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Protection of ureteral stents against infections is a significant current challenge raised by increasing the number of stentings and infections, microbial resistance to conventional antibiotics and multi-drugs treatments, side effects for the patients like damage of surrounding tissue and high morbidity. Surface engineered biomaterials and ureteral stents, reducing biofilm formation and encrustation would contribute to mitigation of the problem. The aim of this review is to present the progress during the last 5 years in the development of surface engineered antimicrobial biomaterials and stents with expectation to raise some new fruitful ideas in this direction. Strategies aimed at preventing, disrupting, or removing adherent microbes and biofilms from biomaterials and ureteral stents are its main subject. Various antibacterial agents, modifications, and coatings as well as preparation, deposition and characterization techniques are among the topics covered. A brief market analysis is also included covering the significance of ureteral stents associated infections and a mode of development of a biofilm. The review of the progress during the last 5 years shows a continuing interest in surface modification and coating employing three principal anti-biofilm strategies: 1) mechanical detachment; 2) killing microbial cells and 3) creation of low-adhesive surfaces. The known surface engineering solutions report a reduced, to some extent, biofilm formation and encrustation of biomaterials and ureteral stents, but none of them is able to totally stop their development. Some new trends are observed, such as complementary antimicrobial protection by coating and flow dynamic; biodegradable coatings releasing antimicrobial agent; quasi irremovable surface coatings, delivering drug or antimicrobial agent as well as new carbon and biodegradable materials; bacteriophages and phage cocktails, etc. Almost all of them are under intense in vitro studies; only few of them were studied in vivo animal models and none in humans. Some of the liquid infused coatings, already tested in animal models, seem to be the closest to clinical application but so far no one has been applied to ureteral stents. This review outlines some future research directions and major challenges in the surface engineered biomaterials and ureteral stents. It gives ideas how, by surface engineering, to approach more closely the “clean” ureteral stent to not allow microbial adhesion and encrustation and thus sharply reduce the ureteral stents associated infections and stent dysfunction. The most important prerequisite of the non-toxic “clean” surface is to be low adhesive. Its anti-biofilm performance could be improved by including bio-surfactant and/or inhibitor of quorum sensing (QS) and/or inhibitor of the crosslinking of the exopolymeric substances (EPSs). The key to identifying a “universal” surface that would repel/release all microbial cells is maybe hidden in the in-depth understanding of the mechanism of the initial reversible adsorption of the EPSs secreted by microbial cells, since it initiates the whole biological cascade of biofilm development.

The aim of this investigation was to develop new antimicrobial collagen/zinc titanate (ZnTiO3) biomaterials using a sol-gel cryogenic draying technology in keeping the native collagen activity. Broad-spectrum antimicrobial activity was demonstrated against Firmicutes (Staphylococcus epidermidis, Bacillus cereus, and Candida lusitaniae) and Gracilicutes (Escherichia coli, Salmonella enterica, and Pseudomonas putida) microorganisms. The antimicrobial activity as well as the cytotoxicity were specific for the different test microorganisms (Gram-positive and Gram-negative bacteria and fungi) and model eukaryotic cells (osteosarcoma, fibroblast, and keratinocyte cells), respectively, and both were depending on the ZnTiO3 concentration. Three mechanisms of the antimicrobial action were supposed, including (i) mechanical demolition of the cell wall and membrane by the crystal nanoparticles of the ZnTiO3 entrapped in the collagen matrix, (ii) chelation of its metal ions, and (iii) formation of free oxygen radicals due to the interaction between the microbial cells and antimicrobial agent. It was concluded that the optimal balance between antimicrobial activity and cytotoxicity could be achieved by a variation of the ZnTiO3 concentration. The antifungal and broad-spectrum antibacterial activity of the studied collagen/ZnTiO3 nanocomposites, combined with a low cytotoxicity, makes them a promising anti-infection biomaterial.

In recent years, many interesting researches published on the study of new nanocomposite materials involves active components such as reduced graphene oxide (RGO), silver nanoparticles (Ag-NPs), and silica, which indicated very interesting properties and applications. The present work demonstrates the preparation of nanocomposite powders with the participation of Ag-NPs, RGO and tetraethyl-orthosilicate (TEOS) using the sol-gel technique. The phase formations are verified by X-ray diffraction analysis. The thermal behavior was studied using differential thermal analysis (DTA/TG) in air. The sensitivity against humidity was tested in a laboratory apparatus made of a thermostatic chamber operating at 25 °C, in which the RH could be varied between 0% and 96%.

