Nanofiber applications in microbial fuel cells for enhanced energy generation: a mini review.

Microbial fuel cells (MFCs) represent simple devices that harness the metabolic activities of microorganisms to produce electrical energy from diverse sources such as organic waste and sustainable biomass. Because of their unique advantage to generate sustainable energy, through the employment of biodegradable and repurposed waste materials, the development of MFCs has garnered considerable interest. Critical elements are typically the electrodes and separator. This mini-review article presents a critical assessment of nanofiber technology used as electrodes and separators in MFCs to enhance energy generation. In particular, the review highlights the application of nanofiber webs in each part of MFCs including anodes, cathodes, and membranes and their influence on energy generation. The role of nanofiber technology in this regard is then analysed in detail, focusing on improved electron transfer rate, enhanced biofilm formation, and enhanced durability and stability. In addition, the challenges and opportunities associated with integrating nanofibers into MFCs are discussed, along with suggestions for future research in this field. Significant developments in MFCs over the past decade have led to a several-fold increase in achievable power density, yet further improvements in performance and the exploration of cost-effective materials remain promising areas for further advancement. This review demonstrates the great promise of nanofiber-based electrodes and separators in future applications of MFCs.

Hospitalizations after Renal Transplantation in Children: Risk Factors, Causes, and Outcomes.

INTRODUCTION: The aims of this study were to evaluate the frequency and causes of hospitalizations in the posttransplant period of children, investigate the risk factors, and evaluate the relationship between hospitalizations and renal prognosis in the long term. METHODS: We retrospectively reviewed the files of pediatric renal transplant patients, followed at least 6 months after kidney transplantation, in our center. Clinical information including age at transplantation, gender, primary disease, donor type, immuno-suppressive medication, hospitalization dates, and indications (infections and non-infectious) during follow-up period and graft outcomes was recorded. RESULTS: A total of 74 children (46 males) were followed up for a median of 54 months. Among them, 69 patients (93.2%) were hospitalized 446 times. The most common cause of hospitalizations was infections (314 times, 70%). Urinary tract infections were the most important cause followed by upper respiratory tract infections. Forty (54%) patients were hospitalized 132 times (29.5%) for non-infectious reasons. The most common non-infectious reason was nonspecific graft dysfunction (19 patients, 30 times), followed by rejection (17 patients, 27 times). Younger age, use of induction therapy, and having congenital anomalies of kidney and urinary tract (CAKUT) were found to be risk factors for increased hospitalization rates (p < 0.05). The number of hospitalizations was found to be negatively affecting the final glomerular filtration rate of transplant recipients (p: 0.04, r: -0.023). CONCLUSION: Patients with CAKUT, who received induction therapy, and small children were hospitalized more frequently after transplantation. Strategies to prevent hospitalizations will achieve a better graft prognosis.

An Investigation of the Constructional Design Components Affecting the Mechanical Response and Cellular Activity of Electrospun Vascular Grafts.

Cardiovascular disease is anticipated to remain the leading cause of death globally. Due to the current problems connected with using autologous arteries for bypass surgery, researchers are developing tissue-engineered vascular grafts (TEVGs). The major goal of vascular tissue engineering is to construct prostheses that closely resemble native blood vessels in terms of morphological, mechanical, and biological features so that these scaffolds can satisfy the functional requirements of the native tissue. In this setting, morphology and cellular investigation are usually prioritized, while mechanical qualities are generally addressed superficially. However, producing grafts with good mechanical properties similar to native vessels is crucial for enhancing the clinical performance of vascular grafts, exposing physiological forces, and preventing graft failure caused by intimal hyperplasia, thrombosis, aneurysm, blood leakage, and occlusion. The scaffold's design and composition play a significant role in determining its mechanical characteristics, including suturability, compliance, tensile strength, burst pressure, and blood permeability. Electrospun prostheses offer various models that can be customized to resemble the extracellular matrix. This review aims to provide a comprehensive and comparative review of recent studies on the mechanical properties of fibrous vascular grafts, emphasizing the influence of structural parameters on mechanical behavior. Additionally, this review provides an overview of permeability and cell growth in electrospun membranes for vascular grafts. This work intends to shed light on the design parameters required to maintain the mechanical stability of vascular grafts placed in the body to produce a temporary backbone and to be biodegraded when necessary, allowing an autologous vessel to take its place.

