Antimicrobial cationic surfactant, cetyltrimethylammonium bromide, induces superoxide stress in Escherichia coli cells

Development of ophthalmic nanoemulsions of β-caryophyllene for the treatment of Acanthamoeba keratitis

Although rare, amoebic keratitis (AK) is a disease caused by Acanthamoeba spp. that can lead to blindness. The drugs currently available for its treatment are very toxic, which has motivated the investigation for more effective and safe therapeutic options. In this study, the in vitro activity of ß-caryophyllene (BCP) was exploited taking into account its action against other protozoans as well as its well-known healing and anti-inflammatory properties (aspects relevant for the AK pathogenesis). On the other hand, high volatilization and oxidation phenomena are found for this compound, which led to its incorporation into nanoemulsions (NEs). Two emulsifying agents were tested, resulting in monodisperse systems with reduced droplet size (<265 nm) and high surface charge (positive and negative for NEs prepared with cetrimonium bromide -CTAB and Phosal® 50+, respectively). NEs prepared with CTAB were shown to be more stable after long-term storage at 4 and 25 °C than those prepared with Phosal®. Pure BCP, at the highest concentration (500 µM), resulted in a level of inhibition of Acanthamoeba trophozoites equivalent to that of reference drug (chlorhexidine). This activity was even greater after oil nanoencapsulation. The reduced droplet size could improve the interaction of the oil with the microorganism, justifying this finding. Changes in surface charge did not impact the activity. Positively charged NEs improved the interaction and retention of BCP in the cornea and thus should be prioritized for further studies.

Multifunctional Drug- and AuNRs-Loaded ROS-Responsive Selenium-Containing Polyurethane Nanofibers for Smart Wound Healing

Elevated levels of ROS, bacterial infection, inflammation, and improper regeneration are the factors that need to be addressed simultaneously for achieving effective wound healing without scar formation. This study focuses on the fabrication of electrospun ROS-responsive selenium-containing polyurethane nanofibers incorporating deferoxamine mesylate (Def), indomethacin (Indo), and gold nanorods (AuNRs) as proangiogenesis, anti-inflammatory, and antibacterial agents for synchronized delivery to a full-thickness wound in vivo. The structure of the fabricated nanofibers was analyzed by various techniques. Toxicity was checked by CCK-8 and hemolytic assays. The efficiency of wound healing in vitro was verified by a transwell assay and cell scratch assay. The wound healing efficiency of the nanofibers was assayed in full-thickness wounds in a rat model. The multifunctional nanofibers had a porous structure, enhanced antioxidation, antibacterial activity, and promoted wound healing. They eradicated TNF-α and IL-6, increased IL-10 expression, and revealed the angiogenic potential by increased expression of HIF-1α, VEGF, and CD31.

Prospects of charged cyclodextrins in biomedical applications

Cyclodextrins (CDs), recognized for their unique ability to form inclusion complexes, have seen broad utilization across various scientific fields. Recently, there has been a surge of interest in the use of charged cyclodextrins for biomedical applications, owing to their enhanced properties, such as superior solubility and improved molecular recognition compared to neutral CDs. Despite the growing literature, a comprehensive review of the biomedical utilisations of multi-charged cyclodextrins is scarce. This review provides a comprehensive exploration of the emerging prospects of charged cyclodextrin-based assemblies in the field of biomedical applications. Focusing on drug delivery systems, the review details how charged CDs enhance drug solubility and stability, reduce toxicity, and enable targeted and controlled drug release. Furthermore, the review highlights the role of charged CDs in gene therapy, notably their potential for DNA/RNA binding, cellular uptake, degradation protection, and targeted gene delivery. The promising potential of charged CDs in antibacterial and antiviral therapies, including photodynamic therapies, biofilm control, and viral replication inhibition, is discussed. Concluding with a future outlook, this review highlights the potential challenges and advancements that could propel charged CDs to the forefront of biomedicine.

A Zero-Valent Sulfur Transporter Helps Podophyllotoxin Uptake into Bacterial Cells in the Presence of CTAB

Podophyllotoxin (PTOX) is naturally produced by the plant Podophyllum species. Some of its derivatives are anticancer drugs, which are produced mainly by using chemical semi-synthesis methods. Recombinant bacteria have great potential in large-scale production of the derivatives of PTOX. In addition to introducing the correct enzymes, the transportation of PTOX into the cells is an important factor, which limits its modification in the bacteria. Here, we improved the cellular uptake of PTOX into Escherichia coli with the help of the zero-valent sulfur transporter YedE1E2 in the presence of cetyltrimethylammonium bromide (CTAB). CTAB promoted the uptake of PTOX, but induced the production of reactive oxygen species. A protein complex (YedE1E2) of YedE1 and YedE2 enabled E. coli cells to resist CTAB by reducing reactive oxygen species, and YedE1E2 was a hypothetical transporter. Further investigation showed that YedE1E2 facilitated the uptake of extracellular zero-valent sulfur across the cytoplasmic membrane and the formation of glutathione persulfide (GSSH) inside the cells. The increased GSSH minimized oxidative stress. Our results indicate that YedE1E2 is a zero-valent sulfur transporter and it also facilitates CTAB-assisted uptake of PTOX by recombinant bacteria.

Antiseptics and mupirocin resistance in clinical, environmental, and colonizing coagulase negative Staphylococcus isolates

BACKGROUND

Coagulase-Negative Staphylococci (CoNS) are opportunistic and nosocomial pathogens. The excessive use of antimicrobial agents, including antiseptics, represents one of the world's major public health problems. This study aimed to test the susceptibility of CoNS to antiseptics.

METHODS

Out of 250 specimens collected from different sections of the hospital, 55 samples were identified as CoNS, categorized into three groups based on their sources: environmental samples (n = 32), healthcare worker carriers samples (n = 14), and clinical infection samples (n = 9). Isolates were examined for susceptibility to antibiotics and antiseptics, such as benzalkonium chloride (BC), cetyltrimethylammonium bromide (CTAB), and chlorhexidine digluconate (CHDG). Mupirocin and antiseptic resistance genes, as well as the mecA gene, were detected using polymerase chain reaction. CoNS isolates with notable resistance to antiseptics and antibiotics were identified using the API-Staph system.

RESULTS

A high frequency of multidrug resistance among CoNS clinical infection isolates was observed. Approximately half of the CoNS isolates from healthcare workers were susceptible to CHDG, but 93% were resistant to BC and CTAB. The frequency of antiseptics and antibiotics resistance genes in CoNS isolates was as follows: qacA/B (51/55; 92.7%), smr (22/55; 40.0%), qacG (1/55; 1.8%), qacH (6/55; 10.9%), qacJ (4/55; 7.3%), mecA (35/55; 63.6%), mupB (10/55; 18.2%), and mupA (7/55; 12.7%). A significant difference in the prevalence of smr gene and qacJ genes between CoNS isolates from healthcare workers and other isolates was reported (P value = 0.032 and ˂0.001, respectively). Four different CoNS species; S. epidermidis, S. chromogene, S. haemolyticus, and S. hominis, were identified by API.

CONCLUSIONS

CoNS isolates colonizing healthcare workers showed a high prevalence of antiseptic resistance genes, while clinical infection samples were more resistant to antibiotics. CHDG demonstrated greater efficacy than BC and CTAB in our hospital.

