Agar Disc Diffusion Assay Research Articles

Sodium Alginate Microneedles Loaded with Vancomycin for Skin Infections

Background: Skin and soft tissue infections (SSTIs) present significant treatment challenges. These infections often require systemic antibiotics such as vancomycin, which poses a risk for increased bacterial resistance. Topical treatments are hindered by the barrier function of the skin, and microneedles (MNs) offer a promising solution, increasing patient compliance and negating the need for traditional needles. Methods: This study focused on the use of sodium alginate MNs for vancomycin delivery directly to the site of infection via a cost-effective micromolding technique. Dissolving polymeric MNs made of sodium alginate and loaded with vancomycin were fabricated and evaluated in terms of their physical properties, delivery ability, and antimicrobial activity. Results: The MNs achieved a 378 μm depth of insertion into ex vivo skin and a 5.0 ± 0 mm zone of inhibition in agar disc diffusion assays. Furthermore, in ex vivo Franz cell experiments, the MNs delivered 34.46 ± 11.31 μg of vancomycin with around 35% efficiency, with 9.88 ± 0.57 μg deposited in the skin after 24 h. Conclusions: These findings suggest that sodium alginate MNs are a viable platform for antimicrobial agent delivery in SSTIs. Future in vivo studies are essential to confirm the safety and effectiveness of this innovative method for clinical use.

Printing amphotericin B on microneedles using matrix-assisted pulsed laser evaporation.

Transdermal delivery of amphotericin B, a pharmacological agent with activity against fungi and parasitic protozoa, is a challenge since amphotericin B exhibits poor solubility in aqueous solutions at physiologic pH values. In this study, we have used a laser-based printing approach known as matrix-assisted pulsed laser evaporation to print amphotericin B on the surfaces of polyglycolic acid microneedles that were prepared using a combination of injection molding and drawing lithography. In a modified agar disk diffusion assay, the amphotericin B-loaded microneedles showed concentration-dependent activity against the yeast Candida albicans. The results of this study suggest that matrix-assisted pulsed laser evaporation may be used to print amphotericin B and other drugs that have complex solubility issues on the surfaces of microneedles.

Biological Activities, DFT Calculations, and Molecular Docking Simulation of Thymol‐Based Compounds

AbstractA set of thymol‐based derivatives (3 a–d) was synthesized and characterized. Quantum chemical calculations were performed to explain the nature of the transitions in the absorption spectra. These new compounds were tested as anticancer agents on human liver (HepG2), lung (A549), and colon (DLD‐1) cancer cell lines using the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide method showing in some cases higher antiproliferative properties than the reference drug cisplatin. All synthesized compounds were also screened for their antimicrobial activity against a representative panel of Gram‐positive and Gram‐negative bacteria plus a pathogenic yeast species (Candida albicans ATCC90028) using agar disc diffusion and broth microdilution assays. Furthermore, we determined the antioxidant activity of these compounds by the DPPH free radical scavenging test. According to the minimum bactericidal concentration, minimum fungicidal concentration, and IC50 values, compound 3 c showed the highest antimicrobial activity, compound 3 d exhibited the highest antioxidant activity, while compounds 3 b and 3 c displayed higher cytotoxic activity than cisplatin against HepG2 and DLD‐1 cell lines albeit no selectivity towards healthy cells (HEK‐293T). Furthermore, docking simulations of the compounds towards two potential molecular targets, namely caspase‐3 protein (PDB ID: 3KJF) and Escherichia coli glucosamine‐6‐phosphate synthase (PDB ID: 2VF5), were performed in order to validate the anticancer and antimicrobial activities, respectively.

Reconciling the monodispersity of bioinspired ZnO nanoparticles on palygorskite nanorods for a well-balanced antibacterial effect and biocompatibility

