The features of self-assembling organic bilayers important to the formation of anisotropic inorganic materials in microgravity conditions

Materials with directional properties are opening new horizons in a variety of applications including chemistry, electronics, and optics. Structural, optical, and electrical properties can be greatly augmented by the fabrication of composite materials with anisotropic microstructures or with anisotropic particles uniformly dispersed in an isotropic matrix. Examples include structural composites, magnetic and optical recording media, photographic film, certain metal and ceramic alloys, and display technologies including flat panel displays. The new applications and the need for model particles in scientific investigations are rapidly out-distancing the ability to synthesize anisotropic particles with specific chemistries and narrowly distributed physical characteristics (e.g. size distribution, shape, and aspect ratio)

The Features of Self-Assembling Organic Bilayers Important to the Formation of Anisotropic Inorganic Materials in Microgravity Conditions

There is a growing need for inorganic anisotropic particles in a variety of materials science applications. Structural, optical, and electrical properties can be greatly augmented by the fabrication of composite materials with anisotropic microstructures or with anisotropic particles uniformly dispersed in an isotropic matrix. Examples include structural composites, magnetic and optical recording media, photographic film, certain metal and ceramic alloys, and display technologies including flat panel displays. While considerable progress has been made toward developing an understanding of the synthesis of powders composed of monodispersed, spherical particles, these efforts have not been transferred to the synthesis of anisotropic nanoparticles. The major objective of the program is to develop a fundamental understanding of the growth of anisotropic particles at organic templates, with emphasis on the chemical and structural aspects of layered organic assemblies that contribute to the formation of anisotropic inorganic particles

Presence of lipids in urine, crystals and stones: Implications for the formation of kidney stones

Presence of lipids in urine, crystals and stones: Implications for the formation of kidney stones.BackgroundCell membranes and their lipids play critical roles in calcification. Specific membrane phospholipids promote the formation of calcium phosphate and become a part of the organic matrix of growing calcification. We propose that membrane lipids also promote the formation of calcium oxalate (CaOx) and calcium phosphate (CaP) containing kidney stones, and become a part of their stone matrix.MethodsHuman urine, crystals of CaOx and CaP produced in the urine of healthy individuals, and urinary stones containing struvite, uric acid, CaOx and CaP crystals for the presence of membrane lipids were analyzed. Crystallization of CaOx monohydrate at Langmuir monolayers of dipalmitoylphosphatidylglycerol (DPPG), dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylserine (DPPS), dioleoylphosphatidylglycerol (DOPG), palmitoyloleoylphosphatidylglycerol (POPG) and dimyristoylphosphatidylglycerol (DMPG) was investigated to directly demonstrate that phospholipid assemblies can catalyze CaOx nucleation.ResultsUrine as well as CaOx and CaP crystals made in the urine and various types of urinary stones investigated contained some lipids. Urine of both CaOx and uric acid stone formers contained significantly more cholesterol, cholesterol ester and triglycerides than urine of healthy subjects. However, urine of CaOx stone formers contained more acidic phospholipids. The organic matrix of calcific stones contained significantly more acidic and complexed phospholipids than uric acid and struvite stones. For each Langmuir monolayer precipitation was heterogeneous and selective with respect to the orientation and morphology of the CaOx crystals. Crystals were predominantly monohydrate, and most often grew singly with the calcium rich (10-1) face toward the monolayer. The number of crystals/mm2 decreased in the order DPPG> DPPC and was inversely proportional to surface pressure and mean molecular area/molecule.ConclusionsStone forming conditions in the kidneys greatly impact their epithelial cells producing significant differences in the urinary lipids between healthy and stone forming individuals. Altered membrane lipids promote face selective nucleation and retention of calcium oxalate crystals, and in the process become a part of the growing crystals and stones

Size dependence of the photoinduced magnetism and long-range ordering in Prussian blue analog nanoparticles of rubidium cobalt hexacyanoferrate

Nanoparticles of rubidium cobalt hexacyanoferrate (Rb$_j$Co$_k$[Fe(CN)$_6$]$_l \cdot n$H$_2$O) were synthesized using different concentrations of the polyvinylpyrrolidone (PVP) to produce four different batches of particles with characteristic diameters ranging from 3 to 13 nm. Upon illumination with white light at 5 K, the magnetization of these particles increases. The long-range ferrimagnetic ordering temperatures and the coercive fields evolve with nanoparticle size. At 2 K, particles with diameters less than approximately 10 nm provide a Curie-like magnetic signal.Comment: 10 pages, 6 figures in text, expanded text and dat

Novel phosphate–phosphonate hybrid nanomaterials applied to biology

International audienceA new process for preparing oligonucleotide arrays is described that uses surface grafting chemistry which is fundamentally different from the electrostatic adsorption and organic covalent binding methods normally employed. Solid supports are modified with a mixed organic/inorganic zirconium phosphonate monolayer film providing a stable, well-defined interface. Oligonucleotide probes terminated with phosphate are spotted directly to the zirconated surface forming a covalent linkage. Specific binding of terminal phosphate groups with minimal binding of the internal phosphate diesters has been demonstrated. On the other hand, the reaction of a bisphosphonate bone resorption inhibitor (Zoledronate) with calcium deficient apatites (CDAs) was studied as a potential route to local drug delivery systems active against bone resorption disorders. A simple mathematical model of the Zoledronate/CDA interaction was designed that correctly described the adsorption of Zoledronate onto CDAs. The resulting Zoledronate-loaded materials were found to release the drug in different phosphate-containing media, with a satisfactory agreement between experimental data and the values predicted from the model