Antifungal activity of gemini quaternary ammonium salts

Exploring the Correlation of Dynamic Surface Tension with Antimicrobial Activities of Quaternary Ammonium-Based Disinfectants

Quaternary ammonium compound (QAC) disinfectants represent one of our first lines of defense against pathogens. Their inhibitory and bactericidal activities are usually tested through minimum inhibitory concentration (MIC) and time-kill assays, but these assays can become cumbersome when screening many compounds. We investigated how the dynamic surface tension (DST) measurements of QACs correlate with these antimicrobial activities by testing a panel of potent and structurally varied QACs against the gram-positive Staphylococcus aureus and the gram-negative Pseudomonas aeruginosa. We found that DST values correlated well with bactericidal activity in real-world disinfection conditions but not with MIC values. Moreover, no correlation between these two antimicrobial activities of QACs (bactericidal and inhibition) was observed. In addition, we observed that the bactericidal activity of our QAC panel against the gram-negative P. aeruginosa was severely affected in the presence of hard water. Interestingly, we found that the counterion of the QAC affects the killing of bacteria in these conditions, a phenomenon not observed in most MIC assessments. Moreover, some of our best-in-class QACs show enhanced bactericidal activity when combined with a commercially available QAC. In conclusion, we determined that an intrinsic physical property of QACs (DST) can be used as a technique to screen for bactericidal activity of QACs in conditions that mimic real-world disinfection conditions.

Anti-adhesive, anti-biofilm and fungicidal action of newly synthesized gemini quaternary ammonium salts

Newly synthesized gemini quaternary ammonium salts (QAS) with different counterions (bromide, hydrogen chloride, methylcarbonate, acetate, lactate), chain lengths (C12, C14, C16) and methylene linker (3xCH2) were tested. Dihydrochlorides and dibromides with 12 carbon atoms in hydrophobic chains were characterized by the highest biological activity against planktonic forms of yeast and yeast-like fungi. The tested gemini surfactants also inhibited the production of filaments by C. albicans. Moreover, they reduced the adhesion of C. albicans cells to the surfaces of stainless steel, silicone and glass, and slightly to polystyrene. In particular, the gemini compounds with 16-carbon alkyl chains were most effective against biofilms. It was also found that the tested surfactants were not cytotoxic to yeast cells. Moreover, dimethylcarbonate (2xC12MeCO3G3) did not cause hemolysis of sheep erythrocytes. Dihydrochlorides, dilactate and diacetate showed no mutagenic potential.

A Combination of β-Aescin and Newly Synthesized Alkylamidobetaines as Modern Components Eradicating the Biofilms of Multidrug-Resistant Clinical Strains of Candida glabrata

The current trend in microbiological research aimed at limiting the development of biofilms of multidrug-resistant microorganisms is increasingly towards the search for possible synergistic effects between various compounds. This work presents a combination of a naturally occurring compound, β-aescin, newly synthesized alkylamidobetaines (AABs) with a general structure-CnTMDAB, and antifungal drugs. The research we conducted consists of several stages. The first stage concerns determining biological activity (antifungal) against selected multidrug-resistant strains of Candida glabrata (C. glabrata) with the highest ability to form biofilms. The second stage of this study determined the activity of β-aescin combinations with antifungal compounds and alkylamidobetaines. In the next stage of this study, the ability to eradicate a biofilm on the polystyrene surface of the combination of β-aescin with alkylamidobetaines was examined. It has been shown that the combination of β-aescin and alkylamidobetaine can firmly remove biofilms and reduce their viability. The last stage of this research was to determine the safety regarding the cytotoxicity of both β-aescin and alkylamidobetaines. Previous studies on the fibroblast cell line have shown that C9 alkylamidobetaine can be safely used as a component of anti-biofilm compounds. This research increases the level of knowledge about the practical possibilities of using anti-biofilm compounds in combined therapies against C. glabrata.

Shifting from Ammonium to Phosphonium Salts: A Promising Strategy to Develop Next-Generation Weapons against Biofilms

Since they are difficult and sometimes impossible to treat, infections sustained by multidrug-resistant (MDR) pathogens, emerging especially in nosocomial environments, are an increasing global public health concern, translating into high mortality and healthcare costs. In addition to having acquired intrinsic abilities to resist available antibiotic treatments, MDR bacteria can transmit genetic material encoding for resistance to non-mutated bacteria, thus strongly decreasing the number of available effective antibiotics. Moreover, several pathogens develop resistance by forming biofilms (BFs), a safe and antibiotic-resistant home for microorganisms. BFs are made of well-organized bacterial communities, encased and protected in a self-produced extracellular polymeric matrix, which impedes antibiotics' ability to reach bacteria, thus causing them to lose efficacy. By adhering to living or abiotic surfaces in healthcare settings, especially in intensive care units where immunocompromised older patients with several comorbidities are hospitalized BFs cause the onset of difficult-to-eradicate infections. In this context, recent studies have demonstrated that quaternary ammonium compounds (QACs), acting as membrane disruptors and initially with a low tendency to develop resistance, have demonstrated anti-BF potentialities. However, a paucity of innovation in this space has driven the emergence of QAC resistance. More recently, quaternary phosphonium salts (QPSs), including tri-phenyl alkyl phosphonium derivatives, achievable by easy one-step reactions and well known as intermediates of the Wittig reaction, have shown promising anti-BF effects in vitro. Here, after an overview of pathogen resistance, BFs, and QACs, we have reviewed the QPSs developed and assayed to this end, so far. Finally, the synthetic strategies used to prepare QPSs have also been provided and discussed to spur the synthesis of novel compounds of this class. We think that the extension of the knowledge about these materials by this review could be a successful approach to finding effective weapons for treating chronic infections and device-associated diseases sustained by BF-producing MDR bacteria.

