Modification of polyvinylidene fluoride membrane by quaternary ammonium compounds loaded on silica nanopollens for mitigating biofouling

Dual functional antibacterial nanofiber membranes: Polyhexamethylene biguanide-integrated alginate-chitosan-dye modified polyamide 56 for single-use biomedical applications

Polyamide 56 (PA56) nanofiber membranes were functionalized with alginate (AG), chitosan (CS), reactive dyes (RG19, RR141), and poly(hexamethylene biguanide) (PHMB) to develop multifunctional antimicrobial membranes for single-use applications. The resulting membranes, PA56-AG-CS-RG19-PHMB and PA56-AG-CS-RR141-PHMB, achieved high antibacterial efficiencies of 97.12 % and 90.65 %, respectively, against Escherichia coli, demonstrating potent bacterial inhibition. The antimicrobial performance results from a synergistic dual mechanism. Chitosan disrupts bacterial adhesion and biofilm formation through electrostatic interactions, while PHMB compromises membrane integrity and interferes with intracellular processes. This combined action enhances bactericidal efficacy. The functionalization strategy also maintained excellent biocompatibility, with minimal cytotoxicity observed in L929 fibroblasts. Optimized concentrations of AG and CS were systematically evaluated to ensure balanced antibacterial performance and mechanical stability. These membranes, designed for single-use, exhibited significantly reduced antibacterial activity upon reuse, supporting their intended application. Overall, the integration of chemical and physical antimicrobial strategies within a nanofiber matrix presents a novel and effective approach. This strategy enables the development of next-generation materials suitable for real-world single-use biomedical applications, including wound dressings, food packaging, and protective textiles.

From Antibacterial to Antibiofilm Targeting: An Emerging Paradigm Shift in the Development of Quaternary Ammonium Compounds (QACs)

In a previous development stage, mostly individual antibacterial activity was a target in the optimization of biologically active compounds and antiseptic agents. Although this targeting is still valuable, a new trend has appeared since the discovery of superhigh resistance of bacterial cells upon their aggregation into groups. Indeed, it is now well established that the great majority of pathogenic germs are found in the environment as surface-associated microbial communities called biofilms. The protective properties of biofilms and microbial resistance, even to high concentrations of biocides, cause many chronic infections in medical settings and lead to serious economic losses in various areas. A paradigm shift from individual bacterial targeting to also affecting more complex cellular frameworks is taking place and involves multiple strategies for combating biofilms with compounds that are effective at different stages of microbiome formation. Quaternary ammonium compounds (QACs) play a key role in many of these treatments and prophylactic techniques on the basis of both the use of individual antibacterial agents and combination technologies. In this review, we summarize the literature data on the effectiveness of using commercially available and newly synthesized QACs, as well as synergistic treatment techniques based on them. As an important focus, techniques for developing and applying antimicrobial coatings that prevent the formation of biofilms on various surfaces over time are discussed. The information analyzed in this review will be useful to researchers and engineers working in many fields, including the development of a new generation of applied materials; understanding biofilm surface growth; and conducting research in medical, pharmaceutical, and materials sciences. Although regular studies of antibacterial activity are still widely conducted, a promising new trend is also to evaluate antibiofilm activity in a comprehensive study in order to meet the current requirements for the development of highly needed practical applications.

Response to Cold Adaption in Acinetobacter johnsonii XY27 from Spoiled Bigeye Tuna (Thunnus obesus): Membrane Protein Composition and Protein Biomarker Identification by Proteomics

Acinetobacter johnsonii is one of the major food-spoilage bacteria and can survive under cold stress. In this study, the membrane composition, membrane permeability, and energy transduction of A. johnsonii XY27 cultured at 4 and 30 °C were examined comparatively by flow cytometry combined with liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry. The Na⁺/K⁺ATPase activity, alkaline phosphatase and ATPase activity, fluorescence intensity, and cell viability in A. johnsonii XY27 increased with the decrease in cultivation temperature. The polyunsaturated fatty acid and monounsaturated fatty acids have a higher content in A. johnsonii XY27 cultured at 4 °C compared to that cultured at 30 °C, in which the contents of methyl palmitoleate, methyl myristoleate, and methyl oleate increased dramatically with decreasing temperature. Comparative proteomics analysis revealed that 31 proteins were downregulated and 4 proteins were upregulated, in which catalase-peroxidase 1 and cold shock proteins as biomarker proteins could effectively control A. johnsonii during cold adaptation.

Mitigating membrane biofouling in biofuel cell system – A review

A biofuel cell (BFC) system can transform chemical energy to electrical energy through electrochemical reactions and biochemical pathways. However, BFC faced several obstacles delaying it from commercialization, such as biofouling. Theoretically, the biofouling phenomenon occurs when microorganisms, algae, fungi, plants, or small animals accumulate on wet surfaces. In most BFC, biofouling occurs by the accumulation of microorganisms forming a biofilm. Amassed biofilm on the anode is desired for power production, however, not on the membrane separator. This phenomenon causes severities toward BFCs when it increases the electrode’s ohmic and charge transfer resistance and impedes the proton transfer, leading to a rapid decline in the system’s power performance. Apart from BFC, other activities impacted by biofouling range from the uranium industry to drug sensors in the medical field. These fields are continuously finding ways to mitigate the biofouling impact in their industries while putting forward the importance of the environment. Thus, this study aims to identify the severity of biofouling occurring on the separator materials for implementation toward the performance of the BFC system. While highlighting successful measures taken by other industries, the effectiveness of methods performed to reduce or mitigate the biofouling effect in BFC was also discussed in this study.

