Gram-negative Bacterial Strains Research Articles

Green synthesis and antibacterial potency of Ag/CuO/ZnO nanoparticles derived from Psidium guajava L. extracts

Nanoparticles, characterized by their unique physicochemical properties, represent a significant frontier in interdisciplinary research, particularly within the realms of biomedicine and environmental science. This investigation delves into the eco-friendly synthesis of silver (Ag), copper oxide (CuO) and zinc oxide (ZnO) nanoparticles utilizing extracts derived from Psidium guajava L. The utilization of these botanical extracts presents a sustainable alternative to traditional nanoparticle fabrication methodologies, aligning with global sustainability imperatives and fostering environmentally conscious practices. The escalating global nanoparticle market, valued at over $30 billion in 2020 and projected to surpass $90 billion by 2027, underscores the economic significance and industrial relevance of nanoparticle research. This research trajectory fuels innovation across a spectrum of sectors, including healthcare, cosmetics and environmental remediation. The commercialization of nanoparticle-based products not only drives substantial revenue streams but also catalyzes advancements in research, development and manufacturing endeavors. Drawing upon aqueous extracts sourced from P. guajava., leaves and fruits, this study capitalizes on their inherent phytochemical composition to serve as stabilizing, reducing and capping agents during nanoparticle synthesis. Employing state-of-the-art characterization techniques such as UV-Vis spectroscopy, FTIR spectroscopy, FE-SEM and EDS facilitates a comprehensive analysis of the synthesized nanoparticles' physicochemical attributes. Assessment of the nanoparticles' antibacterial efficacy against gram-positive (Bacillus subtilis, Staphylococcus aureus) and gram-negative (Escherichia coli, Proteus vulgaris) bacterial strains reveals compelling results. Minimum inhibitory concentrations (MIC) elucidate notable efficacy, notably against P. vulgaris (3.75 mg/mL), S. aureus (7.5 mg/mL) and B. subtilis (10 mg/mL and 12.5 mg/mL), indicative of their potential biomedical applications in combating microbial infections.

Antibacterial and Cell-Viability of Hydroxyapatite Derived from Waste Marine Shell for Biomedical Applications

The present study discusses on the functional groups, structural characterization and thermal behaviour of Crassostrea angulata shell used for the synthesis of a biocompatible hydroxyapatite material. The hydroxyapatite was synthesized from C. angulata shell through precipitation method and characterized using XRD, FTIR, FE-SEM, EDX mapping, HR-TEM and SAED pattern. The formation of hydroxyapatite was confirmed from the high intense X-ray diffraction lines and by the presence of chemical groups such as PO43–, OH– and CO32–. The structural changes during the formation of hydroxyapatite from the thermal decomposition of C. angulata shell were studied through XRD and TG-DTA. The morphology study by FE-SEM indicates that the synthesized hydroxyapatite materials were in the form of clusters of rod-like particles. The SAED patterns and XRD spectral lines confirmed the crystalline nature of the synthesized hydroxyapatite. The antibacterial activity and cell viability assay of prepared hydroxyapatite were studied to assess its suitability in various biomedical applications. The antibacterial activity of hydroxyapatite was assessed against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus saprophyticus) bacterial strains. The cytocompatibility of hydroxyapatite was assessed through an MTT assay using osteoblast cells (MG-63 cell). Thus, the prepared hydroxyapatite shows good antibacterial action and cell viability nature and it can be applied in various biomedical applications.

Flavobacterium nakdongensis sp. nov., Isolated from Fresh Water during the Cyanobacterial Bloom Period.

A novel Gram-negative bacterial strain, 20NA77.7T , was isolated from fresh water of the Nakdong River. Strain 20NA77.7T shared the highest similarity with Flavobacterium indicum GPTSA100-9T (97.91%) and Flavobacterium urocaniciphilum DSM 27078T (96.24%) in the 16S rRNA gene sequence. The digital DNA-DNA hybridization and average nucleotide identity values for strain 20NA77.7T with Flavobacterium species were below 20.8% and 77.33%, respectively. The major fatty acids of strain 20NA77.7T were identified as iso-C15:0, iso-C16:0, iso-C15:1 G, anteiso-C15:0, iso-C15:0 3OH, and isoC16:0 3OH. Strain 20NA77.7T contained phosphatidylethanolamine, one unidentified aminolipid, and three unidentified lipids as polar lipids and menaquinone-6 as menaquinone. The polyphasic evidence supports the classification of strain 20NA77.7T as a novel species belonging to the genus Flavobacterium, for which the name Flavobacterium nakdongensis is proposed. The type strain is 20NA77.7T (= KCTC 102000T = LMG 33137T ).

