TiO2 increased the photostability because the nanoparticulate multilayers acts as a potential filter protecting the drug from damaging light rays reaching the drug crystals. The dissolution rate was increased because the hydrophilic TiO2 nanoparticles increased the aqueous wettability of the drug crystals thereby preventing aggregation in the dissolution medium. This ensured that the maximum drug surface area was exposed to the dissolution medium.

Biological Availability↗