Cell-derived nanovesicles from mesenchymal stem cells as extracellular vesicle-mimetics in wound healing

Wound healing is a dynamic process that involves a series of molecular and cellular events aimed at replacing devitalized and missing cellular components and/or tissue layers.Recently,extracellular vesicles(EVs),naturally cell-secreted lipid membrane-bound vesicles laden with biological cargos including proteins,lipids,and nucleic acids,have drawn wide attention due to their ability to promote wound healing and tissue regeneration.However,current exploitation of EVs as therapeutic agents is limited by their low isolation yields and tedious isolation processes.To circumvent these challenges,bioinspired cell-derived nanovesicles(CDNs)that mimic EVs were obtained by shearing mesenchymal stem cells(MSCs)through membranes with different pore sizes.Physical characterisations and highthroughput proteomics confirmed that MSC-CDNs mimicked MSC-EVs.Moreover,these MSC-CDNs were efficiently uptaken by human dermal fibroblasts and demonstrated a dose-dependent activation of MAPK signalling pathway,resulting in enhancement of cell proliferation,cell migration,secretion of growth factors and extracellular matrix proteins,which all promoted tissue regeneration.Of note,MSC-CDNs enhanced angiogenesis in human dermal microvascular endothelial cells in a 3D PEGfibrin scaffold and animal model,accelerating wound healing in vitro and in vivo.These findings suggest that MSC-CDNs could replace both whole cells and EVs in promoting wound healing and tissue regeneration.

Subcycle control of terahertz waveform polarization using all-optically induced transient metamaterials

Coherent radiation with frequencies ranging from 0.3 to 30 THz has recently become accessible using femtosecond laser technology.These terahertz(THz)waves have already been applied in spectroscopy and imaging and can be manipulated using static optical elements such as lenses,polarizers and filters.However,ultrafast modulation of THz radiation is required as well,for instance,in short-range wireless communication or for preparing shaped THz transients for the coherent control of numerous material excitations.Here,we demonstrate an all-optically created transient metamaterial that allows us to manipulate the polarization of THz waveforms with subcycle switch-on times.The polarization-modulated pulses are potentially interesting for controlling elementary motions such as the vibration of crystal lattices,the rotation of molecules and the precession of spins.

Flexible,robust and highly efficient broadband nonlinear optical materials based on graphene oxide impregnated polymer sheets

We report a simple solution-processed method for the fabrication of low-cost,flexible optical limiting materials based on graphene oxide(GO) impregnated polyvinyl alcohol(PVA) sheets.Such GO–PVA composite sheets display highly efficient broadband optical limiting activities for femtosecond laser pulses at 400,800,and 1400 nm with very low limiting thresholds.Femtosecond pump–probe measurement results revealed that nonlinear absorption played an important role for the observed optical limiting activities.High flexibility and efficient optical limiting activities of these materials allow these composite sheets to be attached to nonplanar optical sensors in order to protect them from light-induced damage.

Surface molecular doping of all-inorganic perovskite using zethrenes molecules

We present an optical and photoelectron spectroscopic study to elucidate the interfacial electronic properties of organic-inorganic semiconductor heterojunctions formed in a kinetically blocked heptazethrene triisopropylsilyl ethynylene (HZ-TIPS) and its homologue,octazethrene (OZ-TIPS) on an all-inorganic perovskite cesium lead bromide (CsPbBr3) surface.The photoluminescence behavior of the underlying perovskites upon differing molecular doping conditions was examined.It turns out that the charge transfer dynamics of thermally-evaporated OZ-TIPS molecule exhibited a faster average lifetime than that of the HZ-TIPS case suggesting the importance of the biradical state in the former molecule.An interfacial dipole was formed at the interface due to the competing interaction between the dispersion force of the bulky TIPS-substituent group and the attractive van der Waals interaction at the first few layers.Photoemission spectroscopy of the physisorbed HZ-TIPS shows chemical shifts,which indicates electron transfer from HZ-TIPS molecules to the CsPbBr3 perovskite single crystal.In contrast,the adsorbed OZ-TIPS molecular layer on CsPbBr3 demonstrates the opposite trend indicating a hole transfer process.The average molecular orientation as determined by near edge X-ray absorption fine structure (NEXAFS) suggests that the HZ-TIPS molecular plane is generally lifted with respect to the perovskite surface.We suggest that the nature of the closed-shell electronic ground state of HZ-TIPS could contribute to the formation of interfacial dipole at the molecule/perovskite interface.

Achieving a high magnetization in sub-nanostructured magnetite films by spin-flipping of tetrahedral Fe3. cations

Magnetite Fe304 （ferrite） has attracted considerable interest for its exceptional physical properties： It is predicted to be a semimetallic ferromagnetic with a high Curie temperature, it displays a metal-insulator transition, and has potential oxide-electronics applications. Here, we fabricate a high-magnetization （〉 1 Tesla） high-resistance （-0.1 Ωcm） sub-nanostructured （grain size 〈 3 nm） Fe304 film via grain-size control and nano-engineering. We report a new phenomenon of spin- flipping of the valence-spin tetrahedral FeB＊ in the sub-nanostructured Fe304 film, which produces the high magnetization. Using soft X-ray magnetic circular dichroism and soft X-ray absorption, both at the Fe L3,2- and O K-edges, and supported by first-principles and charge-transfer multiple calculations, we observe an anomalous enhancement of double exchange, accompanied by a suppression of the superexchange interactions because of the spin-flipping mechanism via oxygen at the grain boundaries. Our result may open avenues for developing spin- manipulated giant magnetic Fe304-based compounds via nano-grain size control.