Antibacterial activities of magnesium oxide (MgO) nanoparticles against foodborne pathogens

The antibacterial activities of magnesium oxide nanoparticles (MgO NP) alone or in combination with other antimicrobials (nisin and ZnO NP) against Escherichia coli O157:H7 and Salmonella Stanley were investigated. The results show that MgO NP have strong bactericidal activity against the pathogens, achieving more than 7 log reductions in bacterial counts. The antibacterial activity of MgO NP increased as the concentrations of MgO increased. A synergistic effect of MgO in combination with nisin was observed as well. However, the addition of ZnO NP to MgO NP did not enhance the antibacterial activity of MgO against both pathogens. Scanning electron microscopy was used to characterize the morphological changes of E. coli O157:H7 before and after antimicrobial treatments. It was revealed that MgO NP treatments distort and damage the cell membrane, resulting in a leakage of intracellular contents and eventually the death of bacterial cells. These results suggest that MgO NP alone or in combination with nisin could potentially be used as an effective antibacterial agent to enhance food safety.     

Nanovesicle encapsulation of antimicrobial peptide P34: physicochemical characterization and mode of action on <Emphasis Type="Italic">Listeria monocytogenes</Emphasis>

Antimicrobial peptide P34, a substance showing antibacterial activity against pathogenic and food spoilage bacteria, was encapsulated in liposomes prepared from partially purified soybean phosphatidylcholine, and their physicochemical characteristics were evaluated. The antimicrobial activity was estimated by agar diffusion assay using Listeria monocytogenes ATCC 7644 as indicator strain. A concentration of 3,200 AU/mL of P34 was encapsulated in nanovesicles and stocked at 4 °C. No significant difference (p > 0.05) in the biological activity of free and encapsulated P34 was observed through 24 days. Size and PDI of liposomes, investigated by light scattering analysis, were on average 150 nm and 0.22 respectively. Zeta potential was −27.42 mV. There was no significant change (p > 0.05) in the physicochemical properties of liposomes during the time of evaluation. The liposomes presented closed spherical morphology as visualized by transmission electron microscopy (TEM). The mode of action of liposome-encapsulated P34 under L. monocytogenes cells was investigated by TEM. Liposomes appeared to adhere but not fuse with the bacterial cell wall, suggesting that the antimicrobial is released from nanovesicles to act against the microorganism. The effect of free and encapsulated P34 was tested against L. monocytogenes, showing that free bacteriocin inhibited the pathogen more quickly than the encapsulated P34. Liposomes prepared with low-cost lipid showed high encapsulation efficiency for a new antimicrobial peptide and were stable during storage. The mode of action against the pathogen L. monocytogenes was characterized.     

Theoretical and antimicrobial activity study for ethyl{4-[3-(1H-imidazole-1-yl)propyl]-3-methyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}acetate

Ethyl{4-[3-(1H-imidazole-1-yl)propyl]-3-methyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}-acetate (I) was synthesized as described in the literature and studied by proton and carbon-13 nuclear magnetic resonance, Fourier transform infrared spectroscopic techniques. Theoretical calculations were performed by the density functional method with 6-311G(d,p) and 6-311++G(d,p) basis sets. Structural parameters of compound I, vibrational frequencies, and chemical shift values were determined. The antimicrobial activity of compound I was tested for seven standard bacteria; Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, Yersinia enterocolitica, Listeria monocytogenes, Shigella flexneri, Pseudomonas aeruginosa, and one standard fungi isolate by microdilution broth assay with Alamar Blue Dye. The in vitro results show that compound I has antimicrobial activity against to two standard bacteria, Shigella flexneri and Listeria monocytogenes. And also, the antifungal activity was not detected against selected fungi isolate, Candida tropicalis.     