In order to study the effect of support on the antibacterial activity of ZnO nanoparticles formed in the bioinspired process, a series of palygorskite (Pal) supported ZnO nanocomposites (ZnO/Pal) were fabricated using licorice extract and the antibacterial actions related to the structure of loaded ZnO nanocomposites was elucidated. The samples were characterized by the means of UV–vis, XRD, TEM, FTIR, TG and XPS, and the antibacterial properties were determined by the agar disk diffusion assay and colony counting assay. The structural analysis revealed that pure ZnO nanoparticles with average grain diameter of about 11 nm were formed in the green bioinspired process and anchored on the surface of Pal nanorods. And with Pal amount decreasing (ZnO loading increased from 10 % to 40 %), the ZnO NPs aggregated intensify and promoted the assembling of ZnO/Pal nanorods into bigger clusters, and four kinds of ZnO/Pal with different morphologies were formed. Among them, 20 % loading of ZnO/Pal showed antibacterial activity comparable to that of 30 % and better than that of 40 %, because ZnO nanoparticles in 20 % ZnO/Pal are monodispersed on Pal nanorods that maintained full exposure and high activity of ZnO NPs as well as better killing efficiency than those with clustered ZnO NPs. The mechanism analysis demonstrated that the bacteria-adsorbed capacity of Pal and the enhanced contact of small ZnO NPs with bacterial cells leading to intensified membrane-damage and intracellular metabolic imbalance are the main bactericidal actions of ZnO/Pal nanocomposites. This study first gave insight into the structure-related antibacterial behavior of ZnO/Pal nanocomposites, and provides an improved green way to design efficient clay-supported ZnO antibacterial nanomaterials.

Efficacy and Synergistic Potential of Cinnamon (Cinnamomum zeylanicum) and Clove (Syzygium aromaticum L. Merr. & Perry) Essential Oils to Control Food-Borne Pathogens in Fresh-Cut Fruits.

The presence of microbial pathogens in ready-to-eat produce represents a serious health problem. The antibacterial activity of cinnamon (Cinnamomum zeylanicum) and clove (Syzygium aromaticum L. Merr. & Perry) essential oils (EOs) was determined toward food-borne pathogens by agar disk diffusion and minimum inhibitory concentration (MIC) assays. The growth kinetics of all strains, both in a buffer suspension assay and "on food" in artificially contaminated samples, were also investigated. The two EOs demonstrated a good antibacterial effect both alone and in combination (EO/EO). The use of EO/EO led to a synergistic antibacterial effect, also confirmed by the growth kinetics studies, where the EOs were active after 10 h of incubation (p < 0.0001) at significantly lower concentrations than those when alone. In the "on food" studies performed on artificially contaminated fruit samples stored at 4 °C for 8 days, the greatest killing activity was observed at the end of the trial (8 days) with a reduction of up to 7 log CFU/g compared to the control. These results confirm the good antibacterial activity of the EOs, which were more effective when used in combination. Data from the "on food" studies suggest cinnamon and clove essential oils, traditionally used in the food industry, as a possible natural alternative to chemical additives.

Antibacterial and Antioxidant Efficacies of Secondary Metabolites from the Roots of Cyphostemma adenocaule: A Combined In Vitro and In Silico Study.

Cyphostemma adenocaule is a therapeutic plant traditionally used to treat rabies, snake bite, diarrhea, and wound healing. To address the bioactive compounds exhibiting these activities, we performed a comprehensive study on the roots of the plant. Thus, the present study aims to inspect the in vitro antioxidant and antibacterial efficacies of compounds isolated from the combined dichloromethane : methanol (1 : 1) and methanol extracts of C. adenocaule along with the in silico study of their interaction with selected protein targets. The silica gel column chromatography technique was used for the isolation of compounds, and the antibacterial and antioxidant activities were evaluated using agar disc diffusion and DPPH radical scavenging assays, respectively. Furthermore, in silico molecular docking screening, pharmacokinetics, and toxicity protocols of the compound isolates were performed to offer the potential applications of the compounds in developing novel medications. A BIOVIA Discovery Studio in combination with AutoDock Vina 4.2 software, SwissADME, and ProTox-II prediction web tools were used to generate the molecular docking, pharmacokinetics, and toxicity profiles, respectively. Notably, the chromatographic separation of the combined extracts yielded six known compounds, namely, β-sitosterol (1), 3-hydroxyisoagatholactone (2), ε-viniferin (3), myricetin (4), tricuspidatol A (5), and parthenocissin A (6). The in vitro antibacterial activities revealed the highest inhibition zone by tricuspidatol A (5) (16.67 ± 0.47), showcasing its potent activity against S. aureus at 2 mg/mL, compared to ciprofloxacin (21.50 ± 0.41). ε-Viniferin (3) (IC50: 0.32 μg/mL) exhibited greater antioxidant activity than the others and displayed promising results compared to ascorbic acid (0.075 μg/mL). The molecular docking study revealed the highest binding affinity by ε-viniferin (3) (-9.9 kcal/mol) against topoisomerase II α. 3-Hydroxyisoagatholactone (2) and ε-viniferin (3) fulfilled Lipinski's rule with no violation, and the organ toxicity predictions revealed that all the compounds showed no cytotoxicity and hepatotoxicity effects. Thus, this study's combined in vitro and in silico outcomes suggest the potential use of the isolated compounds in drug discovery and support the traditional relevance of C. adenocaule.

