Development of a solid‐phase microextraction LC–MS/MS method for determination of oxidative stress biomarkers in biofluids

Recently the connection between oxidative stress and various diseases, including cancer and Alzheimer's, attracts notice as a pathway suitable for diagnostic purposes. 8‐Oxo‐deoxyguanosine and 8‐oxo‐deoxyadenosine produced from the interaction of reactive oxygen species with DNA become prominent as biomarkers. Several methods have been developed for their determination in biofluids, including solid‐phase extraction and enzyme‐linked immunosorbent assays. However, still, there is a need for reliable and fast analytical methods. In this context, solid‐phase microextraction offers many advantages such as flexibility in geometry and applicable sample volume, as well as high adaptability to high‐throughput sampling. In this study, a solid‐phase microextraction method was developed for the determination of 8‐oxo‐deoxyguanosine and 8‐oxo‐deoxyadenosine in biofluids. The extractive phase of solid‐phase microextraction consisted of hydrophilic–lipophilic balanced polymeric particles. In order to develop a solid‐phase microextraction method suitable for the determination of the analytes in saliva and urine, several parameters, including desorption solvent, desorption time, sample pH, and ionic strength, were scrutinized. Analytical figures of merit indicated that the developed method provides reasonable interday and intraday precisions (<15% in both biofluids) with acceptable accuracy. The method provides a limit of quantification for both biomarkers at 5.0 and 10.0 ng/mL levels in saliva and urine matrices, respectively.     

Thermal analysis,crystal structure and magnetic properties of Cr-doped Ni–Mn–Sn high-temperature magnetic shape memory alloys

The superiority of NiMnSn alloy on NiMnGa alloy is far ahead in term of some physical characteristics, and therefore, the development of this alloy group is very important. In this work, Ni₅₀Mn_45−xSn₅Cr_x magnetic shape memory alloys were produced for x = 0, 4, 6, 10 and 12. Thermal analysis was performed on produced alloys in a wide range (200–1000 °C) by using differential scanning calorimetry, thermogravimetric and differential thermal analysis. According to the thermal analysis results, the austenite ↔ martensite transformation temperatures of the NiMnSn alloy decreased with increasing chromium content. Furthermore, the increase in the chromium ratio caused single-phase transformation due to the multiple phase transformation that was observed in the NiMnSn alloy. In addition, the crystal structure and microstructure analyses of the alloys were determined by using X-ray diffraction and scanning electron microscopy–energy-dispersive X-ray spectroscopy. In all cases, martensite and gamma phase were encountered and the gamma phase ratio was found to be increased by chromium addition. The magnetization characteristics were studied by using physical properties measurement systems device, and it was found that the alloys have a considerably small response to magnetic flux.

     

The impact of [1,2,5]chalcogenazolo[3,4-f]-benzo[1,2,3]triazole structure on the optoelectronic properties of conjugated polymers

Two novel conjugated near-infrared (NIR) absorbing donor–acceptor type copolymers comprising benzodithiophene as the donor and [1,2,5]chalcogenazolo[3,4-f]-benzo[1,2,3]triazole derivatives as the acceptors, spaced with thiophene as the π-bridge, were designed and synthesized via Stille polycondensation reaction. The effect of acceptor strength on optoelectronic properties was targeted and investigated. Branched alkyl chains (the extended 2-octyl-1-dodecyl alkyl chain;  C₈C₁₂) were introduced to 5H-[1,2,3]triazolo[4′,5′:4,5]benzo[1,2-c][1,2,5]thiadiazole and 5H-[1,2,3]triazolo[4′,5′:4,5]benzo[1,2-c][1,2,5]selenadiazole for enhanced solubility of polymers which ease the processability hence device constructions. The strongly electron-withdrawing units lead to a substantial change in the absorption properties via promotion of the intramolecular charge transfer band alongside the π–π* transition. The resultant soluble polymers were characterized via cyclic voltammetry to determine highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels as −5.00 and −3.92 eV for PSBT and −4.86 and −4.04 eV for PSeBT, respectively. Electronic band gaps of the copolymers were calculated as 1.08 eV for PSBT and 0.82 eV for PSeBT, respectively. NIR absorbing copolymers were used to construct electrochromic devices.     

B2O3 reinforced polylactic acid/thermoplastic polyethylene glycol shape memory composites

Recently, there has been a great demand for boron-containing compounds (BCCs) with unique biological properties. The demand for the use of these compounds not alone but as additives in composite materials is increasing day by day. In this study, the effect of adding B₂O₃ compound to the blend of PLA and PEG polymers, which is an important biocompatible shape memory polymer, was investigated. In order to examine the effect of increasing B₂O₃ additive on the thermal properties of PLA-PEG blend, it was determined by using a Differential Scanning Calorimetry (DSC) and thermogravimetric analyzer (TGA), and it was seen that while the melting temperature of PEG decreased, the melting temperature of PLA increased. In addition, when the thermal stability of the composites was examined, increasing of thermal stability was observed with the addition of B₂O₃ and a three-step degradation occurred. It was determined that the B₂O₃/PLA-PEG composite was homogeneous by taking X-ray measurements and SEM measurements. The antimicrobial property of the PLA-PEG blend improved with the increasing B₂O₃ contribution were observed from the antimicrobial activity measurements of the composite against 4 different bacteria. However, it was determined that the PLA-PEG blend preserved its shape memory effect with increasing diboron trioxide contribution.