Efficient Antibacterial Agents Research Articles

Assessment of silver and graphitic carbon nitride doped cadmium selenide quantum dots as an efficient dye degrader and antibacterial agent: In silico molecular docking analysis

This study demonstrates the synthesis of co-precipitated cadmium selenide (CdSe) quantum dots (QDs) doped with (2 and 4 wt %) of silver (Ag) and fixed quantity of graphitic carbon nitride (g-C3N4) for catalytic as well as antibacterial potential with molecular docking (MD) analysis. Comprehensive characterizations investigated the structural composition, surface morphology, elemental composition, and optical properties. XRD revealed the multiple phases (hexagonal and cubic) of CdSe with a notable rise in the diffraction peaks intensity upon doping. The optical studies demonstrated the range of absorption peaks, which increased upon doping confirmed through band gap energies significantly altered. TEM study revealed that a sheet of g-C3N4 overlapped with CdSe QDs, and certain nanorod-like structures emerged after Ag doping. HR-TEM was employed for the d-spacing computation of prepared samples and exposed a decreasing trend as the Ag concentration increased. Furthermore, the catalytic activity (CA) performed against RhB dye showed maximum results in the acidic medium with a higher concentration of Ag into g-C3N4 doped CdSe. The efficient bactericidal efficacy was evaluated against S. aureus bacteria with the highest inhibition zone of 13.75 mm for 4% Ag doping, which was further explained by investigating their inhibitory effects on DNA gyrase and tyrosyl-tRNA synthetase via MD.

Graphene quantum dots with covalently bonded gold nanoparticles winning the battle against methicillin-resistant Staphylococcus aureus under blue light

Over the last decades, bacterial resistance has become one of the emerging health threats. Particularly dangerous are bacterial strains resistant to various antibacterial drugs. Herein, we modified graphene quantum dots (GQDs) to produce efficient photo-induced antibacterial agents. GQDs were modified with (a) ethylene-diamine (EDA), (b) with EDA and gold nanoparticles (AuNPs), and (c) 3-amino-1,2,4-triazole (TA) using carbodiimide coupling. Photo-induced antibacterial activity of modified GQDs was tested against 8 bacterial strains. Treatment with modified GQDs and blue light (wavelength of 470 nm) resulted in remarkable antibacterial activity with minimal inhibitory concentrations (MIC) of 7.81 µg mL−1 for K. pneumoniae and S. aureus and 3.9 µg mL−1 against MRSA and E. faecalis. Planar organization of GQDs functionalized with AuNPs allowed direct access of molecular oxygen to AuNPs leading to more efficient 1O2 production as well as the 1O2 production from excited GQDs. Thus, GQDs functionalized with AuNPs showed outstanding efficiency in the battle against several bacterial strains, particularly those that lead to nosocomial infections.

Exploring bee venom and silver nanoparticles for controlling foulbrood pathogen and enhancing lifespan of honeybees

The beekeeping industry plays a crucial role in local economies, contributing significantly to their growth. However, bee colonies often face the threat of American foulbrood (AFB), a dangerous disease caused by the Gram-positive bacterium Paenibacillus larvae (P. l.). While the antibiotic Tylosin has been suggested as a treatment, its bacterial resistance necessitates the search for more effective alternatives. This investigation focused on evaluating the potential of bee venom (BV) and silver nanoparticles (Ag NPs) as antibacterial agents against AFB. In vitro treatments were conducted using isolated AFB bacterial samples, with various concentrations of BV and Ag NPs (average size: 25nm) applied individually and in combination. The treatments were administered under both light and dark conditions. The viability of the treatments was assessed by monitoring the lifespans of treated bees and evaluating the treatment's efficiency within bee populations. Promising results were obtained with the use of Ag NPs, which effectively inhibited the progression of AFB. Moreover, the combination of BV and Ag NPs, known as bee venom/silver nanocomposites (BV/Ag NCs), significantly extended the natural lifespan of bees from 27 to 40 days. Notably, oral administration of BV in varying concentrations (1.53, 3.12, and 6.25 mg/mL) through sugary syrup doubled the bees' lifespan compared to the control group. The study established a significant correlation between the concentration of each treatment and the extent of bacterial inhibition. BV/Ag NCs demonstrated 1.4 times greater bactericidal efficiency under photo-stimulation with visible light compared to darkness, suggesting that light exposure enhances the effectiveness of BV/Ag NCs. The combination of BV and Ag NPs demonstrated enhanced antibacterial efficacy and prolonged honeybee lifespan. These results offer insights that can contribute to the development of safer and more efficient antibacterial agents for maintaining honeybee health.

