Andrey M. Zakharevich

Composite Magnetite and Protein Containing CaCO3 Crystals. External Manipulation and Vaterite → Calcite Recrystallization-Mediated Release Performance

Biocompatibility and high loading capacity of mesoporous CaCO3 vaterite crystals give an option to utilize the polycrystals for a wide range of (bio)applications. Formation and transformations of calcium carbonate polymorphs have been studied for decades, aimed at both basic and applied research interests. Here, composite multilayer-coated calcium carbonate polycrystals containing Fe3O4 magnetite nanoparticles and model protein lysozyme are fabricated. The structure of the composite polycrystals and vaterite → calcite recrystallization kinetics are studied. The recrystallization results in release of both loaded protein and Fe3O4 nanoparticles (magnetic manipulation is thus lost). Fe3O4 nanoparticles enhance the recrystallization that can be induced by reduction of the local pH with citric acid and reduction of the polycrystal crystallinity. Oppositely, the layer-by-layer assembled poly(allylamine hydrochloride)/poly(sodium styrenesulfonate) polyelectrolyte coating significantly inhibits the vaterite → calcite recrystallization (from hours to days) most likely due to suppression of the ion exchange giving an option to easily tune the release kinetics for a wide time scale, for example, for prolonged release. Moreover, the recrystallization of the coated crystals results in formulation of multilayer capsules keeping the feature of external manipulation. This study can help to design multifunctional microstructures with tailor-made characteristics for loading and controlled release as well as for external manipulation.

Nanocrystalline structure of the surface layer of plasma-sprayed hydroxyapatite coatings obtained upon preliminary induction heat treatment of metal base

Biocompatible nanocrystalline hydroxyapatite (HA) coatings for intrabone titanium implants have been obtained by plasma spraying. The HA coatings have an average grain size within 10–30 nm and are characterized by improved characteristics of morphological heterogeneity that is acquired due to the induction heat treatment (IHT) of substrates prior to plasma spray deposition. Based on the data of scanning electron microscopy with computer-aided processing of images, it is established that the average grain size depends on the IHT temperature.

Nanocrystalline structure of surface layer of technical-purity titanium subjected to induction-thermal oxidation

Metal-oxide coatings on a smooth technical-purity titanium surface were produced that were characterized by lamellar, needled, and prismatic shapes of crystals. Regularities of variations in nanometer morphology characteristics of the titanium surface subjected to induction-thermal oxidation are determined.

Structure of Composite Biocompatible Titania Coatings Modified with Hydroxyapatite Nanoparticles

The article describes prospective composite biocompatible titania coatings modified with hydroxyapatite nanoparticles and obtained on intraosseous implants fabricated from commercially pure titanium. Consistency changes of morphological characteristics and crystalline structure, mechanical properties and biocompatibility of experimental titanium implant coatings obtained by the combination of oxidation and surface modification with hydroxyapatite during induction heat treatment are defined.

Nanostructure of biocompatible titania/hydroxyapatite coatings

The article describes prospective composite biocompatible titania coatings modified with hydroxyapatite nanoparticles and obtained on intraosseous implants fabricated from commercially pure titanium VT1-00. Consistency changes of morphological characteristics, crystalline structure, physical and mechanical properties and biocompatibility of experimental titanium implant coatings obtained by the combination of oxidation and surface modification with hydroxyapatite during induction heat treatment are defined.