Applications of quaternary ammonium compounds in the prevention and treatment of oral diseases: State-of-the-art and future directions

OBJECTIVES

The aim of this review is to comprehensively summarize the state-of-the-art developments of quaternary ammonium compounds (QACs) in the prevention and treatment of oral diseases. By discussing the structural diversity and the potential killing mechanism, we try to offer some insights for the future research of QACs.

DATA, SOURCES & STUDY SELECTION

A literature search was conducted in electronic databases (Web of Science, PubMed, Medline, and Scopus). Publications that involved the applications of QACs, especially those related to the prevention and treatment of oral diseases, are included.

RESULTS

We have reviewed the relevant research on QACs over the past two decades. The research results indicate that the current applications are mainly focused on dental material modification and direct pharmacological interventions. Concurrently, challenges such as potential risks to normal tissues and impediments in drug resistance and microbial persistence present certain application constraints. The latest studies have encompassed the exploration of smart materials and nanoparticle formulations.

CONCLUSIONS

The killing mechanism may possess a threshold related to charge density. However, the exact process remains enigmatic. The structural diversity and the exploration of intelligent materials and nanoparticle formulations provide directions in development of novel QACs.

CLINICAL SIGNIFICANCE

The intricate oral anatomy, combined with the multifaceted oral microbiome, necessitates specialized materials for the targeted prevention and treatment of oral pathologies. QACs represent a cohort of compounds distinguished by potent anti-infective and anti-tumor attributes. Innovations in intelligent materials and nanoparticle formulations amplify their potential in significantly advancing the prevention and therapeutic interventions for oral diseases.

Biocidal and antibiofilm activities of arginine-based surfactants against Candida isolates

Amino-acid-based surfactants are a group of compounds that resemble natural amphiphiles and thus are expected to have a low impact on the environment, owing to either the mode of surfactant production or its means of disposal. Within this context, arginine-based tensioactives have gained particular interest, since their cationic nature-in combination with their amphiphilic character-enables them to act as broad-spectrum biocides. This capability is based mainly on their interactive affinity for the microbial envelope that alters the latter's structure and ultimately its function. In the work reported here, we investigated the efficiency of Nα-benzoyl arginine decyl- and dodecylamide against Candida spp. to further our understanding of the antifungal mechanism involved. For the assays, both a Candida albicans and a Candida tropicalis clinical isolates along with a C. albicans-collection strain were used as references. As expected, both arginine-based compounds proved to be effective against the strains tested through inhibiting both the planktonic and the sessile growth. Furthermore, atomic force microscopy techniques and lipid monolayer experiments enabled us to gain insight into the effect of the surfactant on the cellular envelope. The results demonstrated that all the yeasts treated exhibited changes in their exomorphologic structure, with respect to alterations in both roughness and stiffness, relative to the nontreated ones. This finding-in addition to the amphiphiles' proven ability to insert themselves within this model fungal membrane-could explain the changes in the yeast-membrane permeability that could be linked to viability loss and mixed-vesicle release.

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.

The effectiveness of newly synthesized quaternary ammonium salts differing in chain length and type of counterion against priority human pathogens

Quaternary ammonium salts (QAS) commonly occur as active substances in disinfectants. QAS have the important property of coating abiotic surfaces, which prevents adhesion of microorganisms, thus inhibiting biofilm formation. In this study, a group of nine monomeric QAS, differing in the structure and length of the aliphatic chain (C12, C14, C16) and the counterion (methylcarbonate, acetate, bromide), were investigated. The study included an analysis of their action against planktonic forms as well as bacterial biofilms. The compounds were tested for their anti-adhesion properties on stainless steel, polystyrene, silicone and glass surfaces. Moreover, mutagenicity analysis and evaluation of hemolytic properties were performed. It was found that compounds with 16-carbon hydrophobic chains were the most promising against both planktonic forms and biofilms. Tested surfactants (C12, C14, C16) showed anti-adhesion activity but it was dependent on the type of the surface and strain used. The tested compounds at MIC concentrations did not cause hemolysis of sheep blood cells. The type of counterion was not as significant for the activity of the compound as the length of the hydrophobic aliphatic chain.

Fabrication of Encapsulated Gemini Surfactants

(1) Background: Encapsulation of surfactants is an innovative approach that allows not only protection of the active substance, but also its controlled and gradual release. This is primarily used to protect metallic surfaces against corrosion or to create biologically active surfaces. Gemini surfactants are known for their excellent anticorrosion, antimicrobial and surface properties; (2) Methods: In this study, we present an efficient methods of preparation of encapsulated gemini surfactants in form of alginate and gelatin capsules; (3) Results: The analysis of infrared spectra and images of the scanning electron microscope confirm the effectiveness of encapsulation; (4) Conclusions: Gemini surfactants in encapsulated form are promising candidates for corrosion inhibitors and antimicrobials with the possibility of protecting the active substance against environmental factors and the possibility of controlled outflow.

Antimicrobial Activity of Gemini Surfactants with Ether Group in the Spacer Part

Due to their large possibility of the structure modification, alkylammonium gemini surfactants are a rapidly growing class of compounds. They exhibit significant surface, aggregation and antimicrobial properties. Due to the fact that, in order to achieve the desired utility effect, the minimal concentration of compounds are used, they are in line with the principle of greenolution (green evolution) in chemistry. In this study, we present innovative synthesis of the homologous series of gemini surfactants modified at the spacer by the ether group, i.e., 3-oxa-1,5-pentane-bis(N-alkyl-N,N-dimethylammonium bromides). The critical micelle concentrations were determined. The minimal inhibitory concentrations of the synthesized compounds were determined against bacteria Escherichia coli ATCC 10536 and Staphylococcus aureus ATCC 6538; yeast Candida albicans ATCC 10231; and molds Aspergillus niger ATCC 16401 and Penicillium chrysogenum ATCC 60739. We also investigated the relationship between antimicrobial activity and alkyl chain length or the nature of the spacer. The obtained results indicate that the synthesized compounds are effective microbicides with a broad spectrum of biocidal activity.

