scholarly journals Zinc Oxide Nanocomposites—Extracellular Synthesis, Physicochemical Characterization and Antibacterial Potential

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4347 ◽  
Author(s):  
Paweł Pomastowski ◽  
Anna Król-Górniak ◽  
Viorica Railean-Plugaru ◽  
Bogusław Buszewski
Keyword(s):  
Control Sample ◽  
Physicochemical Characterization ◽  
Microscopic Analysis ◽  
Luminescent Properties ◽  
Infrared Range ◽  
Fluorescence Signal ◽  
Bacterial Cells ◽  
Ointment Formulation ◽  
Ph Range ◽  
Organic Deposits

This research presents, for the first time, the potential of the Lactobacillus paracasei LC20 isolated from sweet whey as a novel, effective and accessible source for post-cultured ZnO nanocomposites synthesis. The obtained nanocomposites were subjected to comprehensive characterization by a broad spectrum of instrumental techniques. Results of spectroscopic and microscopic analysis confirmed the hexagonal crystalline structure of ZnO in the nanometer size. The dispersion stability of the obtained nanocomposites was determined based on the zeta potential (ZP) measurements—the average ZP value was found to be −29.15 ± 1.05 mV in the 7–9 pH range. The ZnO nanocomposites (NCs) demonstrated thermal stability up to 130 °C based on the results of thermogravimetric TGA/DTG) analysis. The organic deposit on the nanoparticle surface was recorded by spectroscopic analysis in the infrared range (FT-IR). Results of the spectrometric study exhibited nanostructure-assisted laser desorption/ionization effects and also pointed out the presence of organic deposits and, what is more, allowed us to identify the specific amino acids and peptides present on the ZnO NCs surfaces. In this context, mass spectrometry (MS) data confirmed the nano-ZnO formation mechanism. Moreover, fluorescence data showed an increase in fluorescence signal in the presence of nanocomposites designed for potential use as, e.g., biosensors. Despite ZnO NCs’ luminescent properties, they can also act as promising antiseptic agents against clinically relevant pathogens. Therefore, a pilot study on the antibacterial activity of biologically synthesized ZnO NCs was carried out against four strains (Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae and Pseudomonas aeruginosa) by using MIC (minimal inhibitory concentration). Additionally, the colony forming units (CFU) assay was performed and quantified for all bacterial cells as the percentage of viable cells in comparison to a control sample (untreated culture) The nanocomposites were effective among three pathogens with MIC values in the range of 86.25–172.5 μg/mL and showed potential as a new type of, e.g., medical path or ointment formulation.

scholarly journals Studying antimicrobial-induced morphostructural damage of bacteria by Scanning Electron Microscope

2015 ◽  
Vol 10 (4) ◽  
pp. 870 ◽  
Author(s):  
Shruti Shukla
Keyword(s):  
Cell Wall ◽  
Antimicrobial Agents ◽  
Microscopic Analysis ◽  
Cell Swelling ◽  
Bacterial Cells ◽  
Electron Microscopic ◽  
Morphological Alterations ◽  
Slide Preparation ◽  
Critical Point Drying ◽  
Scanning Electron

<p>In this investigation, a scanning electron microscopy (SEM) method was used to examine the morphostructural changes in bacterial cells induced by antimicrobial agents. SEM-based visual approach is referred the study of bacterial cells and their physiological consequences when affected by antibiotics or antibacterial agents permitting the observation of characteristic morphological defects of cell wall, and provides valuable insights into processes involved in bacterial cell death. This experiment visualized various step-by-step techniques used in the slide preparation of bacterial cells treated with specific antimicrobial agent for analyzing the morphological alterations such as increase of cell wall roughness, cell disruption, cell swelling and lysed cell formation due to loss of intracellular material using SEM analysis when compared with untreated normal cells as a control. The SEM approach used in this visual experiment may analyze the antimicrobial effect of any commercially known or new compounds in a very conducive manner.</p><p><strong>Video Clips</strong></p><p><a href="https://youtube.com/v/WQtp1fV3Zuc">Culturing of bacteria</a>                                                  2 min 54 sec</p><p><a href="https://youtube.com/v/U3RUXFWDgtw">Treatment of bacterial culture by antimicrobials</a>             4 min 21 sec</p><p><a href="https://youtube.com/v/AgeuJg_afeE">Sample pre-treatment</a>                                                4 min 23 sec</p><p><a href="https://youtube.com/v/SI7PU0Uw7Bo">Microscopic slide preparation</a>                                       9 min 27 sec</p><p><a href="https://youtube.com/v/ilX91i4afVM">Critical point drying and ion sputter coating of slides</a>        5 min 52 sec</p><p><a href="https://youtube.com/v/iOp9Mi_O3KE">Scanning Electron Microscopic analysis of coated slides</a>    4 min 18 sec</p>