Adsorptive potential of dispersible chitosan-coated biogenic iron oxide nanocomposite for enhanced anti-bacterial activity against gram-positive and gram-negative bacterial pathogens

The use of various biomaterials, such as plants or microbes, to create nanoparticles (NPs), is seen as a viable strategy in green nanotechnology. The synthesis of low-cost, energy-efficient, nontoxic, ecologically acceptable metallic nanoparticles has recently become a critical topic. The biosynthesis of iron oxide NPs using pomegranate peel extract has been investigated. Biogenic iron oxide NPs were coated with highly porous chitosan as a supporting material to enhance applicability of NPs for wastewater remediation. Biogenic magnetic NPs and its composite were characterized by scanning electron microscope, X-ray diffraction, and Fourier Transformer Infrared spectroscopy (FTIR). Our study focused on the ability of biogenic magnetite Fe3O4 NPs and its bio-composite for removal of As+5 ions from wastewater. Adsorption isotherms were obtained using metal ion concentrations ranging from 5 to 25 mg/L. The Langmuir adsorption model was validated by our data. The reaction kinetics of the adsorption process were pseudo-second order. Interestingly, the bio-composite achieved 90% As+5 removal at pH4. In addition, the prepared nanocomposite was characterized using various analytical techniques to confirm its physicochemical properties. The adsorptive capacity of the nanocomposite was evaluated by studying the removal of pollutants and contaminants from aqueous solutions. Additionally, the antibacterial activity of the nanocomposite was assessed against a panel of clinically relevant Gram-positive and Gram-negative bacterial strains, including Staphylococcus epidermidis (RCMB 9241, ATCC 12228), Staphylococcus saprophyticus (RCMB 010028, ATCC 15305), Enterococcus faecalis (RCMB 010052), Streptococcus salivarius (ATCC 13415), Escherichia coli (RCMB 010052, ATCC 25922), Salmonella enterica serovar Typhimurium (RCMB 006(1), ATCC 14028) and Pseudomonas aeruginosa (ATCC 27853). Our findings have important implications in the field of low-cost, easy, and environmentally friendly water bioremediation.

Ultrasonic-aided preparation of poly(vanillin-co-thiophene)/green Fe₃O₄ nanocomposites via solution mixing for methyl orange adsorption and antibacterial applications

This work describes the preparation of novel nanocomposite materials comprising a newly synthesized semiconducting copolymer, poly(vanillin-co-thiophene) (PVTH), blended with different weight proportions (3 %, 6 %, and 9 % by weight) of greenly synthesized magnetite nanoparticles (GFe3O4 MNPs) via solution mixing, assisted by ultrasonic irradiation. PVTH copolymer was synthesized through the polycondensation of vanillin, a bioderived aldehyde, and thiophene, catalyzed by sulfuric acid. GFe3O4 MNPs were prepared via the coprecipitation method with mint extract as an environmentally friendly stabilizer. The physicochemical properties of the prepared samples were investigated by 1H NMR, 13C NMR, FTIR, XRD, UV–vis, TGA, FE-SEM/Eds, AFM, VSM, tauc plot method and the four-points probe measurement. The samples were evaluated for two applications: methyl orange (MO) adsorption from aqueous solutions and antibacterial activities against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus and Bacillus) bacterial strains. The results showed that ultrasound irradiation facilitated the easy preparation of well-dispersed and homogeneous nanocomposites with combined semiconducting and magnetic properties and improved thermal stability compared to the parent PVTH. The most effective nanocomposite for MO removal was the sample containing 9 % GFe3O4 MNPs, whose adsorption behavior followed pseudo-second-order kinetics and Freundlich isotherm. Its maximum adsorption capacity was 103.79 mg g−1. In addition, all samples showed antibacterial action against the tested bacterial strains, with PVTH showing the highest efficacy, followed by PVTH/GFe3O4 nanocomposites.