Arginine-phenylalanine and arginine-tryptophan-based surfactants as new biocompatible antifungal agents and their synergistic effect with Amphotericin B against fluconazole-resistant Candida strains

In the past two decades, the increase in microbial resistance to conventional antimicrobials has spurred scientists around the world to search tirelessly for new treatments. Synthetic amino acid-based surfactants constitute a promising alternative to conventional antimicrobial compounds. In this work, two new cationic amino acid-based surfactants were synthesized and their physicochemical, antifungal and antibiofilm properties evaluated. The surfactants were based on phenylalanine-arginine (LPAM) and tryptophan-arginine (LTAM) and prepared from renewable raw materials using a simple chemical procedure. The critical micelle concentrations of the new surfactants were determined by conductivity and fluorescence. Micellization of LPAM and LTAM took place at 1.05 and 0.54 mM, respectively. Both exhibited good antifungal activity against fluconazole-resistant Candida spp. strains, with a low minimum inhibitory concentration (8.2 μg/mL). Their mechanism of action involves alterations in cell membrane permeability and mitochondrial damage, leading to death by apoptosis. Furthermore, when LPAM and LTAM were applied with Amphotericin B, a significant synergistic effect was observed against all the studied Candida strains. These new cationic surfactants are also able to disperse biofilms of Candida spp. at low concentrations. The results indicate that LPAM and LTAM have potential application to combat the advance of fungal resistance as well as microbial biofilms.

Biomaterials for human space exploration: A review of their untapped potential

As biomaterial advances make headway into lightweight radiation protection, wound healing dressings, and microbe resistant surfaces, a relevance to human space exploration manifests itself. To address the needs of the human in space, a knowledge of the space environment becomes necessary. Both an understanding of the environment itself and an understanding of the physiological adaptations to that environment must inform design parameters. The space environment permits the fabrication of novel biomaterials that cannot be produced on Earth, but benefit Earth. Similarly, designing a biomaterial to address a space-based challenge may lead to novel biomaterials that will ultimately benefit Earth. This review describes several persistent challenges to human space exploration, a variety of biomaterials that might mitigate those challenges, and considers a special category of space biomaterial. STATEMENT OF SIGNIFICANCE: This work is a review of the major human and environmental challenges facing human spaceflight, and where biomaterials may mitigate some of those challenges. The work is significant because a broad range of biomaterials are applicable to the human space program, but the overlap is not widely known amongst biomaterials researchers who are unfamiliar with the challenges to human spaceflight. Additionaly, there are adaptations to microgravity that mimic the pathology of certain disease states ("terrestrial analogs") where treatments that help the overwhelmingly healthy astronauts can be applied to help those with the desease. Advances in space technology have furthered the technology in that field on Earth. By outlining ways that biomaterials can promote human space exploration, space-driven advances in biomaterials will further biomaterials technology.

Biofilm eradication and antifungal mechanism of action against Candida albicans of cationic dicephalic surfactants with a labile linker

Our research aims to expand the knowledge on relationships between the structure of cationic dicephalic surfactants—N,N-bis[3,3_-(dimethylamine)propyl]alkylamide dihydrochlorides and N,N-bis[3,3_-(trimethylammonio)propyl]alkylamide dibromides (alkyl: n-C9H19, n-C11H23, n-C13H27, n-C15H31)—and their antifungal mechanism of action on Candida albicans. The mentioned groups of amphiphilic substances are characterized by the presence of a weak, hydrochloride cationic center readily undergoing deprotonation, as well as a stable, strong quaternary ammonium group and alkyl chains capable of strong interactions with fungal cells. Strong fungicidal properties and the role in creation and eradication of biofilm of those compounds were discussed in our earlier works, yet their mechanism of action remained unclear. It was shown that investigated surfactants induce strong oxidative stress and cause increase in cell membrane permeability without compromising its continuity, as indicated by increased potassium ion (K⁺) leakage. Thus experiments carried out on the investigated opportunistic pathogen indicate that the mechanism of action of the researched surfactants is different than in the case of the majority of known surfactants. Results presented in this paper significantly broaden the understanding on multifunctional cationic surfactants and their mechanism of action, as well as suggest their possible future applications as surface coating antiadhesives, fungicides and antibiofilm agents in medicine or industry.

Construction, petro-collecting/dispersing capacities, antimicrobial activity, and molecular docking study of new cationic surfactant-sulfonamide conjugates

Surfactants with their diverse activities have been recently involved in controlling the spread of new coronavirus (COVID-19) pandemic as they are capable of disrupting the membrane surrounding the virus. Using hybrids approach, we constructed a novel series of cationic surfactant-sulfonamide conjugates (3a-g) through quaternization of the as-prepared sulfonamide derivatives (2a-g) with n-hexadecyl iodide followed by structural characterization by spectroscopy (IR and NMR). Being collective properties required in petroleum-processing environment, the petro-collecting/dispersing capacities on the surface of waters with different degrees of mineralization, and the antimicrobial performance against microbes and sulfate-reducing bacteria (SRB) that mitigate microbiological corrosion were investigated for the synthesized conjugates. Among these conjugates, 3g (2.5% aq. solution) exhibited the strongest ability to disperse the thin petroleum film on the seawater surface, whereas K_D is 95.33% after 96 h. In diluted form, 3f collected the petroleum layer on distilled water surface (K_max = 32.01) for duration exceeds 4 days. Additionally, almost all compounds revealed high potency and comparable action with standard antimicrobials, especially 3b and 3f, which emphasize their role as potential biocides. Regarding biocidal activity against SRB, 3g causes a significant reduction in the bacterial count from 2.8 × 10⁶ cells/mL to Nil. Moreover, the conducted molecular docking study confirms the strong correlation between RNA polymerase binding with bioactivity against microbes over other studied proteins (threonine synthase and cyclooxygenase-2).

