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

Exploring the correlation of linker structure and antimicrobial activities of pyridinium-based cationic biocides: Aromatic versus aliphatic architectures

Cationic biocides, particularly quaternary ammonium compounds (QACs), play a vital role in controlling microbial infections across various industries, healthcare facilities and households. As their widespread use increased drastically in the last few years due to COVID-19, there is growing concern about the development of resistance among microorganisms exposed to cationic biocides. It is crucial to recognize this threat in advance and respond by modifying and replacing the old generation of commercial biocides. Reported here is the pyridinium-based bis-QACs tuning via combination of two simple synthesis approaches to achieve novel biocide's architectures with mixed linkers. The obtained compounds were subjected to a broad bioactivity assay against a panel of 26 microbial pathogens, including multi-resistant bacterial ESKAPEE strains, fungi and biofilms. Novel hit-compounds showed improved antibacterial and antibiofilm action, rapid bacterial eradication within 15-30 min of exposure and 4.5-fold lower hemotoxicity, as well as lower potential for the development of bacterial resistance compared to commercial lead antiseptic octenidine. Highlighted findings and insights will serve as a good basis for further studies of bis-QACs as highly effective biocides.

Antimicrobial 3D printed gelatin scaffolds for root canal disinfection in regenerative endodontics procedures

Regenerative endodontic procedures (REPs) which aim to promote root development and pulp tissue regeneration in necrotic immature teeth, have emerged as a promising therapeutic approach. A critical determinant of REP success hinges on effective disinfection of the root canal system, which must eliminate microbial contaminants whilst preserving the microenvironment necessary for dental pulp stem cell tissue regeneration. This study reports on the fabrication of biocompatible 3D printed hydrogel scaffolds designed for root canal disinfection. The scaffolds incorporate benzyldimethyldodecylammonium chloride (BDMDAC) a broad-spectrum quaternary ammonium compound characterised by low cytotoxicity and minimal risk of resistance development. BDMDAC loaded gelatin biomaterial inks were systematically evaluated for rheology properties, mechanical stability and drug release properties. Scaffolds containing 150 μg mL-1 and 250 μg mL-1 BDMDAC exhibited excellent antimicrobial efficacy against 5 bacterial pathogens (including 3 endodontic bacteria-Enterococcus faecalis, Porphyromonas gingivalis, and Streptococcus mutans). Cytocompatibility assays using primary human dental pulp stem cells (HDPSCs) derived from 3 donors confirmed over 70% of cell viability. Furthermore, freeze-dried scaffolds demonstrated excellent shelf-life stability for at least six months. Overall, these findings highlight the potential of 3D printed BDMDAC-loaded 3D printed gelatin scaffolds as an effective and cytocompatible platform for root canal disinfection in REPs.

Engineering Antibacterial, Biocompatible, Anti-Oxidant Titanium-Based Implants Using Polyphenols-Chlorhexidine Networks for Bone Regeneration

Implant-associated infections leading to osteolysis and implant loosening are an ongoing clinical challenge. Various strategies have been proposed to equip bone implants with antibacterial properties to prevent infection. However, the cytotoxicity associated with antimicrobial effects adversely impacts the osseointegration. Herein, a facile and safe strategy is proposed to endow bone implants with infection prevention, good cytocompatibility, inflammatory-responsive antimicrobial properties, thus promoting bone healing. The coating is fabricated on the implant through both covalent and non-covalent bonds of polyphenols with chlorhexidine (CHX). The covalent bonds guarantee long-term stability, while non-covalent bonds facilitate early release of CHX. Furthermore, the inclusion of polyphenols reduces the electrophilicity of CHX, inhibits reactive oxygen species generated by CHX, and minimizes interference with the mitochondrial electron transport chain, thereby reducing cellular toxicity. Consequently, the coating effectively fortified the bone implant, successfully impeding bacterial invasion within 7 days in Sprague-Dawley rats and suppressing inflammation as well as bone resorption caused by bacteria during a 60-day femoral implantation, thus facilitated osseointegration on the implant. The study investigated the cytotoxicity associated with mitochondrial interference induced by CHX and proposed a strategy to enhance its cellular compatibility, thereby providing a novel approach for fabricating biocompatible antibacterial bone implants.

Development of Membrane-Targeting Osthole Derivatives Containing Pyridinium Quaternary Ammonium Moieties with Potent Anti-Methicillin-Resistant Staphylococcus aureus Properties

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of hospital- and community-acquired infections, necessitating the development of novel antibacterials. Here, we designed and synthesized 30 osthole derivatives with pyridinium quaternary ammonium moieties. In vitro bioassay showed that compounds 8u and 8ac exhibited potent antibacterial activity against S. aureus ATCC 29213 and ten clinical MRSA isolates (MIC = 0.5-1 μg/mL), with low hemolytic activity, rapid bactericidal effects, and minimal resistance induction. In MRSA-infected mouse models of skin abscesses and sepsis, 8u and 8ac also displayed excellent antibacterial effects and safety, which were comparable to vancomycin. Mechanistic studies revealed that 8u and 8ac selectively target bacterial membranes via binding to phosphatidylglycerol (PG), increasing intracellular reactive oxygen species (ROS), inducing content leakage, and ultimately causing bacterial death. These findings suggest 8u and 8ac as promising novel lead candidates for anti-MRSA drug development.

Minimalistic bis-triarylpyridinium cations: effective antimicrobials against bacterial and fungal pathogens

A series of twelve compounds from the family of 2,4,6-triarylpyridinium cations have been synthesized, chemically characterized (1H, 13C NMR, HRMS), and microbiologically evaluated (MIC determination against S. aureus, E. faecalis, E. coli, P. aeruginosa, and C. albicans). These compounds are quaternary ammonium cations (QACs), classified as either mono-QACs or bis-QACs. The mono-QACs are further divided into those with short (three-carbon) and long (twelve-carbon) pendant chains. An additional structural variable is the number of bromine atoms attached to the aromatic rings, ranging from zero to three. The major findings of this study are: (a) bis-QACs exhibit notably higher antimicrobial activity than mono-QACs; (b) an increased number of bromine atoms on the structure appears to diminish antimicrobial properties and (c) one of the compounds (1a) shows particularly promising properties as a broad spectrum antimicrobial, given its low MICs across all five pathogenic microorganisms studied. Preliminary assays with C. albicans show that 1a has a strong mitochondrial activity, causing a remarkable mitochondrial membrane depolarization in this organelle. Taken together, this study positions triarylpyridinium cations-previously unexplored as antimicrobials-as promising candidates for future drug development, especially in light of the growing concern over drug-resistant microorganisms.

