The performance evaluation of Eugenol and Linalool microencapsulated by PLA on their activities against pathogenic bacteria

The essential oils (EOs) have great potential as a natural alternative to preserve foods against spoilage and poisoning pathogens, and they are healthy and safe. Their incorporation in polymers has been of great interest in active packaging for preserving fresh food. This work aims to evaluate the effect of encapsulation of two different oils (linalool and eugenol) as antimicrobial agent activity against Escherichia coli, Salmonella enterica subsp. enterica serovar Choleraesuis, Staphylococcus aureus, and Listeria monocytogenes. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) evaluated the EOs and their capsules with polylactic acid biopolymer. It was analyzed using the agar disc-diffusion testing method to determine the inhibition zones. The active release curves were constructed to elucidate activity efficiency. The minimum bactericidal concentration (MBC) values on E. coli, Salmonella, S. aureus, and L. monocytogenes were 0.39%, 3.13%, 0.78%, 1.56%, and 0.39%, 12.50%, 0.39%, and 12.50%, for the eugenol and linalool, respectively. To eugenol against E. coli (60 mm) and linalool against Salmonella (32 mm) exhibited relevant inhibition zones results. The EOs released promoted the inhibition zone by the volume of the EOs released over 24 h (2.2 μL/L to eugenol and 1.5 μL/L to linalool). Moreover, UV–vis results determined the active release reporting that the capsules have a prolonged efficiency, continuing to release the active up to 40 days, indicating potential application in active food packaging, extending the shelf life of food.     

Green preparation of hollow mesoporous silica nanosphere inside-loaded gold nanoparticles and the catalytic activity

In this work, an active nano-catalyst with gold nanoparticles loaded in hollow mesoporous silica nanospheres (HMSNs/Au) was prepared by a one-pot sol-gel method, in which gold ions were loaded in hollow mesoporous silica spheres followed by sodium alginate reduction. The characterization of the HMSNs/Au were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N₂ adsorption–desorption isotherms (BET). The high catalytic activity of HMSNs/Au, denoted as apparent turn-over frequency (TOF), was detected by UV-Vis spectrophotometer for the catalytic reduction of 4-nitrophenol (74.5 h^?1) and 2-nitrophenol (108.7 h^?1) in the presence of sodium borohydride solution due to the small gold nanoparticles size and overall exposure of active sites. It is expected that this ecofriendly approach to prepare inorganic composited nanoparticles as high active catalysts based on hollow mesoporous materials was a promising platform for loading noble metal nanoparticles.     

Exploration of the Antimicrobial Effects of Benzothiazolylthiazolidin-4-One and In Silico Mechanistic Investigation

Background: Infectious diseases still affect large populations causing significant morbidity and mortality. Bacterial and fungal infections for centuries were the main factors of death and disability of millions of humans. Despite the progress in the control of infectious diseases, the appearance of resistance of microbes to existing drugs creates the need for the development of new effective antimicrobial agents. In an attempt to improve the antibacterial activity of previously synthesized compounds modifications to their structures were performed. Methods: Nineteen thiazolidinone derivatives with 6-Cl, 4-OMe, 6-CN, 6-adamantan, 4-Me, 6-adamantan substituents at benzothiazole ring were synthesized and evaluated against panel of four bacterial strains S. aureus, L. monocytogenes, E. coli and S. typhimirium and three resistant strains MRSA, E. coli and P. aeruginosa in order to improve activity of previously evaluated 6-OCF₃-benzothiazole-based thiazolidinones. The evaluation of minimum inhibitory and minimum bactericidal concentration was determined by microdilution method. As reference compounds ampicillin and streptomycin were used. Results: All compounds showed antibacterial activity with MIC in range of 0.12–0.75 mg/mL and MBC at 0.25–>1.00 mg/mL The most active compound among all tested appeared to be compound 18, with MIC at 0.10 mg/mL and MBC at 0.12 mg/mL against P. aeruginosa. as well as against resistant strain P. aeruginosa with MIC at 0.06 mg/mL and MBC at 0.12 mg/mL almost equipotent with streptomycin and better than ampicillin. Docking studies predicted that the inhibition of LD-carboxypeptidase is probably the possible mechanism of antibacterial activity of tested compounds. Conclusion: The best improvement of antibacterial activity after modifications was achieved by replacement of 6-OCF₃ substituent in benzothiazole moiety by 6-Cl against S. aureus, MRSA and resistant strain of E. coli by 2.5 folds, while against L. monocytogenes and S. typhimirium from 4 to 5 folds.     

