Preparation and characterization of polyethylene glycol/chitosan composite water-based wound healing lubricant

Antifouling activity of PEGylated chitosan coatings: Impacts of the side chain length and encapsulated ZnO/Ag nanoparticles

PEGylation is regarded as a common antifouling strategy and the effect is normally linked with surface hydrophilicity of the coatings. Herein, the biopolymer chitosan (CS) was grafted by polyethylene glycol (PEG) of different chain lengths (molecular weight 200, 4 k and 100 k Da) to verify if the hydrophilicity of CS-PEG coatings is crucial in determining antifouling activities and if PEG chain length influences biofouling in marine environment. Properties of copolymers such as melting points and crystallinity are affected by grafting PEG. The water contact angle (WCA) of CS-PEG coatings increases with the chain length of grafted PEG, from 27° to 58°. Photocatalyst of zinc oxide-silver (ZnO/Ag) was also studied and its embedment (2 % to CS-PEG) renders the surface of CS-PEG coatings more hydrophobic with WCA increased from 52° to 86°. Antibacterial, anti-diatom, and anti-biofilm activities of the coatings were evaluated in natural sea water. The bacterial density on CS-PEG coatings was dramatically reduced to 4 × 104 compared to the control of 7 × 104 ind/mm2, and further to 2 × 104 for CS-PEG-ZnO/Ag coatings. CS-PEG coatings also strongly inhibit diatoms (120-200 ind/mm2), but the inclusion of ZnO/Ag did not obviously enhance such effect (50-150 ind/mm2). The findings provide useful insights for designing polymer-based antifouling coatings.

Covalent-Organic Framework Nanomaterials: Energy Band Engineering Generating Ultrathin Lubrication Films for Excellent Lubrication

It is, in fact, inevitable for steel to be covered with a layer of iron oxides and/or peroxides on its surface. However, knowledge of its existence and functionality for tribological behaviors is usually ignored. Herein, covalent-organic framework nanomaterials (CONs) composed of three well-screened acceptors and a donor through the imide linkage were fabricated to explore their lubrication performances. The results indicate that the energy-level matching between CONs and iron oxides or peroxides leads to the formation of a Z-scheme heterojunction structure at the rubbing interface. Also, the friction produces an internal electric field in the heterojunction, which drives the negative atomic/ionic species from the sliding interface to immigrate into the pore of CONs and resettle inside to engender the pinning effects, producing a fixed lubrication layer. Synchronously, it also attracts the free CONs in the base oil to form an easy-shear lubrication layer assembling onto the fixed one, producing a lubrication film with two layered configurations. Finally, the unique lubrication film, despite its thickness of a dozen nanometers, still exhibits impressive friction reduction and antiwear. This finding will inspire the technology to utilize the intrinsic surface nature of steel materials to exploit lubricant additives or modulate tribological behaviors.

Fabrication of an all-in-one self-enhanced solid-state electrochemiluminescence sensing platform for the selective detection of spermine

The fabrication of an all-in-one solid-state ECL sensing platform is beneficial not only for expediting the miniaturization of sensing devices, but also, more importantly, for enabling point-of-care applications. In the present work, a self-enhanced solid-state ECL sensing platform is fabricated using newly synthesised silica polyethylene nanoparticles (SiO2-PEI NPs) which generate a co-reactant in situ and easily self-assemble with Ru(bpy)32+ and shows selective and sensitive detection of spermine at physiological pH (7.4). Spermine induces the maximum ECL emission intensity compared to other biogenic amines due to the presence of two secondary amines. A possible ECL reaction mechanism has been proposed based on CV and ECL experiments, DFT calculations, and in situ ECL spectrum analysis. The developed solid-state sensor showed a linear increase in ECL intensity with increasing spermine concentration in the range of 10 nM to 100 nM with an LOD of 12.2 nM. Compared to other biogenic amines in previous works, chemically synthesised SiO2-PEI NPs used in the present study act as an effective label- and enzyme-free sensor, and the new method is observed to be simple and cost-effective, to overcome various limitations of solution-phase ECL and to avoid the usage of any noble metals.

Regulation of cellulase production via calcium signaling in Trichoderma reesei under PEG8000 stress

In this study, the effect of polyethylene glycol 8000 (PEG8000) stress on cellulase biosynthesis in Trichoderma reesei CICC2626 via calcium signaling was investigated, and a plausible mechanism by which intracellular Ca2+ regulates the transcription of cellulase genes was proposed. The results indicated that the total cellulase (filter paper-hydrolyzing activity [FPase]), endoglucanase (carboxymethyl cellulase activity [CMCase]), and β-glucosidase activities of the strain were 1.3-, 1.2-, and 1.3-fold higher than those of the control (no PEG8000 addition) at a final concentration of 1.5% (w/v) PEG8000. Moreover, the transcriptional levels of cellulase genes, protein concentrations, and biomass increased. With the synergistic use of commercial cellulase and T. reesei CICC2626 cellulase to hydrolyze alkali-pretreated rice straw, the released reducing sugar concentration reached 372.7 mg/g, and the cellulose content (22.7%, 0.32 g) was significantly lower than the initial content (62.5%, 1.88 g). Transcriptome data showed that 12 lignocellulose degradation-related genes were significantly upregulated in the presence of 1.5% PEG8000. Furthermore, the addition of Ca2+ inhibitors and deletion of crz1 (calcineurin-responsive zinc finger 1-encoding gene, which is related to the calcium signaling pathway) demonstrated that calcium signaling plays a dominant role in PEG8000-induced cellulase genes overexpression. These results revealed a link between PEG8000 induction and calcium signaling transduction in T. reesei CICC2626. Moreover, this study also provides a novel inducer for enhanced cellulase production. KEY POINTS: • Cellulase biosynthesis in Trichoderma reesei could be enhanced by PEG8000 • PEG8000 could induce a cytosolic Ca2+ burst in Trichoderma reesei • The activated calcium signaling was involved in cellulase biosynthesis.