EFFECT OF DIFFERENT SOLVENT EXTRACTS ON THE YIELD AND IN VITRO ANTIBACTERIAL ACTIVITY, WITH GC-MS ANALYSIS OF ACTIVE EXTRACTS FROM VERNONIA AMYGDALINA LEAVES

Vernonia amygdalina, commonly known as ‘Bitter leaf’, is a small perennial shrub with various medicinal properties including the treatment of stomach disorders, fever symptoms, diabetes, hypertension, and coughs. V. amygdalina is a potent source of antibacterial properties that may be beneficial in preventing bacterial infections and associated diseases such as fever and diarrhea. V. amygdalina also has been extensively studied for its antioxidant, anti-inflammatory, antifungal, anticancer and antidiabetic properties. The present study aims to determine the most efficient solvent for extracting antibacterial-rich V. amygdalina extracts. Dried leaves of V. amygdalina were extracted using several solvents (methanol, ethanol, and dichloromethane) to assess the extraction yield. The antibacterial potential of all extracts against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa was evaluated using the agar disc diffusion assay. The profiling of the active extract was accomplished using gas chromatography coupled with mass spectrometry (GC-MS). Among the solvents tested, ethanol exhibited the highest extraction productivity, with a percentage yield of 49.20%. The dichloromethane extract displayed the highest inhibition zones against all bacteria strains ranging from 16.67 ± 1.20 mm to 21.33 ± 0.5 mm at 200 mg/mL. The GC-MS analysis of dichloromethane extract identified compounds such as phytol, flavonoids, vitamin E, and squalene. The findings of this study revealed that the choice of the extraction solvent is greatly affecting the antibacterial efficacy of V. amygdalina. In conclusion, the efficacy of V. amygdalina against pathogenic bacteria strains could be explored for further pharmaceutical application and should be encouraged in the development and production of new antibiotics.

In Vitro Antibacterial and Antioxidant Activities, Pharmacokinetics, and In Silico Molecular Docking Study of Phytochemicals from the Roots of Ziziphus spina-christi.

Ziziphus spina-christi (Rhamnaceae family) is a medicinal plant traditionally used to treat dandruff, wounds, hair loss, diarrhea, mastitis, abdominal pain, and gastrointestinal complications. To support this, the present work aims to study the in vitro antibacterial and antioxidant activities of compound isolates from the roots of Ziziphus spina-christi along with their in silico computational analyses. Compounds were isolated on silica gel column chromatography and an agar disc diffusion and DPPH radical scavenging assays were employed to study the antibacterial and antioxidant activities, respectively. The ADME and toxicity properties of the compounds were evaluated using SwissADME and ProTox-II online Web tools, respectively. Conversely, the in silico molecular docking studies were attained via a Biovia Discovery Studio Visualizer 2021 in combination with the AutoDock Vina software. The silica gel chromatographic separation of the combined CH2Cl2 : CH3OH (1 : 1) and CH3OH root extracts afforded trimethyl trilinolein (1), stearic acid (2), 13-hydroxyoctadeca-9, 11-dienoic acid (3), β-sitosteryl-3β-glucopyranoside-6'-O-palmitate (4), and stigmasterol (5). Notably, the in vitro antibacterial study revealed the extract and β-sitosteryl-3β-glucopyranoside-6'-O-palmitate (4) with the highest inhibitory activities (15.25 ± 0.35 and 14.25 ± 0.35 mm, respectively) against E. coli compared to ciprofloxacin (21.00 ± 0.35 mm) at 2 mg/mL. The CH2Cl2 : CH3OH (1 : 1) extract (IC50 : 1.51 µg/mL) and β-sitosteryl-3β-glucopyranoside-6'-O-palmitate (4) (IC50 : 5.41 µg/mL) also exhibited auspicious DPPH scavenging activities, followed by stigmasterol (5) (IC50 : 6.88 µg/mL) compared to the ascorbic acid standard (IC50 : 0.46 µg/mL). The molecular docking analyses unveiled the highest binding affinity by β-sitosteryl-3β-glucopyranoside-6'-O-palmitate (4) (-8.0 kcal/mol) against P. aeruginosa PqsA relative to the ciprofloxacin standard (-8.2 kcal/mol). Furthermore, the organ toxicity predictions showed that all the compounds exhibit no hepatotoxicity and cytotoxicity effects and stigmasterol (5) affords drug-likeness protocols. Overall, the combined experimental and computational investigations of this study support the traditional uses of Ziziphus spina-christi for antibacterial and natural antioxidant applications.

