Antibiotic Resistance
In article number 2104885, Runhui Liu, Wei Jiang, Jie Cai, and co‐workers construct quaternized polysaccharide‐based cationic micelles with outstanding biocompatibility, ...excellent broad‐spectrum antimicrobial ability and low propensity for resistance, effective inhibition and eradication of mature bacterial biofilms, and that accelerate MRSA‐infected biofilms wound healing, which provides a new strategy to combat the global health crisis of antibiotic resistance.
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•Quaternary ammonium groups were successfully grafted onto pine bark.•Initial NaOH concentration played an important role in the modification process.•The maximum capacity for ...vanadium was found to be 35 mg/g.•Modified pine bark can be used as a cost-effective adsorbent for vanadium removal.
Chemically modified pine bark was synthesized by using glycidyl trimethyl ammonium chloride (GTMAC) in the presence of sodium hydroxide. Optimization of the modification parameters was performed in order to maximize vanadium removal. Parameters included the initial NaOH concentration (0.01–2% w/v), GTMAC dosage (0.0067–0.0805 mol/g), modification time (1–6 h), modification temperature (40–80 ℃) and volume (25–100 mL). The optimal modification conditions were found to be 0.1% NaOH (w/v), 0.0134 mol/g GTMAC, 3 h and 60 ℃. The initial NaOH concentration played the most important role in successful modification while the GTMAC/NaOH ratio and volume had no significant effect under the studied conditions. Leaching of organic substances from the modified product was minor in comparison with raw pine bark. XPS analysis confirmed that quaternary nitrogen was successfully grafted onto the pine bark and that the BET surface area increased in the modification. The maximum vanadium adsorption capacity of the optimized product was found to be 32.3–35.0 mg/g at different temperatures (20 ℃, 15 ℃ and 5 ℃) at pH 4 with a contact time of 24 h, and the adsorption data was in very good agreement with the Freundlich and Redlich-Peterson models. The adsorption kinetics can be described well by the Elovich equation. Fitting the kinetic data with intra-particle diffusion and Boyd models showed that the adsorption process was controlled by both film and intra-particle diffusion, while intra-particle diffusion was the rate-limiting step. Regeneration studies demonstrated that, as a recyclable product, modified pine bark can be used effectively in real industrial processes for vanadium removal.
Infectious disease caused by methicillin-resistant Staphylococcus aureus (MRSA) seriously threatens public health. The design of antimicrobial peptide mimics (AMPMs) based on natural products (NPs) ...is a new strategy to kill MRSA and slow the development of drug resistance recently. Here, we reported the design and synthesis of novel AMPMs based on harmane skeleton. Notably, compound 9b exhibited comparable or even better anti-MRSA activity in vitro and in vivo with minimum inhibitory concentration (MIC) of 0.5–2 μg/mL than the positive drug vancomycin. The highly active compound 9b not only showed low cytotoxicity, no obvious hemolysis and good plasma stability, but also presented low tendency of developing resistance. Anti-MRSA mechanism revealed that compound 9b could destroy cell wall structure by interacting with lipoteichoic acid and peptidoglycan, cause membrane damage by depolarization, increased permeability and destructed integrity, reduce cell metabolic activity by binding to lactate dehydrogenase (LDH), interfere cellular redox homeostasis, and bind to DNA. Overall, compound 9b killed the MRSA by multi-target mechanism, which provide a promising light for combating the growing MRSA resistance.
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•Quaternized AMPMs based on harmane are designed and synthesized.•Compound 9b possess remarkable anti-MRSA effects in vitro and in vivo.•Compound 9b slow down the development of drug resistance by multi-target mechanism.
Absorbance, as measured at 620nm, as a function of chitosan and TMC concentration added in the medium with E. coli, according to turbidity method after 12h interaction.
Chitosan is largely known for ...its activity against a wide range of microorganisms, in which the most acceptable antimicrobial mechanism is found to include the presence of charged groups in the polymer backbone and their ionic interactions with bacteria wall constituents. This interaction suggests the occurrence of a hydrolysis of the peptidoglycans in the microorganism wall, provoking the leakage of intracellular electrolytes, leading the microorganism to death. The charges present in chitosan chains are generated by protonation of amino groups when in acid medium or they may be introduced via structural modification. This latter can be achieved by a methylation reaction resulting in a quaternized derivative with a higher polymeric charge density. Since the charges in this derivative are permanents, it is expected a most efficient antimicrobial activity. Hence, in the present study, commercial chitosan underwent quaternization processes and both (mother polymer and derivative) were evaluated, in gel form, against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), as model bacteria. The results, as acquired from turbidity measurements, differ between materials with an expressive reduction on the Gram-positive microorganism (S. aureus) growth, while E. coli (Gram-negative) strain was less sensitive to both polymers. Additionally, the antibacterial effectiveness of chitosan was strongly dependent on the concentration, what is discussed in terms of spatial polymer conformation.
