Fabrication and Application of Halloysite Nanotube-Embedded Photocatalytic Nanofibers with Antibacterial Properties.

With decreasing indoor air quality, increased time spent at indoors, and especially with the COVID-19 pandemic, the development of new materials for bacteria and viruses has become even more important. Less material consumption due to the electrospinning process, the easy availability/affordability of the halloysite nanotube (HNT), and the antibacterial effect of both TiO2 and ZnO nanoparticles make the study even more interesting. HNTs have attracted research attention in recent years due to their low cost, high mechanical strength, natural and environmentally friendly structure, and non-toxicity to human health and ecosystem. In this study, HNT-embedded composite nanofiber filters were fabricated as filter materials using the electrospinning method. Photocatalysts (TiO2 and ZnO) were incorporated into the composite nanofibers by the electrospraying method. The results showed that the combination of both HNT/TiO2 and HNT/ZnO additives was successfully integrated into the filter structure. The effect of embedding the HNT and spraying photocatalysts enables the fabrication of composite filters with lower pressure drop, high filtration efficiency, improved mechanical properties, and high antibacterial properties against Escherichia coli, making the nanofibers suitable and promising for face masks and air filter materials.

Thermodynamically designed target-specific DNA probe as an electrochemical hybridization biosensor.

Applications of molecular techniques to elucidate identity or function using biomarkers still remain highly empirical and biosensors are no exception. In the present study, target-specific oligonucleotide probes for E. coli K12 were designed thermodynamically and applied in an electrochemical DNA biosensor setup. Biosensor was prepared by immobilization of a stem-loop structured probe, modified with a thiol functional group at its 5' end and a biotin molecule at its 3' end, on a gold electrode through self-assembly. Mercaptopropionic acid (MPA) was used to optimize the surface probe density of the electrode. Hybridization between the immobilized probe and the target DNA was detected via the electrochemical response of streptavidin-horseradish peroxidase in the presence of the substrate. The amperometric response showed a linear relationship with the target DNA concentration, ranging from 10 and 400 nM, with a correlation coefficient of 0.989. High selectivity and good repeatability of the biosensor showed that the thermodynamic approach to oligonucleotide probe design can be used in development of electrochemical DNA biosensors.

Determination of the effect of proteoliposome concentration on Aquaporin Z incorporated nanofiltration membranes.

We report on the fabrication of AqpZ immobilized flat sheet membranes. The effects of interfacial polymerization conditions as well as proteoliposome concentration were evaluated. Commercial AqpZ were used as positive control for cloned AqpZ. Specific permeate flux of membranes at higher proteoliposome concentrations increased up to 25 times higher than thin film composite membranes; however; MgSO4 rejection is lowered almost to 1.5%. FTIR and SEM confirm immobilization of proteoliposomes. Thermal analysis showed that increasing proteoliposome concentration has no positive effect on the incorporation of proteoliposomes into polyamide structures. On the contrary, at lower proteoliposome concentrations, incorporation of proteoliposomes was found better. When combined membrane performances were compared in terms of specific permeate flux; MgSO4 and humic rejection and flux recovery after humic acid filtration, the performance of cloned AqpZ incorporated membranes (having 0.1 mg/mL proteoliposome concentration and polyamide formed with 2 min piperazine reaction time) improved 1.7 times regarding TFC membranes. According to the results, increasing proteoliposome concentration did not improve nanofiltration membrane performance. On the contrary, lower proteoliposome concentrations were found to be more effective in increasing membrane performance.

Poly(glycidyl methacrylate-co-3-thienylmethylmethacrylate) as an immobilization matrix for microbial glycerol biosensing based on Gluconobacter oxydans.

A commercial strain of Gluconobacter oxydans together with a new co-polymer Poly(glycidyl methacrylate-co-3-thienylmethylmethacrylate) (Poly(GMA-co-MTM)), which provides effective immobilization in the continuous flow system, was used in the sensor design. By taking the advantages of the nano-technology, carbon nanotubes (CNTs) were also added to the cell film and the sensitivity of the sensor was increased about 15 times. During the glycerol analysis in the continuous system, it was shown that composite film was not removed from the electrode surface and film elements were not washed out from the system. Glycerol analyses were performed by using batch loaded continuously flow cell at different flow rates of 1, 2, 4, and 6mL/min. The linear range was found as 2-100mM with the detection limit (LOD) of 0.057mM according to S/N=3. The calibration graphs were obtained for Poly(GMA-co-MTM)/G. oxydans and Poly(GMA-co-MTM)/CNT/G. oxydans biofilm electrodes in FIA mode, and sensitivities were found to be 1.50nA/mM and 19.13nA/mM, respectively. In this study, Poly(GMA-co-MTM) was used for the first time as a microbial matrix and was shown to be an effective immobilization agent.