Synthesis,characterization, and antimicrobial evaluation of a small library of ferrocene-containing acetoacetates and phenyl analogs: the discovery of a potent anticandidal agent

A library of 16 2-substituted methyl acetoacetates containing ferrocenyl or phenyl units was designed to disclose differences in the antimicrobial activity of ferrocene-containing compounds and their phenyl analogs. Two methyl acetoacetates, whose structures do not contain an aromatic nucleus, were also included in order to probe the inherent activity of the scaffold itself. The acetoacetates were synthesized (low-to-good yields) and fully characterized by spectral (MS, IR, UV–Vis, 1D and 2D NMR) and electrochemical (cyclic voltammetry) techniques. Single-crystal X-ray analysis has been performed for methyl 2-acetyl-2-(ferrocenylmethyl)-5-methylhex-4-enoate. All compounds have demonstrated in vitro antimicrobial activity against six bacterial (three Gram-positive and three Gram-negative) and two fungal strains with minimal inhibitory concentration values of 0.0050–20.6  \(\upmu \hbox {mol mL}^{-1}\) . The most active compound was 2-acetyl-2-(ferrocenylmethyl)-4-methylpent-4-enoate whose activity was comparable to that of nystatin against the yeast Candida albicans. Agglomerative hierarchical clustering statistical analysis of the antimicrobial assay data demonstrated that ferrocene-containing compounds have statistically different and greater antimicrobial activity when compared to their phenyl analogs.     

Green synthesis of silver nanoparticle by <Emphasis Type="Italic">Penicillium purpurogenum</Emphasis> NPMF: the process and optimization

An eco-friendly microbial method for synthesis of silver colloid solution with antimicrobial activity is developed using a fungal strain of Penicillium purpurogenum NPMF. It is observed that increase in concentration of AgNO₃ increases the formation of silver nanoparticle. At 5 mM concentration highly populated polydispersed nanoparticles form. Furthermore, change in pH of the reaction mixture leads to change in shape and size of silver nanoparticles. At lower pH two peaks are observed in the absorption spectra showing polydispersity of nanoparticles. However, highly monodispersed spherical nanoparticles of 8–10 nm size form with 1 mM AgNO₃ concentration at pH 8. Antimicrobial activity of nanoparticles is demonstrated against pathogenic gram negative bacteria like Escherichia coli and Pseudomonas aeruginosa, and gram positive bacteria like Staphylococcus aureus. The antimicrobial activity of silver nanoparticles obtained at different initial pH show strong dependence on the surface area and shape of the nanoparticles.     

Evaluation of spin labels for in-cell EPR by analysis of nitroxide reduction in cell extract of Xenopus laevis oocytes

Spin-label electron paramagnetic resonance (SL-EPR) spectroscopy has become a powerful and useful tool for studying structure and dynamics of biomacromolecules. However, utilizing these methods at physiological temperatures for in-cell studies is hampered by reduction of the nitroxide spin labels and thus short half-lives in the cellular environment. Consequently, reduction kinetics of two structurally different nitroxides was investigated in cell extracts of Xenopus laevis oocytes using rapid-scan cw-experiments at X-band. The five member heterocyclic ring nitroxide PCA (3-carboxy-2,2,5,5-tetramethylpyrrolidinyl-1-oxy) under investigation features much higher stability against intracellular reduction than the six member ring analog TOAC (2,2,6,6-tetramethylpiperidine-N-oxyl-4-amino-4-carboxilic acid) and is therefore a suitable spin label type for in-cell EPR. The kinetic data can be described according to the Michaelis–Menten model and thus suggest an enzymatic or enzyme-mediated reduction process.     

Silver nanoparticles with gelatin nanoshells: photochemical facile green synthesis and their antimicrobial activity

In the current study, a facile green synthesis of silver-gelatin core–shell nanostructures (spherical, spherical/cubic hybrid, and cubic, DLS diameter: 4.1–6.9 nm) is reported via the wet chemical synthesis procedure. Sunlight-UV as an available reducing agent cause mild reduction of silver ions into the silver nanoparticles (Ag-NPs). Gelatin protein, as an effective capping/shaping agent, was used in the reaction to self-assemble silver nanostructures. The formation of silver nanostructures and their self-assembly pattern was confirmed by SEM, AFM, and TEM techniques. Further investigations were carried out using zeta-potential, UV–Vis, FTIR, GPC, and TGA/DTG/DTA data. The prepared Ag-NPs showed proper and acceptable antimicrobial activity against three classes of microorganisms (Escherichia coli Gram-negative bacteria, Staphylococcus aureus Gram-positive bacteria, and Candida albicans fungus). The antibacterial and antifungal Ag-NPs exhibit good stability in solution and can be considered as promising candidates for a wide range of biomedical applications.     

