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Quaternary ammonium salts (QAS), as the surface active compounds, are widely used in medicine and industry. Their common application is responsible for the development of microbial resistance to QAS. To overcome, this issue novel surfactants, including gemini-type ones, were developed. These unique compounds are built of two hydrophilic and two hydrophobic parts. The double-head double-tail type of structure enhances their physicochemical properties (like surface activity) and biological activity and makes them a potential candidate for new drugs and disinfectants. Antimicrobial activity is mainly attributed to the biocidal action towards bacteria and fungi in their planktonic and biofilm forms, but the mode of action of gemini QAS is not yet fully understood. Moreover, gemini surfactants are of particular interest towards their application as gene carriers. Cationic charge of gemini QAS and their ability to form liposomes facilitate DNA compaction and transfection of the target cells. Multifunctional nature of gemini QAS is the reason of the long-standing research on mainly their structure-activity relationship.

Hydrogels, possessing high biocompatibility and adaptability to biological tissue, show great usability in medical applications. In this research, a series of novel cross-linked chitosan quaternary ammonium salt loading with gentamicin sulfate (CTMCSG) hydrogel films with different cross-linking degrees were successfully obtained by the reaction of chitosan quaternary ammonium salt (TMCS) and epichlorohydrin. Fourier transform infrared spectroscopy (FTIR), thermal analysis, and scanning electron microscope (SEM) were used to characterize the chemical structure and surface morphology of CTMCSG hydrogel films. The physicochemical property, gentamicin sulphate release behavior, cytotoxicity, and antibacterial activity of the CTMCSG against Escherichia coli and Staphylococcus aureus were determined. Experimental results demonstrated that CTMCSG hydrogel films exhibited good water stability, thermal stability, drug release capacity, as well as antibacterial property. The inhibition zone of CTMCSG hydrogel films against Escherichia coli and Staphylococcus aureus could be up to about 30 mm. Specifically, the increases in maximum decomposition temperature, mechanical property, water content, swelling degree, and a reduction in water vapor permeability of the hydrogel films were observed as the amount of the cross-linking agent increased. The results indicated that the CTMCSG-4 hydrogel film with an interesting physicochemical property, admirable antibacterial activity, and slight cytotoxicity showed the potential value as excellent antibacterial wound dressing.

Besides their positive role, microorganisms are related to a number of undesirable effects, including many diseases, biodeterioration and food spoilage, so when their presence is undesired, they must be controlled. Numerous biocides limiting the development of microorganisms have been proposed, however, in this paper the biocidal and inhibitory activity of quaternary ammonium salts (QASs) and their zwitterionic derivatives is addressed. This paper presents the current state of knowledge about the biocidal activity of QAS and their derivatives. Moreover, the known mechanisms of antimicrobial activity and the problem of emerging resistance to QAS are discussed. The latest trends in the study of surfactants and their potential use are also presented.

Quaternary ammonium salts (QASs) are ubiquitous in nature, being found in organisms ranging from microorganisms to vertebrates (e.g., glycine betaine, carnitine) where they have important cellular functions. QASs are also obtained by chemical synthesis. These compounds, due to their diverse chemical structure (e.g. monomeric QAS or gemini) and their biological properties, are widely used in medicine (as disinfectants, drugs, and DNA carriers), industry, environmental protection and agriculture (as preservatives, biocides, herbicides and fungicides). Discussed chemical compounds reduce the adhesion of microorganisms to various biotic and abiotic surfaces and cause the eradication of biofilms produced by pathogenic microorganisms. The properties of these chemicals depend on their chemical structure (length of the alkyl chain, linker and counterion), which has a direct impact on the physicochemical and biological activity of these compounds. QASs by incorporation into the membranes, inhibit the activity of proteins (H+-ATPase) and disrupt the transport of substances to the cell. Moreover, in the presence of QASs, changes in lipid composition (qualitative and quantitative) of plasma membrane are observed. The widespread use of disinfectants in commercial products can induce resistance in microorganisms to these surfactants and even to antibiotics. In this article we discuss the biological activity of QASs as cationic surfactants against microorganisms and their resistance to these compounds.

For addressing the issue of limited durable antibacterial cotton fabric, this study developed and synthesized quaternary ammonium salt antimicrobial agents. The chemical structure was analyzed by FTIR and 1H NMR. The cotton fabric was subjected to surface modification techniques, such as pad-dry-cure, following the careful selection of appropriate quaternary ammonium salt. The chemical state and surface morphology were evaluated through XPS and SEM. Furthermore, the cotton fabric underwent comprehensive assessments, which included antibacterial testing, laundering cycle testing, evaluation of mechanical properties, and analysis of comfort performance. The results demonstrated that the treated cotton fabric achieved a high bacteriostatic and fungistatic rate of 99.99%, 87.5%, and 99.99% against S. aureus, E. coli, and C. albicans respectively even after 50 laundering cycles, while maintaining exceptional antibacterial effectiveness and laundering durability due to the formation of covalent bonds with the cotton fabric. The treated cotton fabric met AAA grade standards for antibacterial rate without causing any significant decline in mechanical properties. Furthermore, enhancements in hydrophilicity, softness, and wrinkle resistance were observed.

Acidified aqueous solutions of different quaternary ammonium salts were tested for pretreating corn stover compared to control solutions, including single acidic solution and acidified NaCl and NH4Cl solutions. The results revealed that quaternary ammonium salt solutions were more effective in delignification and cellulose saccharification than the control solutions. The chemical structure of these salts significantly influenced the pretreatment efficacy. Notably, benzyltrimethylammonium chloride (BTMAC), a cost-effective option, exhibited remarkable capabilities. It achieved approximately 90% xylan removal, 86% lignin removal, and a 48-h enzymatic glucose yield of up to 93%. The BTMAC solution proved to be recycled for at least four runs while maintaining satisfactory performance. This work contributes valuable insights into the promising potential of standalone QAS solutions, offering a viable and cost-effective option for biomass pretreatment.