Biocompatible protein-based self-assembled nanocomposite as efficient drug nanocarrier and antibacterial agent

To fulfill diverse application-specific purposes, functional nanoparticles encapsulated into protein-based self-assemblies show promising advantages includes easy preparation, high biocompatibility and multiple properties. In this study, the model protein of BSA used for multi-component self-assembly, including hydrophobic Fe3O4 nanoparticles, nano-ZnO and curcumin, was constructed through hydrophobic interactions. The obtained composites of BSA-Fe3O4&ZnO and BSA-Fe3O4&ZnO&curcumin self-assemblies were tested for antibacterial and drug delivery, respectively. It was found that the multicomponents loaded into protein assembly confer a simple yet robust synthetic method resulting in the produced nanocomposites with high stability and desirable biocompatibility. Notably, the protein self-assemblies successfully increased the antibacterial efficacy of hydrophobic ZnO nanoparticles, and promote the intracellular delivery of poorly soluble curcumin to exert significant killing effects against cancer cells. Therefore, the constructed multi-component contained protein self-assembly that enables hydrophobic interactions of compositional nanoparticles holds promising potentials for the versatile uses in biomedical aspects.

CuFe2O4/lignin-based carbon composited photothermal and photodynamic agents for synergetic antibacterial therapy

Bacterial infection has become the second leading cause of death in the world. Exploring a new highly antibacterial catalyst to replace traditional antibacterial agent is crucial for the society development of human beings. In this study, CuFe2O4/Lg-based carbon composited catalysts were rationally constructed by facile hydrothermal method. Lignin-derived carbon with enormous oxygen-containing functional group was beneficial to anchor CuFe2O4 nanoparticles. The close contact interface between CuFe2O4 and Lignin-based carbon material was expected to extend the range of optical absorption and promote the separation and transportation of photogenerated carriers. Under NIR (980 nm, 1.5 W/cm2) light irradiation, the as-prepared CuFe2O4/Lg (20 μg/mL) exhibited excellent photo/photothermal synergetic in vitro (against Escherichia coli and Staphylococcus aureus) and in vivo (against Staphylococcus aureus-infected mouse wound model) antibacterial performance. Furthermore, the cell count assay kit 8 (CCK-8 kit) demonstrated the good biocompatibility of this material. On the basis of the experimental results, a possible antibacterial mechanism based on the synergetic photothermal and photodynamic therapies was proposed. This work presented a lignin- derived carbon-based highly efficient antibacterial disinfection agent with desirable biosafety.

Photoresponsive Multirole Nanoweapon Camouflaged by Hybrid Cell Membrane Vesicles for Efficient Antibacterial Therapy of Pseudomonas aeruginosa-Infected Pneumonia and Wound.