Biosynthesis of silver nanoparticles using <Emphasis Type="Italic">Ocimum sanctum</Emphasis> (Tulsi) leaf extract and screening its antimicrobial activity

Development of green nanotechnology is generating interest of researchers toward ecofriendly biosynthesis of nanoparticles. In this study, biosynthesis of stable silver nanoparticles was done using Tulsi (Ocimum sanctum) leaf extract. These biosynthesized nanoparticles were characterized with the help of UV–vis spectrophotometer, Atomic Absorption Spectroscopy (AAS), Dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Transmission electron microscopy (TEM). Stability of bioreduced silver nanoparticles was analyzed using UV–vis absorption spectra, and their antimicrobial activity was screened against both gram-negative and gram-positive microorganisms. It was observed that O. sanctum leaf extract can reduce silver ions into silver nanoparticles within 8 min of reaction time. Thus, this method can be used for rapid and ecofriendly biosynthesis of stable silver nanoparticles of size range 4–30 nm possessing antimicrobial activity suggesting their possible application in medical industry.     

Selective photoinactivation of <Emphasis Type="Italic">C. albicans</Emphasis> and <Emphasis Type="Italic">C. dubliniensis</Emphasis> with hypericin

The genus Candida includes different species that have the potential to invade and colonize the human body and C. albicans is the most common cause of skin, nail and mucous infections. The increasing resistance against antifungal drugs has renewed the search for new treatment procedures and antimicrobial photodynamic inactivation (PDI) is a propitious candidate. Hypericin (HY) has several wanted properties to be used as a photosensitizer in this technique including a high quantum yield of singlet oxygen generation, a high extinction coefficient near 600 nm, and a relatively low dark toxicity. Although the phototoxicity of HY on several tumor cells has been reported, the data concerning its photoactivity on microorganisms are scarce. The aim of this study was to obtain the experimental parameters to achieve an acceptable selective hypericinphotoinactivation of two species of Candida comparing with fibroblasts and epithelial cells which are the constituents of some potential host tissues, such mucosas, skin and cavities. Microorganisms and cells were incubated with the same HY concentrations and short incubation time followed by irradiation with equal dose of light. The best conditions to kill just Candida were very low HY concentration (0.1–0.4 μg ml⁻¹) incubated by 10 min and irradiated with LED 590 nm with 6 J cm⁻².     

Assessment of thermal and antimicrobial properties of PAN/Zn-Al layered double hydroxide nanocomposites

Polyacrylonitrile-based Zn–Al layered double hydroxide composites (PAN/LDH) have been synthesised with different LDH content by in situ polymerisation technique. The nanocomposites were systematically studied by Fourier transform infrared spectroscopy, X-ray diffraction (XRD), thermo gravimetric analysis (TGA), field emission scanning electron microscope (FE SEM), high resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS) and antibacterial activity measurement. The successful formation of exfoliated nanocomposite was inferred from the XRD patterns and HRTEM images. The thermal decomposition of PAN was enhanced upon nanocomposite (PAN/LDH) formation. The antimicrobial activity of PAN/LDH nanocomposites is evaluated for antibacterial activity against some clinically important bacterial pathogens and the bacterial growth is monitored at different percentage of LDH. The PAN/LDH composites displayed considerable antibacterial activity, on the contrary the virgin PAN did not possess any antibacterial activity. The likely electrostatic interaction among LDH layers with charged surface of bacterial cell is assumed to be responsible for antimicrobial activity. The prepared nanocomposite has appreciable thermal stability in combination with antibacterial activities by which the material is suitable for packaging and fabrication in textile application.     