Quaternary Ammonization Treatment Enhances the Antifouling Activities of Capsaicin-Based Polybenzoxazine Coatings

Marine biofouling is an important factor that affects the service life of marine equipment. In this work, phenol source capsaicin-mimicking N-(4-hydroxy-3-methoxy-benzyl) acrylamide, two amine sources, 3-aminopropyltriethoxysilane (APTES) and furfurylamine (FFA), together with paraformaldehyde were used to prepare two benzoxazine coatings, P(HA) and P(HF). By reaction with iodomethane, the quaternary ammonium group was introduced into the N position of the oxazine ring. Quaternarily ammonified benzoxazine coatings P(HAI) and P(HFI) show exciting antibacterial performance compared to that of the untreated benzoxazine coating. The P(HFI) coating exhibited 93.8%, 96.4%, 99.9%, and 99.9% killing rates for Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Bacillus subtilis, respectively. The quaternary ammonization treatment also precipitated further enhanced anti-alga activity and excellent real-sea antifouling performances. However, the introduction of the ionic groups hindered the thermal polymerization of benzoxazine, leading to more defects on the coating surface, resulting in corrosion resistance that was poorer than that of HA and HF as detected from electrochemical corrosion and neutral salt spray experiments. The corrosion current density of the P(HA) and P(HF) coatings is 2 orders greater than that of the P(HAI) and P(HFI) coatings. Our results shed light on developing new quaternary ammonization treatment routes for polymeric coatings for the desired functions.

One-Step Nanoimprinting of Fe2O3/AgBr Thin Films for Dark-Light Active Antibiofilm and Bacterial-Free Cell Culture Surfaces

The resuscitation of bacteria through biofilms presents a critical challenge in controlling microbial pathogenesis and addressing antimicrobial resistance. Continuous antibiofilm activity, particularly on frequently contacted surfaces, is therefore critical. In this study, a scalable is introduced, one-step fabrication of Fe2O3/AgBr nanoimprints using a polymerizable sol-gel (PSG) approach to create functional nanostructured thin films with strong antimicrobial properties. Fe2O3, a visible-light photocatalyst, is coupled with AgBr, a photosensitizer and dark-active antimicrobial, forming a heterojunction that demonstrated potent antibacterial activity against Escherichia coli and Pseudomonas putida under both dark and light conditions. The heterojunctions exhibit significant biofilm inhibition in the dark, particularly against the robust biofilm-forming P. putida, while visible light irradiation ensures complete biofilm clearance. These surfaces also achieve optimal reactive oxygen species (ROS) production, selectively targeting bacteria without compromising the integrity of mammalian cells. The biocompatibility is confirmed through MTT, TBARS, and apoptosis assays, demonstrating the non-cytotoxic nature of the substrates. Moreover, the surfaces enable cell patterning and recovery of mammalian cells from microbial contamination, highlighting their potential in creating bacterial-free environments for cell culture. This innovative method offers a promising route to next-generation, self-cleaning antimicrobial coatings, combining continuous biofilm inhibition with excellent biocompatibility and scalability.

A wearable antifouling electrochemical sensor integrated with an antimicrobial microneedle array for uric acid detection in interstitial fluid

Wearable microneedle array (MNA) based electrochemical sensors have gained increasing attention for their capability to analyze biomarkers in the interstitial fluid (ISF), enabling noninvasive, continuous monitoring of health parameters. However, challenges such as nonspecific adsorption of biomolecules on the sensor surfaces and the risk of infection at the microneedle penetration sites hinder their practical application. Herein, a wearable dual-layer microneedle patch was prepared to overcome these issues by integrating an antimicrobial microneedle layer with an antifouling sensing layer. The microneedle layer was prepared from polyvinyl alcohol, carboxylated nanocellulose, quaternary ammonium chitosan and carbon nanotubes, and it possessed antimicrobial and mechanical properties necessary for skin penetration, ISF collection and effective transmission to the sensing layer. The sensing layer was prepared from bacterial cellulose, epoxy propyl dimethyl dodecyl ammonium chloride, carbon nanotubes and gold nanoparticles, and it was capable of preventing biofouling and sensing uric acid (UA) in ISF. The wearable MNA based sensor exhibited a linear range of 0.5 μM - 2.5 μM and 9.6 μM - 2.15 mM for UA detection, with a limit of detection of 0.17 μM. Moreover, it was capable of accurately monitoring UA levels in ISF of mice without significant biofouling, as verified by the ELISA method. This innovative wearable sensor based on the MNA effectively balances the antifouling and antimicrobial functions, offering a reliable strategy for the assay of ISF, and making it a promising tool for personalized and decentralized health monitoring.

Challenges of quaternary ammonium antimicrobial agents: Mechanisms, resistance, persistence and impacts on the microecology

Quaternary ammonium compounds (QACs) served as broad spectrum antimicrobial agents are widely applied for surface disinfection, skin and mucous disinfection, and mouthwash. The daily applications of QACs have significantly increased, especially during the COVID-19 pandemic. However, the environmental residues of QACs have demonstrated harmful impacts on the environment, leading to an increase in environmental contamination, resistant microbes and disruption of microecology. The actions of QACs were related to their cationic character, which can impact the negatively charged cell membranes, but the details are still unclear. Moreover, bacteria with lower sensitivity and resistant pathogens have been detected in clinics and environments, while QACs were also reported to induce the formation of bacterial persisters. Even worse, the resistant bacteria even showed co-resistance and cross-resistance with traditional antibiotics, decreasing therapeutic effectiveness, and disrupting the microecology homeostasis. Unfortunately, the resistance and persistence mechanisms of QACs and the effects of QACs on microecology are still not clear, which even neglected during their daily usages. Therefore, we summarized and discussed current understandings on the antimicrobial actions, resistance, persistence and impacts on the microecology to highlight the challenges in the QACs applications and discuss the possible strategies for overcoming their drawbacks.

