Investigation on the lubrication component and mechanism for a biolubricant isolated from the agro-waste resource of Codonopsis pilosula.

Waste plant resource provides a new sustainable feedstock for the biolubricant, and purification of the effective components in biomass oil is vital to improve the performance of biolubricant. In this work, the crude extract of the aerial part of Codonopsis pilosula was divided into four different parts by petroleum ether, ethyl acetate, n-butanol and water, respectively. Their thermal stability, lubricating performances and mechanisms have been systematically investigated. In the four extracts, the petroleum ether extract displays the best thermal stability and lubricating performance over the entire test conditions, and other three extracts are confronted with lubrication failure at high loads and elevated temperatures. Triterpenoid saponin, typical for n-butanol extract exhibit the best lubricity at room temperature, followed by the fatty acid derivatives as phosphatidylcholine; flavonoid, and sugar exhibit poor lubricity. At high temperature, only the petroleum ether extract retains the good lubricity.

Antimicrobial Nanostructured Assemblies with Extremely Low Toxicity and Potent Activity to Eradicate Staphylococcus Aureus Biofilms.

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.

Thermoinduced Crystallization-Driven Self-Assembly of Bioinspired Block Copolymers in Aqueous Solution.

Delicate control over architectures via crystallization-driven self-assembly (CDSA) in aqueous solution, particularly combined with external stimuli, is rare and challenging. Here, we report a stepwise CDSA process thermally initiated from amphiphilic poly(N-allylglycine)-b-poly(N-octylglycine) (PNAG-b-PNOG) conjugated with thiol-terminated triethylene glycol monomethyl ethers ((PNAG-g-EG3)-b-PNOG) in aqueous solution. The diblock copolymers show a reversible thermoresponsive behavior with nearly identical cloud points in both heating and cooling runs. In contrast, the morphology transition of the assemblies is irreversible upon a heating-cooling cycle because of the presence of a confined domain arising from crystalline PNOG, which allows for the achievement of different nanostructured assemblies by the same polymer. We demonstrated that the thermoresponsive property of PNAG-g-EG3 initiates assembly kinetically that is subsequently promoted by crystallization of PNOG thermodynamically. The irreversible morphology transition behavior provides a convenient platform for comparing the cellular uptake efficiency of nanostructured assemblies with various morphologies that are otherwise similar.

Biocompatibility of filomicelles prepared from poly(ethylene glycol)-polylactide diblock copolymers as potential drug carrier.

A series of poly(ethylene glycol)-polylactide (PEG-PLA) diblock copolymers were synthesized by ring-opening polymerization of l-lactide using monomethoxy PEG as macroinitiator and zinc lactate as catalyst. Filomicelles were prepared from the resulting copolymers by co-solvent evaporation method. The biocompatibility of the various filomicelles was evaluated with the aim of assessing their potential as drug carriers. Various aspects of biocompatibility were considered, including agar diffusion test, MTT assay, release of cytokines, hemolytic test, dynamic clotting time, protein adsorption in vitro, and zebrafish embryonic compatibility in vivo. The results revealed that the filomicelles present good cytocompatibility and hemocompatibility in vitro. Moreover, the cumulative effects of filomicelles throughout embryos deveploping stages have no toxicity in vivo. It is thus concluded that filomicelles prepared from PEG-PLA copolymers with outstanding biocompatibility are promising as potential drug carrier.