Progress on mechanical and tribological characterization of 2D materials by AFM force spectroscopy

Two-dimensional(2D)materials are potential candidates for electronic devices due to their unique structures and exceptional physical properties,making them a focal point in nanotechnology research.Accurate assessment of the mechanical and tribological properties of 2D materials is imperative to fully exploit their potential across diverse applications.However,their nanoscale thickness and planar nature pose significant challenges in testing and characterizing their mechanical properties.Among the in situ characterization techniques,atomic force microscopy(AFM)has gained widespread applications in exploring the mechanical behaviour of nanomaterials,because of the easy measurement capability of nano force and displacement from the AFM tips.Specifically,AFM-based force spectroscopy is a common approach for studying the mechanical and tribological properties of 2D materials.This review comprehensively details the methods based on normal force spectroscopy,which are utilized to test and characterize the elastic and fracture properties,adhesion,and fatigue of 2D materials.Additionally,the methods using lateral force spectroscopy can characterize the interfacial properties of 2D materials,including surface friction of 2D materials,shear behaviour of interlayers as well as nanoflake-substrate interfaces.The influence of various factors,such as testing methods,external environments,and the properties of test samples,on the measured mechanical properties is also addressed.In the end,the current challenges and issues in AFM-based measurements of mechanical and tribological properties of 2D materials are discussed,which identifies the trend in the combination of multiple methods concerning the future development of the in situ testing techniques.

Intranasal temperature-sensitive hydrogels of cannabidiol inclusion complex for the treatment of post-traumatic stress disorder

Post-traumatic stress disorder(PTSD)is a psychiatric disease that seriously affects brain function.Currently,selective serotonin reuptake inhibitors(SSRIs)are used to treat PTSD clinically but have decreased efficiency and increased side effects.In this study,nasal cannabidiol inclusion complex temperature-sensitive hydrogels(CBD TSGs)were prepared and evaluated to treat PTSD.Mice model of PTSD was established with conditional fear box.CBD TSGs could significantly improve the spontaneous behavior,exploratory spirit and alleviate tension in open field box,relieve anxiety and tension in elevated plus maze,and reduce the freezing time.Hematoxylin and eosin and c-FOS immunohistochemistry slides showed that the main injured brain areas in PTSD were the prefrontal cortex,amygdala,and hippocampus CA1.CBD TSGs could reduce the level of tumor necrosis factor-a caused by PTSD.Western blot analysis showed that CBD TSGs increased the expression of the 5-HT1 A receptor.Intranasal administration of CBD TSGs was more efficient and had more obvious brain targeting effects than oral administration,as evidenced by the pharmacokinetics and brain tissue distribution of CBD TSGs.Overall,nasal CBD TSGs are safe and effective and have controlled release.There are a novel promising option for the clinical treatment of PTSD.

Predatory bacterial hydrogels for topical treatment of infected wounds

Wound infection is becoming a considerable healthcare crisis due to the abuse of antibiotics and the substantial production of multidrug-resistant bacteria.Seawater immersion wounds usually become a mortal trouble because of the infection of Vibrio vulnificus.Bdellovibrio bacteriovorus,one kind of natural predatory bacteria,is recognized as a promising biological therapy against intractable bacteria.Here,we prepared a B.bacteriovorus-loaded polyvinyl alcohol/alginate hydrogel for the topical treatment of the seawater immersion wounds infected by V.vulnificus.The B.bacteriovorus-loaded hydrogel(BG)owned highly microporous structures with the mean pore size of 90μm,improving the rapid release of B.bacteriovorus from BG when contacting the aqueous surroundings.BG showed high biosafety with no L929 cell toxicity or hemolysis.More importantly,BG exhibited excellent in vitro anti-V.vulnificus effect.The highly effective infected wound treatment effect of BG was evaluated on mouse models,revealing significant reduction of local V.vulnificus,accelerated wound contraction,and alleviated inflammation.Besides the high bacterial inhibition of BG,BG remarkably reduced inflammatory response,promoted collagen deposition,neovascularization and re-epithelization,contributing to wound healing.BG is a promising topical biological formulation against infected wounds.