Unprecedented one-pot synthesis of 3,4-dihydropyrimidine-2-(1h)-ones catalyzed by hydrazine sulfate through Biginelli reaction, ADMET property, molecular docking studies and their antibacterial activity on Bacillus brevis and E. coli

The syntheses of 3,4-dihydropyrimidin-2(1H)-ones by one-pot, three-component condensation of aldehydes, β-ketoesters and urea or thiourea have been made more simple and efficient by using 20 mol% hydrazine sulfate as catalyst. Aldehydes, β-ketoesters and urea are cyclocondensed in the presence of hydrazine sulfate to produce dihydropyrimidines in ethanol under reflux conditions. The advantages of using hydrazine sulfate as a catalyst over the traditional Biginelli reaction conditions include outstanding yields (80–91%) and a shorter (10–15 hours) reaction time. In order to evaluate the antibacterial efficiencies of the synthesized compounds, we have studied the inhibitions of microbial proliferation of both Gram-positive (Bacillus brevis) and Gram-negative (E. coli) bacterial strains in comparison to a control group. The microbial inhibitions occur in the range of 40–98% by different derivatives of dihydropyrimidinones. Molecular docking studies of the synthesized compounds have also been done using software tools such as SwissADME.

Assessment of Bryophyllum pinnatum mediated Ag and ZnO nanoparticles as efficient antimicrobial and cytotoxic agent.

Bryophyllum pinnatum is used to cure infections worldwide. Although the flavonoids of this plant are well known, it is still unknown how much of the plant's Ag and ZnO nanoparticles are beneficial. In the current research work, silver and zinc oxide nanoparticles were prepared using Bryophyllum pinnatum extract. The synthesized particles were characterized by UV-visible spectroscopy, SEM, EDS, XRD and FTIR. Synthesized particles were subjected to evaluation of their bactericidal and antifungal activity at various doses. Uv vis spectra at 400nm corresponding to AgNPs confirmed their synthesis. Strong peaks in the EDS spectra of Ag and ZnO indicate the purity of the sample. The scanning electron microscopic images of ZnONPs showed a size of about 60nm ± 3nm, which demonstrated the presence of triangular-shaped ZnO nanoparticles. Green synthesized nanoparticles showed bactericidal activity against both Gram-positive (Micrococcus luteus, Staphylococcus aureus, Bacillus subtilis) and Gram-negative (Agrobacterium tumifaciens, Salmonella setubal, Enterobacter aerogenes) strains. AgNPs proved to be more effective against Gram-negative bacterial strains compared to Gram-positive owing to MIC values (10 ppm and 20 ppm respectively). Whereas, ZnONPs were found more effective against Gram-positive bacteria with lower MIC values (10 ppm) as compared to Gram-negative ones (20 ppm). Also, the synthesized nanoparticles exhibited moderate dose-dependent antifungal activity against tested fungal strains ranging from 10 to 70%. Cytotoxicity of nanoparticles was found significant using Brine shrimp's lethality assay with IC50 values of 4.09 ppm for AgNPs, 13.72 ppm for ZnONPs, and 24.83 ppm for plant extract. Conclusively, Ag and ZnO nanoparticles were more effective than plant extract and AgNPs had higher activities than those of ZnONPs. Further research is warranted to explore the precise mechanism of action and the potential applications of these nanoparticles in the medical field.

Thymus algeriensis essential oil: Phytochemical investigation, bactericidal activity, synergistic effect with colistin, molecular docking, and dynamics analysis against Gram-negative bacteria resistant to colistin

Due to the increasing resistance prevalence to the last line of antibiotics, such as colistin, and the rising threat of multi-drug resistant bacteria, it is crucial to find alternative therapeutic options. The current study focuses on evaluating antibacterial activities alone and in combination with colistin of Thymus algeriensis essential oil (TA-EO) against colistin-resistant Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli co-harboring mcr-1 gene. GC/MS was used to determine the chemical composition of TA-EO. Disc diffusion and microdilution techniques were used to evaluate the antimicrobial activities of TA-EO. Synergism between colistin and TA-EO was evaluated by checkerboard assay. The major compounds of TA-EO were docked with known enzymes involved in resistance to colistin, as well as the biosynthesis of peptidoglycan and amino acids. GC/MS revealed that TA-EO was of carvacrol chemotype (67.94 %). The TA-EO showed remarkable antibacterial activities against all Gram-negative bacterial strains, with the diameter of inhibition zones varied between 30 and 50 mm and a ratio MBC/MIC equal to 1 for the vast majority of bacterial isolates. Interestingly, the checkerboard showed synergism between TA-EO and colistin against colistin-resistant Escherichia coli co-harboring mcr-1 gene (FICI˂1) and reduced the MIC of colistin by 16- to 512-fold and those of TA-EO by 4- to 16-fold. The docking study demonstrated that carvacrol had high binding free energies against MCR-1, a phosphoethanolamine transferase extracellular domain, and its catalytic domain implicated in resistance to colistin, and undecaprenyl pyrophosphate synthase in complex with magnesium which is involved in bacterial peptidoglycan biosynthesis. The molecular dynamics study for 100-ns also revealed the stability of the MCR-1/carvacrol complex with a constant surface area over the simulation. These results support using carvacrol or TA-EO as a bactericidal agent, either alone or in combination with colistin, to treat infections caused by colistin-resistant Gram-negative bacteria.