Antifungal activity of amino-alcohols based cationic surfactants and in silico, homology modeling, docking and molecular dynamics studies against lanosterol 14-α-demethylase enzyme

Fungi are being responsible for causing serious infections in humans and animals. The opportunistic microorganisms provoke environmental contaminations in health and storage facilities to represent a serious concern to health security. The present work investigates the antifungal activity of two amino-alcohols based cationic surfactants such as C_nEtOH, C_nPrOH (with n = 14 and 16 are the carbon numbers of alkyl chain and EtOH = Ethanol and PrOH = Propanol) against a collection of different Candida species (Candida tropicalis, Candida albicans, Candida auris, Cyberlindnera jadinii, Candida parapsilosis, Candida glabrata and Candida rugosa) respectively. The amino-alcohols based cationic surfactants exhibited good antifungal activity against all Candida strains tested with minimum inhibitory concentrations (MIC) ranging from 0.002 to 0.30 mM. The MIC evaluation shows an increase as a function of the hydrophobicity of all inhibitors against the majority of the Candida strains tested. The different location of the alcoholic OH function in the polar head shows the influence on the availability of N⁺ responsible for electrostatic interactions with the candidate's cell walls, which remains a very important step in the mode of action of quaternary ammonium cationic surfactants. Hence, a 3D structure of lanosterol 14-α-demethylase enzyme from C. auris was constructed by homology modeling using an online SWISS-MODEL server. The predicted model was analyzed by serval servers. Furthermore, a molecular docking study was carried out to better understand the binding mechanism of lanosterol homologous protein with surfactant ligands. Then, the docked complexes lanosterol-surfactants were refined by the molecular dynamic simulation to analyze their interaction behavior during the simulation.Communicated by Ramaswamy H. Sarma.

Novel quaternary ammonium compounds derived from aromatic and cyclic amino acids: Synthesis, physicochemical studies and biological evaluation

Novel quaternary ammonium surfactants (QUATs) derived from phenylalaninyl-proline dipeptide with chain length C₁₂ and C₁₄ were synthesised as potential active ingredients to be used in body cleansing formulations. The physicochemical properties and biological activities of the QUATs were determined in both single and in mixed surfactant system with either the conventional anionic surfactant sodium dodecyl sulphate (SDS) or sodium N-dodecyl prolinate. The C₁₂ QUAT derivative showed antagonistic behaviour in both SDS and sodium N-dodecyl prolinate mixed surfactant system. Comparing the mixed system of the C₁₂ QUAT with SDS and sodium N-dodecyl prolinate, it was found that the latter displayed better antibacterial activity together with the lower ocular irritation. The C₁₂ QUAT-sodium N-dodecyl prolinate mixture were non cytotoxic at a concentration corresponding to its MIC value, showing that the mixture was selective towards bacterial cells rather than mammalian cell lines. Diffusion measurements showed that the sodium N-dodecyl prolinate surfactant consisted of 26 molecules per micelle in water but only 3 molecules per micelle in DMSO/water (1:1). On the other hand, C₁₂ QUAT did not form a micelle in DMSO/Water. Membrane permeability studies of the C₁₂ QUAT and sodium N-dodecyl prolinate showed that these surfactants are capable to penetrate into deeper skin layers to exert their antibacterial and cleansing action and hence can be used as a promising candidate as active ingredients in body wash formulations.

Biological activity of quaternary ammonium salts and resistance of microorganisms to these compounds

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.

Synthesis of Silver Nanoparticles with Gemini Surfactants as Efficient Capping and Stabilizing Agents

The scientific community has paid special attention to silver nanoparticles (AgNPs) in recent years due to their huge technological capacities, particularly in biomedical applications, such as antimicrobials, drug-delivery carriers, device coatings, imaging probes, diagnostic, and optoelectronic platforms. The most popular method of obtaining silver nanoparticles as a colloidal dispersion in aqueous solution is chemical reduction. The choice of the capping agent is particularly important in order to obtain the desired size distribution, shape, and dispersion rate of AgNPs. Gemini alkylammonium salts are named as multifunctional surfactants, and possess a wide variety of applications, which include their use as capping agents for metal nanoparticles synthesis. Because of the high antimicrobial activity of gemini surfactants, AgNPs stabilized by this kind of surfactant may possess unique and strengthened biocidal properties. The present paper presents the synthesis of AgNPs stabilized by gemini surfactants with hexadecyl substituent and variable structure of spacer, obtained via ecofriendly synthesis. UV-Vis spectroscopy and dynamic light scattering were used as analyzing tools in order to confirm physicochemical characterization of the AgNPs (characteristic UV-Vis bands, hydrodynamic diameter of NPs, polydispersity index (PDI)).