In Vitro Antimicrobial Activity of Lavender,Mint, and Rosemary Essential Oils and the Effect of Their Vapours on Growth of Penicillium spp. in a Bread Model System

The chemical composition, antioxidant activity, and antimicrobial properties of three commercially available essential oils: rosemary (REO), lavender (LEO), and mint (MEO), were determined in the current study. Our data revealed that the major components of REO, MEO, and LEO were 1,8-cineole (40.4%), menthol (40.1%), and linalool acetate (35.0%), respectively. The highest DPPH radical-scavenging activity was identified in MEO (36.85 ± 0.49%) among the investigated EOs. Regarding antimicrobial activities, we found that LEO had the strongest inhibitory efficiencies against the growth of Pseudomonas aeruginosa and Candida (C.) tropicalis, MEO against Salmonella (S.) enterica, and REO against Staphylococcus (S.) aureus. The strongest antifungal activity was displayed by mint EO, which totally inhibited the growth of Penicillium (P.) expansum and P. crustosum in all concentrations; the growth of P. citrinum was completely suppressed only by the lowest MEO concentration. The lowest minimal inhibitory concentrations (MICs) against S. enterica, S. aureus, and C. krusei were assessed for MEO. In situ analysis on the bread model showed that 125 µL/L of REO exhibited the lowest mycelial growth inhibition (MGI) of P. citrinum, and 500 µL/L of MEO caused the highest MGI of P. crustosum. Our results allow us to make conclusion that the analysed EOs have promising potential for use as innovative agents in the storage of bakery products in order to extend their shelf-life.     

Methylene Blue/Carbon Dots Composite with Photothermal and Photodynamic Properties: Synthesis,Characterization, and Antibacterial Application

Photodynamic therapy and photothermal therapy provide new ways to combat antibiotic resistance. In this research, methylene blue (MB) as an effective photosensitizer was conjugated with carbon quantum dots (CQDs), the composite product not only possessed good antibacterial properties against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) due to excellent singlet oxygen (¹O₂) production rate and light heat transfer performance, but also showed good biocompatibility. Combined with 808 nm and 660 nm laser irradiation, the minimum bactericidal concentration of CQDs-MB towards S. aureus and E. coli was 5 μm . Therefore, this study provides a potential candidate material based on CQDs for clinical applications.     

中空纳米二氧化硅微球的制备及表征

本文介绍了一种制备中空纳米二氧化硅微球的新方法。利用模板首先合成介孔纳米二氧化硅微球,再用水热反应法,成功制备了非功能化和巯基、氨基功能化中空纳米二氧化硅微球。利用透射电子显微镜,热重分析等手段对其形貌进行了表征。另外,对中空介孔纳米二氧化硅微球的形成机制进行了探讨。     

Synthesis,characterization, and antimicrobial evaluation of some novel anthracene heterocycles derivatives

A series of novel heterocyclic compounds containing anthracene moiety was synthesized. Reaction of (11R,15S)-9,10-dihydro-9,10-[3,4]furanoanthracene-12,14-dione with 2-cyanoacetohydrazide gave 2-cyano-pyrroloanthracen acetamide (1) , which acts as an adaptable material for the synthesis of new heterocyclic compounds. The synthesized compounds were examined for their antimicrobial activity against Escherichia coli and Staphylococcus aureus via p-iodonitrotetrazolium violet formazon assay. The results exhibited great activity against the tested strains with a minimum bactericidal concentration range from 0.636 to 3.8 mg/mL) and 0.159 to 3.6 mg/mL for E coli and S aureus, respectively. Interestingly, the highest activity was recorded for chromene derivative (6) against both strains.     