Investigating the Efficacy of Various Natural Products in Raw Form against Multidrug-Resistant Bacteria.

The alarming increase in antibiotic resistance urges alternative and efficacious antimicrobial solutions. Historically, medicinal plants have been used for therapeutic purposes, such as relieving pain and healing wounds. However, the evaluation of the natural therapeutic effects of medicinal plants in a manner that resembles how humans typically consume them is lacking. Therefore, in this study, many medicinal plants known to have some antimicrobial effects, including Frankincense, Garlic, Myrrh, and Ginger, were evaluated for their direct antibacterial activity in raw form. The direct antimicrobial activity of medicinal plants was evaluated against a variety of Gram-positive and Gram-negative bacterial strains, such as Staphylococcus aureus (S. Aureus), Acinetobacter baumannii and Klebsiella pneumoniae using agar well diffusion method and turbidity measurements in suspension culture. Out of all the tested medicinal plants, only raw garlic (Allium sativum) powder, when dissolved in water or vinegar, offered a straightforward antibacterial activity. A combination of garlic extract and vinegar increased antibacterial activity. Aqueous garlic extracts displayed robust antimicrobial activity against many resistant bacteria. Other medicinal plants used in this study had absent or minimal antibacterial effects. Only garlic in its raw form was effective against antibiotic-resistant bacteria. The increase in the antibacterial activity of garlic when combined with vinegar suggests the synergistic activity of garlic. The straightforward antibacterial action of raw garlic may be strategically harnessed to combat the continuous challenge of increasing antibiotic resistance. This work promotes additional testing of more natural products (in raw form) and assesses their therapeutic effects clinically.

Antibacterial and cytocompatible silver coating for titanium Boston Keratoprosthesis.

The Boston Keratoprosthesis (BKPro) serves as a medical solution for restoring vision in complex cases of corneal blindness. Comprising a front plate made of polymethylmethacrylate (PMMA) and a back plate of titanium (Ti), this device utilizes the beneficial biomaterial properties of Ti. While BKPro demonstrates promising retention rates, infection emerges as a significant concern that impacts its long-term efficacy. However, limited research exists on enhancement of BKPros through intrinsic infection-preventing mechanisms. In this regard, metal ions, especially the well-known Ag+ ions, are a promising alternative to obtain implants with innate antibacterial properties. However, little information is available about the effects of Ag in corneal tissue, especially within human corneal keratocytes (HCKs). In this work, an electrodeposition treatment using a constant pulse is proposed to attach Ag complexes onto rough Ti surfaces, thus providing antibacterial properties without inducing cytotoxicity. Complete physicochemical characterization and ion release studies were carried out with both control and Ag-treated samples. The possible cytotoxic effects in the short and long term were evaluated in vitro with HCKs. Moreover, the antibacterial properties of the silver-treated surfaces were tested against the gram-negative bacterial strain Pseudomonas aeruginosa and the gram-positive strain Staphylococcus epidermidis, that are common contributors to infections in BKPros. Physicochemical characterization confirmed the presence of silver, predominantly in oxide form, with low release of Ag+ ions. Ag-treated surfaces demonstrated no cytotoxicity and promoted long-term proliferation of HCKs. Furthermore, the silver-treated surfaces exhibited a potent antibacterial effect, causing a reduction in bacterial adhesion and evident damage to the bacterial cell walls of P. aeruginosa and S. epidermidis. The low release of Ag+ ions suggested reactive oxygen species (ROS)-mediated oxidative stress imbalance as the bactericidal mechanism of the silver deposits. In conclusion, the proposed electrodeposition technique confers antibacterial protection to the Ti backplate of BKPro, mitigating implant-threatening infections while ensuring non-cytotoxicity within the corneal tissue.

