Molecular Dynamics Simulations of the Short-Chain Fluorocarbon Surfactant PFHXA and the Anionic Surfactant SDS at the Air/Water Interface.

The research and development of alternatives to long-chain fluorocarbon surfactants are desperately needed because they are extremely toxic, difficult to break down, seriously harm the environment, and limit the use of conventional aqueous film-forming foam fire extinguishing agents. In this study, mixed surfactant systems containing the short-chain fluorocarbon surfactant perfluorohexanoic acid (PFHXA) and the hydrocarbon surfactant sodium dodecyl sulfate (SDS) were investigated by molecular dynamics simulation to investigate the microscopic properties at the air/water interface at different molar ratios. Some representative parameters, such as surface tension, degree of order, density distribution, radial distribution function, number of hydrogen bonds, and solvent-accessible surface area, were calculated. Molecular dynamics simulations show that compared with a single type of surfactant, mixtures of surfactants provide superior performance in improving the interfacial properties of the gas-liquid interface. A dense monolayer film is formed by the strong synergistic impact of the two surfactants. Compared to the pure SDS system, the addition of PFHXA caused SDS to be more vertically oriented at the air/water interface with a reduced tilt angle, and a more ordered structure of the mixed surfactants was observed. Hydrogen bonding between SDS headgroups and water molecules is enhanced with the increasing PFHXA. The surface activity is arranged in the following order: PFHXA/SDS = 1:1 > PFHXA/SDS = 3:1 > PFHXA/SDS = 1:3. These results indicate that a degree of synergistic relationship exists between PFHXA and SDS at the air/water interface.

Bioinspired Soft Spine Enables Small-Scale Robotic Rat to Conquer Challenging Environments.

For decades, it has been difficult for small-scale legged robots to conquer challenging environments. To solve this problem, we propose the introduction of a bioinspired soft spine into a small-scale legged robot. By capturing the motion mechanism of rat erector spinae muscles and vertebrae, we designed a cable-driven centrally symmetric soft spine under limited volume and integrated it into our previous robotic rat SQuRo. We called this newly updated robot SQuRo-S. Because of the coupling compliant spine bending and leg locomotion, the environmental adaptability of SQuRo-S significantly improved. We conducted a series of experiments on challenging environments to verify the performance of SQuRo-S. The results demonstrated that SQuRo-S crossed an obstacle of 1.07 body height, thereby outperforming most small-scale legged robots. Remarkably, SQuRo-S traversed a narrow space of 0.86 body width. To the best of our knowledge, SQuRo-S is the first quadruped robot of this scale that is capable of traversing a narrow space with a width smaller than its own width. Moreover, SQuRo-S demonstrated stable walking on mud-sand, pipes, and slopes (20°), and resisted strong external impact and repositioned itself in various body postures. This work provides a new paradigm for enhancing the flexibility and adaptability of small-scale legged robots with spine in challenging environments, and can be easily generalized to the design and development of legged robots with spine of different scales.

Tumor microenvironment-regulating nanomedicine design to fight multi-drug resistant tumors.

The tumor microenvironment (TME) is a very cunning system that enables tumor cells to escape death post-traditional antitumor treatments through the comprehensive effect of different factors, thereby leading to drug resistance. Deep insights into TME characteristics and tumor resistance encourage the construction of nanomedicines that can remodel the TME against drug resistance. Tremendous interest in combining TME-regulation measurement with traditional tumor treatment to fight multidrug-resistant tumors has been inspired by the increasing understanding of the role of TME reconstruction in improving the antitumor efficiency of drug-resistant tumor therapy. This review focuses on the underlying relationships between specific TME characteristics (such as hypoxia, acidity, immunity, microorganisms, and metabolism) and drug resistance in tumor treatments. The exciting antitumor activities strengthened by TME regulation are also discussed in-depth, providing solutions from the perspective of nanomedicine design. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Physiological, biochemical and phytohormone responses of Elymus nutans to α-pinene-induced allelopathy.