Chemical Cleaning Process of Polymeric Nanofibrous Membranes.

Membrane fouling is one of the most significant issues to overcome in membrane-based technologies as it causes a decrease in the membrane flux and increases operational costs. This study investigates the effect of common chemical cleaning agents on polymeric nanofibrous membranes (PNM) prepared by polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), and polyamide 6 (PA6) nanofibers. Common alkaline and acid membrane cleaners were selected as the chemical cleaning agents. Membrane surface morphology was investigated. The PAN PNM were selected and fouled by engine oil and then cleaned by the different chemical cleaning agents at various ratios. The SEM results indicated that the use of chemical agents had some effects on the surface of the nanofibrous membranes. Moreover, alkaline cleaning of the fouled membrane using the Triton X 100 surfactant showed a two to five times higher flux recovery than without using a surfactant. Among the tested chemical agents, the highest flux recovery rate was obtained by a binary solution of 5% sodium hydroxide + Triton for alkaline cleaning, and an individual solution of 1% citric acid for acidic cleaning. The results presented here provide one of the first investigations into the chemical cleaning of nanofiber membranes.

Electrospun Antibacterial Nanomaterials for Wound Dressings Applications.

Chronic wounds are caused by bacterial infections and create major healthcare discomforts; to overcome this issue, wound dressings with antibacterial properties are to be utilized. The requirements of antibacterial wound dressings cannot be fulfilled by traditional wound dressing materials. Hence, to improve and accelerate the process of wound healing, an antibacterial wound dressing is to be designed. Electrospun nanofibers offer a promising solution to the management of wound healing, and numerous options are available to load antibacterial compounds onto the nanofiber webs. This review gives us an overview of some recent advances of electrospun antibacterial nanomaterials used in wound dressings. First, we provide a brief overview of the electrospinning process of nanofibers in wound healing and later discuss electrospun fibers that have incorporated various antimicrobial agents to be used in wound dressings. In addition, we highlight the latest research and patents related to electrospun nanofibers in wound dressing. This review also aims to concentrate on the importance of nanofibers for wound dressing applications and discuss functionalized antibacterial nanofibers in wound dressing.

Fouling and Chemical Cleaning of Microfiltration Membranes: A Mini-Review.

Membrane fouling is one of the main drawbacks encountered during the practical application of membrane separation processes. Cleaning of a membrane is important to reduce fouling and improve membrane performance. Accordingly, an effective cleaning method is currently of crucial importance for membrane separation processes in water treatment. To clean the fouling and improve the overall efficiency of membranes, deep research on the cleaning procedures is needed. So far, physical, chemical, or combination techniques have been used for membrane cleaning. In the current work, we critically reviewed the fouling mechanisms affecting factors of fouling such as the size of particle or solute; membrane microstructure; the interactions between membrane, solute, and solvent; and porosity of the membrane and also examined cleaning methods of microfiltration (MF) membranes such as physical cleaning and chemical cleaning. Herein, we mainly focused on the chemical cleaning process. Factors affecting the chemical cleaning performance, including cleaning time, the concentration of chemical cleaning, and temperature of the cleaning process, were discussed in detail. This review is carried out to enable a better understanding of the membrane cleaning process for an effective membrane separation process.

Hydrophilic Surface-Modified PAN Nanofibrous Membranes for Efficient Oil-Water Emulsion Separation.