Adaptation mechanisms of Listeria monocytogenes to quaternary ammonium compounds

Listeria monocytogenes is ubiquitously found in nature and can easily enter food-processing facilities due to contaminations of raw materials. Several countermeasures are used to combat contamination of food products, for instance, the use of disinfectants that contain quaternary ammonium compounds, such as benzalkonium chloride (BAC) and cetyltrimethylammonium bromide (CTAB). In this study, we assessed the potential of the commonly used wild-type strain EGD-e to adapt to BAC and CTAB under laboratory growth conditions. All BAC-tolerant suppressors exclusively carried mutations in fepR, encoding a TetR-like transcriptional regulator, or its promoter region, likely resulting in the overproduction of the efflux pump FepA. In contrast, CTAB tolerance was associated with mutations in sugR, which regulates the expression of the efflux pumps SugE1 and SugE2. L. monocytogenes strains lacking either FepA or SugE1/2 could still acquire tolerance toward BAC and CTAB. Genomic analysis revealed that the overproduction of the remaining efflux system could compensate for the deleted one, and even in the absence of both efflux systems, tolerant strains could be isolated, which all carried mutations in the diacylglycerol kinase-encoding gene lmo1753 (dgkB). DgkB converts diacylglycerol to phosphatidic acid, which is subsequently reused for the synthesis of phospholipids, suggesting that alterations in membrane composition could be the third adaptation mechanism. IMPORTANCE Survival and proliferation of Listeria monocytogenes in the food industry are ongoing concerns, and while there are various countermeasures to combat contamination of food products, the pathogen still successfully manages to withstand the harsh conditions present in food-processing facilities, resulting in reoccurring outbreaks, subsequent infection, and disease. To counteract the spread of L. monocytogenes, it is crucial to understand and elucidate the underlying mechanism that permits their successful evasion. We present various adaptation mechanisms of L. monocytogenes to withstand two important quaternary ammonium compounds.

The Combination of Corona Discharge Plasma and ε-Polylysine for the Inactivation of Serratia liquefaciens

The purpose of the study was to investigate the mechanism of inactivation of Serratia liquefaciens by different treatments, namely corona discharge plasma (CDP), ε-polylysine (ε-PL), and corona discharge plasma combined with ε-polylysine (CDP plus ε-PL). The results showed that the combined treatment of CDP and ε-PL exhibited significant antibacterial effects. The total number of colonies of S. liquefaciens dropped by 0.49 log CFU/mL following 4 min of CDP treatment, 4MIC ε-PL treatment for 6 h alone decreased the amounts of colonies by 2.11 log CFU/mL, and 6 h of treatment with 4MIC ε-PL after the bacterium was treated with CDP could decrease the number of colonies by 6.77 log CFU/mL. Scanning electron microscopy images showed that the combined treatment of CDP and ε-PL caused the most serious damage to the cell morphology. Electrical conductivity, nucleic acid, and PI staining indicated that the combined treatment dramatically enhanced the permeability of the cell membrane. In addition, the combined treatment led to a significant decrease in SOD and POD enzyme activities in S. liquefaciens, which prevented energy metabolism. Finally, the determination of free and intracellular ε-PL concentrations confirmed that the treatment of CDP could cause the bacteria to bind more ε-PL and exert more significant bacterial inhibition. Therefore, CDP and ε-PL had a synergistic effect in the inhibition of S. liquefaciens.

Versatile dual-channel loop-mediated isothermal amplification assay featuring smartphone imaging enables determination of fecal indicator bacteria in environmental waters

Rapid diagnostic assays are often a critical tool for monitoring water quality in developing and developed countries. Conventional testing requires 24-48 h for incubation, resulting in delayed remediation and increasing the likelihood of negative outcomes. In this study, we report a workflow for detection of E. coli, a common indicator of fecal contamination. Following large volume filtration, E. coli is then solubilized enabling the facile isolation and recovery of genetic material by a thin film microextraction (TFME) device featuring a polymeric ionic liquid (PIL) sorbent. Rapid recovery of pure nucleic acids is achieved using a PIL sorbent with high affinity for DNA to significantly increase mass transfer and facilitate adsorption and desorption of DNA. Downstream detection is performed by a versatile, dual channel loop mediated isothermal amplification (LAMP) assay featuring a colorimetric dye and a sequence-specific molecular beacon. A portable LAMP companion box enables consistent isothermal heating and endpoint smartphone imaging while being powered by a single 12-V battery. Programmable LEDs are switched from white or blue light to facilitate the independent imaging of the colorimetric dye or fluorometric probe following amplification. The methodology positively identified E. coli in environmental samples spiked to concentrations of 6600 colony forming units (CFU) per milliliter and 660 CFU/mL with 100% and 22% positivity, respectively.

The structure of biodegradable surfactants shaped the microbial community, antimicrobial resistance, and potential for horizontal gene transfer

While most household surfactants are biodegradable in aerobic conditions, their biodegradability may obscure their environmental risks. The presence of surfactants in a biological treatment process can lead to the proliferation of antimicrobial-resistance genes (ARG) in the biomass. Surfactants can be cationic, anionic, or zwitterionic, and these different classes may have different effects on the proliferation ARG. Cationic hexadecyltrimethyl-ammonium (CTAB), anionic sodium dodecyl sulfate (SDS), and zwitterionic 3-(decyldimethylammonio)-propanesulfonate inner salt (DAPS) were used to represent the three classes of surfactants in domestic household clean-up products. This study focused on the removal of these surfactants by the O₂-based Membrane Biofilm Reactor (O_2-MBfR) for hotspot scenarios (∼1 mM) and how the three classes of surfactants affected the microbial community's structure and ARG. Given sufficient O₂ delivery, the MBfR provided at least 98% surfactant removal. The presence and biodegradation for each surfactant uniquely shaped the biofilms' microbial communities and the presence of ARG. CTAB had by far the strongest impact and the higher ARG abundance. In particular, Pseudomonas and Stenotrophomonas, the two main genera in the biofilm treating CTAB, were highly correlated to the abundance of ARG for efflux pumps and antibiotic inactivation. CTAB also led to more functional genes relevant to the Type-IV secretion system and protection against oxidative stress, which also could encourage horizontal gene transfer. Our findings highlight that the biodegradation of quaternary ammonium surfactants, while beneficial, can pose public health concerns from its ability to promote the proliferation of ARG.

Spray-Drying Hydrophobic Cellulose Nanocrystal Coatings with Degradable Biocide Release for Marine Antifouling

With increasing awareness about the ecological environment, increased attention has been paid to the application of eco-friendly materials in the field of marine antifouling. In this work, a novel coating having good mechanical strength and static marine antifouling characteristics was fabricated using cellulose nanocrystals (CNCs) as the skeleton material, with in situ growth of SiO₂ as the basic superhydrophobic material and introducing hexadecyl trimethyl ammonium bromide (CTAB) and 4-bromo2-(4-chlorophenyl)-5-(trifluoromethyl)-1H-pyrrole-3-carbonitrile (Econea) into the coating. Due to the high strength and rod structure of CNCs, the coating maintained super-hydrophobicity after 50 cycles of abrasion tests. Moreover, the addition of CTAB during the synthesis of SiO₂ led to the hydrolysis and polycondensation of tetraethyl orthosilicate at the micellar interface. Econea was fully mixed with SiO₂ nanoparticles, thus slowing down the rate of release of Econea. Meanwhile, the adhesion between the coating and the substrate reached 1.9 MPa, which can meet the application requirements for marine environments. The bioassay using bacteria (Escherichia coli) and diatoms (Nitzschia closterium) showed that the rate of inhibition of the coating on bacteria and diatoms could reach 99 and 90%, respectively, after immersion in artificial seawater for 28 days. This research provides a facile and promising fabricating solution of an eco-friendly CNC-based coating having strong antifouling characteristics suitable for marine environments.

