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An unusual meroterpenoid with a pyran ring (diplomeroterpenoid G) was isolated from the methanolic extract of the aerial part of Mimosa pudica together with fourteen known compounds: ...apigenin, tricin, quercetin, chryoeriol, 7,4′-dihydroxylfavone, 5,7,2′,5′-tetrahydroxyflavone, isoorientin, quercetin 3-O-β-d-xylopyranoside, quercetin 3-O-α-l-arabinofuranoside, quercetin 3-O-β-d-glucopyranoside, methylinositol, betulinic acid, oleanolic acid, and β-sitosterol 3-O-β-d-glucopyranoside. Their structures were elucidated by a careful analysis of the spectroscopic data (UV, IR, 1D and 2D NMR), high resolution mass spectrometry, electronic circular dichroism, DFT calculations, and by comparison of their data with those reported in the literature. The antibacterial potential of the methanolic extract and some of the isolated compounds were evaluated on five strains of bacteria. Compound 6 showed the most potent antibacterial activity against Proteus mirabilis (MIC = 32 µg/mL).
This review clearly analyzes the effects of Mw, DD, pH, chemical modification, and chitosan-based composites on the antibacterial properties and mechanism of chitosan. Importantly, this review ...provides a valuable solution to the current problems faced by the current research of chitosan antibacterial activity.
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Chitosan has fascinating antibacterial activity, good biodegradation, outstanding biocompatibility, non-toxicity and excellent physical and chemical properties. As a result, chitosan has been widely used in the field of antibacterial. Chitosan and its derivatives show antibacterial activity against fungi, gram-positive bacteria and gram-negative bacteria. In recent years, there have been some reviews about the antibacterial activity of chitosan and its derivatives. This review adds many valuable concerns on the basis of those previous reviews. For example, composite of chitosan and metal, composite of chitosan and metal oxide, etc. This review will systematically analyze various influencing factors of chitosan, so as to clearly summarize the antibacterial mechanism of chitosan. Finally, the challenges and prospects of chitosan-based materials as antimicrobial agents are assessed and commented.
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Metal chalcogenides have been intensively investigated as antibacterial agents due to their unique structures and superior photoactivities. Herein, various structures of copper ...sulfide (CuS), a metal chalcogenide, such as microspheres (MSs), nanosheets (NSs), and nanoparticles (NPs), were developed in this work for antibacterial applications. A hydrothermal process was utilized to synthesize CuS MSs, CuS NSs, and CuS NPs. Under simulated solar light and near-infrared (NIR) light irradiation, the antibacterial behaviors, reactive oxygen species (ROS) production, and light-driven antibacterial mechanisms of CuS MSs, CuS NSs, and CuS NPs were demonstrated with the bacterium Escherichia coli (E. coli). Bacterial growth curves and ROS generation tests indicated that CuS NSs and CuS NPs had higher light-driven antibacterial activities than that of CuS MSs. ROS of hydroxyl (·OH) and superoxide anion radicals (O2−) were investigated via an electron spin resonance (ESR) spectroscopic analysis by respectively incubating CuS MSs, CuS NSs, and CuS NPs with E. coli under simulated solar light irradiation. Furthermore, E. coli incubated with CuS NPs and CuS NSs showed substantial bacterial degradation after NIR laser irradiation, which was attributed to their photothermal killing effects. Light-driven antibacterial mechanisms of CuS NSs and CuS NPs were investigated, and we discovered that under simulated solar and NIR light irradiation, CuS NSs and CuS NPs produced photoinduced electrons, and the copper ions and photoinduced electrons then reacted with atmospheric moisture to produce hydroxide and superoxide anion radicals and heat, resulting in bacterial mortality.
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•NH2-MIL-125(Ti) was partially modified by –NA chromophore group.•Low proportion modified Ti-MOFs achieve a wide spectral response.•Boosted activity for both Cr(VI) reduction and ...antibacterial was achieved.•A bactericidal mechanism for generating singlet oxygen was put forward.