Water-Based Route to Synthesis of High-Quality UV-Blue Photoluminescing ZnSe/ZnS Core/Shell Quantum Dots and their Physicochemical Characterization

2016 ◽  
Vol 680 ◽  
pp. 553-557 ◽  
Author(s):  
Yong Ling Ding ◽  
Hua Dong Sun ◽  
Kang Ning Sun ◽  
Fu Tian Liu
Keyword(s):  
Ph Value ◽  
Aqueous Media ◽  
Physicochemical Characterization ◽  
Luminescent Properties ◽  
Core Shell ◽  
Reaction Flask ◽  
High Quality ◽  
Shell Nanostructures ◽  
Thiol Ligand ◽  
Znse Nanocrystals

Epitaxially overgrowing a semiconductor material with higher bandgap around the QDs has proven to be a crucial approach for improving the PL efficiency and stability of nanocrystals. In this paper, a ZnS shell was deposited around ZnSe nanocrystal cores via a noninjection approach in aqueous media. The deposition procedure conducted at 100°C in a reaction flask in the presence of the shell precursor compounds, together with the crude ZnSe nanocrystal cores and the thiol ligand glutathione. The influences of various experimental variables, including the reaction time, amount of thiourea, as well as pH value, on the growth rate and luminescent properties of the obtained core/shell nanocrystals have been systematically investigated. In comparison with the original ZnSe nanocrystals, the PL efficiency of the obtained ZnSe/ZnS core/shell nanostructures can be improved significantly with a QY up to 62.8%.

scholarly journals Zeta potential of bacterial cells: Effect of wash buffers

2013 ◽  
Author(s):  
Wenfa Ng
Keyword(s):  
Sodium Chloride ◽  
Ionic Strength ◽  
Zeta Potential ◽  
Cell Surface ◽  
Phosphate Buffer ◽  
Bacterial Cells ◽  
Ph Profile ◽  
Wash Buffer ◽  
Ph Range ◽  
Zeta Potential Analysis

Zeta potential - defined as the electrical charge at the shear plane - is widely used as a proxy for cell surface charge. Consequent of its definition, nonspecific adsorption of ions on the cell surface may alter the value - and polarity - of the measured zeta potential, thereby, leading to erroneous results. Multiple wash and centrifugation steps are commonly used in preparing cells for zeta potential analysis – where various wash buffers (such as 9 g/L sodium chloride and 0.1M sodium nitrate) help remove ions and charged molecules nonspecifically bound to the cell surface. Nevertheless, little information on the wash buffers’ relative efficacies in removing nonspecifically bound ions hamper the comparison of zeta potential results across laboratories even for the same bacterial strain cultured under identical conditions. Thus, the present study sought to evaluate the effect of various wash buffers on zeta potential of bacterial cells grown in two culture media differing in salt content – thereby, allowing potential differential efficacy of buffers in removing nonspecifically adsorbed ions and metabolites to be discerned. Preliminary data revealed that for Escherichia coli DH5α (ATCC 53868) grown in LB Lennox (supplemented with 2 g/L glucose), the zeta potential-pH profile was not significantly different over the pH range from 2 to 12 for deionized water, 9 g/L sodium chloride, and phosphate buffer saline (PBS) wash buffers. As the glucose supplemented LB medium was a low salt medium without a phosphate buffer, it was unlikely that nonspecific adsorption of ions on the cell surface was extensive – thus, supporting the observation that the various wash buffers used did not have differential effect on zeta potential measurement. On the other hand, the zeta potential-pH profile of E. coli grown in a semi-defined medium with a high capacity phosphate buffer system, was significantly different over the pH range from 1 to 12 for deionized water, 9 g/L sodium chloride, 0.1M sodium nitrate, 0.1M sodium acetate, and 0.1M sodium citrate with the extent of difference positively correlated with wash buffers’ ionic strength. A similar relationship was also observed between the measured point of zero charge (pHzpc) and ionic strength of wash buffer, which, taken together, suggested that charge screening might be an important mechanism for removing the adsorbed ions. Collectively, although the experimental data suggests possible use of high ionic strength wash buffer in removing nonspecifically adsorbed ions from bacterial cell surface prior to zeta potential analysis, possible structural damage to the surface from removing intrinsic ions - necessary for stabilizing the bacterial cell wall - could not be discounted.