In order to meet the requirements of the marine environment for microwave absorption (MA) materials, we put forward the strategy of constructing multi-functional composite materials, which integrate microwave absorption, anti-corrosion, and antibacterial properties. Herein, graphene oxide (GO) was used as a template to induce the growth of zeolitic imidazolate framework-8 (ZIF-8), simultaneously as a two-dimensional (2D) nanocontainers to load corrosion inhibitors to achieve pH-responsive and self-healing properties. Finally, quaternary ammonium salt (dimethyl octadecyl(3-trimethoxylsilyl propyl) ammonium chloride (DMAOP)) and sodium ascorbate (VCNa) were introduced to achieve synergistic antibacterial activity and the reduction of GO. The 2D strip-like structure of ZIF-8 was due to the confined growth induced by the electrostatic attraction between ZIF-8 and GO sheets. The as-obtained reduced GO (RGO)/ZIF-8/DMAOP 5 exhibited excellent microwave absorption (MA) properties, with a minimum reflection loss (RL) value of −47.08 dB at 12.73 GHz when the thickness was 2.8 mm. Moreover, the effective absorption bandwidth reached 6.84 GHz. After soaking in 3.5% NaCl solution for 35 days, the RGO/ZIF-8/DMAOP 5 −0.7% coating still achieved an impedance value of 4.585 × 10 7 Ω·cm 2 and a protective efficiency of 99.994%, providing superior anti-corrosion properties. In addition, fantastic antibacterial activity was obtained, with the antibacterial rates of RGO/ZIF-8/DMAOP 10 reaching 99.39% and 100% against Escherichia coli and Staphylococcus aureus . This work could open new avenues towards the development of a new generation of multifunctional MA materials.

Pressure sensitive adhesives are ubiquitous in commodity products such as tapes, bandages, labels, packaging, and insulation. With single use plastics comprising almost half of yearly plastic production, it is essential that the design, synthesis, and decomposition products of future materials, including polymer adhesives, are within the context of a healthy ecosystem along with comparable or superior performance to conventional materials. Here we show a series of sustainable polymeric adhesives, with an eco-design, that perform in both dry and wet environments. The terpolymerization of propylene oxide, glycidyl butyrate, and CO 2 , catalyzed by a cobalt salen complex bearing a quaternary ammonium salt, yields the poly(propylene-co-glycidyl butyrate carbonate)s (PPGBC)s. This polymeric adhesive system, composed of environmentally benign building blocks, implements carbon dioxide sequestration techniques, poses minimal environmental hazards, exhibits varied peel strengths from scotch tape to hot-melt wood-glue, and adheres to metal, glass, wood, and Teflon® surfaces. Adhesives are ubiquitous in commodity products, however it it essential that their synthesis and degradation be sustainable without compromising their performance. Here, the authors report a library of adhesives based on environmentally benign building blocks that perform in both dry and wet environments.

Fusarium wilt of banana is a devastating disease caused by Fusarium oxysporum f. sp. cubense (Foc), of which the “tropical” race 4 strain (Foc4) has a significant impact on the banana industry worldwide. Due to the strong persistence of Foc4 conidia, there is no effective chemical control method up to now. Quaternary ammonium salts (QASs), as cationic fungicides, have great application prospects in the field of inhibiting plant diseases and our previous work showed that polymeric quaternary ammonium salts (PQASs) could effectively inhibit Foc4 conidia in soil. In this paper, we investigate the effects of two kinds of PQASs, i.e. polydimethylsiloxane-polymethacrylate block copolymers, containing quaternary ammonium salts (PDMS-b-QPDMAEMA), poly(methacrylamido propylbenzyl dimethylammonium chloride) (PQD-BC), on the antifungal activities against Foc4, using antifungal bioassays and microscopy. It was found that PQASs had high inhibitory effects on conidia and worked fast. Microscopy showed that PQASs could not only rapidly enter conidia, but also stably adsorb to the surface of conidia and penetrate newly grown hyphae. It was also found that PQASs could affect the hydrophobicity of conidial surfaces, change the composition of the cell wall and destroy its integrity. Over all, this work provides valuable information for the application of PQASs as antifungal agents for inhibiting Foc4.

The formation of gas hydrates is a major issue during the operation of oil and gas pipelines, because gas hydrates cause plugging, thereby disrupting the normal oil and gas flows. A solution is to inject gas hydrate inhibitors such as ionic liquids. Contrary to classical inhibitors, ionic liquids act both as thermodynamic inhibitors and hydrate inhibitors, and as anti-agglomerates. Imidazolium-based ionic liquids have been found efficient for the inhibition of CO2 and CH4 hydrates. For CO2 gas hydrates, N-ethyl-N-methylmorpholinium bromide showed an average depression temperature of 1.72 K at 10 wt% concentration. The induction time of 1-ethyl-3-methyl imidazolium bromide is 36.3 h for CO2 hydrates at 1 wt% concentration. For CH4 hydrates, 1-ethyl-3-methyl-imidazolium chloride showed average depression temperature of 4.80 K at 40 wt%. For mixed gas hydrates of CO2 and CH4, only quaternary ammonium salts have been studied. Tetramethyl ammonium hydroxide shifted the hydrate liquid vapour equilibrium to 1.56 K at 10 wt%, while tetrabutylammonium hydroxide showed an induction time of 0.74 h at 1 wt% concentration.