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•The nanophase-reinforced organic–inorganic hybrid structure was successful constructed.•Using PA as crosslink agent instead of traditional epoxide linked SPI and G-co-Q hybrid.•The ...resultant adhesive has a high performance with excellent flame-retardant, mildew resistance and antibacterial.•The wet shear strength of the resultant plywood increased by 78.7% to 1.09 MPa.•The plywood bonded by our adhesive is the absorption dominated EMI shielding material with low reflection characteristics.
The development of multifunctional adhesive with high bond strength, toughness, mildew resistance, antibacterial properties, flame retardancy, and electromagnetic (EMI) shielding properties has drawn interest and simultaneously presents a challenge in the wood panel industry. Herein, inspired by the organic–inorganic hybrid structure of oysters, an antibacterial agent quaternary ammonium salted hyperbranched polyamide (QHBPA), was synthesized to modify graphene nanosheets (GNSs) via cation-π interaction, eventually forming a G-co-Q hybrid. The G-co-Q hybrid was then combined with soy protein isolate (SPI) and phytic acid (PA) to develop a plywood adhesive with an organic–inorganic hybrid structure via electrostatic interactions and hydrogen bonds. The resultant adhesive exhibited good mildew resistance and antibacterial activity (144 h shelf life). Compared with the SPI adhesive, the dry and wet shear strengths of the plywood with the SPI/PA/G-co-Q adhesive increased by 76.6% and 78.7%, respectively. Meanwhile, non-covalent cross-linking and the formation of an organic–inorganic hybrid structure endowed the adhesive with excellent toughness. Furthermore, the limiting oxygen index (LOI) of the resultant adhesive was 35.5%, reflecting an increase of 49.1% relative to that of the SPI adhesive, indicating that the adhesive possesses superior flame retardancy. Importantly, owing to its unique isolated multilayered structure, the plywood bonded by our adhesive is an absorption dominated EMI shielding material with low reflection characteristics and displays a desirable EMI shielding effectiveness of 43 dB. Therefore, this study provides a creative insight into the design of high value-added and multifunctional plywood with promising application prospects not only in conventional wood-based panels but also in advanced EMI shielding materials.
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•After post-boronation, Q-NFC films show excellent flame retardancy and transparency.•Both boron and lignin enhance flame retardancy of Q-NFC in a synergistic manner.•The presence of ...lignin imparts UV-shielding function to flame-retardant Q-NFC.•Boron-modified Q-NFCs act as fire-extinguishing coatings of papers and PET films.
Developing functional nanocellulose-based materials while well maintaining their inherent excellent attributes is crucial to achieve the value-added applications. However, their inherent flammability largely limits their potential applications in many fields with fire-safety concerns. In this work, an intrinsically flame-retardant nanofibrillated cellulose (NFC) was successfully prepared from kraft and unbleached bamboo pulps, respectively, via a three-step strategy involving quaternized pre-treatment, mechanical disintegration and subsequent borylation. TEM images show that the well-defibrillated cellulose nanofibrils with an average diameter of 5–9 nm were successfully obtained. The morphological, physicochemical, mechanical, thermal and flame-retardant characteristics of NFC suspensions, and their resulting films were systematically characterized. The borylated NFC film from the kraft pulp (B/Q-NFC) exhibits remarkably improved char yield while retaining high degree of fibrillation, optical transparency and mechanical properties of the Q-NFC one. Despite relatively lower optical transmittance and tensile strength, the lignin-containing NFC (L-Q-NFC) from unbleached pulp exhibits better thermal stability and outstanding UV-shielding function. Flame-retardant properties of borylated NFC samples were comprehensively investigated in terms of microscale combustion calorimetry (MCC), limiting oxygen index (LOI), vertical burning, and cone calorimetry tests. A synergistic effect was noted between B and lignin species in promoting flame resistance of Q-NFC matrix (L-B/Q-NFC). When being used as flame-retardant coatings on the filter paper and PET film, both of borylated NFC films display excellent flame-retardancy and smoke-suppression effects. In combination with of surface and bulk chemical composition analysis, TGA results as well as oxygen-permeability and thermal diffusivity measurements, the flame-retardant mechanism of borylated NFC films was elucidated. These favorite features enable them to act as sustainable fire-protective coatings for many fields such as thermal insulation, electronics, separators for lithium-ion battery, etc.
