The dissolution of monosodium urate monohydrate crystals: formulation of a biocompatible buffer solution with potential use in the treatment of gouty arthropathies

The dissolving abilities (DAs) of several aqueous media for microcrystalline monosodium urate monohydrate (MSU, NaC5N4O3H3·H2O) have been investigated using UV spectrophotometry for quantitative analytical determinations and X-ray diffraction, scanning electron microscopy and polarized light optical microscopy to assess structural aspects. High DAs were found for a buffer labeled TMT which contains tris(hydroxymethyl)aminomethane (TRIS), tris(hydroxymethyl)aminomethane hydrochloride (TRIS·HCl), D-mannitol (MAN) and taurine (TAU) and gave DA30=1298(5) mg/L for synthetic MSU after 30 min incubation at 37°C and pH 7.4, most of the dissolution taking place within the first 5-10 min. Semiempirical molecular modelling techniques (ZINDO/1) show a favorable energy balance for the formation of a TRIS-urate-TRIS adduct which might explain the high DA values. Buffers containing linear or dendrimeric polyamines gave DA values which suggest that complex formation toward sodium cations is less important. An ex vivo MSU sample was found to have a significantly lower DA value (DA30=1124(5) mg/L in TMT) as well as a lower crystallinity than its synthetic counterpart, possibly related to the presence of a non-crystalline impurity such as endogenous proteins. Cytotoxicity tests based on the MTT assay were used to check the biocompatibility of the TMT buffer and showed only moderate cell mortality after 24 h contact with the buffer solution

Bioactive glass fiber/polymeric composite as a bone bonding biomaterial

We investigated the concept of a bioactive composite as a femoral hip implant material with the objective of providing both early and long-lasting fixation between the implant and bone tissue. Glass fibers were designed specifically for the application as a fixation vehicle for the composite femoral hip prosthesis. The flexible fibers were amorphous and the tensile strength of the glass fibers was ten times stronger than that of bulk bioactive glass. In vitro surface reactions of the glass fibers resulted in the formation of hydroxycarbonate apatite, indicative of bioactivity in vivo. When the fibers were combined with a polysulfone matrix to form a composite, the composite developed a calcium phosphate surface layer after immersion in a protein-free simulated body fluid. In a protein-containing simulated blood plasma solution, the kinetics of reaction layer formation were slowed, however, eventual formation of a calcium phosphate surface layer was achieved. Bioactive glass fiber/polysulfone composites were implanted in the femoral cortex of the rabbit for six weeks. The interfacial bond strength between the implants and bone was significantly higher than that of all-polysulfone control implants and in the range of coatings which are used clinically. Histologically, bioactive glass fibers at the composite/bone tissue interface resorbed to varying degrees and were replaced by calcified tissue. Finite element models of a femoral hip component in a femur were used to numerically analyze the contribution of degree of fixation and material modulus on cortical bone strains in the proximal medial region of the femur. Strain transfer to the proximal medial cortex was optimized using a low modulus composite material in combination with a proximal third, circumferential bond between the implant and bone. These results were consistent for the case of primary as well as revision hip arthroplasty. We have shown that a bioactive glass fiber composite can provide fixation to bone tissue in a non-load bearing situation for early periods of implantation. Further, the strain patterns which could be achieved by combining a low modulus material with optimized degree of fixation may reduce the severity of adverse bone tissue remodeling about a femoral hip prosthesis

Conversion of CO2 to fuels

This article presents the state of the art and perspectives in the conversion of CO2 into energy products, implementing a Carbon Cyclic Economy strategy. Two conditions are essential for the reduction of CO2 using technologies on stream: (1) Energy necessary for CO2 reduction must come from C-free perennial energy sources (Solar, Wind, Hydro, Geothermal-SWHG), and (2) H2 must be produced from water using SWGH energy. In most innovative systems, hydrogen is not produced, and CO2 and water are co-processed to afford energy-products and oxygen, mimicking natural processes. A variety of products are targeted, from C1 species (CO, CH4, CH3OH) to C2 þ products that may be produced on a large scale. Several technologies can be applied for such conversion