Investigation into the antibacterial behaviour of suspensions of ZnO nanoparticles (ZnO nanofluids)

The antibacterial behaviour of suspensions of zinc oxide nanoparticles (ZnO nanofluids) against E. Coli has been investigated. ZnO nanoparticles from two sources are used to formulate nanofluids. The effects of particle size, concentration and the use of dispersants on the antibacterial behaviour are examined. The results show that the ZnO nanofluids have bacteriostatic activity against E. coli. The antibacterial activity increases with increasing nanoparticle concentration and increases with decreasing particle size. Particle concentration is observed to be more important than particle size under the conditions of this work. The results also show that the use of two types of dispersants (Polyethylene Glycol (PEG) and Polyvinylpyrolidone (PVP)) does not affect much the antibacterial activity of ZnO nanofluids but enhances the stability of the suspensions. SEM analyses of the bacteria before and after treatment with ZnO nanofluids show that the presence of ZnO nanoparticles damages the membrane wall of the bacteria. Electrochemical measurements using a model DOPC monolayer suggest some direct interaction between ZnO nanoparticles and the bacteria membrane at high ZnO concentrations. On visiting from the Tianjin University of Science & Technology, Tianjin, P.R. China.     

Fluorescent Temporin B Derivative and its Binding to Liposomes

Temporins are short (10–13 amino acids) and linear antimicrobial peptides first isolated from the skin of the European red frog, Rana temporaria, and are effective against Gram-positive bacteria and Candida albicans. Similarly to other antimicrobial peptides, the association of temporins to lipid membranes has been concluded to underlie their antimicrobial effects. Accordingly, a detailed understanding of their interactions with phospholipids is needed. We conjugated a fluorophore (Texas Red) to a Cys containing derivative of temporin B (temB) and investigated its binding to liposomes by fluorescence spectroscopy. Circular dichroic spectra for the Cys-mutant recorded in the absence and in the presence of phospholipids were essentially similar to those for temB. A blue shift in the emission spectra and diminished quenching by ferrocyanide (FCN) of Texas Red labeled temporin B (TRC-temB) were seen in the presence of liposomes. Both of these changes can be attributed to the insertion of the Texas Red into the hydrophobic region of the bilayer. Resonance energy transfer, steady state anisotropy, and fluorescence lifetimes further demonstrate the interaction of TRC-temB with liposomes to be enhanced by negatively charged phospholipids. Instead, cholesterol attenuates the association of TRC-temB with membranes. The interactions between TRC-temB and liposomes of varying negative surface charge are driven by electrostatics as well as hydrophobicity. Similarly to native temporin B also TRC-temB forms amyloid type fibers in the presence of negatively charged liposomes. This property is likely to relate to the cytotoxic activity of this peptide.     

Observation of magnetic field-induced contraction of fission yeast cells using optical projection microscopy

The charges in live cells interact with or produce electric fields, which results in enormous dielectric responses, flexoelectricity, and related phenomena. Here we report on a contraction of Schizosaccharomyces pombe (fission yeast) cells induced by magnetic fields, as observed using a phase-sensitive projection imaging technique. Unlike electric fields, magnetic fields only act on moving charges. The observed behavior is therefore quite remarkable, and may result from a contractile Lorentz force acting on diamagnetic screening currents. This would indicate extremely high intracellular charge mobilities. Besides, we observed a large electro-optic response from fission yeast cells.     

Investigations in ultrasound-assisted anticoagulant production by marine Bacillus subtilis ZHX

Anticoagulants are the main drugs for the prevention and treatment of thromboembolism. However, most of the present anticoagulants have shortcomings and novel anticoagulants are in great demand. Marine microorganisms are an important source of new drugs. Therefore, in this study, ultrasound was applied to enhance anticoagulant accumulation by marine Bacillus subtilis ZHX. Ultrasound parameters were optimized by single-factor experiments exploring the effects of ultrasound power, duration, duty cycle and the cell growth phases. The optimum conditions were exponential prophase (5 h) with 25 kHz frequency, 140 W power, and a 40% duty cycle for 5 min. The maximum anticoagulant activity (55.36 U/mL) was 1.73 times that of the control group, and the fermentation time was shortened by 3 h. Under optimal conditions, ultrasound increased the carbon utilization by Bacillus subtilis ZHX without significant changes in morphology, favoring cell growth and anticoagulant production. However, excessive ultrasound caused intracellular damage, which inhibited biomass accumulation, decreasing anticoagulant activity and even leading to cell rupture. This is the first report on the use of ultrasound to enhance anticoagulant production by Bacillus, and it provides useful information for scaling-up the process.     