Carya Illinoinensis-mediated Green Synthesis and Antimicrobial Screening of Zirconium Oxide Nanoparticles: The Promising Antimicrobial Agent

Background: The synthesis of metal-based nanoparticles through conventional methods involves harsh conditions, high costs, and severe environmental threats. To overcome these issues, researchers are nowadays focusing on eco-friendly and low-cost methods for the synthesis of nanoparticles. Finally, several plant-mediated synthesis techniques have been developed, which have various advantages, such as low-cost, environmentally friendly, and easy application. The plant extract not only serves as a reducing agent but also plays a role as a stabilizing agent. The plantmediated synthesis provides new opportunities for cost-effective, environmentally-friendly nanoparticle synthesis with high dispersity and stability. Besides, bio-generated nanoparticles derived from plant extract have promising pharmacological applications, making them potential candidates for future medicines. Aims and Objectives: The current study aimed to synthesize zirconium oxide nanoparticles using Carya illinoinensis extract and examine their physicochemical properties. Additionally, the antimicrobial efficacy of these nanoparticles was evaluated against various pathogens, exploring their potential as potent antimicrobial agents. Method: The synthesized nanoparticles were analyzed and characterized by various techniques like UV-Vis spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Energy Dispersive X-ray spectroscopy (EDX). The UV-visible peak at 216 nm confirmed the formation of ZrO2 nanoparticles. The SEM images clearly showed that nanoparticles were spherical and relatively dispersed, with few agglomerations. The EDX spectra confirmed the existence of zirconium and oxygen as the basic constituents of the sample. TEM images demonstrated nanoparticles as spherical and uniformly dispersed but agglomerated with increasing precursor concentrations and decreasing nanoparticle dispersion. Fluconazole and gentamicin were used as standards in determining the antibacterial and antifungal activities of nanoparticles. Results: Considering the antifungal activity, a maximum zone of inhibition of 16 μg/ml was demonstrated in the case of 2 mM as compared to 4 mM and 6 mM concentrations. The Carya illinoinensismediated ZrO2 nanoparticles were screened against Gram-positive (S. aureus and P. aeruginosa) and Gram-negative (S. typhi and E. coli) bacterial strains. The fabricated nanoparticles exhibited promising action against all microorganisms. Conclusion: In the current study, zirconium oxide nanoparticles were synthesized by using Carya illinoinensis leaves extract as a reducing agent. The antifungal and antibacterial potential of the synthesized nanoparticles were evaluated. The green synthesis method used in this study is preferable to the others as it is more affordable, environmentally benign, and widely accessible.

Enhanced polyhydroxyalkanoate production from Mesobacillus aurentius: Statistical optimization, characterization and industrial application

Synthetic plastics pose a major environmental threat and it is necessary to produce an alternative biopolymer. In the current study, the production of polyhydroxybutyrate (PHB) by Mesobacillus aurentius was enhanced using Response surface methodology (Box–Behnken design). This study explores the potential of aquabiofloc systems as a source of polyhydroxyalkanoates (PHB)-producing bacteria. The optimized medium conditions, as determined by Response Surface Methodology (RSM), included 18.68 g of sucrose, 4.0 g of yeast, an incubation period of 69.57 h, and a pH of 7.1. The ANOVA results revealed that the model developed for predicting PHA yield was highly significant (p < 0.05). The predicted PHA yield was 63.12%, while the experimental yield was 65.35%. The maximum production of PHA was obtained with sucrose and yeast as carbon and nitrogen sources. The extracted polymer was characterized using UV, FTIR, 1H NMR, and SEM-EDAX analysis confirming the polymer to be PHB. The thermal stability of the produced PHA showed degradation temperatures ranging from 310 °C. The mechanical properties of the extracted PHA were also assessed, demonstrating tensile strength and viscosity of 22.4 MPa and 1.23 MPa. respectively. The antimicrobial activity of the produced PHA was evaluated, demonstrating significant inhibitory effects against both Gram-positive and Gram-negative bacterial strains as well as fungal strains. The Cytotoxicity assessment in HepG2 cells indicated that PHB is less toxic in nature. The findings highlight the promising role of marine bacteria, Mesobacillus aurentius, in the development of environmentally friendly biopolymers. This bacterium represents a novel candidate for PHB production, offering a potential alternative to petroleum-based plastics.