Targeting pathogenic fungi, bacteria and fungal-bacterial biofilms by newly synthesized quaternary ammonium derivative of pyridoxine and terbinafine with dual action profile

Many pathogenic bacteria and microscopic fungi form rigid polymicrobial biofilms this way enhancing their resistant to treatment. A series of novel pyridoxine-based quaternary ammonium derivatives of terbinafine characterized by both antifungal and antibacterial activities was designed. The leading compound named KFU-127 exhibits promising antifungal and antibacterial activities against various bacteria and micromycetes in both planktonic and biofilm-embedded forms demonstrating MIC values comparable with those of conventional antifungals and antimicrobials. Similar to other antiseptics like benzalkonium chloride and miramistin, KFU-127 is considerably toxic for eukaryotic cells that limits is application to topical treatment options. On the other hand, KFU-127 reduces the number of viable biofilm-embedded bacteria and C. albicans by 3 orders of magnitude at concentrations 2-4 times lower than those of reference drugs and successfully eradicates S. aureus-C. albicans mixed biofilms. The mechanism of antimicrobial action of KFU-127 is bimodal including both membrane integrity damage and pyridoxal-dependent enzymes targeting. We expect that this bilateral mechanism would result in lower rates of resistance development in both fungal and bacterial pathogens. Taken together, our data suggest KFU-127 as a new promising broad spectrum topical antimicrobial capable of one-shot targeting of bacterial and fungal-bacterial biofilms.

PEGylated Bis-Quaternary Triphenyl-Phosphonium Tosylate Allows for Balanced Antibacterial Activity and Cytotoxicity

Quaternary triphenylphosphonium compounds (TPP⁺) have been widely recognized as an important antimicrobial because of their fast antimicrobial speed and broad antimicrobial spectrum. However, small-molecule TPP⁺ compounds have the defects of toxicity, which is the key factor that limits their practical applications. Here, two mono- and one bis-quaternary phosphonium tosylate compounds with different lengths of oligo(ethylene glycol) (OEG) chains and TPP⁺ as the active moiety were synthesized. Bis-TPP⁺ have a short OEG chain coupling two TPP⁺ at both ends, while mono-TPP⁺ attaches the OEG chain at one end in one molecule. In vitro antibacterial activities were evaluated against both Gram-positive as well as Gram-negative bacteria in terms of the inhibition zone (ZOI) and minimum inhibitory concentration (MIC). To investigate the antibacterial mechanism, β-galactosidase activity was monitored for measuring the degree of membrane permeability correlated to the abilities to disrupt the membranes of bacteria. Moreover, their structure-antibacterial activity and structure-cytotoxicity relationships were further analyzed. The results indicated that bis-TPP⁺ synthesized can reach the sterilization rate 90% or more against Escherichia coli and Staphylococcus aureus at MICs of 3.1 and 1.5 mg/mL, respectively, and meanwhile, the cell proliferation can reach more than 80%. This paper represents an excellent approach for development of bis-TPP⁺ bactericidal molecules that would achieve an optimal balance between antimicrobial activity and cytotoxicity.

The structure - Activity correlation in the family of dicationic imidazolium surfactants: Antimicrobial properties and cytotoxic effect

BACKGROUND

The development of new effective microbicide surfactants and the search for the structure-biological activity relationship is an important and promising problem. Surfactants containing imidazolium fragment attract attention of researchers in the field of chemotherapy, because these compounds often exhibit high antimicrobial activity. The aim of this work is to identify the newly synthesized surfactants from the viewpoint of their potential usefulness in pharmacology and medicine. For this purpose, a detailed study of antimicrobial, hemolytic and cytotoxic activity of dicationic alkylimidazolium surfactants of the m-s-m (Im) series with a variable length of a hydrocarbon tail (m = 10, 12) and a spacer fragment (s = 2, 3, 4) was carried out.

METHODS

Aggregation of surfactants in solutions was estimated by tensiometry and conductivity. Antimicrobial activity was determined by the serial dilution technique. Cytotoxic effects of the test compounds on human cancer and normal cells were estimated by means of the multifunctional Cytell Cell Imaging system. Cell Apoptosis Analysis was made by flow cytometry.

RESULTS

The test compounds show high antimicrobial activity against a wide range of test microorganisms and do not possess high hemolytic activity. Importantly, some of them display a bactericidal activity comparable to ciprofloxacin fluoroquinolone antibiotic against Gram-positive bacteria, including methicillin-resistant strains of S. aureus (MRSA). The cytotoxicity of the compounds against normal and tumor human cell lines has been tested as well, with cytotoxic effect and selectivity strongly controlled by structural factor and kind of cell line. Superior results were revealed for compound 10-4-10 (Im) in the case of HuTu 80 cell line (duodenal adenocarcinoma), for which IC₅₀ value at the level of doxorubicin and a markedly higher selectivity index (SI 7.5) were demonstrated. Flow cytometry assay shows apoptosis-inducing effect of this compound on HuTu 80 cells, through significant changes in the potential of mitochondrial membrane.

MAJOR CONCLUSIONS

Antibacterial properties are shown to be controlled by alkyl chain length, with the highest activity demonstrated by surfactants with decyl tail, with the length of the spacer fragment showing practically no effect. The results indicate that the mechanism of cytotoxic effect of the compounds can be associated with the induction of apoptosis via the mitochondrial pathway.

GENERAL SIGNIFICANCE

Selectivity against pathogenic microorganisms and low toxicity against eukaryotic cells allow considering dicationic imidazolium surfactants as new effective antimicrobial agents. At the same time, high selectivity against some cancer cell lines indicates the prospect of their using as components of new anticancer drugs.