In order to protect the environment, it is important that oily industrial wastewater is degreased before discharging. Membrane filtration is generally preferred for separation of oily wastewater as it does not require any specialised chemical knowledge, and also for its ease of processing, energy efficiency and low maintenance costs. In the present work, hybrid polyacrylonitrile (PAN) nanofibrous membranes were developed for oily wastewater filtration. Membrane surface modification changed nitrile groups on the surface into carboxylic groups, which improve membrane wettability. Subsequently, TiO2 nanoparticles were grafted onto the modified membranes to increase flux and permeability. Following alkaline treatment (NaOH, KOH) of the hydrolysed PAN nanofibres, membrane water permeability increased two- to eight-fold, while TiO2 grafted membrane permeability increase two- to thirteen-fold, compared to unmodified membranes. TiO2 grafted membranes also displayed amphiphilic properties and a decrease in water contact angle from 78.86° to 0°. Our results indicate that modified PAN nanofibrous membranes represent a promising alternative for oily wastewater filtration.

The Clinical Characteristics of Pediatric Non-Infectious Uveitis in Two Tertiary Referral Centers in Turkey.

Purpose: To report the manifestations, patterns of disease, treatment strategies and outcomes in pediatric patients with noninfectious uveitis.Methods: Demographic information of 76 cases was recorded. Symptoms, anatomic location, laterality, visual acuity (VA), intraocular pressure, associated systemic diseases, therapeutic strategies, side effects, complications were reviewed.Results: Thirty-one patients were diagnosed as uveitis on routine surveillance because of underlying systemic disease. The most common anatomic location was intermediate uveitis (34.2%). Juvenile idiopathic arthritis (JIA) was the most common underlying systemic disease (25%). Glaucoma was the most common complication (7.7%). The patients with refractory uveitis received adalimumab (26.5%), infliximab (4.6%) and tocilizumab (3.1%). The mean first-year VA was between 20/32 and 20/20 in 116/140 eyes.Conclusion: Most pediatric noninfectious uveitis cases have bilateral intermediate uveitis. JIA was the most common systemic association. The first-year VA was good in most eyes which may be due to early use of corticosteroid-sparing agents.

Electron-Beam Irradiation of the PLLA/CMS/ß-TCP Composite Nanofibers Obtained by Electrospinning.

Nanofibrous materials produced by electrospinning processes have potential advantages in tissue engineering because of their biocompatibility, biodegradability, biomimetic architecture, and excellent mechanical properties. The aim of the current work is to study the influence of the electron beam on the poly L-lactide acid/ carboxy-methyl starch/ß-tricalcium phosphate (PLLA/CMS/ß-TCP) composite nanofibers for potential applications as bone-tissue scaffolds. The composite nanofibers were prepared by electrospinning in the combination of 5% v/v carboxy-methyl starch (CMS) and 0.25 wt% of ß-TCP with the PLLA as a matrix component. The composites nanofibers were exposed under 5, 30, and 100 kGy of irradiation dose. The electron-beam irradiation showed no morphological damage to the fibers, and slight reduction in the water-contact angle and mechanical strength at the higher-irradiation doses. The chain scission was found to be a dominant effect; the higher doses of electron-beam irradiation thus increased the in vitro degradation rate of the composite nanofibers. The chemical interaction due to irradiation was indicated by the Fourier transform infrared (FTIR) spectrum and thermal behavior was investigated by a differential scanning calorimeter (DSC). The results showed that the electron-beam-induced poly L-lactide acid/carboxy-methyl starch/ß-tricalcium phosphate (PLLA/CMS/ß-TCP) composite nanofibers may have great potential for bone-tissue engineering.

A Review on Membrane Technology and Chemical Surface Modification for the Oily Wastewater Treatment.

Cleaning of wastewater for the environment is an emerging issue for the living organism. The separation of oily wastewater, especially emulsified mixtures, is quite challenged due to a large amount of wastewater produced in daily life. In this review, the membrane technology for oily wastewater treatment is presented. In the first part, the global membrane market, the oil spill accidents and their results are discussed. In the second and third parts, the source of oily wastewater and conventional treatment methods are represented. Among all methods, membrane technology is considered the most efficient method in terms of high separation performance and easy to operation process. In the fourth part, we provide an overview of membrane technology, fouling problem, and how to improve the self-cleaning surface using functional groups for effectively treating oily wastewater. The recent development of surface-modified membranes for oily wastewater separation is investigated. It is believed that this review will promote understanding of membrane technology and the development of surface modification strategies for anti-fouling membranes.