Preclinical evaluation of a novel antibiotic-eluting BioEnvelope for CIED infection prevention

The risk of infection remains a significant concern with cardiovascular implantable electronic devices, necessitating the development of new strategies. This study explores the efficacy of a novel antibiotic-eluting biologic envelope designed to mitigate infection risk through localized antibiotic delivery while preserving the regenerative properties of biological matrix. Antibiotics, rifampin and minocycline, are released through polymer discs, ensuring extended drug release. Utilizing an established model of infection in a New Zealand White rabbit, the study assessed performance against Gram-positive bacterial strains, including common pathogens such as Staphylococcus aureus and S. epidermidis associated with CIED infections, and Gram-negative bacterial strains. Results demonstrated strong antibacterial activity, achieving complete eradication of bacterial colonies and greater than 6-log reductions in colonization for all strains. Pharmacokinetic analysis revealed sustained local antibiotic concentrations at the implantation site for up to 14 days, with minimal systemic exposure, demonstrating the advantages of localized drug delivery. Health outcomes in the antibiotic bioenvelope group were significantly improved, with no signs of infection or abnormal body temperatures, in contrast to the control group. Macroscopic examinations post-necropsy confirmed the absence of infection at the implantation sites of animals receiving the antibiotic bioenvelope. The combination of localized antibiotic delivery in a regenerative matrix positions the antibiotic bioenvelope as a promising solution for preventing CIED-related infections.

Novel copper-drugs bearing dipodal bis-mercaptobenzimidazoles: Synthesis, crystal structures, in vitro biological activities, DNA binding, DFT calculations and molecular docking

Three novel copper(II) complexes, 1–3, bearing dipodal bis-mercaptobenzimidazole derivatives based on ortho-, meta- or para-xylene (L1, L2, and L3) were successfully prepared and characterized by using various spectral techniques, including elemental analysis, FT-IR, 1H NMR, and UV–Vis spectroscopy, LC-MS spectrometry and TGA. The analysis revealed that the ligand/metal molar ratio in all copper(II) complexes is 1:1 and the ligand coordinates as a neutral N-donor onto metal center. Additionally, the crystal structures of L1, L2, L3, and copper(II) complex 2 were determined using single crystal X-ray diffraction (SC-XRD) analysis. Copper(II) complexes 1–3 displayed significant stability at pH range of 4–10. The antibacterial effect of ligands and complexes was tested against both gram-negative (Escherichia coli, E. coli ATCC 25922 PTCC 1399) and gram-positive (Staphylococcus aureus, S. aureus ATCC 6538 PTCC 1112) bacterial strains. It should be noted that the complexes showed enhanced antibacterial activity (up to 99 %) when compared to their free ligands. The in vitro studies of all synthesized compounds consisted of testing them against the human colorectal carcinoma cancer cell line (HCT-116) using the MTT assay. The findings revealed that the copper(II) complexes exhibited lower CC50 values (CC50 ranging from 0.045 mM to 0.135 mM) compared to their corresponding ligands (CC50 ranging from 0.150 mM to 0.240 mM) and carboplatin (CC50 = 0.165 mM), indicating higher anticancer activity of the complexes. Additionally, DAPI staining and fluorescence spectroscopy (at three different temperatures) were performed to further examine the impact of complexes 1–3 on inducing apoptosis and to explore their interaction with DNA, respectively. The results revealed a dynamic quenching mechanism, with hydrophobic forces playing a dominant role in the binding process. The viscosity measurements indicated that all complexes could interact in a groove binding manner with DNA. Density functional theory (DFT) calculations were employed to support the structural and vibrational studies and to predict the chemical reactivity. Docking simulations were conducted to evaluate their behavior of the synthesized compounds towards DNA (PDB: 1BNA). These results suggested that various elements, including NH groups, imidazole rings, thioetheric sulfur atom and sulfate moieties of ligands and complexes, are involved in groove binding with DNA.

Comprehensive phenolic profiling and biological evaluation of Centaurea glastifolia L. (Asteraceae)

The present investigation focused on the comprehensive analysis of the phenolic profile of Centaurea glastifolia L. (Asteraceae) and the assessment of its diverse biological activities. Utilising LC-MS/MS, the phytochemical composition of the 70% methanol extract of Centaurea glastifolia (CG-ME) was thoroughly elucidated, revealing the presence of 30 distinct phytochemical compounds. Notably, major phenolic constituents identified in the extract included quinic acid, chlorogenic acid, luteolin-7-O-glucoside, kaempferol-3-O-glucoside, luteolin, and apigenin-7-O-glucoside. The antioxidant, antibacterial, antiproliferative, and cytotoxic activities of CG-ME were investigated. The CG-ME exhibited a moderate capacity for scavenging DPPH radicals (IC50: 50.05 ± 1.58 µg/mL) and FRAP (63.96 ± 0.39 mg TE/g extract), indicating a moderate level of antioxidant activity. Moreover, CG-ME demonstrated significant antiproliferative effects (GI50: 1.10 and 1.30 µg/mL) on cancer cells (C6 and HTC cancer cell lines, respectively) while displaying low cytotoxicity towards normal cells (LC50: >1000 µg/mL). In terms of antibacterial activity, CG-ME was found to be inactive against tested both Gram-positive and Gram-negative bacterial strains (MIC > 500 µg/mL). The extracts had a promising antiproliferative effect on C6, HeLa, and HT29 cancer cell lines with a less cytotoxic effect (10.5–14.2%) against normal cells.