Antifungal Activity of β-Pinene-Based Hydronopyl Quaternary Ammonium Salts Against Phytopathogenic Fungi

β-Pinene can be used as a cheap source to synthesize a large number of high value-added derivatives. In this study, a series of β-pinene derivatives was prepared, and the antifungal activities of the compounds were assessed against phytopathogenic fungi. Eight N-alkyl hydronopyl diethyl ammonium halide salts were synthesized by the reaction of hydronopyl diethyl ammonium halide with 8 halogenated alkanes. The structures of the synthesized products were characterized by Fourier-transform infrared spectroscopy and nuclear magnetic resonance spectroscopy and mass spectrometry. The antifungal activities of these derivatives were tested against 11 plant pathogens, and the preliminary structure-activity relationship is discussed. Some derivatives exhibited moderate to significant antifungal activity due to the fusion of the hydronopyl, a long-chain alkyl, bromine, and iodine anionic groups. In contrast to the structure-activity relationship of compounds 2a, 2b, and 2c, iodine ions in 2f, 2g, and 2f had a significant effect on enhancing the antifungal activity against Colletotrichum gloeosporioides, S clerotinia sclerotiorum, Phytophthora capsici, Phomopsis, Sphaeropsis sapinea, Glomerella cingulata, and Fusicoccum aesculi. A higher molecular weight could increase the antifungal activity against Fusarium proliferatum, Alternaria kikuchiana, Sclerotinia sclerotiorum, P. capsici, Phomopsis, and S. sapinea. Compounds 2d and 2e exhibited broad-spectrum antifungal activity against the tested strains. These derivatives are expected to be used as precursor molecules for novel pesticide development in further research.

Biological Activity of Quaternary Ammonium Salts and Their Derivatives

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.

Antifungal and antiprotozoal green amino acid-based rhamnolipids: Mode of action, antibiofilm efficiency and selective activity against resistant Candida spp. strains and Acanthamoeba castellanii

Nowadays, infections caused by fungi and protists constitute a serious problem for public health services. The limited number of treatment options coupled with the increasing number of resistant microorganisms makes necessary the development of new non-toxic antifungal and antiprotozoal agents. Cationic amino acid-based rhamnolipids have been recently prepared by our group and exhibited good antibacterial activity. In this work, the antifungal, antibiofilm and antiprotozoal activity of these new rhamnolipids was investigated against a collection of fluconazole-resistant strains of different Candida species and Acanthamoeba castellanii, respectively. The arginine-RLs exhibited good antifungal activity against all fluconazole-resistant Candida spp. strains tested at MICs ranging from 6.5 to 20.7 mg/L. Their mechanism of action involves alterations in the permeability of the cell membranes that provoke death by apoptosis. The Arginine based-RLs also disperse Candida biofilms at low concentrations, similar to the MICs. All RLs tested (anionic and cationic) showed antiprotozoal activity, the arginine derivatives had the best activity killing the Acanthamoeba castellanii at concentrations of 4 mg/L. Interestingly, these surfactants have a wide range of action against yeast and A. castellanii in which they do not show toxicity against keratinocytes and fibroblasts. These results indicate that these new rhamnolipids have a sufficiently wide safety margin to be considered good candidates for several pharmaceutical applications such as combating fungal resistance and microbial biofilms and the formulation of antiprotozoal drugs.

Preparation and Uses of Chlorinated Glycerol Derivatives

Crude glycerol (C3H8O3) is a major by-product of biodiesel production from vegetable oils and animal fats. The increased biodiesel production in the last two decades has forced glycerol production up and prices down. However, crude glycerol from biodiesel production is not of adequate purity for industrial uses, including food, cosmetics and pharmaceuticals. The purification process of crude glycerol to reach the quality standards required by industry is expensive and dificult. Novel uses for crude glycerol can reduce the price of biodiesel and make it an economical alternative to diesel. Moreover, novel uses may improve environmental impact, since crude glycerol disposal is expensive and dificult. Glycerol is a versatile molecule with many potential applications in fermentation processes and synthetic chemistry. It serves as a glucose substitute in microbial growth media and as a precursor in the synthesis of a number of commercial intermediates or fine chemicals. Chlorinated derivatives of glycerol are an important class of such chemicals. The main focus of this review is the conversion of glycerol to chlorinated derivatives, such as epichlorohydrin and chlorohydrins, and their further use in the synthesis of additional downstream products. Downstream products include non-cyclic compounds with allyl, nitrile, azide and other functional groups, as well as oxazolidinones and triazoles, which are cyclic compounds derived from ephichlorohydrin and chlorohydrins. The polymers and ionic liquids, which use glycerol as an initial building block, are highlighted, as well.

Synthesis and characterization of pyridine-based organic salts: Their antibacterial, antibiofilm and wound healing activities

In treating wounds, long lasting infection is considered the major impediment. Drugs are rendered ineffective by pathogenic microorganisms via antibiotic resistance and calls for designing and development of new drugs. Herein, we report synthesis of eight different N-alkylated pyridine-based organic salts QAS 1-8 and their antibacterial, antibiofilm and wound healing activities. 3-(2-R-hydrazinecarbonyl)-1-propylpyridinium Bromide was the parent compound while R group was varying in each salt composed of different aromatic aldehyde moieties. In the antibacterial activity against S. aureus and E. coli, amoxicillin shows IC₅₀ near to 25 µg/mL inhibiting 58 ± 0.4% S. aureus while ceftriaxone inhibited 55 ± 0.5% E. coli at a concentration of 10 µg/mL. The highest IC₅₀ (56 ± 0.5% against S. aureus; 55 ± 0.5% against E. coli) was shown by compound QAS 7 at the concentration of 100 µg/mL; followed by the QAS 6 (55 ± 0.5% against E. coli) and QAS 2 (55 ± 0.5% against E. coli). In the antibiofilm activity, QAS 6, QAS 1 and QAS 8 inhibited 58 ± 0.4% S. aureus at a concentration of 75 µg/mL, while QAS 2 inhibited E. coli at the same concentration and amount. QAS 7, 3 and 1 inhibited almost 90% while QAS 6 inhibited 95 ± 1.1%of E. coli at a concentration of 250 µg/mL. Highest MBIC was provided by QAS 7 (52 ± 0.4%) against S. aureus at a concentration of 50 µg/mL that is very near to the standard amoxicillin. Antibacterial and antibiofilm activity results were also supported by the atomic force microscopy (AFM). In the wound healing activity, QAS 8 healed 90.8 ± 4.3% of the wound in 21 days with an average period of epithelialization (POE) of 19 ± 1.4 days; that is far better than povidone iodine ointment (81.5 ± 3.3% of the wound in the 21 days with 22.4 ± 2.9 days of POE). It is concluded from this study that the synthesized compounds QAS 2, 7 and 8 can be used for further mechanistic studies to be employed as antibacterial, antibiofilm and wound healing agents.