A NA/NH2-MIL-125(Ti) homojunction was prepared by grafting 1-naphthylamine (–NA, a chromophore group) on the –NH2 group in part of NH2-MIL-125(Ti). In-depth investigation of the optical and structural variations was carried out. The results indicated that the lattice structure of NH2-MIL-125(Ti) was well preserved after –NA modification. Whereas NA/NH2-MIL-125(Ti) with 10% –NA ratio exhibited optimal photocurrent response and the lowest charge separation efficiency. In photocatalytic activity experiments, NA/NH2-MIL-125(Ti) showed excellent activity with more than 99% Cr(VI) reduction and 99.999% bactericidal efficiency within 60-min irradiation. Furthermore, the photocatalysts showed good stability after 5 cyclic runs. Then, a mechanism about how the bacteria were killed was proposed, which was mainly contributed by the destruction of the cell membrane by photogenerated singlet oxygen (1O2). The results of this work will open a new route to the synthesis of MOFs for multiple photocatalytic applications.
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•Novel cationic antibacterial CGCDs from chlorhexidine gluconate were obtained.•The antibacterial activity increased as the particle size of the CDs decreased.•Small-scale CDs can ...more easily interfere with DNA molecules.•The antibacterial CGCDs exhibited prominent biocompatibility.
Carbon dots (CDs) have a profound effect on elimination of bacteria, fungi, and viruses, but the lack of an exact mechanism to interact with bacterial cells limits their development. Herein, we separated the CDs derived from chlorhexidine gluconate into three groups with uniformly small-scale, middle-scale, and large-scale particle sizes by using different molecular weight cut-off membranes. These positively charged particles exhibit significant antibacterial activity against the Gram-negative bacteria Escherichia coli and the Gram-positive bacteria Staphylococcus aureus; they can cause an increase in bacterial cell permeability, synergistic destabilization, and broken integrity of the plasma membrane. Impressively, we found that antibacterial activity increases as the size of the CDs decreases. This phenomenon may stem from the differences in cellular uptake and distribution of CDs in the plasma membrane or restriction between the polar functional group and DNA molecule. Our study of the size effect as a target may improve the understanding of killing microorganisms by antibacterial CD drugs.
Successful development of polypyrrole sensitized ZnF2O4/g-C3N4 n-n heterojunction towards Ciprofloxacin degradation, photocatalytic H2 generation and antibacterial activity.
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Fusion of ...heterogeneous photocatalysts with conducting polymers has paid a rising stratagem in the field of photocatalysis owing to its biocompatibility and environment friendliness. In this work a series of polypyrrole (PPY) sensitized zinc ferrite/graphitic carbon nitride (ZFCN) n-n heterojunction (ZFCN@10PPY, ZFCN@20PPY, and ZFCN@30PPY) nanocomposite were fabricated by in-situ polymerization method. Due to low band gap of polypyrrole, it behaves as a photo-sensitizer, supplies surplus numbers of electrons to ZnFe2O4/g-C3N4 n-n heterojunction and improves the photocatalytic performance. The fabricated ZFCN@20PPY exhibits highest photocatalytic activity in comparison to others nanocomposites. The superior photocatalytic performance of ZFCN@20PPY was ascribed to the tunable band structure, synergistic effect of broad absorption upto NIR region, delayed electron-hole recombination and efficient charge transfer across the junction interface which has been well confirmed from UV–Vis DRS, PL and EIS measurement. Further the photocatalytic activity of ZFCN@20PPY was supported by both n-type and p-type photocurrent density i.e. 2.4 and 3.9 mA/cm2 respectively. ZFCN@20PPY shows good photocatalytic performance towards ciprofloxacin degradation (92%) and generation of hydrogen energy (567 μmol). Along with pollutant degradation and energy production ZFCN@20PPY also shows its potential towards antibacterial activities against human pathogenic bacteria like Escherichia coli. These newly designed polymer sensitized n-n heterojunction may offer a promising strategy for maximum light absorption and be authoritative in meeting the environmental claims in the future.
