No abstract

The preparation of a type of innovative cationic copolypeptoid antimicrobials containing various hydrophobic moieties that resemble both structure and membrane‐lytic antibacterial mechanism of natural antimicrobial peptides (AMPs) is reported. By finely tuning the hydrophilic/hydrophobic balance, the polypeptoids exhibit a wide spectrum of antibacterial activity against both Gram‐positive bacteria and Gram‐negative bacteria with the lowest minimum inhibitory concentration (MIC) at only 2 µg mL−1, whereas they also show low haemolytic properties. In particular, high selectivity (>128) is achieved from the polymers with butyl moieties. Moreover, the polypeptoids can readily inhibit the formation of biofilms and effectively eradicate the bacteria embedded in the mature biofilms, which is superior to many natural AMPs and vancomycin. Unlike conventional antibiotics, the polypeptoids possess potent activity against drug‐resistant bacteria without visible resistance development after repeated usage. Notably, the polypeptoid antimicrobials not only have inherently fast bactericidal properties and excellent stability against incubation with human plasma, but also show excellent in vivo antibacterial effect. The prepared antimicrobials, coated onto magnetic nanospheres show recycling properties and enhanced antibacterial activity as combined with near‐infrared (NIR)‐induced photothermal antibacterial therapy.

To further improve the ablation and thermal properties of silicon rubber composite materials, the 3, 13-divinyloctaphenyl double-decker polyhedral oligomeric silsesquioxane (DV-DDSQ) modified additional vinyl-terminated polydimethylsiloxane (VPDMS) was prepared, and the effect of high silica fiber reinforcement on the ablation properties of VPDMS was investigated. The results show that when 0.8phr DV-DDSQ was added, the mass residual rate at 800 C of the composites increased from 40.6% to 51.0%. The linear ablation rate (LAR) as well as mass ablation rate (MAR) of the composites of the DV-DDSQ modified VPDMS, the high silica fiber reinforced VPDMS composite (HSF/VPDMS composite) and the high silica fiber reinforced DV-DDSQ modified VPDMS composite (HSF/DV-DDSQ-VPDMS composite) decreased dramatically compared with raw VPDMS, and it was 16.36%, 35.69%, and 37.17% bring down for LAR and 5.34%, 14.60% and 25.59% for MAR, respectively. The tensile strength and hardness of the DV-DDSQ modified composites increased by 9.52% and 14.13%, respectively, while the elongation at break decreased by 5.99%, compared with the raw VPDMS.

Self‐assembled cationic polymeric nanostructures have been receiving increasing attention for efficient antibacterial agents. In this work, a new type of antibacterial agents is developed by preparing pH‐dependent nanostructured assemblies from cationic copolypeptoid poly(N‐allylglycine)‐b‐poly(N‐octylglycine) (PNAG‐b‐PNOG) modified with cysteamine hydrochloride ((PNAG‐g‐NH2)‐b‐PNOG) driven by crystallization and hydrophobicity of the PNOG blocks. Due to the presence of confined domains arising from crystalline PNOG, persistent spheres and fiber‐like assemblies are obtained from the same polymer upon a heating‐cooling cycle. This allows for direct comparison of antimicrobial efficiency of nanostructured assemblies with various morphologies that are otherwise similar. Both nanostructured assemblies exhibit extremely low toxicity to human red blood cells, irrespective of the presence of the hydrophobic block. Enhanced antimicrobial performance of the fiber‐like micelles compared to the spheres, which result in high selectivity of the fibers, is shown. Notably, the fiber‐like micelles show great efficacy in inhibition of the Staphylococcus aureus (S. aureus) biofilm formations and eradication of the mature biofilms, superior to vancomycin. The micelles also show potent in vivo antimicrobial efficacy in a S. aureus infection mouse skin model. With a systematic study, it is demonstrated that both micelles kill the bacteria through a membrane disruption mechanism. These results imply great potential of polypeptoid assemblies as promising excellent candidates for antibacterial treatment and open up new possibilities for the preparation of a new generation of nanostructured antimicrobials.

Bifunctional reactive polyhedral oligomeric silsesquioxane (POSS) of 3, 13‐divinyl octyphenyl silsesquioxane (DV‐DDSQ) and 3, 13‐dihydro octyphenyl silsesquioxane (DH‐DDSQ) were used as additive to modify ethylene‐propylene‐diene rubber (EPDM), and double vinyl groups or active hydrogen groups of bifunctional reactive POSS (brPOSS) underwent a cross‐linking reaction with the active hydrogen groups and double bonds of EPDM, to investigate the effect of brPOSS regulating functional reaction group on the properties of EPDM. Crosslinking density, mechanical properties, thermal stability and ablation performance of brPOSS modified EPDM were investigated, and the pyrolysis behavior and surface structure of modified EPDM was analyzed by X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Furthermore, the ablation performance of brPOSS modified insulation based on EPDM was investigated. The results showed that the tensile strength of EPDM/DV‐DDSQ and EPDM/DH‐DDSQ increased by 35.8% and 55.3% respectively compared with EPDM; the tear strength increased by 6.4% and 5% than that of EPDM. Moreover, the 5% initial thermal decomposition temperature based on thermogravimetric analysis (TGA) and mass (or linear) ablation rate ablative performance of brPOSS modified EPDM were optimized to a certain extent, and the ablative performance of brPOSS modified insulation based on is significantly improved, the mass ablation rate of DV‐DDSQ/insulation and DH‐DDSQ/insulation decreased by 35.4% and 41.6% respectively, and linear ablation rate decreased by 38.2% and 39.4% respectively.

Polysaccharide conjugates are important renewable materials. If properly designed, they may for example be able to carry drugs, be proactive (e.g., with amino acid substituents) and can carry a charge. These aspects can be particularly useful for biomedical applications. Herein, we report a simple approach to preparing polysaccharide conjugates. Thiol-Michael additions can be mild, modular, and efficient, making them useful tools for post-modification and the tailoring of polysaccharide architecture. In this study, hydroxypropyl cellulose (HPC) and dextran (Dex) were modified by methacrylation. The resulting polysaccharide, bearing α,β-unsaturated esters with tunable DS (methacrylate), was reacted with various thiols, including 2-thioethylamine, cysteine, and thiol functional quaternary ammonium salt through thiol-Michael addition, affording functionalized conjugates. This click-like synthetic approach provided several advantages including a fast reaction rate, high conversion, and the use of water as a solvent. Among these polysaccharide conjugates, the ones bearing quaternary ammonium salts exhibited competitive antimicrobial performance, as supported by a minimum inhibitory concentration (MIC) study and tracked by SEM characterization. Overall, this methodology provides a versatile route to polysaccharide conjugates with diverse functionalities, enabling applications such as antimicrobial activity, gene or drug delivery, and biomimicry.

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As awareness of environmental protection increases, environmentally friendly coatings have been receiving great interest. Zwitterionic polymers are considered promising candidates due to their biocompatibility and excellent antifouling properties. In this paper, a type of polypeptoid containing zwitterions on the side chain was synthesized via ring-opening polymerization (ROP) and post-modification. This obtained polypeptoid was subsequently grafted onto the surface of polydimethylsiloxane (PDMS) via plasma and UV-induced surface polymerization. Surface morphology and protein adsorption tests of the resulting coating were systematically carried out. The results show that the modified coating has excellent antifouling properties and thus has great potential for environmentally friendly coating applications.