Synthesis and characterization of new quaternized galactomannan derivatives with antibacterial activity

The continuous increase in bacterial resistance requires the study and development of new biocompatible antibacterial materials. Galactomannan gum was extracted from endosperms of Dimorphandra gardneriana seeds, modified through quaternization reactions (with NaOH/CHPTAC), and evaluated for antimicrobial activity. Four quaternized derivatives were obtained (QG1-QG4). The derivatives were characterized by FTIR, NMR, and rheology, which confirmed the cationization. The galactomannan structure was theoretically studied, and Zeta potential exhibited positive increase in the charge of quaternized derivatives, changing from -3.2 mV (unmodified galactomannan) to +59.35 mV (QG4). Elemental analysis revealed an increase in degree of substitution (DS) between the derivatives, of which QG4 exhibited the highest DS (0.51). QG4 exhibited a bactericidal effect in the antimicrobial test for determination of minimal inhibitory and bactericidal concentrations, against Gram-positive bacteria. Atomic force microscopy showed an increase in bacterial cell surface roughness and decrease in cell height after treatment with QG4. QG3 and QG4 demonstrated antibiofilm potential, showing 50 % and 40 % of inhibition, respectively. After MTT assay, cell viability was maintained approximately 100 % for all derivatives at concentrations of 20 mg/mL on RAW 264.7 macrophages and 86 % with 250 μg/mL on L929 cells. Galactomannan was successfully modified, demonstrating strong antibacterial activity, concomitant to the increase in DS, Zeta potential and reduction of molar mass, with good biocompatibility. Therefore, this study presents a new material with potential for development of formulations for biomedical applications, from industrial waste, strengthening of the D. gardneriana production chain.

Infective Endocarditis by Biofilm-Producing Methicillin-Resistant Staphylococcus aureus-Pathogenesis, Diagnosis, and Management

Infective endocarditis (IE) is a life-threatening condition with increasing global incidence, primarily caused by Staphylococcus aureus, especially methicillin-resistant strains (MRSA). Biofilm formation by S. aureus is a critical factor in pathogenesis, contributing to antimicrobial resistance and complicating the treatment of infections involving prosthetic valves and cardiovascular devices. Biofilms provide a protective matrix for MRSA, shielding it from antibiotics and host immune defenses, leading to persistent infections and increased complications, particularly in cases involving prosthetic materials. Clinical manifestations range from acute to chronic presentations, with complications such as heart failure, embolic events, and neurological deficits. Diagnosis relies on the Modified Duke Criteria, which have been updated to incorporate modern cardiovascular interventions and advanced imaging techniques, such as PET/CT (positron emission tomography, computed tomography), to improve the detection of biofilm-associated infections. Management of MRSA-associated IE requires prolonged antimicrobial therapy, often with vancomycin or daptomycin, needing a combination of antimicrobials in the setting of prosthetic materials and frequently necessitates surgical intervention to remove infected prosthetic material or repair damaged heart valves. Anticoagulation remains controversial, with novel therapies like dabigatran showing potential benefits in reducing thrombus formation. Despite progress in treatment, biofilm-associated resistance poses ongoing challenges. Emerging therapeutic strategies, including combination antimicrobial regimens, bacteriophage therapy, antimicrobial peptides (AMPs), quorum sensing inhibitors (QSIs), hyperbaric oxygen therapy, and nanoparticle-based drug delivery systems, offer promising approaches to overcoming biofilm-related resistance and improving patient outcomes. This review provides an overview of the pathogenesis, current management guidelines, and future directions for treating biofilm-related MRSA IE.

Development of Naphthalene-Derivative Bis-QACs as Potent Antimicrobials: Unraveling Structure-Activity Relationship and Microbiological Properties

While the pandemic is behind us, the world community faces a global threat of bacterial resistance outbreak. One of the key ways to combat the spread of multi-resistant bacteria is infection prevention and control tactics using modern antiseptic and disinfectant compositions. Herein, we continue the path to unravel the structure-activity relationship (SAR) of potent pyridine-derived biocide class bis-quaternary ammonium compounds (QACs). In this study, twenty dihydroxynaphthalene-derivative bis-QACs were subjected to extensive microbiological analysis on planktonic cells and biofilms of the ESKAPE microorganisms. Among them, hit compounds were superior in their bacteriostatic and bactericidal action to commercial mono-QACs and were comparable to the best bis-QAC antiseptic on the market. SAR analysis indicated that the linker conformation does not significantly affect the activity, though structure symmetry and especially lipophilicity had an influence on antibacterial performance. Furthermore, we delve deeper in investigation of the antimicrobial potential of bis-QACs and conducted a variety of assays, including time-kill kinetics, bacterial resistance formation, cell morphology, and cytotoxicity. Studies showed promising results for compounds 5d and 6d, indicating 2 to 3-fold less cytotoxicity and hemotoxicity compared to commercial QACs. Moreover, SEM imaging revealed that bis-QACs can cause severe membrane damage to S. aureus and P. aeruginosa strains, confirming great potential of novel compounds as antiseptic and disinfectant.

Modification of Antibacterial Copolymers on the Surface of PVA-Based Microfibers via Thermal Cross-Linking and Their Antibacterial Properties

Bacterial infections on material surfaces are a serious public health concern worldwide. Although poly(vinyl alcohol) (PVA)-based materials have great potential as medical devices, they lack antibacterial properties on their surfaces and pose bacterial infection risks during implantation surgery. Copolymers containing antibacterial [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC) units were used to modify the surfaces of chemically cross-linked water-insoluble PVA-based microfibers. The copolymers also had carboxy units that were used to react with the hydroxy group of the PVA-based microfibers via a simple thermal treatment at 135 °C. PVA-based materials containing METAC units exhibit significant swelling due to electrostatic repulsions. Because the copolymers were modified on the extreme surface of the microfibers, no difference in the diameters between unmodified microfibers (PM-fiber) and copolymers with METAC unit-modified microfibers (PM-METAC-fiber), in both the dry and swollen states, was observed. The viable bacterial cell numbers, which were evaluated by colony counting, decreased by exposure to the poly(METAC-co-methacrylic acid (MAAc)) aqueous solution or PM-METAC-fibers. The value of CFU/mL decreased to 0.1% (against B. subtilis) and 3.9% (against E. coli) after contact with the PM-METAC-fibers compared to the PM-fibers. The percentage of hemolysis against rabbit red blood cells was equivalent to that of the negative control, suggesting that PM-METAC-fibers can selectively exhibit antibacterial properties. This modification method can be applied to various PVA-based materials if hydroxy groups are present on their surface. This study provides a facile, cost-effective, and promising strategy to impart antibacterial properties to the surface of PVA-based materials without significantly affecting their physicochemical properties.