Detection of sulfonamide drug in urine using liquid-liquid extraction and surface-enhanced Raman spectroscopy

In this article we have applied liquid-liquid extraction (LLE) as a sample preparation technique for detection of sulfadimethoxine (one of sulfonamide drugs) in urine using surface-enhanced Raman spectroscopy (SERS). SERS substrate based on silver nanoparticles has been prepared by citrate reduction of silver nitrate. Obtained calibration curve (SERS intensity vs. sulfadimethoxine concentration) has been used for detection of sulfadimethoxine in human urine samples artificially contaminated by sulfadimethoxine. Three different solvents (ethyl acetate, diethyl ether, chloroform) have been used for LLE performance tests. Chloroform being found as the most effective one based on calculation of recoveries after SERS measurements. Thus we would like to propose fast (less than 20 minutes), simple and sensitive (detection limit up to 1 μg/ml) test for detecting sulfa drugs in urine using a combination of SERS with LLE with sample volume as low as 100 μL. Such test can be applied for evaluation of the degree of drug extraction from human body and half-life of such drug applied in the course of therapeutic treatments of certain diseases.

Multifunctional silver nanoparticle-doped silica for solid-phase extraction and surface-enhanced Raman scattering detection

AbstractMultifunctional silica gel with embedded silver nanoparticles (SiO2–AgNP) is proposed for application as sorbent for solid-phase extraction (SPE) and simultaneously as substrate for surface-enhanced Raman spectroscopy (SERS) due to their high sorption properties and ability to enhance Raman signal (SERS-active sorbents). SiO2–AgNP was synthesized via alkaline hydrolysis of tetraethyl orthosilicate with simultaneous reduction of silver ions to silver nanoparticles (AgNP) within the SiO2 bulk. Synthesis of AgNP directly to the SiO2 matrix enables to exclude any additional stabilizers for the nanoparticles that educes signal-to-noise ratio during SERS measurement. Apart from Raman spectroscopy, obtained sorbents were also characterized by scanning electron microscopy and UV-visible diffuse reflectance spectroscopy. The influence of AgNO3 concentration used during the SiO2–AgNP synthesis on its gelling time, color, diffuse reflectance spectra, and enhancement of Raman signal was investigated. A Raman enhancement factor of SiO2–AgNP with optimal composition was around 105. Finally, the sorbents were applied for SPE and subsequent SERS detection of model compounds (rhodamine 6G and folic acid). It was found that SPE enables to decrease detectable concentrations by two orders. Therefore, SPE combined with SERS has high potential for further analytical investigations. Graphical abstractᅟ

Micro- and nanostructure of a titanium surface electric-spark-doped with tantalum and modified by high-frequency currents

We have studied the characteristics of the porous microstructure of tantalum coatings obtained by means of electric spark spraying on the surface of commercial grade titanium. It is established that, at an electric spark current within 0.8–2.2 A, a mechanically strong tantalum coating microstructure is formed with an average protrusion size of 5.1–5.4 µm and pore sizes from 3.5 to 9.2 µm. On the nanoscale, a structurally heterogeneous state of coatings has been achieved by subsequent thermal modification at 800–830°C with the aid of high-frequency currents. A metal oxide nanostructure with grain sizes from 40 to 120 nm is formed by short-time (~30 s) thermal modification. The coating hardness reaches 9.5–10.5 GPa at an elastic modulus of 400–550 GPa.

Structure of metal-oxide Ti-Ta-(Ti,Ta)xOy coatings during spark alloying and induction-thermal oxidation

The study focuses on combined spark alloying of titanium and titanium alloy surface and porous matrix structure oxidation. The metal-oxide coatings morphology is the result of melt drop transfer, heat treatment, and oxidation. The study establishes the influence of technological regimes of alloying and oxidation on morphological heterogeneity of metal- oxide system Ti-Ta-(Ti,Ta)xOy.

Superhard oxide coatings formed on titanium treated by high-frequency currents

We have studied the hardness and elastic modulus of rutile (TiO2) oxide coatings formed on the surface of commercial grade VT1-00 titanium treated by high-frequency current (HFC). The mechanism of formation of superhard oxide coatings with thicknesses within 2–3 μm and submicron-grained structure consisting of prismatic crystallites with dimensions of 200–400 nm. It is established that, at high temperatures (within 1000–1200°C) and short HFC treatment durations (30–300 s), the oxide coatings are characterized by hardnesses of about 61–78 GPa and elastic moduli within 330–680 GPa.