Effect of surfactants on SARS-CoV-2: Molecular dynamics simulations

Surfactants are commonly used as disinfection agents in personal care products against bacteria and viruses, including SARS-CoV-2. However, there is a lack of understanding of the molecular mechanisms of the inactivation of viruses by surfactants. Here, we employ coarse grain (CG) and all-atom (AA) molecular dynamics simulations to investigate the interaction between general families of surfactants and the SARS-CoV-2 virus. To this end, we considered a CG model of a full virion. Overall, we found that surfactants have only a small impact on the virus envelope, being inserted into the envelope without dissolving it or generating pores, at the conditions considered here. However, we found that surfactants may induce a deep impact on the spike protein of the virus (responsible for its infectivity), easily covering it and inducing its collapse over the envelope surface of the virus. AA simulations confirmed that both negatively and positively charged surfactants are able to extensively adsorb over the spike protein and get inserted into the virus envelope. Our results suggest that the best strategy for the design of surfactants as virucidal agents will be to focus on those strongly interacting with the spike protein.

A win-win scenario for antibacterial activity and skin mildness of cationic surfactants based on the modulation of host-guest supramolecular conformation

The commercial cationic surfactants (CSAa) with quaternary ammonium (QA) groups have proved to be broad-spectrum bactericide against bacteria, fungi, and viruses. Nevertheless, they inevitably exhibit potent irritation on the skin. In this work, we systematically investigated the regulatory mechanism of the host-guest supramolecular conformation with β-cyclodextrin (β-CD) on the bactericidal performance and skin irritation of CSAa with different head groups and chain lengths. When the ratio of incorporated β-CD is not greater than 1:1, the bactericidal efficiency of CSAa@β-CD (n > 12) remained above 90 % due to the free QA groups and hydrophobic fraction that can act on negatively charged bacterial membranes. And once the ratio of β-CD exceeded 1:1, the β-CD attracted to the bacterial surface by hydrogen bonding might prevent CSAa@β-CD from acting on bacteria, resulting in a decrement in antibacterial performance. Even so, the antibacterial activity of CSAa with long alkyl chains (n = 16, 18) was independent from the complexation of β-CD. Accordingly, both the zein solubilization assay and the neutrophil migration assay on zebrafish skin evidenced that β-CD attenuated the interaction of surfactant with skin model proteins and the inflammatory effect on zebrafish, thereby enhancing skin mildness. In this way, we hope to create a simple but effective brainpower using the host-guest approach to guarantee both bactericidal efficiency and skin mildness without modifying the chemical structure of these commercial biocides.

Coagulation/flocculation-flotation harvest of Microcystis aeruginosa by cationic hydroxyethyl cellulose and Agrobacterium mucopolysaccharides

Efficient biocoagulants/bioflocculants are desired for removal of Microcystis aeruginosa, the dominant harmful bloom-forming cyanobacterium. Herein, we reported cationic hydroxyethyl cellulose (CHEC) inactivated M. aeruginosa cells after forming coagulates and floating-flocculated them with aid of Agrobacterium mucopolysaccharides (AMP) and surfactant. CHEC exhibited cyanocidal activity at 20 mg/L, coagulating 85% of M. aeruginosa biomass within 9 h and decreasing 41% of chlorophyll a after 72 h. AMP acted as an adhesive flocculation aid that accelerated and strengthened the formation of flocs, approaching a maximum in 10 min. Flocs of M. aeruginosa were floated after foaming with cocoamidopropyl betaine (CAB), which facilitated the subsequent filter harvest. 82% of M. aeruginosa biomass was suspended on water surface after treated with the coagulation/flocculation-flotation (CFF) agents containing CHEC (25 mg/L), AMP (177 mg/L) and CAB (0.1 mg/L). All components in CFF agents at the applied concentrations did not inhibit acetylcholinesterase or Vibrio fischeri. Our findings provide new insights in developing bio-based materials for sustainable control of cyanobacterial blooms.

Thymol-Loaded Eudragit RS30D Cationic Nanoparticles-Based Hydrogels for Topical Application in Wounds: In Vitro and In Vivo Evaluation

Natural medicines formulated using nanotechnology-based systems are a rich source of new wound-treating therapeutics. This study aims to develop thymol-loaded cationic polymeric nanoparticles (CPNPs) to enhance the skin retention and wound healing efficacy of thymol. The developed materials exhibited entrapment efficiencies of 56.58 to 68.97%, particle sizes of 36.30 to 99.41 nm, and positively charged zeta potential. In Vitro sustained release of thymol up to 24 h was achieved. Selected thymol CPNPs (F5 and C2) were mixed with methylcellulose to form hydrogels (GF5 and GC2). An In Vivo skin-retention study revealed that GF5 and GC2 showed 3.3- and 3.6-fold higher retention than free thymol, respectively. An In Vitro scratch-wound healing assay revealed a significant acceleration in wound closure at 24 h by 58.09% (GF5) and 57.45% (GC2). The potential for free thymol hydrogel, GF5, and GC2 to combat MRSA in a murine skin model was evaluated. The bacterial counts, recovered from skin lesions and the spleen, were assessed. Although a significant reduction in the bacterial counts recovered from the skin lesions was shown by all three formulations, only GF5 and GC2 were able to reduce the bacterial dissemination to the spleen. Thus, our study suggests that Eudragit RS30D nanoparticles-based hydrogels are a potential delivery system for enhancing thymol skin retention and wound healing activity.

Alteration of Cell Membrane Permeability by Cetyltrimethylammonium Chloride Induces Cell Death in Clinically Important Candida Species

The increased incidence of healthcare-related Candida infection has necessitated the use of effective disinfectants/antiseptics in healthcare settings as a preventive measure to decontaminate the hospital environment and stop the persistent colonization of the offending pathogens. Quanternary ammonium surfactants (QASs), with their promising antimicrobial efficacy, are considered as intriguing and appealing candidates for disinfectants. From this perspective, the present study investigated the antifungal efficacy and action mechanism of the QAS cetyltrimethylammonium chloride (CTAC) against three clinically important Candida species: C. albicans, C. tropicalis, and C. glabrata. CTAC exhibited phenomenal antifungal activity against all tested Candida spp., with minimum inhibitory concentrations (MIC) and minimum fungicidal concentrations (MFC) between 2 and 8 µg/mL. The time−kill kinetics of CTAC (at 2XMIC) demonstrated that an exposure time of 2 h was required to kill 99.9% of the inoculums in all tested strains. An important observation was that CTAC treatment did not influence intracellular reactive oxygen species (ROS), signifying that its phenomenal anticandidal efficacy was not mediated via oxidative stress. In addition, sorbitol supplementation increased CTAC’s MIC values against all tested Candida strains by three times (8−32 μg/mL), indicating that CTAC’s possible antifungal activity involves fungus cell membrane destruction. Interestingly, the increased fluorescence intensity of CTAC-treated cells in both propidium iodide (PI) and DAPI staining assays indicated the impairment of cell plasma membrane and nuclear membrane integrity by CTAC, respectively. Additionally, CTAC at MIC and 2XMIC was sufficient (>80%) to disrupt the mature biofilms of all tested spp., and it inhibited the yeast-to-hyphae transition at sub-MIC in C. albicans. Finally, the non-hemolytic activity of CTAC (upto 32 µg/mL) in human blood cells and HBECs signified its non-toxic nature at the investigated concentrations. Furthermore, thymol and citral, two phytocompounds, together with CTAC, showed synergistic fungicidal effectiveness against C. albicans planktonic cells. Altogether, the data of the present study appreciably broaden our understanding of the antifungal action mechanism of CTAC and support its future translation as a potential disinfectant against Candida-associated healthcare infections.

Bacterial Response to the Surface Aging of PLA Matrices Loaded with Active Compounds

The use of active components in biomaterials improves the properties of existing ones and makes it possible to obtain new devices with antibacterial properties that prevent infections after implantation, thus guaranteeing the success of the implant. In this work, cetyltrimethylammonium bromide (CTAB) and magnesium particles were incorporated into polylactic acid (PLA) films to assess the extent to which progressive aging of the new surfaces resists bacterial colonization processes. For this purpose, the films' surface was characterized by contact angle measurements, ToF-SIMS and AFM, and adhesion, viability and biofilm growth of Staphylococcus epidermidis bacteria on these films were also evaluated. The results show that the inclusion of Mg and CTAB in PLA films changes their surface properties both before and after aging and also modifies bacterial adhesion on the polymer. Complete bactericidal activity is exhibited on non-degraded films and films with CTAB. This antibacterial behavior is maintained after degradation for three months in the case of films containing a higher amount of CTAB.