Insight into the Antibacterial Activities of Pyridinium-Based Cationic Pillar[5]arene with Controllable Hydrophobic Chain Lengths against Staphylococcus aureus

The increasing number of infections caused by pathogenic bacteria has severely affected human society. More and more deaths were originated from Gram-positive methicillin-resistant Staphylococcus aureus (MRSA) infection each year. The potential and excellent bacteriostatic activity and resistance to biofilm formation of pillar[5]arene with different functional groups attract important attention to further study the relationship between antimicrobial activity and cytotoxicity by varying the length of the hydrophobic chain, the number of positive charges, and the hydrophobic/hydrophilic balance of the molecule. In this work, four pyridinium-based cationic pillar[5]arene (PPs) with linear aliphatic chains of different lengths were synthesized. After systematic characterization, their inhibition activities against S. aureus were investigated. It revealed that PP6 (six methylenes in each linker) exhibited excellent inhibition activity against S. aureus (ATCC 6538) with a minimum inhibitory concentration (MIC) of 3.91 μg/mL and a minimum bactericidal concentration (MBC) of 62.50 μg/mL. As expected, PP6 exhibited the strongest antibiofilm ability and negligible antimicrobial resistance even after the 20th passage. A study of the action mechanism of selected PPs on the bacterial membrane depolarization and permeability by transmission electron microscopy (TEM) disclosed that the cationic pyridine groups of PPs inserted into the negatively charged bacterial membranes, thereby leading to membranolysis, cytoplasmic content leakage, and cell death. Importantly, PPs all showed very low toxicity to mammalian cells (L929 and HBZY-1), which provided a significant reference for the construction of hypotoxic antibacterial biomaterials for multiple drug-resistant bacteria based on pyridinium-grafted cationic macrocycles with controllable hydrophobic chain lengths.

Microbiological surveillance result of endoscopes after INTERCEPT Foam Spray: a quasi-experimental pilot study in Singapore

BACKGROUND/AIMS

This study aimed to assess the impact of INTERCEPT Foam Spray (IFS) application on delayed endoscope reprocessing through microbiological surveillance culture (MSC).

METHODS

A quasi-experimental, matched-comparison pilot study was conducted using gastrointestinal endoscopy. IFS was applied to the endoscopes after precleaning and before reprocessing the next day. An equal number of endoscopes, matched by endoscope type, were subjected to routine reprocessing. The MSC were subjected to high-level disinfection to detect any contamination. Data were analyzed using the chi-square test or Fisher exact test (categorical data) and Student t-test (continuous data).

RESULTS

In total, 150 MSCs were collected from 42 endoscopes. Positive MSCs were observed in 4.0% (4/75) of the sprayed group and 1.3% (1/75) of the control group (95% confidence interval, 30.34-0.31; p>0.05), all of which were contributed by colonoscopes. Colonoscope were more prone to positive MSC (mean difference in percentage, p<0.05). Mean spraying hours were not associated with detected growth (11.7% vs. 13.6%; 95% confidence interval, 1.43 to -5.27; p>0.05), with environmental and skin flora being the primary contaminants.

CONCLUSIONS

IFS may be applied when delayed endoscope processing is necessary, but with caution when applied to colonoscopes. However, further research is warranted to verify the result.

Naturally derived 3-aminoquinuclidine salts as new promising therapeutic agents

Quaternary ammonium compounds (QACs) are a biologically active group of chemicals with a wide range of different applications. Due to their strong antibacterial properties and broad spectrum of activity, they are commonly used as ingredients in antiseptics and disinfectants. In recent years, the spread of bacterial resistance to QACs, exacerbated by the spread of infectious diseases, has seriously threatened public health and endangered human lives. Recent trends in this field have suggested the development of a new generation of QACs, in parallel with the study of bacterial resistance mechanisms. In this work, we present a new series of quaternary 3-substituted quinuclidine compounds that exhibit potent activity across clinically relevant bacterial strains. Most of the derivatives had minimal inhibitory concentrations (MICs) in the low single-digit micromolar range. Notably, QApCl and QApBr were selected for further investigation due to their strong antibacterial activity and low toxicity to human cells along with their minimal potential to induce bacterial resistance. These compounds were also able to inhibit the formation of bacterial biofilms more effectively than commercial standard, eradicating the bacterial population within just 15 min of treatment. The candidates employ a membranolytic mode of action, which, in combination with the generation of reactive oxygen species (ROS), destabilizes the bacterial membrane. This treatment results in a loss of cell volume and alterations in surface morphology, ultimately leading to bacterial cell death. The prominent antibacterial potential of quaternary 3-aminoquinuclidines, as exemplified by QApCl and QApBr, paves the way for new trends in the development of novel generation of QACs.

Development of quaternary ammonium based acrylic copolymer antimicrobial coatings for polyurethane tracheoesophageal voice prostheses

Tracheoesophageal voice prostheses (TEPs) are soft polymeric devices used to restore the voices of patients who have undergone total laryngectomy (TL). TEPs are implanted on the tracheoesophageal wall and come in direct contact with food, fluid and air. The environment of an implant is a budding ground for growth of microbes, leading to biofilm formation on the TEP surfaces. Biofilm formation is the leading cause of TEP failure because the biofilm affects its functioning by clogging the air passage over several weeks to a few months. Short useful lifespan of TEPs is a concern for patients undergoing total laryngectomy. To increase the useful lifespan of TEPs, it is imperative to prevent biofilm formation. This problem is addressed in the present study by developing a cationic crosslinked antimicrobial coating that prevents biofilm formation through contact killing. An acrylate-based tetracopolymer poly(methyl methacrylate [MMA]-co-nbutyl acrylate [BA]-co-dimethylaminoethyl methacrylate [DMAEMA]-co-2 hydroxyethyl methacrylate [HEMA]) was synthesized by free radical polymerization and was crosslinked by hexamethylene diisocyanate (THDI) trimer through urethane linkages. The crosslinked tetracopolymer coatings were subjected to quaternary ammonium formation through N-alkylation with iodooctane. Different variants of coatings were synthesized and the tetracopolymer with 22.5% MMA, 22.5% BA, 20% HEMA and 35% DMAEMA showed desirable results. The developed coatings were characterized and tested for safety as well as mechanical and antimicrobial efficacy. The final results showed that the developed coatings exhibited good cytocompatibility, haemocompatibility, mechanical properties and antimicrobial properties for 180 days against E. coli, S. aureus and C. albicans.