Proteomic and microscopic analysis of biofilms formed byListeria monocytogenes568

2005 ◽  
Vol 51 (3) ◽  
pp. 197-208 ◽  
Author(s):  
M A Hefford ◽  
S D'Aoust ◽  
T D Cyr ◽  
J W Austin ◽  
G Sanders ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Stress Response ◽  
Physiological State ◽  
Polyacrylamide Gel Electrophoresis ◽  
Microscopic Analysis ◽  
Test Surface ◽  
Food Borne ◽  
Ph Range ◽  
Regulatory Functions ◽  
Response Envelope

Biofilm formation may be important in the colonization of the food-processing environment by the food-borne pathogen Listeria monocytogenes. Listeria monocytogenes 568 formed adherent multicellular layers on a variety of test surfaces following growth at 37 °C with multiple transfers of the test surface into fresh medium. Microscopic examination of these adherent layers suggest that the cells were surrounded by extracellular material. The presence of a carbohydrate containing extracellular polymeric matrix was confirmed by labelling hydrated adherent layers with fluorescein-conjugated concanavalin A, indicating that these adherent layers are biofilms. To gain insight into the physiological state of cells in these biofilms, the proteomes from biofilm- and planktonic-grown cells from the same cultures were compared using 2-dimensional polyacrylamide gel electrophoresis. Nineteen proteins, which exhibited higher levels of expression in biofilm-grown cells, were successfully identified from the 2-D gels using a combination of MALDI-TOF and MS/MS. Proteins that were found to be more highly expressed in biofilm-grown cells were involved in stress response, envelope and protein synthesis, biosynthesis, energy generation, and regulatory functions. In biofilm-grown cells, many proteins in the pH range 4–6 ran as multiple spots arranged horizontally across the 2-D gels.Key words: Listeria monocytogenes, biofilms, proteomics, stress response.

How kaolinite plays an essential role in remediating oil-polluted seawater

Clay Minerals ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 481-491 ◽  
Author(s):  
S. K. Chaerun ◽  
K. Tazaki
Keyword(s):  
Bacterial Growth ◽  
Cell Walls ◽  
Control Sample ◽  
Experimental Period ◽  
Bacterial Cells ◽  
Kaolinite Clay ◽  
Clay Particles ◽  
Transmission Electron ◽  
Degrading Bacteria ◽  
Energy Dispersive Spectroscope

AbstractAn investigation was carried out on the bioavailability of kaolinite and the role it plays in remediating oil-polluted seawater, since kaolinite is known to enable hydrocarbon-degrading bacteria to grow well. Experimental results revealed that significant amounts of Al and Si dissolved from kaolinite were not observed ((P > 0.05) in comparison with a control sample which contained no kaolinite) in the aqueous phase during the ~24 day experimental period. Transmission electron microscope observations and energy-dispersive spectroscope data revealed that some altered kaolinite particles appeared, connected to intact kaolinite and bacterial cells. Bacterial cells were associated and encrusted with intact and/or altered kaolinite clay particles, where mixed (C, O, Na and Si)-precipitates of kaolinite clays were formed on the surface of hydrocarbon-degrading bacterial cells. However, the uptake of Si (from kaolinite) by bacterial cells appeared to be more prevalent than Al, and there were no significant changes in basal spacings of kaolinite due to these altered kaolinite particles. Separate studies showed that hydrocarbon-degrading bacteria have a high resistance to Si. Thus, the present data suggest that Si from kaolinite may facilitate hydrocarbon-degrading bacterial growth as shown in our previous study (Chaerun et al., 2005), and the C-O-Na-Si complexes on the surfaces of bacterial cell walls may be the stimulator for hydrocarbon-degrading bacterial growth in seawater contaminated with oil spill.

