The treatment of bone defects has plagued clinicians. Exosomes, the naturally secreted nanovesicles by cells, exhibit great potential in bone defect regeneration to realize cell-free therapy. In this work, we successfully revealed that human umbilical cord mesenchymal stem cells-derived exosomes could effectively promote the proliferation, migration, and osteogenic differentiation of a murine calvariae preosteoblast cell line in vitro. Considering the long period of bone regeneration, to effectively exert the reparative effect of exosomes, we synthesized an injectable hydroxyapatite (HAP)-embedded in situ cross-linked hyaluronic acid-alginate (HA-ALG) hydrogel system to durably retain exosomes at the defect sites. Then, we combined the exosomes with the HAP-embedded in situ cross-linked HA-ALG hydrogel system to repair bone defects in rats in vivo. The results showed that the combination of exosomes and composite hydrogel could significantly enhance bone regeneration. Our experiment provides a new strategy for exosome-based therapy, which shows great potential in future tissue and organ repair.

Layer-by-layer (LBL) assembly is a simple and effective method for the fabrication of a three-dimensional (3D) scaffold for nanotechnological and biomedical applications. Herein, a novel 3D scaffold based on an alternate LBL assembly of graphene oxide (GO) nanosheets and fibrinogen nanofibers (Fg NFs) on a silicon substrate was fabricated and utilized to create a 3D hydroxyapatite (HA) scaffold by biomimetic mineralization in 1.5Â simulated body fluid for different nucleation periods. The obtained 3D (GO-NF) n-HA scaffold was characterized using atomic force microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results demonstrate that the Fg NFs could promote the nucleation and growth of HA crystals along the axis. The 3D (GO-NF) 10-HA scaffold composed of 10 layers of GO alternating with 10 layers of NFs was successfully created by LBL assembly and subsequent biomimetic mineralization. The effects of the created 3D (GO-NF) 10-HA scaffolds on the adhesion, morphology, and proliferation of L-929 cells were investigated. The in vitro cell culture indicates that the 3D (GO-NF) 10-HA scaffold has a higher proliferation ability and better cytocompatibility than the other control samples.

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Event-related brain potentials were recorded to investigate electrophysiological correlates of aggression in high and low socioeconomic status (SES) participants who responded to violent and nonviolent images by using a choice reaction time paradigm. ERP data showed that violent images elicited a smaller N2 deflection than did nonviolent images in both high and low SES groups, but there was no difference in N2 amplitudes to aggressive and non-aggressive information as a function of SES. Notably, the latency of N2 in the low SES group was longer than that of the high SES group, suggesting slowness by the low SES group in deploying control responses. In addition, the low SES group exhibited significantly smaller P3 amplitudes to violent images, suggesting a reduction in brain activity known to reflect activation of the aversive motivational system, and this findings link this brain activity to aggressive behavior. As a whole the present findings show that participants low in SES seem to display similar psychophysiological responses to individuals high in aggression.