Bacterial polymers as materials for the development of micro/nanoparticles

Bacterial polysaccharides and polyhydroxyalkanoates present physical and chemical characteristics that impart them diverse functional properties, including the ability to produce structures from nano- to macroscale (e.g., spheres, capsules, beads). Such structures may be specially designed to fulfill the requirements of specific applications in different areas, either alone or conjugated with other polymers by means of ionic interactions, hydrogen bonding, or chemical reactions. The interest on using such biomaterials has been increasing due to their unique functional properties, nontoxicity, biodegradability, and biocompatibility. The fields of application of bacterial polymers-based structures include drug delivery, biomedicine, food products, environment, and agriculture, among others.     

Effect of self-etching dual-curing universal adhesive system application on bond strength of dentin resinous liners dentin

Purpose: The aim of this study was to evaluate the influence of previous application of an adhesive system on bond strength of resinous liner materials to dentin. Methods: Ninety bovine incisors crowns had a 6 × 6 mm area of dentin exposed, with minimum of 2 mm thickness. They were embedded in acrylic resin, and the dentin was polished with P600 SiC sandpaper for 30 s to standardize the smear layer. The specimens were divided into 6 groups (n = 15) according to the application or not of a self-etching system (Futurabond U – Voco) and the type of resinous liner used: A+Ionoseal (adhesive and Ionoseal – Voco); Ionoseal (Ionoseal only); A+Vitrebond (adhesive and Vitrebond – 3M/ESPE); Vitrebond (Vitrebond only); A+Ionosit (adhesive and Ionosit – DMG) and Ionosit (Ionosit only). Adhesives were used following manufacturer’s instructions, and the liner materials were applied inside a 2-mm-depth matrix and light-cured for 20 s. The bond strength was measured by microtensile test, using a universal testing machine with a cross-speed of 1 mm/min. Data were analyzed using one-way ANOVA and Tukey’s test (p < 0.05). Results: The adhesive system application increased bond strength of all liners tested. Ionoseal presented the highest bond strength when the adhesive system was used and exhibited similar performance to Vitrebond without adhesive. Ionosit without adhesive showed the smallest bond strength compared with the other liners tested. Conclusion: The application of an adhesive system prior to the use of the resinous liners improved the bond strength to dentin and should be preconized.     

Processing and characterization of porous titanium for implants by using NaCl as space holder

Porous samples of commercially pure titanium (CP Ti) were fabricated by using sodium chloride (NaCl) as space-holder with percentages between 40 and 70 vol%. The dissolution of NaCl in distilled water, the structural integrity of samples and the reproducibility of the procedure were studied as a step prior to sintering. All these parameters were evaluated in terms of the compaction pressure, temperature and agitation of water, and dissolution time. The characterization of samples included density, porosity and dynamic Young's modulus. The results indicate that the most efficient lixiviation, according to the desired balance of properties, was by immersion in hot water, without agitation and for prolonged cycles of immersion time.     

Microstructural Evolution of HSLA ISO 3183 X80M (API 5L X80) Friction Stir Welded Joints

Evaluation was made of friction stir welded joints, identifying conditions that resulted in satisfactory welded joints free from defects and with microstructural characteristics that provided good mechanical properties. Microstructural characterization and cooling curve analysis of the joints with lower and higher heat inputs evidenced deformation below and above the non-recrystallization temperature (T_nr) and dynamic recrystallization during microstructural evolution. Microscopy analyses showed acicular ferrite, bainitic ferrite, and coalesced bainite microstructures in the stir zone of the cold weld (lower heat input), while the stir zone of the hot weld (higher heat input) contained bainitic ferrite, acicular ferrite, coalesced bainite, martensite, and dispersed carbides. Granular bainite and dispersed carbides were observed in all the heat affected zones. Analysis of the microstructural transformations, together with the thermal history of the joints, showed that the variable that had the greatest influence on the morphology of the bainite (granular bainite/bainitic ferrite) was the deformation temperature.     

Development of Novel DNA Cleavage Systems Based on Copper Complexes. Synthesis and Characterisation of Cu(II) Complexes of Hydroxyflavones

Copper(II) complexes of several hydroxyflavones were prepared and characterised through their physico-chemical properties. The nuclease activity of three synthesised complexes is reported. These copper(II) complexes present more nuclease activity than the ligands and the copper(II) ion.     

Ionic liquid crystals from β-diketonyl containing pyridinium cations and tetrachlorozincate anions

In this work, an approach towards ionic liquid crystals is strategically designed. A pyridine group has been attached to an 1,3-diketone containing an alkyloxyphenyl R substituent (R = C₆H₄OC_nH_2n+1; n = 10–18) and protonated with hydrochloric acid towards the formation of the chloride salts of 2-[3-(4-n-alkyloxyphenyl)propane-1,3-dion-1-yl]pyridinium cations [OO^R(n)py]Cl (I), which have been proved to be non-mesomorphic. Reaction of these organic–inorganic compounds (I) with ZnCl₂ yields to the ionic liquid crystals of the type bis{2-[3-(4-n-alkyloxyphenyl)propane-1,3-dion-1-yl]pyridinium}tetrachlorozincate [OO^R(n)py]₂[ZnCl₄] (II).The crystalline structure of compounds [OO^R(12)py]Cl and [OO^R(10)py]₂[ZnCl₄] as representative examples of both kinds of salts have been solved and discussed. Both compounds exhibit layered structures containing cationic and anionic sublayers. In addition for the tetrachlorozincate salt [OO^R(16)py]₂[ZnCl₄] structural relationships between the mesophases and the crystalline phase are proposed on the basis of the variable-temperature small-angle X-ray diffraction studies.     

Polycyclic N-benzamido imides with potent activity against vaccinia virus

The synthesis and antiviral activity of a series of novel polycyclic analogues of the orthopoxvirus egress inhibitor tecovirimat (ST‐246) is presented. Several of these compounds display sub‐micromolar activity against vaccinia virus, and were more potent than cidofovir (CDV). The more active compounds were about 10‐fold more active than CDV, with minimum cytotoxic concentrations above 100 μM . Chemical manipulations of the two carbon–carbon double bonds present in the compounds were carried out to further explore the structure–activity relationships of these new polycyclic imides. Hydrogenation of the two carbon–carbon double bonds decreases antiviral activity, whereas either cyclopropanation or epoxidation of the double bonds fully eliminates the antiviral activity.