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The current study reports on investigation of pure ZnO nanoparticles (NPs) and Ag/ZnO nanocomposites (NCs) in which Ag noble metal mixed at different concentration (0.5%, 1.0% and ...2.0%) in the presence of Ocimum tenuiflorum (Tulsi) plant seed extract (PSE). The structural, optical, electrical and chemical properties of green synthesized NPs and NCs have been monitored using diffrent analytical techniques such as XRD, SEM, TEM, EDX, UV-Vis, FTIR, EIS and EPR. Further the antimicrobial and dye degradation activity of green synthesized pure ZnO-NPs and 0.5%, 1.0% and 2.0% Ag/ZnO-NCs had been examined. The result showed that synthesized 1.0% Ag/ZnO-NCs possessed a good photocatalytic and antimicrobial activity as compared to pure ZnO-NPs and other prepared Ag/ZnO-NCs. Based on the outcomes of reactive oxygen species (ROS) detection, the improved antimicrobial and dye degradation activities of Ag/ZnO-NCs were attributed due to more ROS formation, as Ag particles on the surface of ZnO are in support of electron transfer, which could improve ROS formation by one-electron reduction of oxygen.
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•Clove essential oil (CEO) was encapsulated into chitosan nanoparticles.•FTIR, X-ray diffraction and DSC confirmed the successful loading of CEO.•Sizes of CEO-loaded nanoparticles ...ranged from 223 to 444 nm.•Encapsulation improved the antioxidant and antibacterial activity of CEO.
One of the recent trends in the food industry is application of natural antioxidant/antimicrobial agents. In this study, essential oil of clove buds was extracted and encapsulated in chitosan nanoparticles using a two-step technique of emulsion-ionic gelation. A good retention rate (55.8–73.4 %) of clove essential oil (CEO) loaded in chitosan nanoparticles was confirmed. Also, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses revealed the success of CEO encapsulation. Scanning electron microscopy (SEM) images illustrated regular distribution and spherical shape of nanoparticles with a size range of 223−444 nm. The antioxidant activity of CEO-loaded chitosan nanoparticles was higher than free CEO. Similarly, CEO-loaded chitosan nanoparticles had a high antibacterial activity against L. monocytogenes and S. aureus (inhibition halo diameter of 4.80–4.78 cm). This technique could improve the efficiency of CEO in food products and a delivery system for novel applications such as active packaging.
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•Ultralow-cost and sustainable complex coacervate-based adhesive is reported.•Adhesives consist of interpenetrating positively charged TA-PAE complex clusters.•Coacervates overcome ...the challenges of adhesion in harsh underwater environments.•“TAPA-pulp” attraction promotes wet and cohesive strength of coacervate matrix.•Integrated super-high adhesive capability and antibacterial activity is achieved.
Bioinspired underwater adhesives with tough and stable performance are increasingly in demand for biomedical and engineering applications. However, the current methods of synthesizing them usually require sophisticated chemical conjugation or modification and expensive adhesive building blocks. Here, by taking advantage of the catecholic and polyelectrolyte features of mussel foot proteins, we report a facile yet powerful strategy to the development of a strong and cost-effective self-coacervating adhesive based on a coacervation-induced adhesion mechanism. The adhesive comprises a low-cost, commercially available cationic polyelectrolyte—polyamidoamine-epichlorohydrin (PAE)—that is crosslinked in situ by naturally occurring dendritic molecules of tannic acid (TA). A complex coacervate gel (TAPA) is formed after directly mixing pyrogallol-containing TA with PAE polycation. With the gel matrix serving as a robust adhesive when applied underwater to various substrates owing to its synergistic azetidinium–phenolic electrostatic and hydrogen bonding interactions. Compared to previously reported catechol-based adhesives, the polyelectrolyte coacervate gel has a widely tunable underwater adhesive strength (50.8 ± 6.8 to 604.8 ± 9.5 kPa) in wide ranges of pH (3–11) and ionic strength (0–1 M NaCl) and displays reusable adhesiveness (<10 cycles). This adhesive strength increases substantially in basic conditions (pH > 9), which trigger the self-crosslinking of PAE chains. By synergistically combining electrostatic adsorption and macroscopic-scale interactions, the incorporated nanocellulose fillers further contribute to the strong cohesion of coacervate adhesives. The easy-to-prepare TAPA adhesive also has excellent antibacterial activity. This in-situ formation strategy opens an innovative and facile route to mimic the self-coacervation and adhesion stability of biomimetic source, leading to a multifunctional bonding solution for biological/engineering adhesive applications.