Bushy-Tailed QACs: The Development of Multicationic Quaternary Ammonium Compounds with a High Degree of Alkyl Chain Substitution

Quaternary ammonium compounds have served as a first line of protection for human health as surface disinfectants and sanitizers for nearly a century. However, increasing levels of bacterial resistance have spurred the development of novel QAC architectures. In light of the observed reduction in eukaryotic cell toxicity when the alkyl chains on QACs are shorter in nature (≤10 C), we prepared 47 QAC architectures that bear multiple short alkyl chains appended to up to three cationic groups, thus rendering them "bushy-tailed" multiQACs. Antibacterial activity was strong (often ~1-4 μM) in a varied set of bushy-tailed architectures, though observed therapeutic indices were not significantly improved over QAC structures bearing fewer and longer alkyl chains.

Calcium Peroxide-Based Hydrogels Enable Biphasic Release of Hydrogen Peroxide for Infected Wound Healing

Wound infection is a major factor affecting the speed and quality of wound healing. While hydrogen peroxide (H2O2) is recognized for its antibacterial capacity and facilitation of wound healing, its administration requires careful dosage differentiation. Inappropriately matched dosages can protract the healing of infected wounds. Herein, a calcium peroxide-based hydrogel (CPO-Alg hydrogel) is fabricated to enable a biphasic tapered release of H2O2, ensuring robust initial antimicrobial activity followed by sustained promotion of cellular proliferation of wound healing. The design of the hydrogel allowed for the calcium peroxide nanoparticles (CPO NPs) being in two spatial niches within the gel framework. When applied to infectious wounds, CPO NPs with weak constraints are promptly released out of the gel, penetrating into infected regions to serve as antibacterial agents that eliminate bacteria and biofilms at high concentrations. Conversely, the entrapped CPO NPs structurally integrated into the gel remain confined, thus gradually degrading and allowing a mild release of H2O2 through hydrolysis in a moist environment that contributes to the cell growth in the later stage. The CPO-Alg hydrogel represents an innovative and practical solution for the antimicrobial protection of chronic wounds, offering promising prospects for advancing wound healing.

The Highly Durable Antibacterial Gel-like Coatings for Textiles

Hospital-acquired infections are considered a priority for public health systems since they pose a significant burden for society. High-touch surfaces of healthcare centers, including textiles, provide a suitable environment for pathogenic bacteria to grow, necessitating incorporating effective antibacterial agents into textiles. This paper introduces a highly durable antibacterial gel-like solution, Silver Shell™ finish, which contains chitosan-bound silver chloride microparticles. The study investigates the coating's environmental impact, health risks, and durability during repeated washing. The structure of the Silver Shell™ finish was studied using transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). The TEM images showed a core-shell structure, with chitosan forming a protective shell around groupings of silver microparticles. The field-emission scanning electron microscopy (FESEM) demonstrated the uniform deposition of Silver Shell™ on the surfaces of the fabrics. AATCC Test Method 100 was employed to quantitatively analyze the antibacterial properties of the fabrics coated with silver microparticles. Two types of bacteria, Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), were used in this study. The antibacterial results showed that after 75 wash cycles, a 100% reduction for both S. aureus and E. coli in the coated samples using crosslinking agents was observed. The coated samples without a crosslinking agent exhibited 99.88% and 99.81% reductions for S. aureus and E. coli after 50 washing cycles. To compare the antibacterial properties toward non-pathogenic and pathogenic strains of the same species, MG1655 model E. coli strain (ATCC 29213) and a multidrug-resistant clinical isolate were used. The results showed the antibacterial efficiency of the Silver ShellTM solution (up to 99.99% reduction) coated on cotton fabric. AATCC-147 was performed to investigate the coated samples' leaching properties and the crosslinking agent's effects against S. aureus and E. coli. All coated samples demonstrated remarkable antibacterial efficacy, even after 75 wash cycles. The crosslinking agent facilitated durable attachment between the silver microparticles and cotton substrate, minimizing the release of particles from the fabrics. Color measurements were conducted to assess the color differences resulting from the coating process. The results indicated fixation values of 44%, 32%, and 28% following 25, 50, and 75 washing cycles, respectively.

pH-Responsive Charge Convertible Hyperbranched Poly(ionic liquid) Nanoassembly with High Biocompatibility for Resistance-Free Antimicrobial Applications

As a potential alternative to antibiotics, hyperbranched poly(ionic liquid)s (HPILs) have demonstrated significant potential in combating bacterial biofilms. However, their high cation density poses a high risk of toxicity, greatly limiting their in vivo applications. In this study, we constructed a biocompatible HPIL (HPIL-Glu) from a hyperbranched polyurea core with modified terminals featuring charge-convertible ionic liquids. These ionic liquid moieties consist of an ammonium-based cation and a gluconate (Glu) organic counter. HPIL-Glu could form a homogeneous nanoassembly in water and exhibited a pH-responsive charge conversion property. Under neutral conditions, Glu shielded the positively charged surface, minimizing the toxicity. In a mildly acidic environment, Glu protonation exposes cationic moieties to biofilm eradication. Comprehensive antimicrobial assessments demonstrate that HPIL-Glu effectively kills bacteria and promotes the healing of bacteria-infected chronic wounds. Furthermore, prolonged exposure to HPIL-Glu does not induce antimicrobial resistance.

Chimeric Amphiphilic Disinfectants: Quaternary Ammonium/Quaternary Phosphonium Hybrid Structures

Cationic biocides play a crucial role in the disinfection of domestic and healthcare surfaces. Due to the rise of bacterial resistance towards common cationic disinfectants like quaternary ammonium compounds (QACs), the development of novel actives is necessary for effective infection prevention and control. Toward this end, a series of 15 chimeric biscationic amphiphilic compounds, bearing both ammonium and phosphonium residues, were prepared to probe the structure and efficacy of mixed cationic ammonium-phosphonium structures. Compounds were obtained in two steps and good yields, with straightforward and chromatography-free purifications. Antibacterial activity evaluation of these compounds against a panel of seven bacterial strains, including two MRSA strains as well as opportunistic pathogen A. baumannii, were encouraging, as low micromolar inhibitory activity was observed for multiple structures. Alkyl chain length on the ammonium group was, as expected, a major determinant of bioactivity. In addition, high therapeutic indexes (up to 125-fold) for triphenyl phosphonium-bearing amphiphiles were observed when comparing antimicrobial activity to mammalian cell lysis activity.