Stepping toward the carbon circular economy (CCE): Integration of solar chemistry and biosystems for an effective CO2 conversion into added value chemicals and fuels

The substitution of fossil-C is an urgent task for both the scarcity of resources and stopping the emission of green-house gases, (GHGs) that impact the climate of our planet. The transfer to the atmosphere of heat, due to the inefficiency of conversion of chemical energy into other forms of energy, and CO2 is also causing the increase of atmospheric water vapor, a stronger and more abundant greenhouse gas than CO2: all actors (heat, CO2 and H2Ov) concur to increase the temperature of the planet. Partial substitution of fossil-C can be achieved by using biomass, but that alone cannot produce all the energy and goods necessary for our society. Carbon will still be present in our future, but the solution to our problems is integrating solar chemistry and biotechnologies for using atmospheric CO2. This chapter, after an introduction to Carbon Circular Economy-CCE and CO2 utilization in Chemical Industry, considers the various options available of using solar energy for CO2 conversion into energy vectors that may allow to continue to use the existing infrastructures in transport and every-day life. Two options are considered: (i) solar-based water splitting and use of H2 for chemo-catalytic CO2 conversion using known processes, or (ii) photo-co-processing of water and CO2 to afford energy products and chemicals without H2 generation, a most innovative technology. The state of the art is provided and barriers to overcome for a large-scale exploitation of the two options are highlighted. The contribution to fossil-C substitution that may come from integration of solar chemistry with material science and biotechnology concludes this chapter

Opto-Electronic Characterization of Photocatalysts Based on p,n-Junction Ternary and Quaternary Mixed Oxides Semiconductors (Cu2O-In2O3 and Cu2O-In2O3-TiO2)

Semiconductor materials are the basis of electronic devices employed in the communication and media industry. In the present work, we report the synthesis and characterization of mixed metal oxides (MOs) as p,n-junction photocatalysts, and demonstrate the correlation between the preparation technique and the properties of the materials. Solid-state UV-visible diffuse reflectance spectroscopy (UV-VIS DRS) allowed for the determination of the light absorption properties and the optical energy gap. X-ray photoelectron spectroscopy (XPS) allowed for the determination of the surface speciation and composition and for the determination of the valence band edge. The opto-electronic behavior was evaluated measuring the photocurrent generated after absorption of chopped visible light in a 3-electrode cell. Scanning electron microscopy (SEM) measurements allowed for auxiliary characterization of size and morphology, showing the formation of composites for the ternary Cu2O-In2O3 p,n-mixed oxide, and even more for the quaternary Cu2O-In2O3-TiO2 MO. Light absorption spectra and photocurrent-time curves mainly depend upon the composition of MOs, while the optical energy gap and defective absorption tail are closely related to the preparation methodology, time and thermal treatment. Qualitative electronic band structures of semiconductors are also presented

Opto-Electronic Characterization of Photocatalysts Based on <i>p</i>,<i>n</i>-Junction Ternary and Quaternary Mixed Oxides Semiconductors (Cu₂O-In₂O₃ and Cu₂O-In₂O₃-TiO₂)

Semiconductor materials are the basis of electronic devices employed in the communication and media industry. In the present work, we report the synthesis and characterization of mixed metal oxides (MOs) as p,n-junction photocatalysts, and demonstrate the correlation between the preparation technique and the properties of the materials. Solid-state UV-visible diffuse reflectance spectroscopy (UV-VIS DRS) allowed for the determination of the light absorption properties and the optical energy gap. X-ray photoelectron spectroscopy (XPS) allowed for the determination of the surface speciation and composition and for the determination of the valence band edge. The opto-electronic behavior was evaluated measuring the photocurrent generated after absorption of chopped visible light in a 3-electrode cell. Scanning electron microscopy (SEM) measurements allowed for auxiliary characterization of size and morphology, showing the formation of composites for the ternary Cu2O-In2O3 p,n-mixed oxide, and even more for the quaternary Cu2O-In2O3-TiO2 MO. Light absorption spectra and photocurrent-time curves mainly depend upon the composition of MOs, while the optical energy gap and defective absorption tail are closely related to the preparation methodology, time and thermal treatment. Qualitative electronic band structures of semiconductors are also presented