Toughened chitosan-based composite membranes with antibiofouling and antibacterial properties via incorporation of benzalkonium chloride

Biofouling due to biofilm formation is a major problem in ultrafiltration membrane applications. In this work, a potential approach to solve this issue has been developed by functionalization of chitosan-based membranes with benzalkonium chloride (BKC). The chitosan composite membranes consisting of poly(ethylene glycol) (PEG), multiwalled carbon nanotubes (MWCNT), and BKC were synthesized by mixing the membrane precursors and the antibacterial solution, and casting via an inversed phase technique. The effects of the BKC content on the morphology and performance of the membranes are investigated by varying the BKC feed compositions. The composite membranes demonstrate better antibacterial efficacy against Staphylococcus aureus than Escherichia coli. The permeability and selectivity performances of the composites as filter membranes are examined by employing a dead-end filtration system. Interestingly, enhanced toughness of the membranes is observed as a function of the BKC content. Mechanisms of the structural formation are investigated. The results from SEM, XRD, and FTIR spectroscopy revealed that MWCNT/BKC are located as nanoclusters with π–π stacking interactions, and are covered by PEG chains. The shape of the dispersed domains is spherical at low BKC contents, but becomes elongated at high BKC contents. These act as soft domains with an anisotropic shape with toughening of the brittle chitosan matrix, leading to enhanced durability of the membranes, especially in ultrafiltration applications. The composite membranes also demonstrate improved rejection in dead-end ultrafiltration systems due to high porosity, high hydrophilicity, and the positive charges of the membrane surface.

Chitosan/PEG/MWCNT/BKC membranes exhibit enhanced antibiofouling properties against S. aureus and E. coli. MWCNT/BKC are located as dispersed nano-clusters with π–π stacking interactions in the chitosan matrix, and are coved by PEG chains.

New details of assembling bioactive films from dispersions of amphiphilic molecules on titania surfaces

Tailoring the surface properties of materials for biomedical applications is important to avoid clinical complications. Forming thin layers of amphiphilic molecules with apolar regions that facilitate attractive intermolecular interactions, can be a suitable and versatile approach to achieve hydrophobic surface modification and provide functional antibacterial properties. Aiming to correlate layer structure and properties starting from film formation, octadecylphosphonic acid (ODPA) and dimethyloctadecyl (3-trimethoxysilylpropyl) ammonium chloride (DMOAP) layers were adsorbed onto smooth titania surfaces. Then the films were studied by atomic force microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS), and their interactions with aqueous environments were characterized by contact angle and zeta potential measurements. In addition, antibacterial assays were performed using E. coli and S. mutants to reveal the antibacterial properties effected by the surface modification. Immediately after sputter deposition, titania was hydrophilic; however, after air storage and adsorption of DMOAP or ODPA, an increase in the water contact angle was observed. XPS investigations after layer formation and after antibacterial tests revealed that the attachment of layers assembled from ODPA on titania substrates is considerably stronger and more stable than that observed for DMOAP films. Heat treatment strongly affects DMOAP layers. Furthermore, DMOAP layers are not stable under biological conditions.

Structure–property relationship of amphiphilic molecules on smooth substrates was explored through a multi-step approach and its influence on biological activity.

Antifouling and antibacterial behavior of membranes containing quaternary ammonium and zwitterionic polymers

To overcome the organic-/bio- fouling of the membrane, a dual-functional ultrafiltration membrane containing quaternary ammonium and zwitterionic polymers via quaternization and surface radical polymerization was designed, and its antifouling and antibacterial behavior was studied. In this work, poly(vinylidene fluoride)/poly(methyl methacrylate-co-dimethylamino-2-ethyl methacrylate) (PVDF/P(MMA-co-DMAEMA)) blend membrane was quaternized by p-chloromethyl styrene (p-CMS), and the double bonds were introduced onto the membrane surface, which further participated in the polymerization of zwitterionic monomers on the membrane surface. The results indicated that the resultant membrane exhibited obviously improved hydrophilicity and weak positive charge (isoelectric point, 7.49). The membrane presented higher flux recovery ratio and lower protein adhesion compared with the pure PVDF membrane. Meanwhile, the membrane showed high-efficiency broad-spectrum antibacterial performance, that is, the bacteria killing efficiency of S. aureus and E. coli reached 98.2% and 97.0%, respectively. Moreover, the membrane effectively inhibited bacterial adhesion, which is important for the long-term antibacterial properties of membrane. This antifouling and antibacterial PVDF membrane may have potential in the long-term filtration process, especially when dealing with microbiologically contaminated water.