Chemical Constitution and Antimicrobial Activity of Kefir Fermented Beverage

Kefir beverage (KB) is a fermented milk initiated by kefir grains rich with starter probiotics. The KB produced in this study seemed to contain many chemical compounds elucidated by gas chromatography–mass spectrometry (GC-MS) and IR spectra. These compounds could be classified into different chemical groups such as alcohols, phenols, esters, fatty esters, unsaturated fatty esters, steroids, polyalkenes, heterocyclic compounds and aromatic aldehydes. Both KB and neutralized kefir beverage (NKB) inhibited some pathogenic bacteria including Escherichia coli ATCC11229 (E. coli), Listeria monocytogenes ATCC 4957 (L. monocytogenes), Bacillus cereus ATCC 14579 (B. cereus), Salmonella typhimurium ATCC 14028 (Sal. typhimurium) as well as some tested fungal strains such as Aspergillus flavus ATCC 16872 (A. flavus) and Aspergillus niger ATCC 20611 (A. niger), but the inhibitory activity of KB was more powerful than that obtained by NKB. It also appeared to contain four lactic acid bacteria species, one acetic acid bacterium and two yeast species. Finally, the KB inhibited distinctively both S. aureus and Sal. typhimurium bacteria in a brain heart infusion broth and in some Egyptian fruit juices, including those made with apples, guava, strawberries and tomatoes.     

Preparation of quaternarized N-halamine-grafted graphene oxide nanocomposites and synergetic antibacterial properties

At present, frequent outbreaks of bacteria and viruses have seriously affected people's normal lives. Therefore, the study of broad-spectrum antibacterial nanocomposites is very promising. However, most antibacterial materials have some disadvantages, such as single bactericidal mechanisms and unrepeatable use. Based on the current situation, a kind of nanocomposite with three structures of graphene oxide (GO), quaternary ammonium salt (QAs) and N-halamine was prepared, which showed synergistic effect to improve antibacterial activity and combined with a variety of sterilization mechanisms. Meanwhile, GO can provide richer ways of sterilization and high specific surface area, which is conducive to the grafting of quaternarized N-halamine. The advantages of physical sterilization of GO, charge adsorption of QAs, reuse of N-halamine and efficient sterilization are fully utilized. The results showed that the quaternarized N-halamine-grafted GO was obtained successfully. GO grafted with quaternarized N-halamine polymer showed strong speedy bactericidal activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) (99%). It had good storage and regeneration properties.     

可用于色谱固定相的介孔氧化硅球材料的合成

采用非离子型嵌段高分子表面活性剂EO₂₀PO₃₀EO₂₀ (P65)为结构导向剂, 正硅酸乙酯为硅源, 在酸性介质中, 静置法制备了微米级介孔氧化硅球. 通过改变合成温度、反应时间或者无机盐KCl的加入量, 可以调节介孔氧化硅球的直径(9.0～17.6 μm); 加入1,3,5-三甲苯(TMB)或者调节水热温度, 可以调节介孔氧化硅球的孔径(2.3～4.8 nm). 采用X射线衍射(XRD)、N₂吸附-脱附、扫描电镜(SEM)、激光散射粒度分布和对溶菌酶的吸附等方法, 对介孔氧化硅球的结构、孔性质、形貌、吸附性质等进行了表征. 实验发现, 孔径较小的介孔氧化硅球(≤4.3 nm)对溶菌酶的吸附不明显(≤42 mg/g), 而孔径(4.8 nm)大于溶菌酶直径的材料对溶菌酶有较大的吸附量(192 mg/g), 说明孔径均匀可调的介孔氧化硅球材料可以很好地用作体积排阻色谱柱的固定相.     