Glass formation ability in three different sections: WO 3 –ZnO–Nd 2 O 3 ; (100-x) (0.8WO 3 ·0.1ZnO·0.1Nd 2 O 3 )·xAl 2 O 3 , x = 5–30 mol% and 90(xWO 3 ·yZnO·zNd 2 O 3 )·10Al 2 O 3 from WO 3 –ZnO-Nd 2 O 3 –Al 2 O 3 system is investigated by melt quenching technique. Glasses are obtained from the compositions with a high WO 3 content (65–75 mol%). According to DTA data the glass transition temperature (T g ) is in the range 508–525 °C and the glass crystallisation temperature (T x ) is around 600 °C. Neodymium tungstates, Al 2 (WO 4 ) 3 , ZnWO 4 and WO 3 are identified in the XRD patterns of quenched samples beyond the glass formation region. The structure of glasses is studied by IR, Raman and DR-UV–Vis spectroscopies. It is established that the amorphous network is built up mainly by WO 6 octahedra, connected by W–O–W bridges. This structure does not satisfy the classical concept for the formation of an amorphous network which is built up by MeO 4 tetrahedra.

The aim of this study is preparation, characterization, and biological activity evaluation of 2 new collagen composites, Collagen/(Ag/RGO) and Collagen/(Ag/RGO/SiO2) with expected antimicrobial activity. The loading of collagen matrix by self-prepared Ag/RGO and Ag/RGO/SiO2 was varied. The morphology of these antimicrobial agents, as well as of the corresponding collagen composites, was observed by SEM. Their biological activity was evaluated against 3 Gram-negative and 3 Gram-positive microbial strains, as well as against 3 type eukaryotic cells: osteoblast, fibroblast, and epithelial. Dependent on the concentration of Ag/RGO, well pronounced activity against Gram-negative bacterium (E. coli), fungus (C. Lusistaniae) and 2 Gram-positive bacteria (S. epidermidis and B. cereus) was found for Collagen/(Ag/RGO) composites at weight ratios of 2:1, 2:0.8, and 2:0.6, at the last one accompanied by low cytotoxicity. Dependent on the concentration of Ag/RGO/SiO2 biological activity was found for the Collagen/(Ag/RGO/SiO2) composites also, better expressed than that of Collagen/(Ag/RGO) composites with the same level of antimicrobial agent loading. The experimental results demonstrated that the doping of RGO with Ag nanoparticles increases the antimicrobial activity of the Collagen/(Ag/RGO) composites. Improving its dispersion, the silane matrix in the Ag/RGO/SiO2 additionally increases the biological activity of the studied Collagen/(Ag/RGO/SiO2) composites and their well-pronounced, broad spectrum (against 3 Gram-negative, 2 Gram-positive bacteria and a fungus), antimicrobial activity is similar to that of the broad spectrum antibiotics. The novel Collagen/(Ag/RGO) and Collagen/(Ag/RGO/SiO2) composites are promising antimicrobial collagen biomaterials that widen the assortment of such for variety biomedical applications. Keywords: Collagen/(Ag/RGO) and Collagen/(Ag/RGO/SiO2) Composites; Cytotoxicity to Eukaryotic Cells: Fibroblast, Osteoblast and Epithelial; Antimicrobial Activity: 3 Gram-Negative (S. Enterica, P. Aeruginosa and E. Coli)

Bulk superconducting composites containing Bi 1.6 Pb 0.4 Sr 2 Ca 2 Cu 3 O z (BPSCCO) and La 0.6 Pb 0.4 MnO 3 (LPMO) ceramics have been produced and investigated. The initial components were prepared by a solid-state reaction. The submicron powders mixed in weight ratio 99/1, 97/3, and 95/5 BSCCO/LPMO were heat treated at 840 °C for 24 h in oxygen atmosphere. The transformation and degradation of composites were studied in details by XRD, scanning electron microscopy (SEM), and the method of energy dispersive X-ray spectroscopy (EDX). It was established that the superconducting BPSCCO-2212 phase is predominate in the composites. Part of the ferromagnetic La 0.6 Pb 0.4 MnO 3 phase was transformed in more complicated solid solution preliminary expressed by the formulae La (1− x − y ) Pb x (Sr,Ca) y Mn 1− z Cu z O 3 . AC magnetization M AC ( T ) and hysteresis loops M ( H ) of the composites were performed by Physical Property Measurement System (PPMS). It was observed the presence of both superconducting and magnetic phases in the composites after heat treatment.