The Production of Bioethanol from Carob Pods (Ceratonia siliqua L.)

2020 ◽  
Vol 4 (2) ◽  
pp. 202-213
Author(s):  
David Camilleri ◽  
Frederick Lia
Keyword(s):  
Fermentation Broth ◽  
Control Sample ◽  
Thiamine Hydrochloride ◽  
Ceratonia Siliqua ◽  
Uv Detector ◽  
Time Intervals ◽  
Carob Powder ◽  
Ceratonia Siliqua L ◽  
Ph Range ◽  
Refractive Index Detector

This study seeks to investigate the use of carob (Ceratonia siliqua. L) as a potential source of bioethanol production. In addition, an attempt to optimize the method through sulfuric acid hydrolysis was carried out and the optimum pH range for carob fermentation was studied at pH 2.5, 4.5 and 7.5. Samples of both foreign and locally originating carob were used and any discrepancy in fermentation performance with respect to origin was noted. Each fermentation setup was prepared with 66 gL-1 carob powder, inoculated with 1gL-1 Saccharomyces cerevisiae yeast strain and supplemented with 0.6 mgL-1 thiamine hydrochloride. A total of 36 fermentation broth samples taken at 24-hour time intervals were analysed for different fermentation variables to monitor the progression of fermentation. Changes in total acidity and reducing sugar were analysed through titration techniques and pH. A quantitative sugar profile based on fructose, glucose and sucrose was constructed using an in-house validated method by HPLC-Refractive Index detector. Ethanolic content of the fermentation broth was determined through an in-house validated method by HPLC-UV detector. A significant change (p < 0.05) in ethanol content across time, was detected, with the highest ethanol concentration being achieved in the unhydrolysed control sample with 1.19% v/v from 66gL-1 carob powder.

scholarly journals Profluorescent Fluoroquinolone-Nitroxides for Investigating Antibiotic–Bacterial Interactions

Antibiotics ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 19 ◽  
Author(s):  
Anthony Verderosa ◽  
Rabeb Dhouib ◽  
Kathryn Fairfull-Smith ◽  
Makrina Totsika
Keyword(s):  
Fluorescent Probes ◽  
Antimicrobial Properties ◽  
Chemical Processes ◽  
Cell Entry ◽  
Fluorescence Signal ◽  
Bacterial Cells ◽  
Significant Suppression ◽  
Bacterial Interactions ◽  
Radical Trapping ◽  
Nitroxide Probe

Fluorescent probes are widely used for imaging and measuring dynamic processes in living cells. Fluorescent antibiotics are valuable tools for examining antibiotic–bacterial interactions, antimicrobial resistance and elucidating antibiotic modes of action. Profluorescent nitroxides are ‘switch on’ fluorescent probes used to visualize and monitor intracellular free radical and redox processes in biological systems. Here, we have combined the inherent fluorescent and antimicrobial properties of the fluoroquinolone core structure with the fluorescence suppression capabilities of a nitroxide to produce the first example of a profluorescent fluoroquinolone-nitroxide probe. Fluoroquinolone-nitroxide (FN) 14 exhibited significant suppression of fluorescence (>36-fold), which could be restored via radical trapping (fluoroquinolone-methoxyamine 17) or reduction to the corresponding hydroxylamine 20. Importantly, FN 14 was able to enter both Gram-positive and Gram-negative bacterial cells, emitted a measurable fluorescence signal upon cell entry (switch on), and retained antibacterial activity. In conclusion, profluorescent nitroxide antibiotics offer a new powerful tool for visualizing antibiotic–bacterial interactions and researching intracellular chemical processes.