Limonene synergistically augments fluconazole susceptibility in clinical Candida isolates from cleft lip and palate patients.

Cleft lip and palate (CLP) patients are prone to Candida infections (oral thrush) mainly due to poor oral hygiene, repetitive surgeries, and orthodontic procedures. This study was undertaken to evaluate the antifungal efficacy of limonene against clinical Candida isolates from CLP patients. The antifungal efficacy of limonene was studied alone and in combination with fluconazole (FLC) against six standards, twenty nine FLC sensitive, and three FLC resistant clinical strains using broth dilution, checkerboard microdilution, agar disk diffusion, growth curves, and spot assays. This nontoxic monoterpene gave low minimum inhibitory concentration (MIC) values of 300-375 µg/mL and 500-520 µg/mL for FLC susceptible and FLC resistant strains, respectively. It showed synergistic interaction with FLC in all clinical and standard Candida strains (fractional inhibitory concentration (FIC) index ≤0.5). Significant chemosensitization of FLC was observed even against resistant clinical isolates. Complete suppression of fungal growth was observed when using combinations. Negligible toxicity, easy availability, and potent antifungal properties suggest that limonene and FLC combinations in appropriate doses can make excellent antifungal mouthwashes during CLP treatment pre and post surgery. Impending in vivo studies are needed to validate the present data.

Antibiotic Susceptibility of Lactic Acid Bacteria Isolated From Cow, Goat, Donkey, Buffalo, Sheep, Camel and Human Milk

Breast milk is a very important factor in regulating gastrointestinal function, improving the immune system and preventing acute illnesses (e.g. acute otitis media), especially during breastfeeding. Breast milk allows beneficial bacteria such as bifidobacteria and lactobacillus species to colonise the newborn intestin*e instead of potential enteropathogenic bacteria such as streptococci and escherichia coli. The aim of the study was to compare the antibiotic resistance of Lactic acid bacteria members isolated from different milk samples. Six milk samples were collected from each of seven different milk sources (donkey, goat, cow, buffalo, sheep, camel and human). The MRS and M-17 medium were used with the double layer sandwich method for isolation of LAB members selected from typic colonies, gram-positive, catalase-negative used in the study. The isolated 42 LAB species were determined antibiotic susceptibility with 9 standart antibiotic discs such as tetracycline, penicillin, kanamycin, streptomycin, rifampin, gentamicin, chloramphenicol, teicoplanin, ciprofloxacin by agar disc diffusion assay test. The 18 LAB isolate were resistant to penicillin, 16 isolate to kanamycin, 14 isolate to gentamicin. LAB isolates such as H1, H4, H5 from Human milk and LAB isolate such as D1 from donkey milk was considered as MDR isolates because they were resistant to at least four of the tested drugs. Among the milks, sheep, camel, buffalo and goat milks were found to be more sensitive to antibiotics on average in the group.

Exploring the Bioactive Potential of Calostoma insigne, an Endangered Culinary Puffball Mushroom, from Northeastern Thailand.