Curcumin-loaded gold nanoparticles with enhanced antibacterial efficacy and wound healing properties in diabetic rats

Diabetic wounds pose a significant global health challenge. Although curcumin exhibits promising wound healing and antibacterial properties, its clinical potential is limited by low aqueous solubility, and poor tissue penetration. This study aimed to address these challenges and enhance the wound healing efficacy of curcumin by loading it onto gold nanoparticles (AuNPs). The properties of the AuNPs, including particle size, polydispersity index (PDI), zeta potential, percent drug entrapment efficiency (%EE) and UV–Vis spectra were significantly influenced by the curcumin/gold chloride molar ratio used in the synthesis of AuNPs. The optimal formulation (F2) exhibited the smallest particle size (41.77 ± 6.8 nm), reasonable PDI (0.59 ± 0.17), high %EE (94.43 ± 0.25 %), a moderate zeta potential (−8.44 ± 1.69 mV), and a well-defined surface Plasmon resonance peak at 526 nm. Formulation F2 was incorporated into Pluronic® F127 gel to facilitate its application to the skin. Both curcumin AuNPs solution and gel showed sustained drug release and higher skin permeation parameters compared with the free drug solution. AuNPs significantly enhanced curcumin’s antibacterial efficacy by lowering the minimum inhibitory concentrations and enhancing antibacterial biofilm activity against various Gram-positive and Gram-negative bacterial strains. In a diabetic wound rat model, AuNPs-loaded curcumin exhibited superior wound healing attributes compared to the free drug. Specifically, it demonstrated improved wound healing percentage, reduced wound oxidative stress, increased wound collagen deposition, heightened anti-inflammatory effects, and enhanced angiogenesis. These findings underscore the potential of AuNPs as efficacious delivery systems of curcumin for improved wound healing applications.

Antibacterial activity of Au(I), Pt(II), and Ir(III) biotin conjugates prepared by the iClick reaction: influence of the metal coordination sphere on the biological activity.

A series of biotin-functionalized transition metal complexes was prepared by iClick reaction from the corresponding azido complexes with a novel alkyne-functionalized biotin derivative ([Au(triazolatoR,R')(PPh3)], [Pt(dpb)(triazolatoR,R')], [Pt(triazolatoR,R')(terpy)]PF6, and [Ir(ppy)(triazolatoR,R')(terpy)]PF6 with dpb = 1,3-di(2-pyridyl)benzene, ppy = 2-phenylpyridine, and terpy = 2,2':6',2''-terpyridine and R = C6H5, R' = biotin). The complexes were compared to reference compounds lacking the biotin moiety. The binding affinity toward avidin and streptavidin was evaluated with the HABA assay as well as isothermal titration calorimetry (ITC). All compounds exhibit the same binding stoichiometry of complex-to-avidin of 4:1, but the ITC results show that the octahedral Ir(III) compound exhibits a higher binding affinity than the square-planar Pt(II) complex. The antibacterial activity of the compounds was evaluated on a series of Gram-negative and Gram-positive bacterial strains. In particular, the neutral Au(I) and Pt(II) complexes showed significant antibacterial activity against Staphylococcus aureus and Enterococcus faecium at very low micromolar concentrations. The cytotoxicity against a range of eukaryotic cell lines was studied and revealed that the octahedral Ir(III) complex was non-toxic, while the square-planar Pt(II) and linear Au(I) complexes displayed non-selective micromolar activity.

Epiphytic Yeasts from South Romania for Preventing Food Microbial Contamination.