Molecular co-localization of multiple drugs in a nanoscopic delivery vehicle for potential synergistic remediation of multi-drug resistant bacteria

Anti-microbial resistant infection is predicted to be alarming in upcoming years. In the present study, we proposed co-localization of two model drugs viz., rifampicin and benzothiazole used in anti-tuberculosis and anti-fungal agents respectively in a nanoscopic cationic micelle (cetyl triethyl ammonium bromide) with hydrodynamic diameter of 2.69 nm. Sterilization effect of the co-localized micellar formulation against a model multi-drug resistant bacterial strain viz., Methicillin resistant Staphylococcus aureus was also investigated. 99.88% decrease of bacterial growth in terms of colony forming unit was observed using the developed formulation. While Dynamic Light Scattering and Forsters Resonance Energy Transfer between benzothiazole and rifampicin show co-localization of the drugs in the nanoscopic micellar environment, analysis of time-resolved fluorescence decays by Infelta-Tachiya model and the probability distribution of the donor-acceptor distance fluctuations for 5 μM,10 μM and 15 μM acceptor concentrations confirm efficacy of the co-localization. Energy transfer efficiency and the donor acceptor distance are found to be 46% and 20.9 Å respectively. We have also used a detailed computational biology framework to rationalize the sterilization effect of our indigenous formulation. It has to be noted that the drugs used in our studies are not being used for their conventional indication. Rather the co-localization of the drugs in the micellar environment shows a completely different indication of their use in the remediation of multi-drug resistant bacteria revealing the re-purposing of the drugs for potential use in hospital-born multi-drug resistant bacterial infection.

Enhancing Biocide Efficacy: Targeting Extracellular DNA for Marine Biofilm Disruption

Biofilm formation is a global health, safety and economic concern. The extracellular composition of deleterious multispecies biofilms remains uncanvassed, leading to an absence of targeted biofilm mitigation strategies. Besides economic incentives, drive also exists from industry and research to develop and apply environmentally sustainable chemical treatments (biocides); especially in engineered systems associated with the marine environment. Recently, extracellular DNA (eDNA) was implicated as a critical structural polymer in marine biofilms. Additionally, an environmentally sustainable, multi-functional biocide was also introduced to manage corrosion and biofilm formation. To anticipate biofilm tolerance acquisition to chemical treatments and reduce biocide application quantities, the present research investigated eDNA as a target for biofilm dispersal and potential enhancement of biocide function. Results indicate that mature biofilm viability can be reduced by two-fold using reduced concentrations of the biocide alone (1 mM instead of the recommended 10 mM). Importantly, through the incorporation of an eDNA degradation stage, biocide function could be enhanced by a further ~90% (one further log reduction in viability). Biofilm architecture analysis post-treatment revealed that endonuclease targeting of the matrix allowed greater biocide penetration, leading to the observed viability reduction. Biofilm matrix eDNA is a promising target for biofilm dispersal and antimicrobial enhancement in clinical and engineered systems.

Oxidative Stress and Histopathological Changes in Gills and Kidneys of Cyprinus carpio following Exposure to Benzethonium Chloride, a Cationic Surfactant

One cationic surfactant with a wide spectrum of microbiocidal activity is benzethonium chloride (BEC). Despite being widely used, the toxicity data on vertebrate organisms are limited. Therefore, we aimed to evaluate within this study the acute toxicity of BEC on the gills and kidneys of Cyprinus carpio (European carp). An alteration of the antioxidant enzymes activities (glutathione reductase, glutathione peroxidase and glutathione S-transferase) was noticed after 96 h of exposure, along with an elevation of lipid peroxidation and decreased concentration of reduced glutathione, which confirmed that BEC was able to induce toxicity to these tissues. These metabolic effects were correlated with unspecific structural changes observed in gills and kidneys, having moderate degree of severity (such as an increase of melanomacrophages aggregation incidence and cytoplasm vacuolation of goblet cells in collecting tubules) and generally being compatible with life for the exposure time studied. The most severe structural effects were observed in gills after 96 h, noticing a lamellar aneurysm, hemorrhages and lamellar epithelium disruption due to the blood vessels and pillar cells damages and increased blood flow inside the lamellae. By our research we can confirm the utility of biochemical and histological analyses in the fish organs as tools for monitoring the water quality and ecotoxicological potential of chemicals.

Microcystins can be extracted from Microcystis aeruginosa using amino acid-derived biosurfactants

Microcystin, a cyanotoxin produced by Microcystis aeruginosa growing in eutrophic waters, can promote liver tumors in people ingesting contaminated water. To date, water treatment systems have not been effective in removing or degrading these cyanotoxins. In this work, we investigated the inhibitory activity of surfactants on the growth of M. aeruginosa and their application to extract the intracellular produced cyanotoxins. The experiments involving growth inhibition and extraction of cyanotoxins were carried out using the non-biodegradable surfactant cetyl trimethyl ammonium bromide (CTAB) in addition to other biodegradable surfactants. These were Tween 80 and surfactants derived from amino acids and peptides, respectively, from arginine, SDA, and hydrolyzed peptone, SDP. We demonstrated that the tested surfactants could be used to inhibit the growth of M. aeruginosa. At this point, CTAB and SDA proved to be the most competent surfactants in reducing cyanobacterial growth. Moreover, microcystins have been successfully removed from the water employing a cloud point extraction protocol based on the use of these surfactants and ammonium sulfate.

Recent progress of silver-containing photocatalysts for water disinfection under visible light irradiation: A review

Photocatalysis has emerged as an environmentally friendly approach for microbial disinfection. The development of visible-light-driven (VLD) photocatalysts for water pollution remediation is imperative, considering that visible light constitutes a substantial fraction of the solar spectrum. The modification of photocatalysts by Ag/AgX (X = Cl, Br, I) deposition can be used to improve photocatalytic efficiencies. This is achieved by preventing photogenerated electron-hole pairs recombination through electron trapping mechanisms. With the introduction of silver NPs, visible light absorption can also be increased through its SPR enhancement. Silver also possesses excellent antimicrobial properties. Consequently, a novel class of Ag/AgX-containing hybrid materials has recently emerged as a promising candidate for water disinfection. This review summarizes the latest advances in the synthesis of Ag/AgX-containing photocatalysts using various synthetic methods. The microbial disinfection efficiencies of the as-prepared materials, the main reactive oxygen species and disinfection mechanisms are also reviewed in detail. Finally, some areas that need to be improved are discussed along with new insights as perspectives for future developments in this field.

DELOS Nanovesicles-Based Hydrogels: An Advanced Formulation for Topical Use

Topical delivery has received great attention due to its localized drug delivery, its patient compliance, and its low risk for side effects. Recent developments have focused on studying new drug delivery systems as a strategy for addressing the challenges of current topical treatments. Here we describe the advances on an innovative drug delivery platform called DELOS nanovesicles for topical drug delivery. Previously, the production of DELOS nanovesicles demonstrated potentiality for the topical treatment of complex wounds, achieving well-tolerated liquid dispersions by this route. Here, research efforts have been focused on designing these nanocarriers with the best skin tolerability to be applied even to damaged skin, and on exploring the feasibility of adapting the colloidal dispersions to a more suitable dosage form for topical application. Accordingly, these drug delivery systems have been efficiently evolved to a hydrogel using Methocel^TM K4M, presenting proper stability and rheological properties. Further, the integrity of these nanocarriers when being gellified has been confirmed by cryo-transmission electron microscopy and by Förster resonance energy transfer analysis with fluorescent-labeled DELOS nanovesicles, which is a crucial characterization not widely reported in the literature. Additionally, in vitro experiments have shown that recombinant human Epidermal Growth Factor (rhEGF) protein integrated into gellified DELOS nanovesicles exhibits an enhanced bioactivity compared to the liquid form. Therefore, these studies suggest that such a drug delivery system is maintained unaltered when hydrogellified, becoming the DELOS nanovesicles-based hydrogels, an advanced formulation for topical use.