Spectroscopic properties of pharmacologically active phenols

The IR Fourier-transform spectra of pharmacologically active phenol molecules in solutions in CCl₄ and in the crystalline state have been studied. Phenol derivatives with different directivities and different levels of pharmacological efficiency have been examined. Based on analysis of the IR spectra of screened phenols, the antimicrobial activity of phenols with free hydroxyl groups has been shown to be highest. The high antimicrobial activity of aminophenols is related to the formation of intramolecular hydrogen bonds. For aminophenols that are active against herpesviruses, O-H...N hydrogen bonds are formed in molecules. The main characteristic of the high antiviral activity against A-type influenza is predominance of intramolecular hydrogen bonds of the O-H...O=C type in molecules. Sulfur-containing aminophenols, which manifest activity against HIV infection, are characterized by the occurrence of hydrogen bonds that involve the participation of the OH, NH, and SO₂ groups.     

注射用针剂药物的拉曼散射光谱研究

本文从药品鉴别的角度出发,首先论述了拉曼光谱分析技术并测试了九种针剂药品的拉曼光谱,通过分析讨论相关药品的拉曼光谱得出了几点结论:(1)某些药品的拉曼峰较多,特征峰值较强,频移范围比较广,例如:氟尿嘧啶,依托泊苷,异烟肼,克林霉素磷酸酯。(2)某些药品拉曼峰较弱,或是没有明显的特征峰,例如:硫酸阿米卡星,甲氧苄啶,利巴韦林,葡萄糖依诺沙星,硫酸庆大霉素。(3)在分析频率及其相对强度时发现,在某一频率下正对的峰高和面积较大,则其相对强度较大,例如:氟尿嘧啶,异烟肼,硫酸阿米卡星,甲氧苄啶,葡萄糖依诺沙星。虽然得到的结论还不能满足对药品的品质鉴定,但通过拉曼光谱分析技术在药品鉴别中的应用,给出了一些药品的拉曼特征谱,为药品的鉴别提供了参考依据。可以说利用光谱分析技术对药品进行鉴别是完全可行的。     

Versatile Fluorescent Carbon Dots from Citric Acid and Cysteine with Antimicrobial,Anti-biofilm,Antioxidant, and AChE Enzyme Inhibition Capabilities

Nanostructured fluorescent particles derived from natural molecules were prepared by a green synthesis technique employing a microwave method. The precursors citric acid (CA) and cysteine (Cys) were used in the preparation of S- and N-doped Cys carbon dots (Cys CDs). Synthesis was completed in 3 min. The graphitic structure revealed by XRD analysis of Cys CDs dots had good water dispersity, with diameters in the range of 2–20 nm determined by TEM analysis. The isoelectric point of the S, N-doped CDs was pH value for 5.2. The prepared Cys CDs displayed excellent fluorescence intensity with a high quantum yield of 75.6?±?2.1%. Strong antimicrobial capability of Cys CDs was observed with 12.5 mg/mL minimum bactericidal concentration (MBC) against gram-positive and gram-negative bacteria with the highest antimicrobial activity obtained against Staphylococcus aureus. Furthermore, Cys CDs provided total biofilm eradication and inhibition abilities against Pseudomonas aeruginosa at 25 mg/mL concentration. Cys CDs are promising antioxidant materials with 1.3?±?0.1 μmol Trolox equivalent/g antioxidant capacity. Finally, Cys CDs were also shown to inhibit the acetylcholinesterase (AChE) enzyme, which is used in the treatment of Alzheimer’s disease, even at the low concentration of 100 μg/mL.