Exploring effective antibacterial approaches for targeted treatment of pathogenic bacterial infections with reduced drug resistance is of great significance. Combinational treatment modality that leverages different therapeutic components can improve the overall effectiveness and minimize adverse effects, thus displaying considerable potential against bacterial infections. Herein, red blood cell membrane fuses with macrophage membrane to develop hybrid cell membrane shell, which further camouflages around drug-loaded liposome to fabricate biomimetic liposome (AB@LRM) for precise antibacterial therapy. Specifically, photoactive agent black phosphorus quantum dots (BPQDs) and classical antibiotics amikacin (AM) are loaded in AB@LRM to accurately target the inflammatory sites through the guidance of macrophage membrane and long residence capability of red blood cell membrane, eventually exerting efficacious antibacterial activities. Besides, due to the excellent photothermal and photodynamic properties, BPQDs act as an efficient antibacterial agent when exposed to near-infrared laser irradiation, dramatically increasing the sensitivity of bacteria to antibiotics. Consequently, the synergistic sterilizing effect produced by AB@LRM further restricts bacterial resistance. Upon laser irradiation, AB@LRM shows superior anti-inflammatory and antibacterial properties in models of P. aeruginosa-infected pneumonia and wounds. Hence, this light-activatable antibacterial nanoplatform with good biocompatibility presents great potential to advance the clinical development in the treatment of bacterial infections.

White light-driven enhanced cerium-doped carbon dots activity to combat multidrug-resistant bacterial infection

Infections caused by multidrug-resistant (MDR) bacteria are increasing and becoming an urgent global health crisis. The discovery and development of novel antibacterial agents to combat MDR are highly desirable. Here, we report the fabrication of cerium-doped carbon dots (CeCDs) with a simple hydrothermal method, which exhibit intrinsic broad efficacy against MDR bacteria including clinical isolates while maintaining low cytotoxicity and hemolytic effects. Importantly, the antibacterial activity of CeCDs is dramatically improved owing to the generation of reactive oxygen species (ROS) upon white light irradiation. Comprehensive analyses revealed that the CeCDs can penetrate the bacterial wall, disrupt the cell membrane, and prevent the biofilm formation, possibly hindering the bacterial resistance development. And the interaction of CeCDs with lipopolysaccharide (LPS) may contribute to the higher activity against Gram-negative bacteria strains. The treatment of CeCDs in a murine skin infection model can significantly reduce the number of bacteria on infected sites and accelerate wound healing by irradiation with light. Overall, CeCDs show great promise as low-cost and efficient antibacterial agents for chronic wounds and may be served as a powerful weapon to fight against the growing threat of MDR bacterial infection.

Carbohydrate polymers based MnO2 nanostructures for catalytic and antibacterial activity; kinetic modeling and molecular docking analysis

In this project, cellulose nanocrystal-CNC, chitosan-CS, and starch-St doped MnO2 nanostructures (NSs) were synthesized by a co-precipitation approach. The motive of this research was to evaluate the effect of CNC, CS, and St on catalytic activity, kinetic adsorption, and antimicrobial potency with molecular docking (MD) analysis of MnO2. The hydrophilic head of polymers interacts with MnO2 NSs to regulate the growth, recombination rate, and stability of nanostructures. Notably, St-doped MnO2 exhibited the highest catalytic potency in an acidic medium in comparison to basic and neutral media. The kinetic modeling (pseudo-1st, pseudo-2nd order, Elovich, and intra-particle diffusion model) suggests that the adsorption of RhB dye by the NSs follows the pseudo-second-order kinetics. Among all samples, CNC-MnO2 and St-MnO2 proved to be an efficient antibacterial agents against E. coli and s. aureus bacteria, respectively. Findings revealed that polymer-based MnO2 nanostructures were the most efficient inhibitors of DNA gyrase against E. coli and S. aureus.

Fabrication of photo-induced molecular superoxide radical generator for highly efficient therapy against bacterial wound infection

The pressing need for highly efficient antibacterial strategies arises from the prevalence of microbial biofilm infections and the emergence of rapidly evolving antibiotic-resistant strains of pathogenic bacteria. Photodynamic therapy represents a highly efficient and compelling antibacterial approach, offering promising prospects for effective control of the development of bacterial resistance. However, the effectiveness of many photosensitizers is limited due to the reduced generation of reactive oxygen species (ROS) in hypoxic microenvironment, which commonly occur in pathological conditions such as inflammatory and bacteria-infected wounds. Herein, we designed and prepared two phenothiazine-derived photosensitizers (NB-1 and NB-2), which can effectively generate superoxide anion radicals (O2●–) through the type I process. Both photosensitizers demonstrate significant efficacy in vitro for the eradication of broad-spectrum bacteria. Moreover, NB-2 possesses distinct advantages including strong membrane binding and strong generation of O2●–, rendering it an exceptionally efficient antibacterial agent against mature biofilms. In addition, laser activated NB-2 could be applied to treat MRSA-infected wound in vivo, which offers new opportunities for potential practical applications.