Morphological and structural evolution of mesoporous silicas in a mild buffer solution and lysozyme adsorption

Mesoporous silicas with various morphologies and structures were synthesized with the aid of 2,2,4-trimethylpentane (TMP) in the presence of nonionic surfactant P123 [(EO)20(PO)70(EO)20] as a structure-directing agent under mild reaction conditions (HAc-NaAc buffer solution, pH 4.4). The ropelike particles formed by end-to-end interconnected nanorods were obtained at a TMP/P123 weight ratio of 0.5. It is noteworthy to mention that the mesoporous nanorods have channels running parallel to the short axis. The silica hollow spheres can be obtained at a higher TMP/P123 weight ratio because of the fusion of the primary nanorods around the interface of the O/W emulsion. Initial synthesis temperatures of 15, 25, and 40 degrees C can lead to mesoporous silicas with highly ordered 2D hexagonal mesostructure, vesicular mesostructure, and mesostructured cellular foams (MCF), respectively. The mesoporous silicas exhibit high adsorption capacity (up to 536 mg g(-1)) and very rapid (<5 min to reach equilibrium) lysozyme immobilization. More importantly, it is revealed that mesoporous silica hollow spheres with rugged surfaces can greatly accelerate the adsorption rate of the enzyme during the adsorption process.     

Facile synthesis of monodisperse microspheres and gigantic hollow shells of mesoporous silica in mixed water-ethanol solvents

Mesoporous silica materials with a variety of morphologies, such as monodisperse microspheres, gigantic hollow structures comprising a thin shell with a hole, and gigantic hollow structures consisting of an outer thin shell and an inner layer composed of many small spheres, have been readily synthesized in mixed water-ethanol solvents at room temperature using cetyltrimethylammonium bromide (CTAB) as the template. The obtained mesoporous silica generally shows a disordered mesostructure with typical average pore sizes ranging from 3.1 to 3.8 nm. The effects of the water-to-ethanol volume ratio (r), the volume content of tetraethyl orthosilicate TEOS (x), and the CTAB concentration in the solution on the final morphology of the mesoporous silica products have been investigated. The growth process of gigantic hollow shells of mesoporous silica through templating emulsion droplets of TEOS in mixed water-ethanol solution has been monitored directly with optical microscopy. Generally, the morphology of mesoporous silica can be regulated from microspheres through gigantic hollow structures composed of small spheres to gigantic hollow structures with a thin shell by increasing the water-to-ethanol volume ratio, increasing the TEOS volume content, or decreasing the CTAB concentration. A plausible mechanism for the morphological regulation of mesoporous silica by adjusting various experimental parameters has been put forward by considering the existing state of the unhydrolyzed and partially hydrolyzed TEOS in the synthesis system.     

Variations in the radiation sensitivity of foodborne pathogens associated with complex ready-to-eat food products

Foodborne illness outbreaks and product recalls are occasionally associated with ready-to-eat (RTE) sandwiches and other “heat and eat” multi-component RTE products. Ionizing radiation can inactivate foodborne pathogens on meat and poultry, fruits and vegetables, seafood, and RTE meat products. However, less data are available on the ability of low-dose ionizing radiation, doses under 5 kGy typically used for pasteurization purposes, to inactivate pathogenic bacteria on complex multi-component food products. In this study, the efficacy of ionizing radiation to inactivate Salmonella spp., Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O157:H7, and Yersinia enterocolitica on RTE foods including a “frankfurter on a roll”, a “beef cheeseburger on a bun” and a “vegetarian cheeseburger on a bun” was investigated. The average D-10 values, the radiation dose needed to inactivate 1 log₁₀ of pathogen, by bacterium species, were 0.61, 0.54, 0.47, 0.36 and 0.15 kGy for Salmonella spp., S. aureus, L. monocytogenes, E. coli O157:H7, and Y. enterocolitica, respectively when inoculated onto the three product types. These results indicate that irradiation may be an effective means for inactivating common foodborne pathogens including Salmonella spp, S. aureus, L. monocytogenes, E. coli O157:H7 and Y. enterocolitica in complex RTE food products such as ‘heat and eat” sandwich products.     