     

Antitumor evaluation and 3D-QSAR studies of a new series of the spiropyrroloquinoline isoindolinone/aza-isoindolinone derivatives by comparative molecular field analysis (CoMFA)

In current study, antitumor activity of two series of the newly synthesized spiropyrroloquinoline isoindolinone and spiropyrroloquinoline aza-isoindolinone scaffolds was evaluated against three human breast normal and cancer cell lines (MCF-10A, MCF-7 and SK-BR-3) and compared with cytotoxicity values of doxorubicin and colchicine as the standard drugs. It was found that several compounds were endowed with cytotoxicity in the low micromolar range. Among these two series, compounds 6i, 6j, 6k and 7l, 7m, 7n, 7o containing 3-ethyl-1H-indole moiety were found to be highly effective against both cancer cell lines ranging from \(0.080 \pm 0.001\) to \(11.91 \pm 1.39\,\upmu \hbox {M}\) in comparison with the corresponding analogs. Compared with human cancer cells, the most potent compounds did not show high cytotoxicity against human breast normal MCF-10A cells. Generally, most of the evaluated compounds 6a–l and 7a–o series showed more antitumor activity against SK-BR-3 than MCF-7 cells. Moreover, comparative molecular field analysis (CoMFA) as a popular tools of three-dimensional quantitative structure–activity relationship (3D-QSAR) studies was carried out on 27 spiropyrroloquinolineisoindolinone and spiropyrroloquinolineaza-isoindolinone derivatives with antitumor activity against on SK-BR-3 cells. The obtained CoMFA models showed statistically excellent performance, which also possessed good predictive ability for an external test set. The results confirm the important effect of molecular steric and electrostatic interactions of these compounds on in vitro cytotoxicity against SK-BR-3.     

Multiple Emulsion Templating of Hybrid Ag/SiO2 Capsules for Antibacterial Applications

Silver nanoparticles (NPs) encapsulated in amorphous silica shells are synthesized and evaluated for their antibacterial action using the Gram‐negative Escherichia coli bacterium. These inorganic capsules are synthesized using a new approach that comprises the use of oil‐in‐water‐in‐oil (O/W/O) multiple emulsions to fabricate SiO₂ capsules incorporating organically capped Ag NPs. This strategy is explored as a mean to promote the bioadhesion of the microorganisms to the silica rough surfaces while still keeping the system with a high surface area for the active metal. The results have shown that the hybrid capsules enable a slow release of cationic silver from the interior of the silica microsphere to the external medium probably through the pore channels in the shell. The antibacterial activity against E. coli is mainly determined by the Ag⁺ ion release rate, suggesting that these particulates can be employed as a robust system for prolonged used as an antimicrobial material.     

Compartmentalized Encapsulation of Two Antibiotics in Porous Nanoparticles: an Efficient Strategy to Treat Intracellular Infections

Combinatorial drug therapies emerge among the most promising strategies to treat complex pathologies such as cancer and severe infections. Biocompatible nanoparticles of mesoporous iron carboxylate metal–organic framework (nanoMOFs) are used here to address the challenging aspects related to the coincorporation of two antibiotics. Amoxicillin and potassium clavulanate, a typical example of drugs used in tandem, are efficiently coincorporated with payloads up to 36 wt%. Due to the occurrence of two distinct pore sizes/apertures within the MOF architecture, each drug is able to infiltrate the porous framework and localize within separate compartments. Molecular simulations predict drug loadings and locations consistent with experimental findings. Drug loaded nanoMOFs that are internalized by Staphylococcus aureus infected macrophages are able to colocalize with the pathogen, which in turn leads to an alleviation of bacterial infection. The data also reveal potential antibacterial properties of nanoMOFs alone as well as their ability to deliver a high payload of drugs to fight intracellular bacteria. These results pave the way toward the design of engineered “all‐in‐one” nanocarriers in which both the loaded drugs and their carrier play a role in fighting intracellular infections.