Regulating molecular brush structure on cotton textiles for efficient antibacterial properties

The molecular brush structures have been developed on cotton textiles for long-term and efficient broad-spectrum antimicrobial performances through the cooperation of alkyl-chain and quaternary ammonium sites. Results show that efficient antibacterial performances can be achieved by the regulation of the alkyl chain length and quaternary ammonium sites. The antibacterial efficiency of the optimized molecular brush structure of [3-(N,N-Dimethylamino)propyl]trimethoxysilane with cetyl modification on cotton textiles (CT-DM-16) can reach more than 99 % against both E. coli and S. aureus. Alkyl-chain grafting displayed significantly improvement in the antibacterial activity against S. aureus with (N,N-Diethyl-3-aminopropyl)trimethoxysilane modification on cotton textiles (CT-DE) based materials. The positive N sites and alkyl chains played important roles in the antibacterial process. Proteomic analysis reveals that the contributions of cytoskeleton and membrane-enclosed lumen in differentially expressed proteins have been increased for the S. aureus antibacterial process, confirming the promoted puncture capacity with alkyl-chain grafting. Theoretical calculations indicate that the positive charge of N sites can be enhanced through alkyl-chain grafting, and the possible distortion of the brush structure in application can further increase the positive charge of N sites. Uncovering the regulation mechanism is considered to be important guidance to develop novel and practical antibacterial materials.

Pillar[n]arenes in the Fight against Biofilms: Current Developments and Future Perspectives

The global surge in bacterial infections, compounded by the alarming escalation of drug-resistant strains, has evolved into a critical public health crisis. Among the challenges posed, biofilms stand out due to their formidable resistance to conventional antibiotics. This review delves into the burgeoning potential of pillar[n]arenes, distinctive macrocyclic host molecules, as promising anti-biofilm agents. The review is structured into two main sections, each dedicated to exploring distinct facets of pillar[n]arene applications. The first section scrutinizes functionalized pillar[n]arenes with a particular emphasis on cationic derivatives. This analysis reveals their significant efficacy in inhibiting biofilm formation, underscoring the pivotal role of specific chemical attributes in combating microbial communities. The second section of the review shifts its focus to inclusion complexes, elucidating how pillar[n]arenes serve as encapsulation platforms for antibiotics. This encapsulation enhances the stability of antibiotics and enables a controlled release, thereby amplifying their antibacterial activity. The examination of inclusion complexes provides valuable insights into the potential synergy between pillar[n]arenes and traditional antibiotics, offering a novel avenue for overcoming biofilm resistance. This comprehensive review highlights the escalating global threat of bacterial infections and the urgent need for innovative strategies to counteract drug-resistant biofilms. The unique properties of pillar[n]arenes, both as functionalized molecules and as inclusion complex hosts, position them as promising candidates in the quest for effective anti-biofilm agents. The exploration of their distinct mechanisms opens new avenues for research and development in the ongoing battle against bacterial infections and biofilm-related health challenges.

Dynamic Antimicrobial Poly(disulfide) Coatings Exfoliate Biofilms On Demand Via Triggered Depolymerization

Bacterial biofilms are notoriously problematic in applications ranging from biomedical implants to ship hulls. Cationic, amphiphilic antibacterial surface coatings delay the onset of biofilm formation by killing microbes on contact, but they lose effectiveness over time due to non-specific binding of biomass and biofilm formation. Harsh treatment methods are required to forcibly expel the biomass and regenerate a clean surface. Here, a simple, dynamically reversible method of polymer surface coating that enables both chemical killing on contact, and on-demand mechanical delamination of surface-bound biofilms, by triggered depolymerization of the underlying antimicrobial coating layer, is developed. Antimicrobial polymer derivatives based on α-lipoic acid (LA) undergo dynamic and reversible polymerization into polydisulfides functionalized with biocidal quaternary ammonium salt groups. These coatings kill >99.9% of Staphylococcus aureus cells, repeatedly for 15 cycles without loss of activity, for moderate microbial challenges (≈105 colony-forming units (CFU) mL-1, 1 h), but they ultimately foul under intense challenges (≈107 CFU mL-1, 5 days). The attached biofilms are then exfoliated from the polymer surface by UV-triggered degradation in an aqueous solution at neutral pH. This work provides a simple strategy for antimicrobial coatings that can kill bacteria on contact for extended timescales, followed by triggered biofilm removal under mild conditions.

Application of an Antibacterial Coating Layer via Amine-Terminated Hyperbranched Zirconium-Polysiloxane for Stainless Steel Orthodontic Brackets

The massive growth of various microorganisms on the orthodontic bracket can form plaques and cause diseases. A novel amine-terminated hyperbranched zirconium-polysiloxane (HPZP) antimicrobial coating was developed for an orthodontic stainless steel tank (SST). After synthesizing HPZP and HPZP-Ag coatings, their structures were characterized by nuclear magnetic resonance spectroscopy, scanning electron microscopy, thickness measurement, contact angle detection, mechanical stability testing, and corrosion testing. The cell toxicity of the two coatings to human gingival fibroblasts (hGFs) and human oral keratinocytes (hOKs) was detected by cell counting kit eight assays, and SST, HPZP@SST, and HPZP-Ag@SST were cocultured with Staphylococcus aureus, Escherichia coli, and Streptococcus mutans for 24 hr to detect the antibacterial properties of the coatings, respectively. The results show that the coatings are about 10 μm, and the water contact angle of HPZP coating is significantly higher than that of HPZP-Ag coating (P < 0.01). Both coatings can be uniformly and densely distributed on SST and have good mechanical stability and corrosion resistance. The cell counting test showed that HPZP coating and HPZP-Ag coating were less toxic to cells compared with SST, and the toxicity of HPZP-Ag coating was greater than that of HPZP coating, with the cell survival rate greater than 80% after 72 hr cocultured with hGFs and hOKs. The antibacterial test showed that the number of bacteria on the surface of different materials was ranked from small to large: HPZP@SST < HPZP-Ag@SST < SST and 800 μg/mL HPZP@SST showed a better bactericidal ability than 400 μg/mL after cocultured with S. aureus, E. coli, and S. mutans, respectively (all P < 0.05). The results showed that HPZP coating had a better effect than HPZP-Ag coating, with effective antibacterial and biocompatible properties, which had the potential to be applied in orthodontic process management.

