Bienzymatic modification of polymeric membranes to mitigate biofouling

© 2019 Elsevier B.V. Staphylococcus aureus and Staphylococcus epidermidis are considered as major human pathogens and their resistance to antibiotic treatment and host defense systems can be increased due to the formation of biofilms. The biofilm-associated biofouling of industrial surfaces, particularly membranes, remains a serious concern that challenges investigators to develop practical solutions for the reduction of their impact. The present study developed antibacterial membrane surfaces that can mitigate biofilm formation. α-Amylase and lysozyme, as antibacterial enzymes, were covalently immobilized on polydopamine/cyanuric chloride functionalized polyethersulfone (PES) membranes to form biocompatible antibacterial surfaces. Several methods including SEM, AFM, Bradford, water contact angle goniometry, and surface free energy measurement techniques have been used to demonstrate the attachment of enzymes onto PES membranes by changing the physicochemical properties of the surface. The two enzymatic systems alter the membrane surface chemistry by rendering lower free surface energy and higher hydrophilicity, which leads to the creation of a layer of hydration energy barrier preventing microorganisms from being anchored on the surface. Those microorganisms that managed to overcome the energy barrier and get attached to the surface are attached by the enzymes' bond cleavage functionality. This multilevel defense system protects the membrane against any biofilm formation. The results of microtiter test and flow cytometry assay indicated that α-amylase/lysozyme mixture treated membrane samples came with more than 87% removal of biofilms. The results of the biofouling experiment in a dead-end cell demonstrated that the modified membrane surface had only a slightly impaired water flow compared to an unmodified membrane, which was due to the removal of biofilms by the enzymes’ activity. The results also showed that the modification of membranes with antibacterial enzymes could create a new biotechnological horizon to prevent biofilm formation

Domino P-µMB: A New Approach for the Sequential Immobilization of Enzymes Using Polydopamine/Polyethyleneimine Chemistry and Microfabrication

© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Developing a facile approach for the manipulation of the direction and order of the enzymatic reactions via sequential immobilization on inexpensive substrates is a continuous demand. Herein, a new methodology is introduced that allows making a desired enzymatic reaction pathway on a paper-based microfluidic-membrane based biosensor (P-µMB). Although the method is universal, here, as a proof-of-concept, the sequential immobilization of α-amylase, glucose oxidase (GOx) and horseradish peroxidase (HRP) is presented for fabricating a P-µMB. To this end, hydrophilic polydopamine/polyethyleneimine patterns are created on the hydrophobic polypropylene membrane using 3D printing and a polydimethylsiloxane (PDMS) mold, and a coating layer of silver nanoparticles (AgNPs) is used to modify the patterns. The enzymes are then individually immobilized on the desired locations with another set of PDMS molds. It is observed that AgNPs P-µMB in the sequential immobilization system has stable activity at various temperature and pH regimes, high selectivity toward starch, wide-range linear sensitivity, and a limit of detection of 0.002% w/w starch. A smartphone camera is used for the quantitative analysis of the analyte with the mean gray intensity as the analytical parameter. This developed system provides a platform for further sequential immobilization of other types of biological elements

Surface modification of polypropylene membrane for the removal of iodine using polydopamine chemistry.

The development of stable and effective iodine removal systems would be highly desirable in addressing environmental issues relevant to water contamination. In the present research, a novel iodine adsorbent was synthesized by self-polymerization of dopamine (PDA) onto inert polypropylene (PP) membrane. This PP/PDA membrane was thoroughly characterized and its susrface propeties was analyzed by various analytical techniques indcluding field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH), contact angle, and surface free energy measurement. The PP/PDA membranes were subsequently used for batchwise removal of iodine at different temperatures (25-70 °C), pH (2-7), and surface areas (1-10 cm2) to understand the underlying adsorption phenomena and to estimate the membrane capacity for iodine uptake. The increase in temperature and pH both led to higher adsorption of iodine. The present approach showed a removal efficiency of over 75% for iodine using 10 cm2 PP/PDA membrane (18.87 m2 g-1) within 2 h at moderate temperatures (∼50 °C) and pH > 4, about 15 fold compared to the PP control membrane. The adsorption kinetics and isotherms were well fitted to the pseudo-second-order kinetic and Langmuir isotherm models (R2 > 0.99). This adsorbent can be recycled and reused at least six times with stable iodine adsorption. These findings were attributed to the homogenous monolayer adsorption of the iodide on the surface due to the presence of catechol and amine groups in the PP/PDA membrane. This study proposes an efficient adsorbent for iodine removal