The α-pinene is the main allelochemical of many weeds that inhibit the growth of Elymus nutans, an important forage and ecological restoration herbage. However, the response changes of α-pinene-induced allelopathy to E. nutans is still unclear. Here, we investigated the physiological, biochemical and phytohormone changes of E. nutans exposed to different α-pinene concentrations. The α-pinene-stress had no significant effect on height and fresh weight (FW) of seedlings. The water-soluble proteins, the soluble sugars and proline (Pro) strengthened seedlings immunity at 5 and 10 µL L-1 α-pinene. Superoxide dismutase (SOD) and ascorbate peroxidase (APX) increased at 5 µL L-1 α-pinene to resist stress. APX reduced the membrane lipid peroxidation quickly at 10 µL L-1 α-pinene. The high-activity of peroxidase (POD), APX along with the high level of GSH contributed to the cellular redox equilibrium at 15 µL L-1 α-pinene. The POD, glutathione reductase (GR) activity and glutathione (GSH) level remained stable at 20 µL L-1 α-pinene. The changes in antioxidant enzymes and antioxidants indicated that E. nutans was effective in counteracting the harmful effects generated by hydrogen peroxide (H2O2). The α-pinene caused severe phytotoxic effects in E. nutans seedlings at 15 and 20 µL L-1. Endogenous signal nitric oxide (NO) and cell membrane damage product Pro accumulated in leaves of E. nutans seedlings at 15 and 20 µL L-1 α-pinene, while lipid peroxidation product malondialdehyde (MDA) accumulated. The chlorophylls (Chls), chlorophyll a (Chl a), chlorophyll b (Chl b) content decreased, and biomass of seedlings was severely inhibited at 20 µL L-1 α-pinene. The α-pinene caused phytotoxic effects on E. nutans seedlings mainly through breaking the balance of the membrane system rather than with reactive oxygen species (ROS) productionat 15 and 20 µL L-1 α-pinene. Additionally, phytohormone levels were altered by α-pinene-stress. Abscisic acid (ABA) and indole acetic acid (IAA) of E. nutans seedlings were sensitive to α-pinene. As for the degree of α-pinene stress, salicylic acid (SA) and jasmonic acid (JA) played an important role in resisting allelopathic effects at 15 µL L-1 α-pinene. The ABA, Zeatin, SA, gibberellin 7 (GA7), JA and IAA levels increased at 20 µL L-1 α-pinene. The α-pinene had a greatest impact on ABA and IAA levels. Collectively, our results suggest that E. nutans seedlings were effective in counteracting the harmful effects at 5 and 10 µL L-1 α-pinene, and they were severely stressed at 15 and 20 µL L-1 α-pinene. Our findings provided references for understanding the allelopathic mechanism about allelochemicals to plants.

Scaffold 3D-Printed from Metallic Nanoparticles-Containing Ink Simultaneously Eradicates Tumor and Repairs Tumor-Associated Bone Defects.

Bone metastasis occurs in about 70% of breast cancer patients. The surgical resection of metastatic tumors often leads to bone erosion and destruction, which greatly hinders the treatment and prognosis of breast cancer patients with bone metastasis. Herein, a bifunctional scaffold 3D-printed from nanoink is fabricated to simultaneously eliminate the tumor cells and repair the tumor-associated bone defects. The metallic polydopamine (PDA) nanoparticles (FeMg-NPs) may effectively load and sustainably release the metal ions Fe3+ and Mg2+ in situ. Fe3+ exerts a chemodynamic therapy to synergize with the photothermal therapy induced by PDA with effective photothermal conversion under NIR laser, which efficiently eliminates the bone-metastatic tumor. Meanwhile, the sustained release of osteoinductive Mg2+ from the bony porous 3D scaffold enhances the new bone formation in the bone defects. Taken together, the implantation of scaffold (FeMg-SC) 3D-printed from the FeMg-NPs-containing nanoink provides a novel strategy to simultaneously eradicate bone-metastatic tumor and repair the tumor-associated bone defects.

Comprehensive evaluation of the allelopathic potential of Elymus nutans.

Elymus nutans has been widely planted together with other perennial grasses for rebuilding degraded alpine meadow atop the Qinghai-Tibetan Plateau. However, the rebuilt sown pastures begin to decline a few years after establishing. One of the possible causes for the degradation of sown grassland may come from allelopathy of planted grasses. The purpose of this study was to examine allelopathic potential of Elymus nutans. Three types of aqueous extract from Elymus nutans and its root zone soil were prepared, and 5 highland crops and 5 perennial grasses were used as recipient plants. Elymus nutans exhibited strong allelopathic potential on germination and seedling growth of 5 crops, but different crops or perennial grasses respond to the extract differently. The pieces aqueous extract have stronger inhibition than whole plant extract and root zone soil extract. Hordeum vulgar var. nudum, Avena sativa, and Festuca sinensis were the most affected, while Chenopodium quinoa and Elymus sibiricus were the least affected. Elymus nutans presented less influence on Poa pratensis and Poa crymophylla than on Festuca sinensis. It is recommended that the species combination of mixture for restoration should be considered for allopathic effects on the coseeding to decrease the seeding rate ratio of Elymus nutans. The annual dicot crop seeds of Chenopodium quinoa and Brassica napus can be used as alternative subsequent crop for the seed field of Elymus nutans monoculture.