A polycrystalline La 0.6 Pb 0.4 MnO 3 sample, demonstrating predominantly a single phase behavior (hexagonal structure (R-3c) with the lattice parameters a = b =5.5009 (4) A, c =13.3744 (10) A, α = β =90°, γ =120°) was prepared by solid state reaction in oxygen atmosphere. A second pelletization and sintering processes assisted in a closer packing of the grains in the sample. The saturation and spontaneous magnetizations of the sample, measured at 4 K and 300 K were M sat =75.8 emu/g, 48 emu/g and M s =66.2 emu/g, 26 emu/g, respectively. The sample demonstrated a relatively high magneto-resistance effect (−32.3% at 4 K and 10 kOe). The resistance R showed a small progressive decrease in cyclic magnetic field H at 300 K and a hysteresis arose in the R vs H dependence at low temperatures.

Bulk superconducting (SC) ceramics containing BPSCCO and LPMO (Lanthanum/Lead – manganite phase) have been produced. The initial components were prepared by a low-temperature Pechini method. The submicron powders in weight ratio 90/10 Bi1.6Pb0.4Sr2Ca2Cu3Oz/La0.6Pb0.4MnO3 (nominal composition) were heat treated at 840°C. The duration of the heat treatment effect (60 and 100 h) of the composite on the transformation of the microstructure was studied. The obtained composites were analyzed by scanning electron microscopy (SEM) and by the method of energy-dispersive X-ray spectroscopy (EDX). They contain several phases. It was established that the SC 2212 phase is predominate in the composite. The phase La0.6Pb0.4MnO3 transforms in solid solution with preliminary composition La0.5(Sr + Ca)0.5Mn1− z Cu z O3, which after full replacement of the La and Mn ions leads to the appearance of phases with nominal composition Sr1− x Ca x CuO y . AC and DC magnetization measurements were used to study the SC and magnetic ...

In a previous paper (Shalaby A, Yaneva V, Staneva A, Aleksandrov L, Iordanova R, Dimitriev Y, Nanoscience & nanotechnology – nanostructured materials application and innovation transfer (14), ISSN 1313-8995, 2014) we studied reduced graphene oxide (RGO)/SiO2 composite material by adding a small amount of RGO to silica in order to avoid the aggregation process and to solve the problems connected with the exfoliation and distribution of the sheets inside the composites. But from a practical point we needed to study the effect of high amounts of RGO on the composites at different temperatures. The purpose of this investigation is to study the effect of RGO on phase transformations of the composites heated at 200, 400 and 800 °C. The sol-Gel method was used to obtain the RGO/SiO2 composite by mixing high amounts of RGO with tetraethyl orthosilicate (TEOS). Data are presented for the transformation of the nanocomposites with increasing temperature in air atmosphere. RGO nanosheets were prepared by chemical exfoliation of purified natural graphite using the Hummers and Offeman method (Hummers WS, Offeman RE, J Am Chem Soc 80:1339, 1958) to obtain graphite oxide. Then the material was exfoliated to reduced graphene nanosheets by ultrasonication and reduction process using sodium borohydride (NaBH4). Characterization of the material was performed by X-ray powder diffraction (XRD), infrared (IR) spectroscopy and scanning electron microscopy (SEM) analysis. In our previous studies we found that all samples with small amounts of RGO are amorphous up to 800 °C. By increasing the amount of RGO (20 %) crystal phases appear at 200, 400 and 800 °C. The carbon phases disappear above 400 °C and cristobalite is found at 800 °C. From the IR spectra it was established that the band related to Si-OH vibration is converted to a small shoulder at 400 °C, and the bands corresponding to vibrations of water molecules around 3,448 and 1,635 cm−1 were drastically reduced by increasing the temperature. The dominant band at 1,099.2 cm−1 (800 °C) is connected with the stretching vibration of Si-O bonds in SiO4 tetrahedrons. SEM images of RGO/SiO2 nanocomposites present randomly aggregated stacks of small sheets imbedded in an amorphous matrix.

Ferromagnetic glass–crystalline materials were produced by sintering of glasses from the systems Bi 2O3–B2O3–MnO and crystalline phase La0.6Sr0.4MnO3. The appropriate preparation procedure was applied as follows: synthesis of the starting components, mixing, milling, pressing and sintering at selected temperatures. The steps of the technological scheme were controlled by X-ray diffraction and infrared spectroscopy. Small crystals with size in the order of 1–5 µm were detected by transmission electron microscopy observations [TEM] after heath treatment. The magnetic properties were studied by a vibrating sample magnetometer [VSM] and the Curie temperature was detected at 353 K. The presence of a narrow hysteresis loop proves the ferromagnetic properties of the materials.  2003 Elsevier SAS. All rights reserved.