In vitroandin vivostudy of hazardous effects of Ag nanoparticles and Arginine-treated multi walled carbon nanotubes on blood cells: Application in hemodialysis membranes

One of the novel applications of the nanostructures is the modification and development of membranes for hemocompatibility of hemodialysis. The toxicity and hemocompatibility of Ag nanoparticles and arginine-treated multiwalled carbon nanotubes (MWNT-Arg) and possibility of their application in membrane technology are investigated here. MWNT-Arg is prepared by amidation reactions, followed by characterization by FTIR spectroscopy, Raman spectroscopy, and thermogravimetric analysis. The results showed a good hemocompatibility and the hemolytic rates in the presence of both MWNT-Arg and Ag nanoparticles. The hemolytic rate of Ag nanoparticles was lower than that of MWNT-Arg. In vivo study revealed that Ag nanoparticle and MWNT-Arg decreased Hematocrit and mean number of red blood cells (RBC) statistically at concentration of 100 μg mL-1. The mean decrease of RBC and Hematocrit for Ag nanoparticles (18% for Hematocrit and 5.8 × 1,000,000/μL) was more than MWNT-Arg (20% for Hematocrit and 6 × 1000000/μL). In addition, MWNT-Arg and Ag nanoparticles had a direct influence on the White Blood Cell (WBC) drop. Regarding both nanostructures, although the number of WBC increased in initial concentration, it decreased significantly at the concentration of 100 μg mL-1. It is worth mentioning that the toxicity of Ag nanoparticle on WBC was higher than that of MWNT-Arg. Because of potent antimicrobial activity and relative hemocompatibility, MWNT-Arg could be considered as a new candidate for biomedical applications in the future especially for hemodialysis membranes

Ion Selective Nanochannels: From Critical Principles to Sensing and Biosensing Applications

Nanochannels offer significant practical advantages in many fields due to their interesting characteristics, such as flexibility in shape and size, robustness, low-cost and their ability to be modified based on the required applications. The effectiveness of ion separation in nanochannels can be assessed based on the selective transport of the desired ions and the rate of the transportation process. This paper aims to provide an extensive review of ion-based nanochannels, including their working principles and ion-selective behaviors. Nanochannel fabrication strategies and their applications are discussed. Key nanochannel design factors and their roles in governing ion-selective transport are also reviewed. The contribution of size, charge, wettability, and recognition ability of the nanochannels on the selectivity mechanisms are discussed. Specific consideration is made to nanochannel applications in sensing and biosensing assays. Finally, an attempt is made to address the commercial implementation and future outlook of the nanochannels to guide researchers in emerging avenues of research

Ion Selective Nanochannels: From Critical Principles to Sensing and Biosensing Applications

Nanochannels offer significant practical advantages in many fields due to their interesting characteristics, such as flexibility in shape and size, robustness, low-cost and their ability to be modified based on the required applications. The effectiveness of ion separation in nanochannels can be assessed based on the selective transport of the desired ions and the rate of the transportation process. This paper aims to provide an extensive review of ion-based nanochannels, including their working principles and ion-selective behaviors. Nanochannel fabrication strategies and their applications are discussed. Key nanochannel design factors and their roles in governing ion-selective transport are also reviewed. The contribution of size, charge, wettability, and recognition ability of the nanochannels on the selectivity mechanisms are discussed. Specific consideration is made to nanochannel applications in sensing and biosensing assays. Finally, an attempt is made to address the commercial implementation and future outlook of the nanochannels to guide researchers in emerging avenues of research. © 2021 Wiley-VCH Gmb

Recent developments in enzyme immobilization technology for high-throughput processing in food industries.

The demand for food and beverage markets has increased as a result of population increase and in view of health awareness. The quality of products from food processing industry has to be improved economically by incorporating greener methodologies that enhances the safety and shelf life via the enzymes application while maintaining the essential nutritional qualities. The utilization of enzymes is rendered more favorable in industrial practices via the modification of their characteristics as attested by studies on enzyme immobilization pertaining to different stages of food and beverage processing; these studies have enhanced the catalytic activity, stability of enzymes and lowered the overall cost. However, the harsh conditions of industrial processes continue to increase the propensity of enzyme destabilization thus shortening their industrial lifespan namely enzyme leaching, recoverability, uncontrollable orientation and the lack of a general procedure. Innovative studies have strived to provide new tools and materials for the development of systems offering new possibilities for industrial applications of enzymes. Herein, an effort has been made to present up-to-date developments on enzyme immobilization and current challenges in the food and beverage industries in terms of enhancing the enzyme stability