Calostoma insigne puffball mushrooms are only found in forests with rich biodiversity in very few countries including Thailand, and their biofunctions remain largely unexplored. This study used the agar disk diffusion assay, the anti-glucosidase assay, and the 3, 4, 5-dimethylthiazol-2-yl-2-5-diphenyltetrazolium bromide (MTT) assay to evaluate the bioactive potential of these endangered puffball mushrooms. Internal transcribed spacer (ITS) gene analysis identified C. insigne, a puffball mushroom with green, globose, and spiny spores. Fourier-transform infrared spectroscopy (FTIR) analysis confirmed the polysaccharide structure while scanning electron microscopy (SEM) revealed a fiber-like network. The ethanolic gelatinous fruiting body extract exhibited 1,1-diphenyl-2-picrylhydrazyl (DPPH)-scavenging capacity (57.96%), a ferric ion-reducing antioxidant power (FRAP) value of 1.73 mg FeSO4/g, and α-glucosidase inhibition (73.18%). C. insigne cytotoxicity was effective towards HT-29 colon cancer cells using the MTT assay (IC50 of 770.6 µg/mL at 72 h) and also showed antiproliferative capacity (IC50 of 297.1 µg/mL). This puffball mushroom stimulated apoptotic genes and proteins (caspase-3, Bax, and p21) via an intrinsic apoptotic pathway in HT-29 cells. In the laboratory, the medium formula consisting of 20% potato, 2% sucrose, and 0.2% peptone was optimal to increase fungal mycelial biomass (2.74 g DW/100 mL), with propagation at pH 5.0 and 30 °C. Puffball mushrooms are consumed as local foods and also confer several potential health benefits, making them worthy of conservation for sustainable utilization.

Biological evaluations and computational studies of newly synthesized thymol-based Schiff bases as anticancer, antimicrobial and antioxidant agents

Three new thymol-based molecules were synthesized and evaluated as anticancer, antimicrobial and antioxidant agents. Liver, colon, lung and prostate cancer cell lines were utilized in cytotoxicity tests. The results demonstrated that synthesized molecules had a cytotoxic effect against the screened cell lines. One of the molecules (4a) was found to have a higher efficacy towards the colon cancer cell line (DLD-1) with an IC50 value of 12.39 µM and the other (4c) towards the prostate cancer cell line (PC3) with an IC50 value of 7.67 µM than the positive control drug cisplatin. To assess the antimicrobial activity of molecules (4a–c), Gram-positive bacteria, Gram-negative bacteria and yeast were subjected to agar disc diffusion and broth microdilution assays. The investigation of antioxidant potential was conducted using the DPPH radical scavenging activity assay. While all compounds displayed strong cytotoxic and antioxidant properties, they exhibited only moderate antimicrobial activity. Molecular docking studies were performed on epidermal growth factor receptor (EGFR), vascular endothelial growth factor receptor 2 (VEGFR-2), focal adhesion kinase (FAK), B-Raf and phosphoinositide 3-kinase (PI3K). The binding energies and interactions obtained from the docking results of compounds (4a–c) supported the experimental results. Drug similarity rates and pharmacokinetic properties were analyzed with the absorption, distribution, metabolism and excretion (ADME) method. Geometric parameters such as chemical potential (µ), electrophilicity index (ω) and chemical softness (σ) of compounds (4a–c) were calculated using the 6-31*G basis set B3LYP method. Communicated by Ramaswamy H. Sarma

Novel lactoferrin-conjugated gallium complex to treat Pseudomonas aeruginosa wound infection

Pseudomonas aeruginosa is one of the leading causes of opportunistic infections such as chronic wound infection that could lead to multiple organ failure and death. Gallium (Ga3+) ions are known to inhibit P. aeruginosa growth and biofilm formation but require carrier for localized controlled delivery. Lactoferrin (LTf), a two-lobed protein, can deliver Ga3+ at sites of infection. This study aimed to develop a Ga-LTf complex for the treatment of wound infection. The characterisation of the Ga-LTf complex was conducted using differential scanning calorimetry (DSC), Infra-Red (FTIR) and Inductive Coupled Plasma Optical Emission Spectrometry (ICP-OES). The antibacterial activity was assessed by agar disc diffusion, liquid broth and biofilm inhibition assays using the colony forming units (CFUs). The healing capacity and biocompatibility were evaluated using a P.aeruginosa infected wound in a rat model. DSC analyses showed thermal transition consistent with apo-lactoferrin; FTIR confirmed the complexation of gallium to lactoferrin. ICP-OES confirmed the controlled local delivery of Ga3+. Ga-LTf showed a 0.57 log10 CFUs reduction at 24 h compared with untreated control in planktonic liquid broth assay. Ga-LTf showed the highest antibiofilm activity with a 2.24 log10 CFUs reduction at 24 h. Furthermore, Ga-LTf complex is biocompatible without any adverse effect on brain, kidney, liver and spleen of rats tested in this study. Ga-LTf can be potentially promising novel therapeutic agent to treat pathogenic bacterial infections.