Multiple Applications of a Novel Cationic Gemini Surfactant: Anti-Microbial, Anti-Biofilm, Biocide, Salinity Corrosion Inhibitor, and Biofilm Dispersion (Part II)

The Egyptian petroleum industries are incurring severe problems with corrosion, particularly corrosion that is induced by sulfidogenic microbial activities in harsh salinity environments despite extensively using biocides and metal corrosion inhibitors. Therefore, in this study, a synthesized cationic gemini surfactant (SCGS) was tested as a broad-spectrum antimicrobial, anti-bacterial, anti-candida, anti-fungal, anti-biofilm (anti-adhesive), and bio-dispersion agent. The SCGS was evaluated as a biocide against environmental sulfidogenic-bacteria and as a corrosion inhibitor for a high salinity cultivated medium. The SCGS displayed wide spectrum antimicrobial activity with minimum bactericidal/fungicidal inhibitory concentrations. The SCGS demonstrated anti-bacterial, anti-biofilm, and bio-dispersion activity. The SCGS exhibited bactericidal activity against environmental sulfidogenic bacteria and the highest corrosion inhibition efficiency of 93.8% at 5 mM. Additionally, the SCGS demonstrated bio-dispersion activity against the environmental sulfidogenic bacteria at 5.49% salinity. In conclusion, this study provides a novel synthesized cationic surfactant with many applications in the oil and gas industry: as broad-spectrum antimicrobial and anti-biofilm agents, corrosion inhibition for high salinity, biocides for environmentally sulfidogenic bacteria, and as bio-dispersion agents.

Antifungal Activity of Morpholine and Piperidine Based Surfactants

Microorganisms have the remarkable capacity to develop resistance to antimicrobial agents. This is of particular concern for fungal pathogens which cause devastating invasive infections with limited treatment options. Thus the need for new antifungal agents is undeniable. This work presents the antifungal properties of four surfactant groups, namely two groups of sulfobetaines and two groups of quaternary ammonium compounds, all morpholine and piperidine derivatives, against drug susceptible or drug resistant Candida albicans and Cryptococcus neoformans. The values of minimum inhibitory and fungicidal concentrations were determined. As follows from the results, the activities of the obtained compounds differed, however the most active agents from each homologous series of compounds, such as P16S3, P16S4 and C16S3, were pointed out.

Highly hydrophilic cationic gold nanorods stabilized by novel quaternary ammonium surfactant with negligible cytotoxicity

The photothermal cancer therapy using cationic gold nanorods (GNRs) stabilized by quaternary ammonium salts (QAS) have a great potential to enhance conventional cancer treatment as it promises the effective eradication of cancer cells including cells resistant to radio- and chemo-therapy and the stimulation of anti-tumor immune response. However, as the cytotoxicity of the conventional alkanethiol-QAS compounds limits their utility in medicine, here we developed GNRs modified by novel highly hydrophilic cationic surfactant composed of the quaternary ammonium group and ethylene glycol chain N,N,N-trimethyl-3,6,9,12,15-pentaoxaheptadecyl-17-sulfanyl-1-ammonium bromide (POSAB) showing insignificant cytotoxicity in the free state. Surface modification of GNRs by POSAB allowed to prepare nanoparticles with good stability in water, high cellular uptake and localization in lysosomes that are a promising alternative to alkanethiol-stabilized GNRs especially for biomedical applications.

Synthesis of Novel Benzimidazolium Gemini Surfactants and Evaluation of Their Anti-Candida Activity

Owing to the rise in antimicrobial and chemotherapeutic drug resistance, there is a desperate need to formulate newer as well as more effective agents. With this perspective, here we outline the synthesis of two novel gemini surfactants with different substitutions at the nitrogen atom of the benzimidazolium ring. Both the compounds induced significant reductions in Candida growth in various yeast strains. The reduction in Candida growth seemed likely through the reduction in ergosterol biosynthesis: a sterol constituent of yeast cell membranes. Different concentrations of both compounds were used to determine the cellular ergosterol content which indicates an important disordering of the ergosterol biosynthetic pathway. Cytotoxic studies were carried out using HEK 293 (human embryonic-kidney cells) and Galleria mellonella larvae (an in vivo model of antimicrobial studies). Administration of both the compounds to G. mellonella larvae diseased by the yeast Candida albicans resulted in increased survival indicating their in vivo activity.