Fabrication and Characterization of Carboxymethyl Starch/Poly(l-Lactide) Acid/ß-Tricalcium Phosphate Composite Nanofibers via Electrospinning.

A natural polymer of carboxymethyl starch (CMS) was used in combination with the inorganic mineral of ß-Tricalcium Phosphate (ß-TCP) and Poly l-lactide (PLLA) to prepare composite nanofibers with the potential to be used as a biomedical membrane. ß-TCP contents varied in the range of 0.25% to 1% in the composition of PLLA and CMS. A mixed composition of these organic and inorganic materials was electro-spun to produce composite nanofibers. Morphological investigation indicated that smooth and uniform nanofibers could be produced via this technique. The average of the nanofiber diameters was slightly increased from 190 to 265 nm with the ß-TCP content but some agglomeration of particles began to impede in the fiber at a higher content of ß-TCP. It was observed that the fibers were damaged at a higher content of ß-TCP nanoparticles. With the presence of higher ß-TCP, the wettability of the PLLA was also improved, as indicated by the water contact angle measurement from 127.3° to 118°. The crystallization in the composite decreased, as shown in the changes in glass transition (Tg) and melting temperature (Tm) by differential scanning calorimeter (DSC) and X-ray diffraction analysis. Increases in ß-TCP contributed to weaker mechanical strength, from 8.5 to 5.7 MPa, due to imperfect fiber structure.

Polyvinyl Butyral (PVB) Nanofiber/Nanoparticle-Covered Yarns for Antibacterial Textile Surfaces.

In this study, nanoparticle-incorporated nanofiber-covered yarns were prepared using a custom-made needle-free electrospinning system. The ultimate goal of this work was to prepare functional nanofibrous surfaces with antibacterial properties and realize high-speed production. As antibacterial agents, we used various amounts of copper oxide (CuO) and vanadium (V) oxide (V2O5) nanoparticles (NPs). Three yarn preparation speeds (100 m/min, 150 m/min, and 200 m/min) were used for the nanofiber-covered yarn. The results indicate a relationship between the yarn speed, quantity of NPs, and antibacterial efficiency of the material. We found a higher yarn speed to be associated with a lower reduction in bacteria. NP-loaded nanofiber yarns were proven to have excellent antibacterial properties against Gram-negative Escherichia coli (E. coli). CuO exhibited a greater inhibition and bactericidal effect against E. coli than V2O5. In brief, the studied samples are good candidates for use in antibacterial textile surface applications, such as wastewater filtration. As greater attention is being drawn to this field, this work provides new insights regarding the antibacterial textile surfaces of nanofiber-covered yarns.

Surface-Modified Nanofibrous PVDF Membranes for Liquid Separation Technology.

Preparing easily scaled up, cost-effective, and recyclable membranes for separation technology is challenging. In the present study, a unique and new type of modified polyvinylidene fluoride (PVDF) nanofibrous membrane was prepared for the separation of oil-water emulsions. Surface modification was done in two steps. In the first step, dehydrofluorination of PVDF membranes was done using an alkaline solution. After the first step, oil removal and permeability of the membranes were dramatically improved. In the second step, TiO2 nanoparticles were grafted onto the surface of the membranes. After adding TiO2 nanoparticles, membranes exhibited outstanding anti-fouling and self-cleaning performance. The as-prepared membranes can be of great use in new green separation technology and have great potential to deal with the separation of oil-water emulsions in the near future.

Influence of Electrospinning Parameters on the Hydrophilicity of Electrospun Polycaprolactone Nanofibres.