Essential activation of Na(+)-H+ exchange by [H+]i in HL-60 cells

1990 ◽  
Vol 259 (3) ◽  
pp. C490-C502 ◽  
Author(s):  
D. Restrepo ◽  
D. S. Cho ◽  
M. J. Kron
Keyword(s):  
Exchange Rate ◽  
Low Ph ◽  
Hill Coefficient ◽  
Fluorescence Signal ◽  
Half Saturation Constant ◽  
Wide Range ◽  
Simple Kinetic Model ◽  
Hill Coefficients ◽  
Ph Range ◽  
The Hill

The intracellular pH (pHi) dependence of the rate of Na(+)-H+ exchange was determined in undifferentiated promyelocytic HL-60 cells by measuring alkalinization rates using the fluorescent pHi indicator 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF). BCECF was calibrated in the pH range from 5 to 7 using the nigericin technique of Thomas and co-workers (J. A. Thomas, R. N. Buchsbaum, A. Zimniak, and E. Racker. Biochemistry 18: 2210-2218, 1979). Exchange rate increases as pHi is lowered below pH 7.00. At low pH (pH below 6.3), the dependence of Na(+)-H+ exchange rate on intracellular proton activity is well fitted by the Michaelis-Menten equation with a maximum exchange velocity of 33.7 +/- 2.4 mmol H(+).1 cell water-1.min-1 and a half-saturation constant of 1.35 +/- 0.28 microM (corresponding to a minus log of the Michaelis constant of 5.89). However, a Hill plot reveals that the Hill coefficient changes gradually from one to two when pH is changed from 5 to 7, ruling out Michaelian kinetics. The dependence of exchange flux on internal protons is well fit in the full pH range from 5 to 7 by a simple kinetic model (essential activation) with modifier and transport sites for internal proton binding. At low pH, failure to correct BCECF measurement of pHi for contribution to fluorescence signal from extracellular dye and for quenching of intracellular BCECF leads to an artifactual increase in the measured Hill coefficient. These two findings (increase in Hill coefficient as pHi is increased and artifactual increase in Hill coefficient because of methodological reasons) provide a good explanation for the wide range of Hill coefficients reported in the literature.

Granule contents from rat polymorphonuclear leukocytes: antimicrobial properties and characterization

1986 ◽  
Vol 32 (6) ◽  
pp. 498-504 ◽  
Author(s):  
Richard L. Hodinka ◽  
Malcolm C. Modrzakowski
Keyword(s):  
Antibacterial Properties ◽  
Antimicrobial Properties ◽  
Bacterial Cells ◽  
Gram Positive Bacteria ◽  
Properties And Characterization ◽  
Bacterial Mutants ◽  
Killing Action ◽  
Gram Negative Organisms ◽  
Ph Range ◽  
Static Conditions

The nonoxidative antibacterial properties of isolated rat polymorphonuclear leukocyte granule contents were examined using Salmonella typhimurium LT-2 and a series of progressively rough lipopolysaccharide mutants of this strain as target bacteria. The granule extract was most active at 37 °C, with a substantial decrease in activity observed at lower temperatures. Deep rough bacterial mutants were killed best within a pH range of 6–8, while killing of mutants with increased lipopolysaccharide content was most efficient at an acid pH of 5. The activity of the extract was dependent on incubation time but was independent of the number of bacterial cells present in the assay mixture. The killing action of the granule extract was inhibited by the cations Na+, K+, Mg2+, Ca, and Fe2+. The degree of inhibition was dependent on the type and concentration of ion used. Rough mutants grown with aeration to log phase were killed more efficiently than the same mutants grown to stationary phase under static conditions. Also, gram-positive bacteria were more susceptible to the extract than were gram-negative organisms.

Na2EDTA-assisted hydrothermal synthesis and luminescent properties of YVO4:Eu3+ with different morphologies in a wide pH range

2009 ◽  
Vol 156 (1-3) ◽  
pp. 42-47 ◽  
Author(s):  
Juan Wang ◽  
Yunhua Xu ◽  
Mirabbos Hojamberdiev ◽  
Jianhong Peng ◽  
Gangqiang Zhu
Keyword(s):  
Hydrothermal Synthesis ◽  
Luminescent Properties ◽  
Wide Ph Range ◽  
Ph Range
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