Cationic Surfactant-Natural Clay Complex as a Novel Agent Against Acanthamoeba castellanii Belonging to the T4 Genotype

BACKGROUND

Acanthamoeba is a protozoan pathogen that is widely distributed in the environment. Given the opportunity, it can cause a serious eye infection known as Acanthamoeba keratitis as well as a fatal brain infection known as granulomatous amoebic encephalitis. Inappropriate use of contact lenses can contribute to contracting Acanthamoeba keratitis, and contact lens disinfectants are not always effective in eradicating Acanthamoeba. Therefore, there is a need to develop novel antimicrobial agents with efficient antiamoebic properties.

OBJECTIVE

In this study, we tested octadecyltrimethylammonium (ODTMA)-clay (montmorillonite) complex as a novel antiamoebic agent.

METHODS

Using A. castellanii belonging to the T4 genotype of keratitis origin, amobicidal assays were performed to determine the effects of ODTMA-cay complex on the viability of parasites at various concentrations ranging from 10 to 100 μg. Adhesion and cytopathogenicity assays were performed to investigate ODTMA effects on A. castellanii-mediated binding and damage to human cells. Encystation and excystation assays were conducted to establish ODTMA-mediated inhibitory effects against the cyst stage of A. castellanii.

RESULTS

Using cell survival assays, the results revealed that ODTMA-clay complex exhibited amobicidal activity against keratitis-causing A. castellanii in a dose-dependent manner. Pretreatment of A. castellanii with ODTMA-clay complex inhibited parasite adhesion to as well as parasite-mediated human cell damage. Using encystation and excystation assays, it was revealed that ODTMA-clay complex inhibited A. castellanii cysts at 100 μg (P<0.05).

CONCLUSION

To the best of our knowledge, for the first time, it was shown that ODTMA-clay complex exhibited anti-Acanthamoebic activities. The possibility of adding ODTMA-clay in a contact lens cleaning solution to formulate effective disinfectants is discussed further.

Characterization of Magnesium-Polylactic Acid Films Casted on Different Substrates and Doped with Diverse Amounts of CTAB

Polylactic acid (PLA) is a good candidate for the manufacture of polymeric biodegradable biomaterials. The inclusion of metallic particles and surfactants solves its mechanical limitations and improves its wettability, respectively. In this work, cetyltrimethylammonium bromide (CTAB) and magnesium particles have been incorporated into PLA films to evaluate the changes produced in the polymeric matrix cast on glass and silicone substrates. For this purpose, the surface of the films has been characterized by means of contact angle measurements and ToF-SIMS. Depth profiles and SEM images of the cross sections of the films have also been obtained to study their morphology. The results show that the CTAB in the polymer matrix with and without magnesium improves the wettability of the films, making them more suitable for cell adhesion. The higher the hydrophilicity, the higher the surfactant concentration. The depth profiles show, for the first time, that, depending on the surfactant concentration and the presence of Mg, there is a layer-like distribution near the surface where, in addition to the CTAB + PLA mixture, a surfactant exclusion zone can be seen. This new structure could be relevant in in vitro/in vivo situations when the degradation processes remove the film components in a sequential form.

Micro-structural investigations on oppositely charged mixed surfactant gels with potential dermal applications

Dicarboxylic amino acid-based surfactants (N-dodecyl derivatives of -aminomalonate, -aspartate, and -glutamate) in combination with hexadecyltrimethylammonium bromide (HTAB) form a variety of aggregates. Composition and concentration-dependent mixtures exhibit liquid crystal, gel, precipitate, and clear isotropic phases. Liquid crystalline patterns, formed by surfactant mixtures, were identified by polarizing optical microscopy. FE-SEM studies reveal the existence of surface morphologies of different mixed aggregates. Phase transition and associated weight loss were found to depend on the composition where thermotropic behaviours were revealed through combined differential scanning calorimetry and thermogravimetric studies. Systems comprising more than 60 mol% HTAB demonstrate shear-thinning behaviour. Gels cause insignificant toxicity to human peripheral lymphocytes and irritation to bare mouse skin; they do not display the symptoms of cutaneous irritation, neutrophilic invasion, and inflammation (erythema, edema, and skin thinning) as evidenced by cumulative irritancy index score. Gels also exhibit substantial antibacterial effects on Staphylococcus aureus, a potent causative agent of skin and soft tissue infections, suggesting its possible application as a vehicle for topical dermatological drug delivery.

Varied-shaped gold nanoparticles with nanogram killing efficiency as potential antimicrobial surface coatings for the medical devices

Medical device-associated infections are a serious medical threat, particularly for patients with impaired mobility and/or advanced age. Despite a variety of antimicrobial coatings for medical devices being explored to date, only a limited number have been introduced for clinical use. Research into new bactericidal agents with the ability to eradicate pathogens, limit biofilm formation, and exhibit satisfactory biocompatibility, is therefore necessary and urgent. In this study, a series of varied-morphology gold nanoparticles in shapes of rods, peanuts, stars and spherical-like, porous ones with potent antibacterial activity were synthesized and thoroughly tested against spectrum of Candida albicans, Pseudomonas aeruginosa, Staphylococcus aureus clinical strains, as well as spectrum of uropathogenic Escherichia coli isolates. The optimization of gold nanoparticles synthesis allowed to develop nanomaterials, which are proved to be significantly more potent against tested microbes compared with the gold nanoformulations reported to date. Notably, their antimicrobial spectrum includes strains with different drug resistance mechanisms. Facile and cost-efficient synthesis of gold nanoparticles, remarkable bactericidal efficiency at nanogram doses, and low toxicity, underline their potential for development as a new coatings, as indicated by the example of urological catheters. The presented research fills a gap in microbial studies of non-spherical gold nanoparticles for the development of antimicrobial coatings targeting multidrug-resistant pathogens responsible for device-associated nosocomial infections.

Cationic zinc (II) phthalocyanine nanoemulsions for photodynamic inactivation of resistant bacterial strains

BACKGROUND

The growing emergence of microbial resistance to antibiotics represents a worldwide challenge. Antimicrobial photodynamic inactivation (aPDI) has been introduced as an alternative technique, especially when combined with nanotechnology. Therefore, this study was designed to investigate the therapeutic merits of combined aPDI and nanoemulsion in infections caused by resistant bacterial strains.

METHODS

Cationic zinc (II) phthalocyanine nanoemulsions (ZnPc-NE) were prepared using isopropyl myristate (IPM) as oil phase, egg phosphatidylcholine (egg PC) as emulsifier, and N-cetyl-N,N,N-trimethyl ammonium bromide (CTAB). Nanoemulsions were characterized for particle size, polydispersity, zeta potential, viscosity, and skin deposition. The in-vitro aPDI was investigated on human resistant pathogens; gram-positive methicillin-resistant Staphylococcus aureus (MRSA) and gram-negative Multidrug-resistant strain of Escherichia coli (MDR E. coli), under different experimental conditions. In addition, in-vivo model of abrasion wound infected by MDR E. coli was induced in rats to investigate the therapeutic potential of the selected formulation.

RESULTS

It was evident that the selected ZnPc formulation (20 % IPM, 2 % egg PC and 0.5 % CTAB) displayed a particle size of 209.9 nm, zeta potential +73.1 mV, and 23.66 % deposition of ZnPc in skin layers. Furthermore, the selected formulation combined with light achieved almost 100 % eradication of the two bacterial strains, with superior bacterial load reduction and wound healing propertiesin-vivo, compared to either the nanoemulsion formulation or laser alone.