Epiphytic yeasts represent an important source for the development of novel strategies aiming to combat food microbial contamination. The present study deals with the characterization of nine yeast strains belonging to Starmerella, Candida, Metschinikowia, Lachancea, Kodamaea and Pichia genera, isolated from the surface of plants from the Botanical Garden "Dimitrie Brandza" (Bucharest, Romania) for use as antimicrobial and probiotic agents. The tests involved the determination of the safe status, cell growth under stress conditions, and activity against pathogenic Candida and bacteria strains, respectively, as well as phytopathogenic filamentous fungi and lipolytic activity. None of the nine strains showed all the characteristics for virulence and pathogenicity, with the rare positive results being explained rather by their adaptability to the habitats of origin. The strains Lachancea thermotolerans CMGB-ST12 and Kodamaea ohmeri CMGB-ST19 grew at 37 °C; Metschnikowia reukaufii CMGB-ST21.2, M. reukaufii CMGB-ST.8.1 and M. reukaufii CMGB ST10 grew in the presence of 10% NaCl, while L. thermotolerans CMGB-ST12 and K. ohmeri CMGB-ST19 tolerated both acidic and alkaline pH values well (3.0 to 12.0). The studied yeast strains showed good antimicrobial activity against Candida krusei, Candida albicans and Gram-negative bacterial strains, with K. ohmeri CMGB-ST19 and Pichia membranaefaciens CMGB-ST53 inhibiting up to 100% the development of filamentous fungi. All the strains produced lipases for tributyrin hydrolysis, the best producer being Starmerella bombi CMGB-ST1, and only Candida magnoliae CMGB-ST8.2 tested positive against other probiotic yeasts. Overall, our nine yeast strains show high potential for industrial applications, for obtaining probiotic products and for preventing the development of a wide range of microbial food contaminants.

IN VITRO ANTIMICROBIAL ACTIVITIES OF VARIOUS SOLVENT EXTRACTS DERIVED FROM VIOLA ODORATA

The primary objective of this study was to assess the antimicrobial activities of various polar and nonpolar solvent extracts derived from the leaves of Viola odorata. The disc diffusion method was employed to test the antimicrobial susceptibility against a diverse range of pathogenic microorganisms, including Escherichia coli, Erwinia carotovora, Klebsiella pneumoniae, Bacillus subtilis, Pseudomonas aeruginosa, Salmonella typhi, Staphylococcus aureus and the fungus Candida albicans. The results indicated that isobutanol and ethyl acetate fractions exhibited significantly higher antimicrobial activity compared to petroleum ether, crude, chloroform and aqueous fractions. Among the tested bacteria, E. carotovora was the most susceptible bacterium to all the extracts of V. odorata, whereas S. typhi demonstrated the highest resistance. The isobutanol extract inhibited the proliferation of E. carotovora by 62 % at a concentration of 2 mg disc-1, while the ethyl acetate extract achieved 53% inhibition under the same conditions. Additionally, our findings revealed that the overall antimicrobial activity of V. odorata leaves was consistently effective against both Gram-positive and Gram-negative bacterial strains.

Nitrogen Vacancy Modulation of Tungsten Nitride Peroxidase-Mimetic Activity for Bacterial Infection Therapy.

Bacterial infections claim millions of lives every year, with the escalating menace of microbial antibiotic resistance compounding this global crisis. Nanozymes, poised as prospective substitutes for antibiotics, present a significant frontier in antibacterial therapy, yet their precise enzymatic origins remain elusive. With the continuous development of nanozymes, the applications of elemental N-modulated nanozymes have spanned multiple fields, including sensing and detection, infection therapy, cancer treatment, and pollutant degradation. The introduction of nitrogen into nanozymes not only broadens their application range but also holds significant importance for the design of catalysts in biomedical research. The synergistic interplay between W and N induces pivotal alterations in electronic configurations, endowing tungsten nitride (WN) with a peroxidase-like functionality. Furthermore, the introduction of N vacancies augments the nanozyme activity, thus amplifying the catalytic potential of WN nanostructures. Rigorous theoretical modeling and empirical validation corroborate the genesis of the enzyme activity. The meticulously engineered WN nanoflower architecture exhibits an exceptional ability in traversing bacterial surfaces, exerting potent bactericidal effects through direct physical interactions. Additionally, the topological intricacies of these nanostructures facilitate precise targeting of generated radicals on bacterial surfaces, culminating in exceptional bactericidal efficacy against both Gram-negative and Gram-positive bacterial strains along with notable inhibition of bacterial biofilm formation. Importantly, assessments using a skin infection model underscore the proficiency of WN nanoflowers in effectively clearing bacterial infections and fostering wound healing. This pioneering research illuminates the realm of pseudoenzyme activity and bacterial capture-killing strategies, promising a fertile ground for the development of innovative, high-performance artificial peroxidases.