Biological activity of glycine and alanine derivatives of quaternary ammonium salts (QASs) against micro-organisms

Quaternary ammonium salts (QASs) are commonly used in medicine, agriculture and industry and their wide usage caused the development of microbial resistance, thus there is still a need for new effective antimicrobial agents. Present work describes the biological activity of alanine- (DMALM-n) and glycine-derived (DMGM-n) QASs against planktonic and biofilm forms of micro-organisms. The antimicrobial activity was dependent mainly on the hydrocarbon chain length and surfactants with 12-16 atoms of carbon in the alkyl chain were the most active ones. The lowest MIC value was determined for DMALM-14 against Rhodotorula rubra and Saccharomyces cerevisiae (2·5 µmol l^{- 1} ). Generally, alanine derivatives showed stronger effects against micro-organisms than glycine-derived QASs. Alanine-derived surfactants with 12-16 carbons in the alkyl chain had antiadhesive properties on the polystyrene surface, preventing cell attachment (about 70% of inhibition for C. albicans and 40% for S. epidermidis). Strong adhesion reduction was also observed on the stainless steel surface and the highest reduction was observed for C. albicans cells incubated on surface pretreated with DMGM-16. Moreover, DMGM-16 and DMALM-16 prevented C. albicans filamentation, one of the determinants of cell adhesion. Surfactants with C₁₆ alkyl chain (DMGM-16 and DMALM-16) eradicated bacterial and yeast biofilm (from 60 to 90% of reduction observed after incubation of the previously grown biofilm in the presence of the highest tested concentration of the surfactant - 400 µmol l^{- 1} ) and reduced its viability. Strong antimicrobial activity as well as antiadhesive properties make alanine- and glycine-derived QASs the potential candidates for future application as disinfectants. SIGNIFICANCE AND IMPACT OF THE STUDY: Cationic surfactants are used in many fields, among others in medicine, cosmetic and pharmaceutical industry. Their usage on a large scale caused the development of microbial resistance mechanisms to such compounds. Thus, there is a need to synthesize new surfactants with potential application as effective disinfectants to combat both planktonic and biofilm forms of micro-organisms. Present work focuses on the antimicrobial activity of chosen quaternary ammonium salts.

Antifungal Activity of Arginine-Based Surfactants

Background:

Amino acid based surfactants constitute an important class of surface active biomolecules showing remarkable biocompatible properties. Antimicrobial activity is one of the most remarkable biological properties of this kind of surfactants, which have been widely studied against a broad spectrum of microorganisms. However, the antifungal activity of this kind of compound has been less well investigated. The aim of this work is the study of the antifungal activity of two novel argininebased surfactants (Nα-benzoyl-arginine decylamide, Bz-Arg-NHC10 and Nα-benzoyl-arginine dodecylamide, Bz-Arg-NHC12), obtained by an enzymatic strategy, against phytopathogenic filamentous fungi and dermatophyte strains.

Methods:

Four phytopathogenic fungi (Fusarium oxysporum, Fusarium solani, Colletotrichum gloeosporioides and Colletotrichum lindemuthianum) and two human pathogenic fungi (dermatophytes Trichophyton rubrum and Trichophyton mentagrophytes) were tested. Inhibition of vegetative growth and conidia germination was investigated for the phytopathogenic fungi. In order to elucidate the possible mechanism of biocide action, membrane integrity, as well as the production of reactive oxygen species (ROS) were evaluated. Additionally, the inhibition of germination of dermatophyte microconidia due to both arginine-based surfactants was studied. Minimum inhibitory concentration, as well as the concentration that inhibits 50% of germination were determined for both compounds and both fungal strains.

Results:

For the vegetative growth of phytopathogenic fungi, the most potent arginine-based compound was Bz-Arg-NHC10. All the tested compounds interfered with the conidia development of the studied species. Investigation of the possible mechanism of toxicity towards phytopathogenic fungi indicated direct damage of the plasma membrane and production of ROS. For the two strains of dermatophyte fungi tested, all the proved compounds showed similar fungistatic efficacy.

Conclusion:

: Bz-Arg-NHC10 and Bz-Arg-NHC12 were demonstrated to have broad biocidal ability against the proliferative vegetative form and the asexual reproductive conidia. Results suggest that both membrane permeabilization and induction of oxidative stress are part of the antifungal mechanisms involved in the interruption of normal conidia development by Bz-Arg-NHCn, leading to cell death.

Activity of gemini quaternary ammonium salts against microorganisms

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.

Cationic surfactants as antifungal agents

Fungi-in being responsible for causing diseases in animals and humans as well as environmental contaminations in health and storage facilities-represent a serious concern to health security. Surfactants are a group of chemical compounds used in a broad spectrum of applications. The recently considered potential employment of cationic surfactants as antifungal or fungistatic agents has become a prominent issue in the development of antifungal strategies, especially if such surface-active agents can be synthesized in an eco-friendly manner. In this review, we describe the antifungal effect and the reported mechanisms of action of several types of cationic surfactants and also include a discussion of the contribution of these surfactants to the inhibition of yeast-based-biofilm formation. Furthermore, the putative mechanism of arginine-based tensioactive compounds as antifungal agents and their applications are also analyzed.

Penetrating cations induce pleiotropic drug resistance in yeast

Substrates of pleiotropic drug resistance (PDR) transporters can induce the expression of corresponding transporter genes by binding to their transcription factors. Penetrating cations are substrates of PDR transporters and theoretically may also activate the expression of transporter genes. However, the accumulation of penetrating cations inside mitochondria may prevent the sensing of these molecules. Thus, whether penetrating cations induce PDR is unclear. Using Saccharomyces cerevisiae as a model, we studied the effects of penetrating cations on the activation of PDR. We found that the lipophilic cation dodecyltriphenylphosphonium (C₁₂TPP) induced the expression of the plasma membrane PDR transporter genes PDR5, SNQ2 and YOR1. Moreover, a 1-hour incubation with C₁₂TPP increased the concentration of Pdr5p and Snq2p and prevented the accumulation of the PDR transporter substrate Nile red. The transcription factor PDR1 was required to mediate these effects, while PDR3 was dispensable. The deletion of the YAP1 or RTG2 genes encoding components of the mitochondria-to-nucleus signalling pathway did not prevent the C₁₂TPP-induced increase in Pdr5-GFP. Taken together, our data suggest (i) that the sequestration of lipophilic cations inside mitochondria does not significantly inhibit sensing by PDR activators and (ii) that the activation mechanisms do not require mitochondria as a signalling module.