Structural Element of Vitamin U-Mimicking Antibacterial Polypeptide with Ultrahigh Selectivity for Effectively Treating MRSA Infections

Antimicrobial peptides (AMPs) exhibit mighty antibacterial properties without inducing drug resistance. Achieving much higher selectivity of AMPs towards bacteria and normal cells has always been a continuous goal to be pursued. Herein, a series of sulfonium-based polypeptides with different degrees of branching and polymerization were synthesized by mimicking the structure of vitamin U. The polypeptide, G2 -PM-1H+ , shows both potent antibacterial activity and the highest selectivity index of 16000 among the reported AMPs or peptoids (e.g., the known index of 9600 for recorded peptoid in "Angew. Chem. Int. Ed., 2020, 59, 6412."), which can be attributed to the high positive charge density of sulfonium and the regulation of hydrophobic chains in the structure. The antibacterial mechanisms of G2 -PM-1H+ are primarily ascribed to the interaction with the membrane, production of reactive oxygen species (ROS), and disfunction of ribosomes. Meanwhile, altering the degree of alkylation leads to selective antibacteria against either gram-positive or gram-negative bacteria in a mixed-bacteria model. Additionally, both in vitro and in vivo experiments demonstrated that G2 -PM-1H+ exhibited superior efficacy against methicillin-resistant Staphylococcus aureus (MRSA) compared to vancomycin. Together, these results show that G2 -PM-1H+ possesses high biocompatibility and is a potential pharmaceutical candidate in combating bacteria significantly threatening human health.

Strategies for combating antibiotic resistance in bacterial biofilms

Biofilms, which are complexes of microorganisms that adhere to surfaces and secrete protective extracellular matrices, wield substantial influence across diverse domains such as medicine, industry, and environmental science. Despite ongoing challenges posed by biofilms in clinical medicine, research in this field remains dynamic and indeterminate. This article provides a contemporary assessment of biofilms and their treatment, with a focus on recent advances, to chronicle the evolving landscape of biofilm research.

Towards Antibacterial Agents: Synthesis and Biological Activity of Multivalent Amide Derivatives of Thiacalix[4]arene with Hydroxyl and Amine Groups

Antimicrobial resistance to modern antibiotics stimulates the search for new ways to synthesize and modify antimicrobial drugs. The development of synthetic approaches that can easily change different fragments of the molecule is a promising solution to this problem. In this work, a synthetic approach was developed to obtain multivalent thiacalix[4]arene derivatives containing different number of amine and hydroxyl groups. A series of macrocyclic compounds in cone, partial cone, and 1,3-alternate stereoisomeric forms containing -NHCH2CH2R (R = NH2, N(CH3)2, and OH) and -N(CH2CH2OH)2 terminal fragments, and their model non-macrocyclic analogues were obtained. The antibacterial activity against Gram-positive (Staphylococcus aureus, Bacillus cereus, and Enterococcus faecalis) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacterial strains and cytotoxicity of the obtained compounds were studied. Structure-activity relationships were established: (1) the macrocyclic compounds had high antibacterial activity, while the monomeric compounds had low activity; (2) the compounds in cone and partial cone conformations had better antibacterial activity compared to the compounds in 1,3-alternate stereoisomeric form; (3) the macrocyclic compounds containing -NHCH2CH2N(CH3)2 terminal fragments had the highest antibacterial activity; (4) introduction of additional terminal hydroxyl groups led to a significant decrease in antibacterial activity; (5) the compounds in partial cone conformation had significant bactericidal activity against all studied cell strains; the best selectivity was observed for the compounds in cone conformation. The mechanism of antibacterial activity of lead compounds with terminal fragments -NHCH2CH2N(CH3)2 was proved using model negatively charged POPG vesicles, i.e., the addition of these compounds led to an increase in the size and zeta potential of the vesicles. The obtained results open up the possibility of using the synthesized macrocyclic compounds as promising antibacterial agents.

d-tyrosine enhances disoctyl dimethyl ammonium chloride on alleviating SRB corrosion

Microbiologically influenced corrosion (MIC) caused by sulfate reducing bacteria (SRB) is a serious challenge in many industries, but biofilm greatly decreases the toxicity of bactericides to cell inside. d-amino acids are potential enhancers for bactericides due to their excellent performance on biofilm inhibition. However, the mechanism of d-amino acid cooperating with bactericides for MIC inhibition is still unknown. In this study, d-tyrosine（D-Tyr）and disoctyl dimethyl ammonium chloride (DDAC) were selected as the typical d-amino acid and bactericide, respectively, to evaluate their synergetic inhibition on the corrosion caused by Desulfovibrio vulgaris. D-Tyr obviously enhanced the role of DDAC in inhibiting corrosion with high corrosion inhibition efficiency at 77.23 %. The attachment of EPS and live cells on the coupon surface decreased in the presence of D-Try, leading to more cells directly exposed to DDAC. Besides, D-Try decreased the amount of live cells on the surface and thus reduced the utilization of Fe by SRB and corrosion current. Moreover, dead cells settling to the coupon surface may form a protective lay to retard the contact between live SRB and Fe, leading to slow cathode reaction and less corrosion. Therefore, D-Tyr can reduce the coverage of biofilm, thereby reducing its protective effect on SRB and achieving better corrosion inhibition effect. This work provides a new strategy for improving bactericides and inhibiting MIC.

Oxygen-Containing Quaternary Phosphonium Salts (oxy-QPSs): Synthesis, Properties, and Cellulose Dissolution

In the present study, the synthesis of oxygen-containing quaternary phosphonium salts (oxy-QPSs) was described. Within this work, structure-property relationships of oxy-QPSs were estimated by systematic analysis of physical-chemical properties. The influence of the oxygen-containing substituent was examined by comparing the properties of oxy-QPSs in homology series as well as with phosphonium analog-included alkyl side chains. The crystal structure analysis showed that the oxygen introduction influences the conformation of the side chain of the oxy-QPS. It was found that oxy-QPSs, using an aprotic co-solvent, dimethylsulfoxide (DMSO), can dissolve microcrystalline cellulose. The cellulose dissolution in oxy-QPSs appeared to be dependent on the functional group in the cation and anion nature. For the selected conditions, dissolution of up to 5 wt% of cellulose was observed. The antimicrobial activity of oxy-QPSs under study was expected to be low. The biocompatibility of oxy-QPSs with fermentative microbes was tested on non-pathogenic Saccharomyces cerevisiae, Lactobacillus plantarum, and Bacillus subtilis. This reliably allows one to safely address the combined biomass destruction and enzyme hydrolysis processes in one pot.