Green synthesis of ZnO NPs with long-lasting and ultra-high antimicrobial activity

The continual onslaught of pathogenic microorganisms against humans, coupled with the escalating global challenge of antibiotic resistance, has led to a pervasive health crisis. To produce efficient antibacterial agents and combat bacterial resistance, zinc oxide nanoparticles (ZnO NPs) were synthesized, through green synthesis method by using Magnolia officinalis, Goldthread, and Lonicera japonica as extracts, respectively. Notably, there were no additional chemical reagents used in the synthesis route, emphasizing its eco-friendly nature. The antimicrobial efficacy of these ZnO NPs was assessed against Escherichia coli, Staphylococcus aureus, and Botrytis cinerea. The results revealed the ZnO NPs exceptional antimicrobial properties, demonstrating a minimum antimicrobial concentration (MIC) of 10 mg/L. Magnolia officinalis-ZnO NPs (M-ZnO NPs) exhibited 99.99 % antimicrobial activity against both E. coli and Staphylococcus aureus, along with 99.63 % effectiveness against Botrytis cinerea. Additionally, it was observed that the antibacterial characteristics of ZnO NPs exhibited minimal degradation after being stored in ambient air conditions at standard room temperature for a half-year. This study conclusively affirms the potent antimicrobial efficacy of green-synthesized ZnO nanoparticles. Transmission electron microscopy revealed that the particle size of ZnO NPs is 20–40 nm. Plant extracts contribute to the reduction processes of metal ions, and can also control the size and stability of formed nanostructures while avoiding the use of hazardous solvents. This green synthesis results in smaller particle sizes and sustains a long-term high antibacterial effect. Overall, this research expands the prospects for development involving nanomaterials, offering promising avenues for further exploration and innovation in this field.

Antibacterial activity of molybdenum disulfide and green silver nanoparticles reduced by tea tree essential oil compounds

The increasing resistance of microorganisms against antibiotics puts at risk the human being. This event requires urgently developing strategies for producing alternative antibacterial agents. The combination of green silver nanoparticles (reduced by essential oil) and molybdenum disulfide can be synergistically explored given the interaction of components. Herein, it is reported the response of isolated and combined components with resulting outstanding kinetics of kill-time (complete elimination of Staphylococcus aureus and Escherichia coli after four hours of contact), effective action against biofilm formation (~99% of inhibition in the biofilm formation). These results confirm that the intercalation of silver nanoparticles between exfoliated sheets of MoS2 represents a promising strategy to develop efficient antibacterial agents against Gram-positive and Gram-negative bacteria.

Molecular Basis of Yeasts Antimicrobial Activity-Developing Innovative Strategies for Biomedicine and Biocontrol.

In the context of the growing concern regarding the appearance and spread of emerging pathogens with high resistance to chemically synthetized biocides, the development of new agents for crops and human protection has become an emergency. In this context, the yeasts present a huge potential as eco-friendly agents due to their widespread nature in various habitats and to their wide range of antagonistic mechanisms. The present review focuses on some of the major yeast antimicrobial mechanisms, their molecular basis and practical applications in biocontrol and biomedicine. The synthesis of killer toxins, encoded by dsRNA virus-like particles, dsDNA plasmids or chromosomal genes, is encountered in a wide range of yeast species from nature and industry and can affect the development of phytopathogenic fungi and other yeast strains, as well as human pathogenic bacteria. The group of the "red yeasts" is gaining more interest over the last years, not only as natural producers of carotenoids and rhodotorulic acid with active role in cell protection against the oxidative stress, but also due to their ability to inhibit the growth of pathogenic yeasts, fungi and bacteria using these compounds and the mechanism of competition for nutritive substrate. Finally, the biosurfactants produced by yeasts characterized by high stability, specificity and biodegrability have proven abilities to inhibit phytopathogenic fungi growth and mycelia formation and to act as efficient antibacterial and antibiofilm formation agents for biomedicine. In conclusion, the antimicrobial activity of yeasts represents a direction of research with numerous possibilities of bioeconomic valorization as innovative strategies to combat pathogenic microorganisms.