To investigate the influences of quaternization/hydroxypropylsulfonation on viscosity stability, adhesion to fibers and film properties of oxidized tapioca starch (OTS) for ameliorating its end-use ...ability in applications such as warp-sizing and paper-making, a series of quaternized and hydroxypropylsulfonated OTS (QHOTS) samples were synthesized by simultaneous quaternization and hydroxypropylsulfonation of OTS with
-(3-chloro-2-hydroxypropyl) trimethylammonium chloride (CHPTAC) and 3-chloro-2-hydroxy-1-propanesulfonic acid sodium salt (CHPS-Na). The QHOTS granules were characterized by Fourier transform infra-red spectroscopic and scanning electron microscope techniques. Apparent viscosity and viscosity stability were determined, and adhesion was evaluated by measuring the bonding force of starch to the fibers. Film properties were also estimated in terms of tensile strength, breaking elongation, bending endurance, degree of crystallinity, and moisture regain. It was showed that quaternization/hydroxypropylsulfonation was capable of obviously improving viscosity stability of gelatinized OTS paste, enhancing bonding forces of OTS to cotton and polylactic acid (PLA) fibers, increasing breaking elongation, bending endurance and moisture regain of film and decreasing its tensile strength and degree of crystallinity, thereby obviously stabilizing paste viscosity, improving adhesion to fibers and lessening film brittleness. Increasing the level of quaternization/hydroxypropylsulfonation favored improvement in the stability, enhancement in adhesion and decrease in brittleness. The QHOTS showed potential in the applications of cotton and PLA sizing.
Although phosphoric acid doped polybenzimidazole has been proposed as promising high-temperature proton exchange membrane, the poor absorption and immobilization ability of phosphoric acid in the ...membrane hinders its long-term stability. In this work, high-temperature proton exchange membranes with high phosphoric acid uptake and retention ability are fabricated thorough solvent casting of an alkali-free quaternized poly(4,4’-diphenylether-5,5’-bibenzimidazole) (OPBI), followed by doping of phosphoric acid. The optimized membrane with quaternization degree of 50% possesses a high acid-doping-level of 18.8 and an anhydrous conductivity of 85 mS cm−1 at 160 °C. Stability tests reveal that anhydrous proton conductivity remains unchanged during continuous 100 h treatment at 160 °C and it remains 91.7% of its initial value after 100 h treatment at 80 °C under 40% RH. The thus-assembled single cell exhibits the maximum power density values of 0.355, 0.495, and 0.584 Wcm−2 at 160 °C under back pressure of 0, 100, and 200 kPa using hydrogen as fuel and air as oxidant gas.
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•Quaternized PBI was synthesized through an alkali-free strategy.•The optimized membrane exhibited high doping level and great retention ability of acid.•Proton conductivity of the optimized membrane reached 0.085 Scm−1 at 160 °C.•Single cell delivered a power density of 0.58 Wcm−2 at 160 °C under 200 kPa back pressure.
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•Thin film composite membranes were grafted with polyethylenimine (PEI).•Activation step converted carboxyl groups into amine-reactive esters.•Quaternization of amine with iodomethane ...further enhanced NH4+ rejection.•Modified membranes dewatered real wastewater and enriched NH4+.•PEI grafting and quaternization are facile and practical methods for NH4+ recovery.
In this study, we aimed to recover and enrich NH4+ from real wastewater using forward osmosis (FO). Positively-charged thin film composite (TFC) membranes were developed via chemical grafting with positively-charged polyethyleneimine (PEI). The TFC membrane surface was first activated using 1-ethyl-3-(3-dimethylaminopropyl) carboimide (EDC) and n-hydroxysuccinimide (NHS) to convert the carboxyl groups of polyamide into amine-reactive NHS esters. PEI grafting significantly increased the NH4+ retention in the feed solution. To further improve the NH4+ rejection, quaternization of the amine functional groups of PEI was conducted with iodomethane. Quaternization was found to further increase NH4+ rejection, up to over 98.5%, while maintaining similar water permeability with the PEI-grafted TFC membrane. Fouling control of the pristine and amine-modified TFC membranes were also demonstrated, and the quaternary amine-modified TFC membrane exhibited superior fouling resistance against organic and biological foulants. The amine-modified TFC membranes were evaluated for applicability for dewatering and NH4+ enrichment of real industrial wastewater. NH4+ enrichment using the PEI-grafted membranes was observed following wastewater dewatering, indicating the high NH4+ retention ability of the TFC membranes modified via amine grafting and quaternization. Wastewater dewatering of 90.3 and 92.4% were achieved using TFC-PEI-10 and TFC-qPEI, respectively.
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