CONCLUSION

ZnPc nanoemulsion improved antimicrobial photodynamic therapy in inactivating resistant bacterial infections and provided a promising therapeutic means of treating serious infections, and hence could be applied in diseases caused by other bacterial strains.

Increased expression of antibiotic-resistance genes in biofilm communities upon exposure to cetyltrimethylammonium bromide (CTAB) and other stress conditions

Quaternary ammonium compounds (QAC, e.g., cetyltrimethylammonium bromide, (CTAB)) are widely used as surfactants and disinfectants. QAC already are commonly found in wastewaters, and their concentration could increase, since QAC are recommended to inactivate the SARS-CoV-2 (COVID-19) virus. Exposure of bacteria to QAC can lead to proliferation of antibiotic resistance genes (ARG). In particular, O₂-based membrane biofilm reactors (O₂-MBfRs) achieved excellent CTAB biodegradation, but ARG increased in their biofilms. Here, we applied meta-transcriptomic analyses to assess the impacts of CTAB exposure and operating conditions on microbial community's composition and ARG expression in the O₂-MBfRs. Two opportunistic pathogens, Pseudomonas aeruginosa and Stenotrophomonas maltophilia, dominated the microbial communities and were associated with the presence of ARG. Operating conditions that imposed stress on the biofilms, i.e., limited supplies of O₂ and nitrogen or a high loading of CTAB, led to large increases in ARG expression, particularly for genes conferring antibiotic-target protection. Important within the efflux pumps was the Resistance-Nodulation-Division (RND) family, which may have been active in exporting CTAB from cells. Oxidative stress appeared to be the key factor that triggered ARG proliferation by selecting intrinsically resistant species and accentuating the expression of ARG. Our findings suggest that means to mitigate the spread of ARG, such as shown here in a O₂-based membrane biofilm reactor, need to consider the impacts of stressors, including QAC exposure and stressful operating conditions.

Reduced Biofilm Formation at the Air-Liquid-Solid Interface via Introduction of Surfactants

Reduced biofilm formation is highly desirable in applications ranging from transportation to separations and healthcare. Biofilms often form at the three-phase interface where air, liquid, and solid coexist due to the close proximity to nutrients and oxygen. Reducing biofilm formation at the triple interface presents challenges because of the conflicting requirements for hydrophobicity at the air-solid interface (for self-cleaning properties) and for hydrophilicity at the liquid-solid interface (for reduced foulant adhesion). Meeting those needs simultaneously likely entails a dynamic surface, capable of shifting the surface energy landscape in response to wetting conditions and thus enabling hydrophobicity in air and hydrophilicity in water. Here, we designed a facile approach to render existing surfaces resistant to biofilm formation at the triple interface. By adding trace amounts (∼0.1 mM) of surfactants, biofilm formation of Pseudomonas aeruginosa (known to form biofilm at the triple interface) was reduced on all surfaces tested, ranging from hydrophilic to hydrophobic, polar to nonpolar. That reduced fouling was not a result of the known antimicrobial effects. Instead, it was attributed to the surface-adsorbed surfactants that dynamically control surface energy at the triple interface. To further understand the effect of surfactant-surface interactions on biofilm reduction, we systematically varied the surfactant charge type and surface properties (surface energy and charge). Electrostatic interactions between surfactants and surfaces were identified as an influential factor when predicting the relative fouling reduction upon introduction of surfactants. Nevertheless, biofilm formation was reduced even on the charge-neutral, fluorinated surface made of poly(1H, 1H, 2H, 2H-perfluorodecyl acrylate) by more than 2-fold simply via adding 0.2 mM dodecyl trimethylammonium chloride or 0.3 mM sodium dodecyl sulfate. Given its robustness, this strategy is broadly applicable for reducing fouling on existing surfaces, which in turn improves the cost-effectiveness of membrane separations and mitigates contaminations and nosocomial infections in healthcare.

Facet-dependent gold nanocrystals for effective photothermal killing of bacteria

Gold-based plasmonic nanocrystals have been extensively developed for noninvasive photothermal therapy. In this study, gold nanorods (AuNRs) with (200) plane and gold nanobipyramids (AuNBPs) with (111) plane were utilized as photothermal agents for noninvasive photothermal therapy. With longitudinal surface plasma bands at ~808 nm, both of AuNRs and AuNBPs revealed photothermal capability and reversibility of laser response under 808-nm near-infrared (NIR) laser irradiation. Moreover, AuNBPs with (111) plane exhibited higher photothermal performance than that of AuNRs with (200) plane under NIR laser irradiation. Density function theory (DFT) simulations revealed that water adsorption energy followed the order Au(111) < Au(100), indicating that the water was easily desorbed on the Au(111) surface for photothermal heating. For the photothermal therapy against Escherichia coli (E. coli), AuNBPs also exhibited higher efficiency compared to that of AuNRs under NIR laser irradiation. Combination of experimental photothermal therapy and DFT simulations demonstrated that AuNBPs with (111) plane were better photothermal agents than that of AuNRs with (100) plane.

Removal of Salmonella Typhimurium Biofilm from Food Contact Surfaces Using Quercus infectoria Gall Extract in Combination with a Surfactant

Quercus infectoria (nutgall) has been reported to possess antimicrobial activities against a wide range of pathogens. Nevertheless, the biofilm removal effect of nutgall extract has not been widely investigated. In this study, we therefore evaluated the effect of nutgall extract in combination with cetrimonium bromide (CTAB) against preformed biofilm of Salmonella Typhimurium on polypropylene (PP) and stainless steel (SS) coupons in comparison with other sanitizers. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of nutgall extract and surfactants (CTAB and sodium dodecyl sulfate; SDS) were assessed. CTAB showed a more efficient antimicrobial activity than SDS and was selected to use in combination with nutgall extract for removing biofilm. To determine the biofilm removal efficacy, the PP and SS coupons were individually submerged in 2x MBC of nutgall extract (256 mg/ml) + 2x MBC of CTAB (2.5 mg/ml), nutgall extract alone (256 mg/ml), CTAB alone (2.5 mg/ml), distilled water, and 100 ppm sodium hypochlorite for 5, 15, and 30 min. The remaining sessile cells in biofilm were determined. Overall, the greatest biofilm removal efficacy was observed with nutgall extract + CTAB; the biofilm removal efficacy of sanitizers tended to increase with the exposure time. The SEM analysis demonstrated that S. Typhimurium biofilm on PP and SS coupons after exposure to nutgall extract + CTAB for 30 min displayed morphological alterations with wrinkles. This study suggests nutgall extract + CTAB may be an alternative to commonly used sanitizers to remove biofilm from food contact surfaces in the food industry and household.

Cetyltrimethylammonium Bromide (CTAB)-Loaded SiO2-Ag Mesoporous Nanocomposite as an Efficient Antibacterial Agent

To date, Ag-based nanomaterials have demonstrated a high potential to overcome antibiotic resistance issues. However, bare Ag nanomaterials are prone to agglomeration in the biological environment, which results in a loss of antibacterial activity over time. Furthermore, it is still challenging to collect small-sized Ag nanomaterials right after the synthesis process. In this study, spherical-shaped Ag nanoparticles (NPs) (~6–10 nm) were attached on the surface of cetyltrimethylammonium bromide (CTAB)-loaded mesoporous silica nanoparticles (MSNs) (~100–110 nm). Antibacterial activity tests suggested that the obtained nanocomposite can be used as a highly efficient antibacterial agent against both Gram-negative and Gram-positive bacterial strains. The minimum inhibitory concentration (MIC) recalculated to pure Ag weight in nanocomposite was found to be ~1.84 µg/mL (for Escherichia coli) and ~0.92 µg/mL (for Staphylococcus aureus)—significantly smaller compared to values reported to date. The improved antibacterial activity of the prepared nanocomposite can be attributed to the even distribution of non-aggregated Ag NPs per volume unit and the presence of CTAB in the nanocomposite pores.