In the present study, PCL (polycaprolactone) nanofibres were produced by the electrospinning method. The use of PCL electrospun biopolymer in biomedical applications has attracted considerable interest due to its chemical resistance, biodegradability, biocompatibility, and non-toxic characteristics. However, the hydrophobic nature of PCL polymer restricts the useage of PCL nanofibres for the cell adhesion and absorption. A hydrophilic and biocompatible PCL electrospun mat with a low water contact angle is an attractive strategy for development in tissue engineering and wound dressing. In this study, we demonstrate a feasible and simple method to produce hydrophilic PCL nanofibres for possible application in wound dressing. Chloroform/ethanol (EtOH) and chloroform/dimethylformamide (DMF) mixtures were used as two different solvent systems. The impact of the polymeric solution concentration, applied voltage, and solvent mixtures on the fibre surface morphology and water contact angle was investigated. Consequently, bead structures were observed at low concentrations but disappeared with increases in the concentration. It was observed that the size of beads decreased and the diameter of fibres increased with increasing voltage. The wettability of the webs changed from hydrophobic to hydrophilic with changes of the polymer concentration. The contact angle of the nanofibre mats decreased in both solvent systems as the concentration increased. The results showed that the lowest contact angle was obtained in 24% wt. PCL+chloroform/EtOH solution and was 68°. The highest contact angle was obtained in 4% wt. PCL+chloroform/EtOH solution and was 112°. Using this method, the surface hydrophilicity of the PCL nanofibres improved easily without any surface treatment.

Electrospun Polyacrylonitrile Nanofibrous Membranes for Point-of-Use Water and Air Cleaning.

Novel electrospun polyacrylonitrile (PAN) nanofibrous membranes were prepared by using heat-press lamination under various conditions. The air permeability and the burst-pressure tests were run to select the membranes for point-of-use air and water cleaning. Membrane characterization was performed by using scanning electron microscopy, contact angle, and average pore size measurements. Selected membranes were used for both air dust filtration and cross-flow water filtration tests. Air dust filter results indicated that electrospun PAN nanofibrous membranes showed very high air-dust filtration efficiency of more than 99.99 % in between PM0.3 and PM2.5, whereas cross-flow filtration test showed very high water permeability over 600 L/(m2hbar) after 6 h of operation. Combining their excellent efficiency and water permeability, these membranes offer an ideal solution to filter both air and water pollutants.

Incorporation of PVDF Nanofibre Multilayers into Functional Structure for Filtration Applications.

Membranes are considered as a promising technology for separation and filtration processes. Here, novel polyvinylidene fluoride (PVDF) nanofibrous multilayer membranes were fabricated by wire-based industrial electrospinning equipment following by a lamination process. The lamination process was optimised under various applied temperature, force of lamination, and lamination time. Air permeability and burst-pressure tests were run to determine the optimum membranes for filtration application. The structures of the prepared membranes were characterised by scanning electron microscopy and pore-size analysis. The hydrophilic properties of the membranes were evaluated using water contact angle measurement, and the mechanical strength of the membranes was analysed. Air and water filtration tests were run to find the possible application of prepared membranes. The air filtration results showed that membranes had high filtration efficiencies: Over 99.00% for PM2.5, and PM0.1. The water filtration results indicated that permeability of the membranes changed from 288 to 3275 L/m²hbar. The successful preparation of such an interesting material may provide a new approach for the design and development of electrospun filter membranes.

Effect of Laminating Pressure on Polymeric Multilayer Nanofibrous Membranes for Liquid Filtration.

In the new century, electrospun nanofibrous webs are widely employed in various applications due to their specific surface area and porous structure with narrow pore size. The mechanical properties have a major influence on the applications of nanofiber webs. Lamination technology is an important method for improving the mechanical strength of nanofiber webs. In this study, the influence of laminating pressure on the properties of polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF) nanofibers/laminate was investigated. Heat-press lamination was carried out at three different pressures, and the surface morphologies of the multilayer nanofibrous membranes were observed under an optical microscope. In addition, air permeability, water filtration, and contact angle experiments were performed to examine the effect of laminating pressure on the breathability, water permeability and surface wettability of multilayer nanofibrous membranes. A bursting strength test was developed and applied to measure the maximum bursting pressure of the nanofibers from the laminated surface. A water filtration test was performed using a cross-flow unit. Based on the results of the tests, the optimum laminating pressure was determined for both PAN and PVDF multilayer nanofibrous membranes to prepare suitable microfilters for liquid filtration.

