Improved antifouling potential of polyether sulfone polymeric membrane containing silver nanoparticles: self-cleaning membranes

Recent Advances on the Fabrication of Antifouling Phase-Inversion Membranes by Physical Blending Modification Method

Membrane technology is an essential tool for water treatment and biomedical applications. Despite their extensive use in these fields, polymeric-based membranes still face several challenges, including instability, low mechanical strength, and propensity to fouling. The latter point has attracted the attention of numerous teams worldwide developing antifouling materials for membranes and interfaces. A convenient method to prepare antifouling membranes is via physical blending (or simply blending), which is a one-step method that consists of mixing the main matrix polymer and the antifouling material prior to casting and film formation by a phase inversion process. This review focuses on the recent development (past 10 years) of antifouling membranes via this method and uses different phase-inversion processes including liquid-induced phase separation, vapor induced phase separation, and thermally induced phase separation. Antifouling materials used in these recent studies including polymers, metals, ceramics, and carbon-based and porous nanomaterials are also surveyed. Furthermore, the assessment of antifouling properties and performances are extensively summarized. Finally, we conclude this review with a list of technical and scientific challenges that still need to be overcome to improve the functional properties and widen the range of applications of antifouling membranes prepared by blending modification.

Enhancing efficacy of existing antibacterials against selected multiple drug resistant bacteria using cinnamic acid-coated magnetic iron oxide and mesoporous silica nanoparticles

Developing new antibacterial drugs by using traditional ways is insufficient to meet existing challenges; hence, new strategies in the field of antibacterial discovery are necessary. An alternative strategy is to improve the efficacy of currently available antibiotics. Herein, the antibacterial efficacy of drugs (Cefixime, Sulfamethoxazole, and Moxifloxacin) and drug-loaded cinnamic acid-coated magnetic iron oxide and mesoporous silica nanoparticles (NPs) was elucidated versus Gram-negative bacteria (Pseudomonas aeruginosa, Klebsiella pneumoniae, neuropathogenic Escherichia coli K1 and Serratia marcescens) and Gram-positive bacteria (Methicillin-resistant Staphylococcus aureus (MRSA), Streptococcus pyogenes, Streptococcus pneumoniae, and Bacillus cereus). NPs were synthesized by co-precipitation and the Stöber method, and characterized by Fourier transform-infrared spectroscopy, Zetasizer, and Atomic force microscopy. Lactate dehydrogenase (LDH) assays were accomplished to determine drug cytotoxicity against human cells. Spherical NPs in the range of 118-362 nm were successfully synthesized. Antibacterial assays revealed that drugs conjugated with NPs portray enhanced bactericidal efficacies against multiple drug resistant bacteria compared to the drugs alone. Of note, Cefixime-conjugated NPs against Escherichia coli K1 and Methicillin- resistant Staphylococcus aureus, resulted in the complete eradication of all bacterial isolates tested at significantly lower concentrations compared to the antibiotics alone. Likewise, conjugation of Moxifloxacin resulted in the complete elimination of E. coli K1 and MRSA. Of note, nano-formulated drugs presented negligible cytotoxicity against human cells. These results depict potent, and enhanced efficacy of nano-formulated drugs against medically important bacteria and can be used as alternatives to current antibiotics. Future in vivo studies and clinical studies are warranted in prospective years to realize these expectations.

Unveiling the Potential Role of Nanozymes in Combating the COVID-19 Outbreak

The current coronavirus disease 2019 (COVID-19) outbreak is considered as one of the biggest public health challenges and medical emergencies of the century. A global health emergency demands an urgent development of rapid diagnostic tools and advanced therapeutics for the mitigation of COVID-19. To cope with the current crisis, nanotechnology offers a number of approaches based on abundance and versatile functioning. Despite major developments in early diagnostics and control of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), there is still a need to find effective nanomaterials with low cost, high stability and easy use. Nanozymes are nanomaterials with innate enzyme-like characteristics and exhibit great potential for various biomedical applications such as disease diagnosis and anti-viral agents. Overall the potential and contribution of nanozymes in the fight against SARS-CoV-2 infection i.e., rapid detection, inhibition of the virus at various stages, and effective vaccine development strategies, is not fully explored. This paper discusses the utility and potential of nanozymes from the perspective of COVID-19. Moreover, future research directions and potential applications of nanozymes are highlighted to overcome the challenges related to early diagnosis and therapeutics development for the SARS-CoV-2. We anticipate the current perspective will play an effective role in the existing response to the COVID-19 crisis.

