Supramolecular Gels Incorporating Cordyline terminalis Leaf Extract as a Polyphenol Release Scaffold for Biomedical Applications

Cordyline terminalis leaf extract (aqCT) possesses abundant polyphenols and other bioactive compounds, which are encapsulated in gelatin–polyethylene glycol–tyramine (GPT)/alpha-cyclodextrin (α-CD) gels to form the additional functional materials for biomedical applications. In this study, the gel compositions are optimized, and the GPT/α-CD ratios equal to or less than one half for solidification are found. The gelation time varies from 40.7 min to 5.0 h depending on the increase in GPT/α-CD ratios and aqCT amount. The aqCT extract disturbs the hydrogen bonding and host–guest inclusion of GPT/α-CD gel networks, postponing the gelation. Scanning electron microscope observation shows that all gels with or without aqCT possess a microarchitecture and porosity. GPT/α-CD/aqCT gels could release polyphenols from 110 to 350 nmol/mL at the first hour and sustainably from 5.5 to 20.2 nmol/mL for the following hours, which is controlled by feeding the aqCT amount and gel properties. GPT/α-CD/aqCT gels achieved significant antioxidant activity through a 100% scavenging DPPH radical. In addition, all gels are non-cytotoxic with a cell viability more than 85%. Especially, the GPT3.75α-CD10.5aqCT gels with aqCT amount of 3.1–12.5 mg/mL immensely enhanced the cell proliferation of GPT3.75α-CD10.5 gel without extract. These results suggest that the inherent bioactivities of aqCT endowed the resulting GPT/α-CD/aqCT gels with effective antioxidant and high biocompatibility, and natural polyphenols sustainably release a unique platform for a drug delivery system or other biomedical applications.

Effect of earthworm Eisenia fetida epidermal mucus on the vitality and pathogenicity of Beauveria bassiana

Beauveria bassiana is one of the most widely studied and used entomopathogenic fungus as biopesticide. In the biological control of pests, B. bassiana will persist in the soil after application, and will inevitably contact with earthworms, especially the epigeic earthworm species. So, what are the effects of earthworm and its epidermal mucus on the activity of B. bassiana? We employed the epigeic earthworm Eisenia fetida, B. bassiana TST05 strain, and the insect Atrijuglans hetaohei mature larvae to study the impact of earthworm epidermal mucus on the vitality and pathogenicity of B. bassiana to insect. Methods included scanning electron microscope observation, detection of spore germination, fungal extracellular enzyme activity, and infection testing to A. hetaohei. The results showed that the B. bassiana spores may attach to the cuticle of E. fetida but they could be covered by the epidermal mucus and became rough and shrunken. After treatment with the epidermal mucus, the spore germination and extracellular enzymes of B. bassiana was significantly inhibited. Inoculation of A. hetaohei larvae with a mixture of B. bassiana and mucus showed that the mucus could reduce the pathogenicity of B. bassiana to the insect, resulting in a slower disease course and lower mortality. It was concluded that the epidermal mucus of the earthworm E. fetida can inhibit the activity of B. bassiana, as well as the infectivity and pathogenicity of fungus to target insects. However, after treatment with epidermal mucus the surviving B. bassiana still had certain infectivity to insects. This is of great significance for the application of B. bassiana in biological control of pests.

Tensile Creep Behavior of Single-Crystal High-Entropy Superalloy at Intermediate Temperature

In this study, we investigated the creep deformation mechanism of a single-crystal high-entropy superalloy (HESA) with the spherical γ′ precipitates at 760 °C. Before the creep tests, long-term aging tests at 760 °C without load were conducted, which showed Ostwald ripening of the secondary γ′ precipitates up to 50 h. The creep tests revealed that in the range of 500 and 600 MPa at 760 °C, the creep deformation mechanism of HESA was independent of applied stress in both the primary and secondary creep regions. The deformation mechanism of HESA was further investigated under the condition of 760 °C and 520 MPa by performing creep interrupted tests and microstructural analysis. Scanning electron microscope observation showed elongated γ′ precipitates along the applied stress axis near the ruptured surface. This could have been caused by the multi-slip around <100> preceded by the lattice rotation into <100> along the tensile axis, which was confirmed by the electron backscatter diffraction analysis. Transmission electron microscope observation of the creep interrupted and ruptured specimens showed bypass and climb motion of dislocations in the 2-h interrupted, shearing of the γ′ precipitates by the paired straight dislocations in the 50-h interrupted, and shearing of the γ′ precipitates by both the straight and the curved paired dislocations in the ruptured specimens, respectively. The secondary γ′ precipitates do not affect creep behavior as long as the deformation mechanism is a bypass and climb motion of dislocations.