Molecular encapsulation of the protocatechuic and vanillic acid derivatives with β-cyclodextrin: Structural determination, antibacterial assessment, and molecular docking analysis

The phenolic chemical framework represents one of the most utilized structural motifs in the pursuit of innovative biologically active compounds. Particularly, the urgency for efficient antibacterial agents is still ongoing, especially due to rising bacterial resistance to common therapeutics. The physicochemical profile and efficiency of bioactive agents could be enhanced by their inclusion with cyclodextrins. In this study, the encapsulation of four protocatechuic and vanillic acid derivatives was performed in the reactions with β-cyclodextrin. The host-guest interactions and the formation of inclusion systems were confirmed by NMR, IR, and XRPD spectra. The Job's plot assay revealed the 1:1 stoichiometric ratio in the formed inclusion complexes, whereas the molecular docking analysis exposed the most favorable inclusion modes of guest molecules within the β-cyclodextrin cavity. The in vitro antibacterial investigations performed on selected G+ and G−bacteria revealed significantly enhanced activity of inclusion complexes in comparison to guest molecules. In general, the tested substances exhibited antibacterial activity with the MIC50 values determined in the range of 0.20–7.98 mM. Here, L. monocytogenes (G+) and E. coli (G−) strains were most sensitive to the treatment with guests and inclusion complexes. In several cases, the investigated compounds exerted comparable or higher activity than vancomycin. The present findings indicate that encapsulation of the selected phenolic compounds is favorable for improving their antibacterial profile, which could contribute to the endeavor for more efficient antibiotic therapy.

Synergistic effect of Silver-Nanodiamond composite as an efficient antibacterial agent against E. coli and S. aureus

Bacterial antimicrobial resistance (BAMR) seems to pose the greatest threat to public health, food safety, and agriculture in this century. The development of novel efficient antimicrobial agents to combat bacterial infections has become a global issue. Silver nanoparticles (Ag NPs) appeared as a feasible alternative to antibiotics. However, Ag NPs face cost, toxicity, and aggregation issues which limit their antibacterial activity. This work aims to stabilize Ag NPs with enhanced antimicrobial activity at comparatively lower Ag concentrations to prevent bacterial infections. For this purpose, the Ag core was covered with nanodiamonds (NDs). Ag-NDs composite have been synthesized by microplasma technique. TEM analysis confirmed the presence of both Ag and NDs in the Ag-NDs composite. A particle size (∼19 nm) was reported for Ag-NDs at the highest concentration as compared to Ag NPs (∼3 nm). The conduction band of the diamond acted as an extremely strong reducing agent for Ag NPs. The large surface area of NDs stabilized the Ag NPs. A redshift (∼400 nm–406 nm) in UV–visible spectra of the Ag-NDs composite indicated the formation of bigger-sized Ag NPs after incorporating NDs. XRD and LIBS analysis verified the increase in intensity of Ag-NPs by increasing ND concentration. The presence of functional groups including OH, CH, and Ag/Ag2O was confirmed by FTIR. Bacterial inhibition growth appeared to be a dose-dependent process. The minimum inhibition concentration value of Ag-NDs composite at the highest NDs concentration against E. coli (∼ 0.69 μg/ml) and S. aureus (∼44 μg/ml). This is the first study to report the smallest MIC for E. coli (<1 μg/ml). Ag-ND composites emerged to be more efficient than Ag NPs and preferred to be used against BAMR. The enhanced antibacterial activity of the Ag-NDs composite makes it a potential candidate for antibiotics, food products, and pesticides.