Treatment Processes for Microbial Resistance Mitigation: The Technological Contribution to Tackle the Problem of Antibiotic Resistance

Advances generated in medicine, science, and technology have contributed to a better quality of life in recent years; however, antimicrobial resistance has also benefited from these advances, creating various environmental and health problems. Several determinants may explain the problem of antimicrobial resistance, such as wastewater treatment plants that represent a powerful agent for the promotion of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARG), and are an important factor in mitigating the problem. This article focuses on reviewing current technologies for ARB and ARG removal treatments, which include disinfection, constructed wetlands, advanced oxidation processes (AOP), anaerobic, aerobic, or combined treatments, and nanomaterial-based treatments. Some of these technologies are highly intensive, such as AOP; however, other technologies require long treatment times or high doses of oxidizing agents. From this review, it can be concluded that treatment technologies must be significantly enhanced before the environmental and heath problems associated with antimicrobial resistance can be effectively solved. In either case, it is necessary to achieve total removal of bacteria and genes to avoid the possibility of regrowth given by the favorable environmental conditions at treatment plant facilities.

Three-Dimensional Stable Cation-Exchange Membrane with Enhanced Mechanical, Electrochemical, and Antibacterial Performance by in Situ Synthesis of Silver Nanoparticles

In this study, a simple and facile approach was proposed to synthesize silver nanoparticles (AgNPs) loaded cation-exchange membranes (CEMs). A wide analytical study involving scanning electronic microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy was accomplished to corroborate that the in situ generated AgNPs were uniformly dispersed in the polymer matrix. In addition, as a result of the proposed synthesis strategy, the cross-linking structure inside the membrane was formed. The proper particle size and dispersibility of the AgNPs improved the mechanical properties of the membranes. Besides, the optimal AgNP-loaded CEM exhibited excellent bacterial killing activities against Gram-negative bacteria and showed a controlled improvement in the electrochemical performance of the prepared membranes. These effects were caused by the obtained distribution of AgNPs near ion-exchange groups that increased the aggregation of water molecules around them, improving the efficiency of ion transport due the formation of array broad ion-transport channels. The optimized CEM [sulfonated polysulfone (60SPSF)-C3#-Ag-2] exhibited an enhanced NaCl removal ratio of 67.5% with a high current efficiency (96.9%) and a low energy consumption (5.84 kWh kg^-1). The distance of the inhibition zone from the boundary of the membrane of SPSF-C3#-Ag-2 reached 4.8 mm. These results led us to suggest that the proposed synthesis strategy may have potential applications in the field of antibacterial and desalting ion-exchange membranes.

Polymer Concentration and Solvent Variation Correlation with the Morphology and Water Filtration Analysis of Polyether Sulfone Microfiltration Membrane

Microfiltration flat sheet membranes of polyether sulfone (PES) were fabricated by incorporating varying concentrations of polymer and investigated the influence of substituting solvents. The membranes were prepared via immersion precipitation method. Different solvents that included NMP (N-methyl-2-pyrrolidone), DMF (dimethylformamide), and THF (tetrahydrofuran) were used to analyse their effect on the performance and morphology of the prepared membranes. Two different coagulation bath temperatures were used to investigate the kinetics of membrane formation and subsequent effect on membrane performance. The maximum water flux of 141 ml/cm2.h was observed using 21% of PES concentration in NMP + THF cosolvent system. The highest tensile strength of 29.15 MPa was observed using membrane prepared with 21% PES concentration in NMP as solvent and coagulation bath temperature of 25°C. The highest hydraulic membrane resistance was reported for membrane prepared with 21% PES concentration in NMP as solvent. Moreover, the lowest contact angle of 67° was observed for membrane prepared with 15% of PES concentration in NMP as solvent with coagulation bath temperature of 28°C. Furthermore, the Hansen solubility parameter was used to study the effect on the thermodynamics of membrane formation and found to be in good correlation with experimental observation and approach in the present work.

Microcystis aeruginosa Synergistically Facilitate the Photocatalytic Degradation of Tetracycline Hydrochloride and Cr(VI) on PAN/TiO2/Ag Nanofiber Mats

Cyanobacterial blooms can cause serious damage to aquatic ecosystems. However, we have demonstrated that typical algae-blooming species Microcystis aeruginosa (M. aeruginosa) combined with photocatalysts could synergistically facilitate the photodecontamination of tetracycline hydrochloride (TC) and Cr(VI). In this study, for the first time, harmful algae were successfully converted into photoreactive bionano hybrid materials by immobilizing M. aeruginosa cells onto polyacrylonitrile (PAN)-TiO2/Ag hybrid nanofibers, and their photocatalytic activity was evaluated. The addition of M. aeruginosa significantly improved the photodecontamination, and the reaction rate constant (k) values of TC and Cr(VI) degradation by M. aeruginosa-PAN/TiO2/Ag nanofiber mats were 2.4 and 1.5-fold higher than that of bare PAN/TiO2/Ag nanofiber. Photoreaction caused damage to algae cells, but no microcystin was found that had been photodegraded simultaneously. The effects of various active species were also investigated, and the photodegradation mechanism was proposed. Recycling tests revealed that this flexible M. aeruginosa-PAN/TiO2/Ag hybrid mat had potential application in the removal of mixed organic and inorganic pollutants with high efficiency and without secondary pollutants. Thus, harmful algae blooms could serve as an efficient materials to remove toxic pollutants in a sustainable way under visible light irradiation.