Evaluation of Anthocyanin Content,Antioxidant Potential and Antimicrobial Activity of Black,Purple and Blue Colored Wheat Flour and Wheat-Grass Juice against Common Human Pathogens

The present study aimed to analyze the antioxidant and antimicrobial activity of anthocyanins extracted from colored wheat flour and wheat-grass juice against human pathogens. The total anthocyanin content and antioxidant potential in colored wheat flour and wheat-grass juice extracts were significantly higher than white flour and wheat-grass juice extracts. Ultra-performance liquid chromatography showed the maximum number of anthocyanin peaks in black wheat, with delphinidin-3-o-galactoside chloride, delphinidin-3-o-glucoside chloride, and cyanindin-3-o-glucoside chloride as the major contributors. Among flour extracts, maximum zones of inhibition against Staphylococcus aureus (MTCC 1934), Pseudomonas aeruginosa (MTCC 1434), Escherichia coli, and Candida albicans (MTCC 227) were produced by black flour extract, having the highest anthocyanin content. It exhibited a minimum microbicidal concentration (MMC) of 200 mg/mL against E. coli and C. albicans; and 100 and 150 mg/mL against S. aureus and P. aeruginosa, respectively. Black and purple flour extracts exhibited a minimum inhibitory concentration (MIC) of 50 mg/mL against S. aureus and P. aeruginosa. White flour extracts did not show MMC against E. coli and C. albicans. Among wheat-grass juice extracts, black wheat-grass was most effective and showed an MIC of 100–150 mg/mL against all pathogens. It exhibited an MMC of 200 mg/mL against S. aureus and P. aeruginosa. Hence, anthocyanin-rich colored wheat could be of nutraceutical importance.     

A General Route to Hollow Mesoporous Rare‐Earth Silicate Nanospheres as a Catalyst Support

Hollow mesoporous structures have recently aroused intense research interest owing to their unique structural features. Herein, an effective and precisely controlled synthesis of hollow rare‐earth silicate spheres with mesoporous shells is reported for the first time, produced by a simple hydrothermal method, using silica spheres as the silica precursors. The as‐prepared hollow rare‐earth silicate spheres have large specific surface area, high pore volume, and controllable structure parameters. The results demonstrate that the selection of the chelating reagent plays critical roles in forming the hollow mesoporous structures. In addition, a simple and low‐energy‐consuming approach to synthesize highly stable and dispersive gold nanoparticle–yttrium silicate (AuNPs/YSiO) hollow nanocomposites has also been developed. The reduction of 4‐nitrophenol with AuNPs/YSiO hollow nanocomposites as the catalyst has clearly demonstrated that the hollow rare‐earth silicate spheres are good carriers for Au nanoparticles. This strategy can be extended as a general approach to prepare multifunctional yolk–shell structures with diverse compositions and morphologies simply by replacing silica spheres with silica‐coated nanocomposites.     

Diazenyl schiff bases: Synthesis,spectral analysis,antimicrobial studies and cytotoxic activity on human colorectal carcinoma cell line (HCT-116)

A series of diazenyl schiff bases have been synthesized by reaction of salicylaldehyde containing azo dyes with various substituted aniline derivatives in the presence of acetic acid as catalyst. The structures of diazenyl derivatives were determined by FTIR, UV–vis, ¹H NMR, ¹³C NMR, CHN analysis, fluorimetric and mass spectroscopic studies. The synthesized derivatives were screened for their in vitro antimicrobial activity against various Gram-positive (S. aureus, B. subtilis, B. cereus), Gram-negative (S. typhi, S. enterica, E. coli, P. aeruginosa) bacterial and fungal (C. albicans, A. niger and A. fumigatus) strains, using cefadroxil (antibacterial) and fluconazole (antifungal) as standard drugs. The diazenyl schiff bases were also screened for their cytotoxicity against human colorectal carcinoma cell line (HCT-116) using 5-fluorouracil as standard drug by Sulforhodamine-B Stain (SRB) assay. The schiff bases exhibited significant activity toward both Gram-positive, Gram-negative bacterial and fungal strains. Most of the synthesized derivatives showed high activity against S. enterica. 4-((2,5-Dichlorophenyl)diazenyl)-2-((3-bromophenylimino)methyl)phenol (SBN-40) was found to be very active against S. aureus, B. cereus and E. coli, with MIC = 0.69 (µM/ml × 10²). The compound 4-((2-bromophenyl)diazenyl)-2-((4-nitrophenylimino)methyl)phenol (SBN-13) possessed comparable activity (IC₅₀ = 7.5 µg/ml) to the standard drug 5-fluorouracil (IC₅₀ = 3.0 µg/ml) against human colorectal carcinoma cell line (HCT-116).     