Preparation of Fouling-Resistant Nanofibrous Composite Membranes for Separation of Oily Wastewater.

A facile and low-cost method has been developed for separation of oily wastewater. Polyvinylidene fluoride/polyacrylonitrile (PVDF/PAN) nanofibers laminated on a supporting layer were tested. In order to create highly permeable and fouling-resistant membranes, surface modifications of both fibers were conducted. The results of oily wastewater separation showed that, after low vacuum microwave plasma treatment with Argon (Ar) and chemical modification with sodium hydroxide (NaOH), the membranes had excellent hydrophilicity, due to the formation of active carboxylic groups. However, the membrane performance failed during the cleaning procedures. Titanium dioxide (TiO2) was grafted onto the surface of membranes to give them highly permeable and fouling-resistance properties. The results of the self-cleaning experiment indicated that grafting of TiO2 on the surface of the membranes after their pre-treatment with Ar plasma and NaOH increased the permeability and the anti-fouling properties. A new surface modification method using a combination of plasma and chemical treatment was introduced.

The role of tissue harmonic imaging ultrasound combined with power Doppler ultrasound in the diagnosis of childhood febrile urinary tract infections.

AIM: This study assessed the ability of tissue harmonic imaging ultrasound combined with power Doppler ultrasound in the detection of childhood febrile urinary tract infections in comparison with the gold standard reference method: Tc-99m dimercaptosuccinicacid renal cortical scintigraphy. MATERIAL AND METHODS: This prospective study included 60 patients who were hospitalized with a first episode of febrile urinary tract infections. All children were examined with dimercaptosuccinicacid scan and tissue harmonic imaging ultrasound combined with power Doppler ultrasound within the first 3 days of admission. RESULTS: Signs indicative of acute infection were observed in 29 patients according to the results of tissue harmonic imaging ultrasound combined with power Doppler ultrasound while dimercaptosuccinicacid scan revealed abnormal findings in 33 patients. The sensitivity, specificity, positive predictive value and negative predictive value of tissue harmonic imaging combined with power Doppler ultrasound using dimercaptosuccinicacid scintigraphy as the reference method in patients diagnosed with first episode febrile urinary tract infections were calculated as 57.58% (95% confidence interval: 40.81%-72.76%); 62.96% (95% confidence interval: 44.23%-78.47%); 65.52% (95% confidence interval: 52.04%-77%); 54.84% (95% confidence interval: 41.54%-67.52%); respectively. CONCLUSIONS: Although current results exhibit inadequate success of power Doppler ultrasound, this practical and radiation-free method may soon be comprise a part of the routine ultrasonographic evaluation of febrile urinary tract infections of childhood if patients are evaluated early and under appropriate sedation.

Acquired bartter-like syndrome associated with colistin use in a preterm infant.

Acquired Bartter-like syndrome (BLS), characterized by hypokalemic metabolic alkalosis, hypomagnesemia, hypocalcemia, and normal kidney function, can be induced by diuretics or antibiotics. It is a very rare condition and only anecdotal cases mostly in adults were reported. Although tubulopathy associated with colistin was reported in adults, to the best of our knowledge, colistin-associated BLS neither in adults nor in children has been reported in the literature. We here report a-28-week, 740 g female preterm infant who developed BLS just after colistin treatment for Acinetobacter baumannii infection and recovered few days after the drug cessation, and discuss the possible association of colistin and tubulopathy. More research on colistin pharmacokinetics and pharmacodynamics in critically ill patients and preterm infants is needed to guide adequate colistin dosing at the least toxicity.