Heterocyclic-Based Analogues against Sarcine-Ricin Loop RNA from Escherichia coli: In Silico Molecular Docking Study and Machine Learning Classifiers.

Heterocyclic-based drugs have strong bioactivities, are active pharmacophores, and are used to design several antibacterial drugs. Due to the diverse biodynamic properties of well-known heterocyclic cores, such as quinoline, indole, and its derivatives, they have a special place in the chemistry of nitrogen-containing heterocyclic molecules. The objective of this study is to analyze the interaction of several heterocyclic molecules using molecular docking and machine learning approaches to find out the possible antibacterial drugs. The molecular docking analysis of heterocyclic-based analogues against the sarcin-Ricin Loop RNA from E. coli with a C2667-2'-OCF3 modification (PDB ID: 6ZYB) is discussed. Many heterocyclic-based derivatives show several residual interaction, affinity, and hydrogen bonding with sarcin-Ricin Loop RNA from E. coli with a C2667-2'-OCF3 alteration which are identified by the investigation of in silico molecular docking analysis of such heterocyclic derivatives. The dataset from the molecular docking study was used for additional optimum analysis, and the molecular descriptors were classified using a variety of machine learning classifiers, including the GB Classifier, CB Classifier, RF Classifier, SV Classifier, KNN Classifier, and Voting Classifier. The research presented here showed that heterocyclic derivatives may operate as potent antibacterial agents when combined with other compounds to produce highly efficient antibacterial agents.

Nanomaterials with Enzyme-like Properties for Combatting Foodborne Pathogen Infections: Classifications, Mechanisms, and Applications in Food Preservation.

During the transportation and storage of food, foodborne spoilage caused by bacterial and biofilm infection is prone to occur, leading to issues such as short shelf life, economic loss, and sensory quality instability. Therefore, the development of novel and efficient antibacterial agents capable of efficiently inhibiting bacteria throughout various stages of food processing, transportation, and storage is strongly recommended by researchers. The emergence of nanozymes is considered to be an effective candidate for inhibiting foodborne bacteria agents in the food industry. As potent antibacterial agents, nanozymes have the advantages of low cost, high stability, strong broad-spectrum antibacterial ability, and biocompatibility. Herein, we aim to summarize the classification status of various nanozymes. Furthermore, the general catalytic bacteriostatic mechanism of nanozymes against intracellular bacteria, planktonic bacteria, and biofilm activities are highlighted, mainly concerning the destruction of cell walls and/or membranes, reactive oxygen species regulation, HOBr/Cl generation, damage of intracellular components, and so forth. In particular, the review focuses on the pivotal role of nanozymes as antibacterial agents and delivery vehicles in the fields of food preservation applications. We look forward to the future prospects, especially in the field of food preservation, to promote broader applications based on antimicrobial nanozymes.

Green Preparation and Antibacterial Activity Evaluation of AgNPs-Blumea balsamifera Oil Nanoemulsion.

Bacterial infection is a thorny problem, and it is of great significance to developing green and efficient biological antibacterial agents that can replace antibiotics. This study aimed to rapidly prepare a new type of green antibacterial nanoemulsion containing silver nanoparticles in one step by using Blumea balsamifera oil (BBO) as an oil phase and tea saponin (TS) as a natural emulsifier and reducing agent. The optimum preparation conditions of the AgNPs@BBO-TS NE were determined, as well as its physicochemical properties and antibacterial activity in vitro being investigated. The results showed that the average particle size of the AgNPs@BBO-TS NE was 249.47 ± 6.23 nm, the PDI was 0.239 ± 0.003, and the zeta potential was -35.82 ± 4.26 mV. The produced AgNPs@BBO-TS NE showed good stability after centrifugation and 30-day storage. Moreover, the AgNPs@BBO-TS NE had an excellent antimicrobial effect on Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. These results demonstrated that the AgNPs@BBO-TS NE produced in this study can be used as an efficient and green antibacterial agent in the biomedical field.