Synthesis, antimicrobial, DFT, and in silico pharmacokinetic profiling of nitroaldol quinoline derivatives: A comprehensive exploration for designing potential oral antibacterial agents targeting DNA-gyrase

This study presents a thorough exploration of the synthesis, biological activities, and molecular properties of a novel series of β-nitroaldol quinoline derivatives (4a-4i). Structural characterization utilized FTIR, 1H NMR, 13C NMR, and mass spectrometry, providing a comprehensive understanding of the synthesized derivatives. Moreover, anti-microbial properties were evaluated using agar disk diffusion assay against five pathogenic strains, including Gram-negative and Gram-positive bacteria, as well as a fungal strain. Notably, compound 4e demonstrated strong anti-fungal and anti-bacterial activities (MIC = 25 µg/ml). A detailed analysis of molecular orbitals, total density of state, vibrational characteristics, global reactivity descriptors, molecular electrostatic potential, topological QTAIM analysis, and molecular docking provided nuanced insights into the reactivity, electronic properties, and potential interactions of the synthesized compounds. These findings contribute valuable information to the design and synthesis of compounds targeting bacterial DNA-gyrase. Furthermore, in silico predictions using the SwissADME online server indicated that all compounds comply with Lipinski's rule of five, suggesting their potential as orally active drugs. The compounds demonstrated commendable water solubility, passed various filters, and exhibited bioavailability scores, indicating promising oral bioavailability. The percentage of oral absorption ranged from 75.39% to 78.58%, signifying high permeability. Computational analysis of pharmacokinetic parameters revealed favorable characteristics, including gastrointestinal absorption and minimal inhibitory effects on specific enzymes.

Superior Performance of Iron-Coated Silver Nanoparticles and Cefoxitin as an Antibiotic Composite Against Methicillin-Resistant Staphylococcus aureus (MRSA): A Population Study.

The synergistic effects of antimicrobial nanostructures with antibiotics present a promising solution for overcoming resistance in methicillin-resistant Staphylococcus aureus (MRSA). Previous studies have introduced iron as a novel coating for silver nanoparticles (AgNPs) to enhance both economic efficiency and potency against S. aureus. However, there are currently no available data on the potential of these novel nanostructures to reverse MRSA resistance. To address this gap, a population study was conducted within the MRSA community, collecting a total of 48 S. aureus isolates from skin lesions. Among these, 21 isolates (43.75%) exhibited cefoxitin resistance as determined by agar disk diffusion assay. Subsequently, a PCR test confirmed the presence of the mecA gene in 20 isolates, verifying them as MRSA. These results highlight the cefoxitin disk diffusion susceptibility test as an accurate screening method for predicting mecA-mediated resistance in MRSA. Synergy tests were performed on cefoxitin, serving as a marker antibiotic, and iron-coated AgNPs (Fe@AgNPs) in a combination study using the checkerboard assay. The average minimal inhibitory concentration (MIC) and fractional inhibitory concentration (FIC) of cefoxitin were calculated as 11.55mg/mL and 3.61mg/mL, respectively. The findings indicated a synergistic effect (FIC index < 0.5) between Fe@AgNPs and cefoxitin against 90% of MRSA infections, while an additive effect (0.5 ≤ FIC index ≤ 1) could be expected in 10% of infections. These results suggest that Fe@AgNPs could serve as an economically viable candidate for co-administration with antibiotics to reverse resistance in MRSA infections within skin lesions. Such findings may pave the way for the development of future treatment strategies against MRSA infections.

Carbon Dots from Tire Waste for the Photodegradation of Methyl Orange Dye, Antimicrobial Activity, and Molecular Docking Study.

In this study, solvothermal pathway was employed for the synthesis of P, N codoped C-dot using tire waste as a sustainable source of carbon and nitrogen. Comprehensive analyses encompassing X-ray diffraction (XRD) analysis, Transmission Electron Microscopy (TEM), FT-IR, cyclic voltammetry, and UV-Vis spectra were used to assess the crystalline structure, purity, size, fluorescence up-conversion, and morphological attributes of the nanomaterial. Subsequently, the produced C-dots were evaluated for their efficacy in the photocatalytic degradation of methylene blue and methyl orange dyes, demonstrating notable success in degrading methyl orange dye within eight hours in the visible region. Furthermore, the same nanomaterial was applied for carrying out agar disk-diffusion assays against a spectrum of microorganisms. Results revealed substantial inhibition zones against Methicillin-Resistant Staphylococcus aureus (MRSA), Escherichia coli, and Pseudomonas aeruginosa. Elucidating the antimicrobial mechanism, molecular-docking simulations were excuted using on AutoDock Vina with designated ligands. The results indicated a strong binding affinity of the C-dots with certain proteins associated with antibacterial activity. This observation suggests that the synthesized C-dots effectively engage with the active sites of these proteins, indicating their potential as promising antibacterial agents. Importantly, this study implies that C-dots do not induce protein denaturation, thereby warranting further investigation of their utility as antibacterial agents.