Combinatorial Screening of Cationic Lipidoids Reveals How Molecular Conformation Affects Membrane-Targeting Antimicrobial Activity

The search for next-generation antibacterial compounds that overcome the development of resistance can be facilitated by identifying how to target the cell membrane of bacteria. Understanding the key molecular features that enable interactions with lipids and lead to membrane disruption is therefore crucial. Here, we employ a library of lipid-like compounds (lipidoids) comprising modular structures with tunable hydrophobic and hydrophilic architecture to shed light on how the chemical functionality and molecular shape of synthetic amphiphilic compounds determine their activity against bacterial membranes. Synthesized from combinations of 8 different polyamines as headgroups and 13 acrylates as tails, 104 different lipidoids are tested for activity against a model Gram-positive bacterial strain (Bacillus subtilis). Results from the combinatorial screening assay show that lipidoids with the most potent antimicrobial properties (down to 2 μM) have intermediate tail hydrophobicity (i.e., c log P values between 3 and 4) and lower headgroup charge density (i.e., longer spacers between charged amines). However, the most important factor appeared to be the ability of a lipidoid to self-assemble into an inverse hexagonal liquid crystalline phase, as observed by small-angle X-ray scattering (SAXS) analysis. The lipidoids active at lowest concentrations, which induced the most significant membrane damage during propidium iodide (PI) permeabilization assays, were those that aggregated into highly curved inverse hexagonal liquid crystal phases. These observations suggest that the introduction of strong curvature stress into the membrane is one way to maximize membrane disruption and lipidoid antimicrobial activity. Lipidoids that demonstrated the ability to furnish this phase consisted of either (i) branched or linear headgroups with shorter linear tails or (ii) cyclic headgroups with 4 bulky nonlinear tails. On the contrary, lipidoids previously observed to adopt disc-like conformations that pack into bicontinuous cubic phases were significantly less effective against B. subtilis. The discovery of these structure-property relationships demonstrates that it is not simply a balance of hydrophobic and hydrophilic moieties that govern membrane-active antibacterial activity, but also their intrinsic curvature and collective behavior.

Multiheaded Cationic Surfactants with Dedicated Functionalities: Design, Synthetic Strategies, Self-Assembly and Performance

Contemporary research concerning surfactant science and technology comprises a variety of requirements relating to the design of surfactant structures with widely varying architectures to achieve physicochemical properties and dedicated functionality. Such approaches are necessary to make them applicable to modern technologies, such as nanostructure engineering, surface structurization or fine chemicals, e.g., magnetic surfactants, biocidal agents, capping and stabilizing reagents or reactive agents at interfaces. Even slight modifications of a surfactant's molecular structure with respect to the conventional single-head-single-tail design allow for various custom-designed products. Among them, multicharge structures are the most intriguing. Their preparation requires specific synthetic routes that enable both main amphiphilic compound synthesis using appropriate step-by-step reaction strategies or coupling approaches as well as further derivatization toward specific features such as magnetic properties. Some of the most challenging aspects of multicharge cationic surfactants relate to their use at different interfaces for stable nanostructures formation, applying capping effects or complexation with polyelectrolytes. Multiheaded cationic surfactants exhibit strong antimicrobial and antiviral activity, allowing them to be implemented in various biomedical fields, especially biofilm prevention and eradication. Therefore, recent advances in synthetic strategies for multiheaded cationic surfactants, their self-aggregation and performance are scrutinized in this up-to-date review, emphasizing their applications in different fields such as building blocks in nanostructure engineering and their use as fine chemicals.

Preparation strategy of hydrogel microsphere and its application in skin repair

In recent years, hydrogel microsphere has attracted much attention due to its great potential in the field of skin repair. This paper reviewed the recent progress in the preparation strategy of hydrogel microsphere and its application in skin repair. In this review, several preparation methods of hydrogel microsphere were summarized in detail. In addition, the related research progress of hydrogel microspheres for skin repair was reviewed, and focused on the application of bioactive microspheres, antibacterial microspheres, hemostatic microspheres, and hydrogel microspheres as delivery platforms (hydrogel microspheres as a microcarrier of drugs, bioactive factors, or cells) in the field of skin repair. Finally, the limitations and future prospects of the development of hydrogel microspheres and its application in the field of skin repair were presented. It is hoped that this review can provide a valuable reference for the development of the preparation strategy of hydrogel microspheres and promote the application of hydrogel microspheres in skin repair.

The Antimicrobial and Antibiofilm Potential of New Water-Soluble Tris-Quaternary Ammonium Compounds

The invention and innovation of highly effective antimicrobials are always crucial tasks for medical and organic chemistry, especially at the current time, when there is a serious threat of shortages of effective antimicrobials following the pandemic. In the study presented in this article, we established a new approach to synthesizing three novel series of bioactive water-soluble tris-quaternary ammonium compounds using an optimized one-pot method, and we assessed their antimicrobial and antibiofilm potential. Five pathogenic microorganisms of the ESKAPE group, including highly resistant clinical isolates, were used as the test samples. Moreover, we highlighted the dependence of antibacterial activity from the hydrophilic-hydrophobic balance of the QACs and noted the significant performance of the desired products on biofilms with MBEC as low as 16 mg/L against bacteria and 8 mg/L against fungi. Particularly notable was the high activity against Pseudomonas aeruginosa and Acinetobacter baumannii, which are among the most resilient bacteria known. The presented work will provide useful insights for future research on the topic.

Multicationic Quaternary Ammonium Compounds: A Framework for Combating Bacterial Resistance

During previous stages of research, high biocidal activity toward microorganism archival strains has been used as the main indicator in the development of new antiseptic formulations. Although this factor remains one of the most important characteristics of biocide efficiency, the scale of antimicrobial resistance spread causes serious concern. Therefore, focus shifts toward the development of formulations with a stable effect even in the case of prolonged contact with pathogens. Here, we introduce an original isocyanuric acid alkylation method with the use of available alkyl dichlorides, which opened access to a wide panel of multi-QACs with alkyl chains of various lengths between the nitrogen atoms of triazine and pyridine cycles. We used a complex approach for the resulting series of 17 compounds, including their antibiofilm properties, bacterial tolerance development, and antimicrobial activity toward multiresistant pathogenic strains. As a result of these efforts, available compounds have shown higher levels of antibacterial activity against ESKAPE pathogens than widely used commercial QACs. Hit compounds possessed high activity toward clinical bacterial strains and have also demonstrated a long-term biocidal effect without significant development of microorganism tolerance. The overall results indicated a high level of antibacterial activity and the broad application prospects of multi-QACs based on isocyanuric acid against multiresistant bacterial strains.