Cetrimonium bromide promotes the clearance of lipids by activating the TFEB-mediated autophagosome-lysosome pathway in hepatic cells

Autophagy plays a key role in the metabolism of macromolecules via the degradative abilities of the lysosome. Transcription factor EB (TFEB) regulates autophagosome biogenesis and lysosome function, and promoting TFEB activity has emerged as a potential strategy for the treatment of metabolic disorders. Herein, we report that cetrimonium bromide (CTAB; a quaternary ammonium compound) promotes autophagy and lysosomal biogenesis by inducing the nuclear translocation of TFEB in hepatic cells. Knockdown of TFEB mediated by short hairpin RNA inhibits CTAB-induced autophagy and lysosomal biogenesis. Mechanistically, CTAB treatment inhibits the Akt-mTORC1 signaling pathway. Moreover, CTAB treatment significantly increases lipid metabolism in both palmitate- and oleate-treated HepG2 cells, and this increase was attenuated by knockdown of TFEB. Collectively, our results indicate that CTAB activates the autophagosome-lysosome pathway via inducing the nuclear translocation of TFEB by inhibiting the mTORC1 signaling pathway. These results add to the collective understanding of TFEB function and provide new insights into CTAB-mediated lipid metabolism.

A comprehensive review on antimicrobial face masks: an emerging weapon in fighting pandemics

The world has witnessed several incidents of epidemics and pandemics since the beginning of human existence. The gruesome effects of microbial threats create considerable repercussions on the healthcare systems. The continually evolving nature of causative viruses due to mutation or re-assortment sometimes makes existing medicines and vaccines inactive. As a rapid response to such outbreaks, much emphasis has been placed on personal protective equipment (PPE), especially face mask, to prevent infectious diseases from airborne pathogens. Wearing face masks in public reduce disease transmission and creates a sense of community solidarity in collectively fighting the pandemic. However, excessive use of single-use polymer-based face masks can pose a significant challenge to the environment and is increasingly evident in the ongoing COVID-19 pandemic. On the contrary, face masks with inherent antimicrobial properties can help in real-time deactivation of microorganisms enabling multiple-use and reduces secondary infections. Given the advantages, several efforts are made incorporating natural and synthetic antimicrobial agents (AMA) to produce face mask with enhanced safety, and the literature about such efforts are summarised. The review also discusses the literature concerning the current and future market potential and environmental impacts of face masks. Among the AMA tested, metal and metal-oxide based materials are more popular and relatively matured technology. However, the repeated use of such a face mask may pose a danger to the user and environment due to leaching/detachment of nanoparticles. So careful consideration is required to select AMA and their incorporation methods to reduce their leaching and environmental impacts. Also, systematic studies are required to establish short-term and long-term benefits.

Novel esterquat-based herbicidal ionic liquids incorporating MCPA and MCPP for simultaneous stimulation of maize growth and fighting cornflower

Modern agricultural practices are often based on the use of mixtures of specific herbicides to achieve efficient crop protection. The major drawbacks of commercial herbicidal formulations include the necessity to incorporate toxic surfactants and high volatility of active substances. Transformation of herbicides into herbicidal ionic liquids (HILs) seems to be a promising alternative which allows to almost completely reduce volatility due to ionic interactions. In the scope of this research, we transformed (2-methyl-4-chlorophenoxy)acetic acid (MCPA) into a quaternary ester (esterquat) with the use of derivatives of 2-dimethylaminoethanol. The obtained esterquats were later coupled with (±)-2-(4-chloro-2-methylphenoxy)propionic acid (MCPP) in the form of an anion. The combination of MCPA and MCPA is commonly applied in the UK, EU countries and also in the USA to increase the spectrum of targeted weed species. In the framework of this study, novel HILs with an esterquat moiety incorporating a long alkyl chain (C₈, C₉, C₁₀, C₁₁, C₁₂, C₁₄) were prepared and characterized in terms of basic physicochemical properties (solubility and volatility) as well as biodegradability. Their phytotoxicity was assessed towards cornflower (Centaurea cyanus) as a model weed and maize (Zea mays) as a crop plant. The presence of the esterquat cation contributed to satisfactory solubility in water and other low polar solvents, which eliminates the need to add exogenous adjuvants. Further experiments indicated that the tested HILs stimulated the germination stage of maize and maintained high herbicidal activity towards cornflower. No significant differences in terms of properties were observed in case of HILs which included alkyl substituents with an odd number of carbon atoms. Future studies should be focused on structural modifications in order to improve the biodegradability as well as field studies for evaluation of commercial applications.

Multifunctional cationic surfactants with a labile amide linker as efficient antifungal agents-mechanisms of action

Our research aimed to expand the knowledge of relationships between the structure of multifunctional cationic dicephalic surfactants with a labile linker-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 possible mechanism of action on fungal cells using the model organism Saccharomyces cerevisiae. General studies performed on surfactants suggest that in most cases, their main mechanism of action is based on perforation of the cell membranes and cell disruption. Experiments carried out in this work with cationic dicephalic surfactants seem to modify our understanding of this issue. It was found that the investigated compounds did not cause perforation of the cell membrane and could only interact with it, increasing its permeability. The surfactants tested can probably penetrate inside the cells, causing numerous morphological changes, and contribute to disorders in the lipid metabolism of the cell resulting in the formation of lipid droplet aggregates. This research also showed that the compounds cause severe oxidative stress within the cells studied, including increased production of superoxide anion radicals and mitochondrial oxidative stress. Dicephalic cationic surfactants due to their biodegradability do not accumulate in the environment and in the future may be used as effective antifungal compounds in industry as well as medicine, which will be environmentally friendly. KEY POINTS: • Dicephalic cationic surfactants do not induce disruption of the cell membrane. • Surfactants could infiltrate into the cells and cause accumulation of lipids. • Surfactants could cause acute oxidative stress in yeast cells. • Compounds present multimodal mechanism of action. Graphical abstract.

Modeling Gas-Liquid Interfaces by Dissipative Particle Dynamics: Adsorption and Surface Tension of Cetyl Trimethyl Ammonium Bromide at the Air-Water Interface

Adsorption of surfactants at gas-liquid interfaces that causes reduction in the surface tension is a classical problem in colloid and interface science with multiple practical applications in oil and gas recovery, separations, cosmetics, personal care, and biomedicine. Here, we develop an original coarse-grained model of the liquid-gas interface within the conventional dissipative particle dynamics (DPD) framework with the goal of quantitatively predicting the surface tension in the presence of surfactants. As a practical case-study example, we explore the adsorption of the cationic surfactant cetyl trimethyl ammonium bromide (CTAB) on the air-water interface. The gas phase is modeled as a DPD fluid composed of fictitious hard-core "gas" beads with exponentially decaying repulsive potentials to prevent penetration of the liquid phase components. A rigorous parametrization scheme is proposed based on matching the bulk and interfacial properties of water and octane taken as the reference compounds. Quantitative agreement between the simulated and experimental surface tension of CTAB solutions is found for a wide range of bulk surfactant concentrations (∼10^-3 to ∼1 mmol/L) with the reduction of the surface tension from ∼72 mN/m (pure water) to the limiting value of ∼37.5 mN/m at the critical micelle concentration. The gas phase DPD model with the proposed parametrization scheme can be extended and applied to modeling various gas-liquid interfaces with surfactant and lipid monolayers, such as bubble suspensions, foams, froths, etc.