Microporous Silica Hollow Nanospheres Templated by Anionic Polypeptide

Anionic polypeptide, the poly(sodium L-glutamate), was applied to fabricate microporous silica hollow nanospheres templated by the secondary structures of the polypeptide as porogens. In the synthesis, 3-aminopropyltrimethoxysilane (APMS) and tetraethyl orthosilicate (TEOS) were used as the silica sources, and the coassembly followed the mechanism of the anionic surfactant-templated mesoporous silica (AMS) through a S_-N₊-I_- pathway, where S indicates the anionic polypeptide, I indicates inorganic precursors (TEOS), and N indicates costructure-directing agent (APMS), which interacted with the negatively charged anionic polypeptide secondary structures electrostatically and cocondensed with silica source to form the silica framework. The product was subjected to characterizations of X-ray diffraction (XRD), infrared (IR) spectroscopy, thermogravimetric (TG) analysis, scanning electron microscopy (SEM), transmitted electron microscopy (TEM), and nitrogen adsorption-desorption measurement. It was found that the pH value of the synthesis solution was an important factor to the morphological control of the silica products. Besides the microporous hollow nanospheres, microporous submicron silica solid and hollow spheres were also obtained facilely by changing the synthesis parameters. Our study further implied that anionic polypeptides, which were able to control mineralization of calcium carbonate and calcium phosphate, could also induce silica condensation in the presence of proper silica precursors. It was also expected that functional calcium carbonate (phosphate)/silica-nanocomposite materials would be fabricated under the control of the anionic polypeptide.     

Synthesis and Antibacterial Activity of New Azole,Diazole and Triazole Derivatives Based on p-Aminobenzoic Acid

The p-aminobenzoic acid was applied for the synthesis of substituted 1-phenyl-5-oxopyrrolidine derivatives containing benzimidazole, azole, oxadiazole, triazole, dihydrazone, and dithiosemicarbazide moieties in the structure. All the obtained compounds were evaluated for their in vitro antimicrobial activity against Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Salmonella enteritidis, Escherichia coli, and Pseudomonas aeruginosa by using MIC and MBC assays. This study showed a good bactericidal activity of γ-amino acid and benzimidazoles derivatives. The antimicrobial activity of the most promising compounds was higher than ampicillin. Furthermore, two benzimidazoles demonstrated good antimicrobial activity against L. monocytogenes (MIC 15.62 µg/mL) that was four times more potent than ampicillin (MIC 65 µg/mL). Further studies are needed to better understand the mechanism of the antimicrobial activity as well as to generate antimicrobial compounds based on the 1-phenyl-5-oxopyrrolidine scaffold.     

Hollow mesoporous silica sphere-embedded composite separator for high-performance lithium-ion battery

Journal of Solid State Electrochemistry - A high-performance composite separator based on hollow mesoporous silica spheres, poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), and...     

Antibacterial Activity of a Kind of Novel Schiff Base and Its 3d,4f Complexes

The microcalorimetric method was used to study the antibacterial activity on the bacteria's multiplying metabolism and the non-multiplying metabolism. The metabolism thermogenic curves of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), under the action of the synthesized Schiff base and its 3d,4f complexes (2L, 2LZnYb), were obtained. The results showed that the multiplying metabolism and the non-multiplying metabolism of bacteria could be analyzed by the thermogenic curves using the thermokinetic equations. On the multiplying metabolism, the two compounds (2L, 2LZnYb) have strong activity for E. coli. (IC₅₀ (half-inhibitory concentration) is 6.1 and 5.1 mg·L⁻¹, respectively) and weak activity for S. aureus (IC₅₀ is 310.1 and 595.9 mg·L⁻¹, respectively). The introduction of Zn and Yb with the compound slightly increased the inhibition on the multiplying metabolism of E. coli but greatly decreased the effect on that of S. aureus. The activity of these two compounds showed great difference on the non-multiplying metabolism. Regardless of E. coli or S. aureus, 2L showed a notable inhibition and MSC₅₀ (the minimum stationary-cidal concentration 50) of 2L was 6.4 and 209.7 mg·L⁻¹ for the two microorganisms, respectively. Thus, 2L may become a novel kind of potential antibacterial candidate.