Ocimum sanctum-mediated co/cu/zn-doped magnesium oxide nanoparticles: Photocatalytic, antibacterial, and antioxidant properties for environmental remediation

This research intends to formulate Ocimum sanctum mediated pure and transition metal (Co2+/Cu2+/Zn2+) doped magnesium oxide nanoparticles (MgO NPs). The cubic structure of so synthesized MgO NPs was confirmed by XRD analysis. As per UV–visible spectral analysis, band gap (Eg) is tuned upon doping; doping with Co, Cu and Zn, their respective Eg are 1.65 eV, 1.96 eV and 3.66 eV in relation to MgO, Eg = 3.50 eV. The average particle size decreased from 17 nm for MgO NPs to 8–13 nm for doped MgO NPs, based on TEM analysis. EDX and XPS analysis verified the presence of Mg, O and dopants, Co, Cu and Zn in synthesized NPs. SEM investigations showed that NPs are agglomerated and spherical. Zn–MgO NPs outperform Co/Cu doped MgO NPs in their photocatalytic efficacy and comparative degradation of methyl orange (MO) and malachite green (MG) dyes confirmed that they are more efficient in degrading MG. Antibacterial investigation revealed that Cu and Zn doped MgO NPs are efficient antibacterial agents against B. subtilis and E. coli than MgO NPs. In this study, Co–MgO NPs were ineffective as antibacterial agents. S. aureus was found resistant to all NPs. Using the DPPH radical scavenging technique, these biosynthesized nanoparticles displayed 62–69 % antioxidant activity.

Structure optimizing of flavonoids against both MRSA and VRE

Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE) cause more than 100,000 deaths each year, which need efficient and non-resistant antibacterial agents. SAR analysis of 162 flavonoids from the plant in this paper suggested that lipophilic group at C-3 was crucial, and then 63 novel flavonoid derivatives were designed and total synthesized. Among them, the most promising K15 displayed potent bactericidal activity against clinically isolated MRSA and VRE (MICs = 0.25–1.00 μg/mL) with low toxicity and high membrane selectivity. Moreover, mechanism insights revealed that K15 avoided resistance by disrupting biofilm and targeting the membrane, while vancomycin caused 256 times resistance against MRSA, and ampicillin caused 16 times resistance against VRE by the same 20 generations inducing. K15 eliminated residual bacteria in mice skin MRSA-infected model (>99 %) and abdominal VRE-infected model (>92 %), which was superior to vancomycin and ampicillin.

Carbon Nanodisks Decorated with Guanidinylated Hyperbranched Polyethyleneimine Derivatives as Efficient Antibacterial Agents.

Non-toxic carbon-based hybrid nanomaterials based on carbon nanodisks were synthesized and assessed as novel antibacterial agents. Specifically, acid-treated carbon nanodisks (oxCNDs), as a safe alternative material to graphene oxide, interacted through covalent and non-covalent bonding with guanidinylated hyperbranched polyethyleneimine derivatives (GPEI5K and GPEI25K), affording the oxCNDs@GPEI5K and oxCNDs@GPEI25K hybrids. Their physico-chemical characterization confirmed the successful and homogenous attachment of GPEIs on the surface of oxCNDs, which, due to the presence of guanidinium groups, offered them improved aqueous stability. Moreover, the antibacterial activity of oxCNDs@GPEIs was evaluated against Gram-negative E. coli and Gram-positive S. aureus bacteria. It was found that both hybrids exhibited enhanced antibacterial activity, with oxCNDs@GPEI5K being more active than oxCNDs@GPEI25K. Their MIC and MBC values were found to be much lower than those of oxCNDs, revealing that the GPEI attachment endowed the hybrids with enhanced antibacterial properties. These improved properties were attributed to the polycationic character of the oxCNDs@GPEIs, which enables effective interaction with the bacterial cytoplasmic membrane and cell walls, leading to cell envelope damage, and eventually cell lysis. Finally, oxCNDs@GPEIs showed minimal cytotoxicity on mammalian cells, indicating that these hybrid nanomaterials have great potential to be used as safe and efficient antibacterial agents.