The antimicrobial effect and mechanism of the Artemisia argyi essential oil against bacteria and fungus.

Artemisia argyi is a traditional Chinese herb with antibacterial, antifungal, and antitumor activities. The essential oil of Artemisia argyi was extracted using the steam distillation method in this study. The chemical composition of the essential oil was analyzed using the gas chromatography-mass spectrometry method. Agar disc diffusion and double-broth dilution assays were used to detect the antimicrobial activity of the essential oil. Subsequently, the antimicrobial mechanisms were explored through cytomembrane permeability assay and electron microscopy. Based on gas chromatography-mass spectrometry analysis, 25 compounds were detected, including 13.76% cineole, 6.77% terpinen-4-ol, 6.68% 3-dione, 1,7,7-trimethyl-, 4.07% 3-cyclohexen-1-ol, 4-methyl-1-(1-methylethyl)-acetate, 3.58% 1-isopropyl-2-methylbenzene, and 1.58% g-terpinene. The essential oil was tested for antimicrobial activity, and the IC50 values for Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Listeria monocytogenes, Pseudomonas aeruginosa, Streptococcus pneumoniae, and Candida albicans were determined to be 25.51 ± 2.29, 49.53 ± 0.86, 52.40 ± 1.49, 52.76 ± 1.60, 73.99 ± 1.38, 65.52 ± 0.95, and 214.98 ± 3.27μgmL-1, respectively. For essential oil interaction with cytoderm, the microorganisms treated by 1 × IC50 and 2 × IC50 concentration of essential oil both represented positive test results. Additionally, the alkaline phosphatase levels showed a direct correlation with concentration and treatment duration (range from 0 to 8h). The interaction between essential oils and the cytomembrane was investigated by examining samples containing one of three test strains (Staphylococcus aureus, Escherichia coli, and Candida albicans), essential oil, and voltage-sensitive fluorescent dye disc35. The results demonstrated a significant increase in fluorescence levels within the solution upon introduction of the essential oil-treated strains. The findings of our research suggest that the essential oil disrupts the cytoderm and cytomembrane, thereby exhibiting antimicrobial activity.

Ocular antibacterial chitosan-maleic acid hydrogels: In vitro and in vivo studies for a promising approach with enhanced mucoadhesion

The aim was to design and evaluate a chitosan-based conjugate providing high mucoadhesiveness and antibacterial activity for ocular infections treatment. Chitosan was conjugated with maleic acid via amide bond formation and infrared spectroscopy. Furthermore, 2,4,6-Trinitrobenzene sulfonic acid (TNBS) allowed characterization and quantification of conjugated groups, respectively. Biocompatibility was tested via hemolysis assay and Hen's Egg-Chorioallantoic membrane test. Characterization of the pH and osmolarity of hydrogels was followed by mucoadhesion assessment utilizing rheology. In addition, antibacterial studies were carried out towards Escherichia coli by broth microdilution test and agar-disk diffusion assay. In vivo studies were carried out following the already established Draize test and determining pharmacokinetic profile of dexamethasone in aqueous humour. The conjugate exhibited a degree of modification of 50.05 % and no toxicity or irritability. Moreover, mucoadhesive properties were enhanced in 2.68-fold and 1.81-fold for elastic and viscous modulus, respectively. Furthermore, rheological synergism revealed the presence of a gel-like structure. Additionally, broth microdilution and agar disk diffusion studies exhibited enhancement in antibacterial activity. Finally, in vivo studies manifested that hydrogels were highly tolerated, evidencing promising characteristics of the developed conjugate. The conjugate presented promising antimicrobial, long lasting mucoadhesive features and highly improved pharmacokinetics, leading to a revolutionizing approach in the treatment of ocular bacterial infections.