Rapid and sensitive identification of uropathogenic Escherichia coli using a surface-enhanced-Raman-scattering-based biochip

Rapid, selective and sensitive sensing of bacteria remains challenging. We report on a highly sensitive and reproducible surface-enhanced Raman spectroscopy (SERS)-based sensing approach for the detection of uropathogenic Escherichia coli (E. coli) bacteria in urine. The assay is based on the specific capture of the bacteria followed by interaction with cetyltrimethylammonium bromide (CTAB)-stabilised gold nanorods (Au NRS) as SERS markers. High sensitivity up to 10 CFU mL^-1 is achieved by optimizing the capture interface based on hydrogenated amorphous silicon a-Si:H thin films. The integration of CH₃O-PEG750 onto a-Si:H gives the sensing interface an efficient anti-fouling character, while covalent linkage of antibodies directed against the major type-1 fimbrial pilin FimA of the human pathogen E. coli results in the specific trapping of fimbriated E. coli onto the SERS substrate and their spectral fingerprint identification.

Surface Wiping Test to Study Biocide -Cinnamaldehyde Combination to Improve Efficiency in Surface Disinfection

Disinfection is crucial to control and prevent microbial pathogens on surfaces. Nonetheless, disinfectants misuse in routine disinfection has increased the concern on their impact on bacterial resistance and cross-resistance. This work aims to develop a formulation for surface disinfection based on the combination of a natural product, cinnamaldehyde, and a widely used biocide, cetyltrimethylammonium bromide. The wiping method was based on the Wiperator test (ASTM E2967−15) and the efficacy evaluation of surface disinfection wipes test (EN 16615:2015). After formulation optimization, the wiping of a contaminated surface with 6.24 log₁₀ colony-forming units (CFU) of Escherichia coli or 7.10 log₁₀ CFU of Staphylococcus aureus led to a reduction of 4.35 log₁₀ CFU and 4.27 log₁₀ CFU when the wipe was impregnated with the formulation in comparison with 2.45 log₁₀ CFU and 1.50 log₁₀ CFU as a result of mechanical action only for E. coli and S. aureus, respectively. Furthermore, the formulation prevented the transfer of bacteria to clean surfaces. The work presented highlights the potential of a combinatorial approach of a classic biocide with a phytochemical for the development of disinfectant formulations, with the advantage of reducing the concentration of synthetic biocides, which reduces the potentially negative environmental and public health impacts from their routine use.

Joint effect of surfactants and cephalexin on the formation of Escherichia coli filament

Both antibiotics and surfactants commonly exist in natural environment and have generated great concerns due to their biological influence on the ecosystem. A major concern lies in the capacity of antibiotics to induce bacterial filaments formation, which has potential health risks. However, their joint effect is not clear so far. Here, we studied the joint effect of cephalexin (Cex), a typical antibiotic, and differently charged surfactants on the formation of E. coli filaments. Three kinds of surfactants characterized by different charges were used: cationic surfactant (CTAB), anionic surfactant (SDS) and nonionic surfactant (Tween). Data showed that Cex alone caused the formation of E. coli filaments, elongating their maximum profile from ca. 2 μm (a single E. coli cell) to tens of micrometers (an E. coli filament). A joint use of surfactants with Cex could produce even longer E. coli filaments, elongating the maximum length of the bacteria to larger than 100 μm. The capacity order of different surfactants under their optimum concentrations to produce elongated E. coli filaments was Tween > SDS > CTAB. The E. coli filaments were characterized with a normal DNA distribution and a good cell membrane integrity. We measured the stiffness of bacterial cell wall by atomic force microscopy and correlated the elongation capacity of the E. coli filaments to the stiffness of cell wall. Zeta potential measurement indicated that inserting into or being bound to the cell surface in a large quantity was tested not to be the major way that surfactants interacted with bacteria.

Biocide Potentiation Using Cinnamic Phytochemicals and Derivatives

Surface disinfection is of utmost importance in the prevention of bacterial infections. This study aims to assess the ability of ten phytochemicals and related derivatives as potentiators of two commonly used biocides-cetyltrimethylammonium bromide (CTAB) and lactic acid (LA). LA in combination with cinnamic, hydrocinnamic, α-methylcinnamic, and α-fluorocinnamic acids had a factional inhibitory concentration index (FICI) ≤ 1 for Escherichia coli and Staphylococcus aureus. Several phytochemicals/derivatives in combination with biocides improved the biocidal efficacy against early sessile bacteria. The most effective combination was LA with allyl cinnamate (2.98 ± 0.76 log CFU.cm^-2 reduction) against E. coli. The combination with CTAB was successful for most phytochemicals/derivatives with a maximum bactericidal efficacy against sessile E. coli when combined with allyl cinnamate (2.20 ± 0.07 log CFU.cm^-2 reduction) and for S. aureus when combined with α-methylcinnamic acid (1.68 ± 0.30 log CFU.cm^-2 reduction). This study highlights the potential of phytochemicals and their derivatives to be used in biocide formulations.

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.

Preferential Accumulation of Phospholipid-PEG and Cholesterol-PEG Decorated Gold Nanorods into Human Skin Layers and Their Photothermal-Based Antibacterial Activity

Herein, a library of gold nanorods (GNR) decorated with polyethylene glycol-thiol (PEG-SH) containing different functionalities were synthesized and characterized by optical absorption spectroscopy, zeta potential, dynamic light scattering (DLS), transmission electron microscope (TEM) and proton nuclear magnetic resonance (1H-NMR). The colloidal stability of GNR when exposed to skin, and their preferential accumulation into excised human skin layers were investigated. Confocal laser scanning microscopy, transmission electron microscope (TEM) and inductively coupled plasma-optical emission spectroscopy (ICP-OES) were utilized to track the penetration of GNR into different skin layers. The results demonstrated that cholesterol-PEG coated GNR were preferentially loaded up in the upper layers of skin (stratum corneum), while phospholipid-PEG coated counterparts were drastically deposited in skin dermis. Neutral methoxy-PEG-coated GNR were distributed in both SC and dermis skin layers, while charged GNR (anionic-carboxylic acid-PEG-GNR and cationic-amine-PEG-GNR) revealed a minimal accumulation into skin. DSPE-PEG-GNR and Chol-PEG-GNR demonstrated antibacterial activities against Staphylococcus aureus (S aureus) at MIC values of 0.011 nM and 0.75 nM, respectively. Photothermal treatment for S. aureus at sub-MIC concentrations resulted in a significant bactericidal effect when using Chol-PEG-GNR but not DSPE-PEG-GNR. Gold-based nanoscale systems have great value as a promising platform for skin diseases therapy.

Surfactants: Role in biofilm management and cellular behaviour

Appropriate and effective wound cleaning represents an important process that is necessary for preparing the wound for improved wound healing and for helping to dislodge biofilms. Wound cleaning is of paramount importance to wound bed preparation for helping to enhance wound healing. Surfactant applications in wound care may represent an important area in the cleaning continuum. However, understanding of the role and significance of surfactants in wound cleansing, biofilm prevention and control, and enhancing cellular viability and proliferation is currently lacking. Despite this, some recent evidence on poloxamer-based surfactants where the surfactants are present in high concentration have been shown to have an important role to play in biofilm management; matrix metalloproteinase modulation; reducing inflammation; and enhancing cellular proliferation, behaviour, and viability. Consequently, this review aims to discuss the role, mode of action, and clinical significance of the use of medically accepted surfactants, with a focus on concentrated poloxamer-based surfactants, to wound healing but, more specifically, the role they may play in biofilm management and effects on cellular repair.

Supramolecular Antibacterial Materials for Combatting Antibiotic Resistance

Antibiotic-resistant bacteria have emerged as a severe threat to human health. As effective antibacterial therapies, supramolecular materials display unprecedented advantages because of the flexible and tunable nature of their noncovalent interactions with biomolecules and the ability to incorporate various active agents in their platforms. Herein, supramolecular antibacterial materials are discussed using a format that focuses on their fundamental active elements and on recent advances including material selection, fabrication methods, structural characterization, and activity performance.