Biological properties of experimental dental alginate modified for self-disinfection using green nanotechnology

ObjectivesDisinfection of alginate impression materials is a mandatory step to prevent cross-infection in dental clinics. However, alginate disinfection methods are time-consuming and exert a negative impact on accuracy and mechanical properties. Thus, this study aimed to prepare disinfecting agents (CHX and AgNO3) and silver nanoparticles reduced by a natural plant extract to produce a self-disinfecting dental alginate.MethodsConventional alginate impression material was used in this study. Silver nitrate (0.2% AgNO3 group) and chlorohexidine (0.2% CHX group) solutions were prepared using distilled water, and these solutions were later employed for alginate preparation. Moreover, a 90% aqueous plant extract was prepared from Boswellia sacra (BS) oleoresin and used to reduce silver nitrate to form silver nanoparticles that were incorporated in the dental alginate preparation (BS+AgNPs group). The plant extract was characterized by gas chromatography/mass spectrometry (GC/MS) analysis while green-synthesized silver nanoparticles (AgNPs) were characterized by UV-visible (UV–vis) spectroscopy and scanning electron microscopy (SEM). An agar disc diffusion assay was used to test the antimicrobial activity against Candida albicans, Streptococcus mutans, Escherichia coli, methicillin-resistant and susceptible Staphylococcus aureus strains, and Micrococcus luteus. Agar plates were incubated at 37 ± 1 °C for 24 h to allow microbial growth. Diameters of the circular inhibition zones formed around each specimen were measured digitally by using ImageJ software.ResultsChemical analysis of the plant extract revealed the presence of 41 volatile and semi-volatile active compounds. UV–Vis spectrophotometry, SEM, and EDX confirmed the formation of spherical silver nanoparticles using the BS extract. CHX, AgNO3, and the BS+AgNPs modified groups showed significantly larger inhibition zones than the control group against all tested strains. BS+AgNPs and CHX groups showed comparable efficacy against all tested strains except for Staphylococcus aureus, where the CHX-modified alginate had a significantly higher effect.Conclusions and clinical relevanceCHX, silver nitrate, and biosynthesized silver nanoparticles could be promising inexpensive potential candidates for the preparation of a self-disinfecting alginate impression material without affecting its performance. Green synthesis of metal nanoparticles using Boswellia sacra extract could be a very safe, efficient, and nontoxic way with the additional advantage of a synergistic action between metal ions and the phytotherapeutic agents of the plant extract.

In-vitro antibacterial activity and mechanism of Monarda didyma essential oils against Carbapenem-resistant Klebsiella pneumoniae

To fight the global epidemic of drug-resistant bacteria, essential oils have gained increasing attention as a new source of antibiotics. The antimicrobial activity of Monarda didyma essential oils (MDEO) for the Carbapenem-resistant Klebsiella pneumoniae (CRKP) strains were determined by agar disc diffusion assay and broth microdilution assay. To further understand MDEO efficacy, a time-growth curve was performed. The biofilm formation of CRKP were determined by crystalline violet staining method, additionally, changes in intracellular Adenosine triphosphate (ATP), protein, Alkaline phosphatase (AKP) activities, and membrane integrity were investigated to assess the influence of MDEO on cell membrane damage. Finally, the activities of key enzymes in the tricarboxylic acid (TCA) pathways and pentose phosphate (PPP) pathways were examined to determine the effect of MDEO on the respiratory metabolism of CRKP. This study presents the antibacterial mechanism of MDEO against CRKP with a minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 1.25 mg/ml. To understand MDEO efficacy, a time-kill kinetics approach was performed. The bactericidal effect of MDEO was evident at 2 h compared to the control at its MIC and 2MIC. Surface electron microscopic and ATP assay studies provided evidence for the multi-target action of MDEO against CRKP. MDEO could inhibit CRKP biofilm formation. MDEO could also cause irreversible damage to the CRKP cell membrane, resulting in the leakage of biological macromolecules (protein, ATP) and the reduction of intracellular enzymes (AKP) activities. Finally, MDEO affected the pathways of respiratory metabolism, such as PPP and TCA pathways. MDEO could reduce the activity of key enzymes (Glucose-6-phosphate dehydrogenase, citrate synthase, isocitrate dehydrogenase, and α-ketoglutarate dehydrogenase) in the PPP and TCA pathways to exert its biological effects against CRKP. These results suggest MDEO can exert inhibitory effects on CRKP, and potential mechanisms of action including inhibition of biofilm formation, damage of cell membrane structure and inhibition of energy metabolism.