Bioinspired MXene-Based User-Interactive Electronic Skin for Digital and Visual Dual-Channel Sensing

User-interactive electronic skin(e-skin) that could convert mechanical stimuli into distinguishable outputs displays tremendous potential for wearable devices and health care applications. However, the existing devices have the disadvantages such as complex integration procedure and lack of the intuitive signal display function. Here, we present a bioinspired user-interactive e-skin, which is simple in structure and can synchronously achieve digital electrical response and optical visualization upon external mechanical stimulus. The e-skin comprises a conductive layer with a carbon nanotubes/cellulose nanofibers/MXene nanohybrid network featuring remarkable electromechanical behaviors, and a stretchable elastomer layer, which is composed of silicone rubber and thermochromic pigments. Furthermore, the conductive nanohybrid network with outstanding Joule heating performance can generate controllable thermal energy under voltage input and then achieve the dynamic coloration of silicone-based elastomer. Especially, such an innovative fusion strategy of digital data and visual images enables the e-skin to monitor human activities with evermore intuition and accuracy. The simple design philosophy and reliable operation of the demonstrated e-skin are expected to provide an ideal platform for next-generation flexible electronics.

Glycerol solutions of highly concentrated biomineral counter-ions towards water-responsive mineralization: Demonstration on bacterial cellulose and its application in hard tissue repair

Mineralization has found widespread use in the fabrication of composite biomaterials for hard tissue regeneration.The current mineralization processes are mainly carried out in neutral aqueous solutions of biomineral counter-ions(a pair of cation and anion that form the corresponding minerals at certain conditions),which are stable only at very low concentrations.This typically results in inefficient mineralization and weak control over biomineral formation.Here,we find that,in the organic solvent glycerol,a variety of biomineral counter-ions(e.g.,Ca/PO_(4),Ca/CO_(3),Ca/SO_(4),Mg/PO_(4),or Fe/OH)corresponding to distinct biominerals at significantly high concentrations(up to hundreds-fold greater than those of simulated body fluid(SBF))are able to form translucent and stable solutions(mineralizing solution of highly concentrated counter-ions(MSCIs)),and mineralization can be triggered upon them with external solvents(e.g.,water or ethanol).Furthermore,with pristine bacterial cellulose(BC)membrane as a model,we demonstrate an effective and controllable mineralization performance of MSCIs on organic substrates.This approach not only forms the homogeneous biominerals on the BC fibers and in the interspaces,but also provides regulations over mineralization rate,mineral content,phase,and dopants.The resulting mineralized BC membranes(MBCs)exhibit high cytocompatibility and favor the proliferation of rat bone marrow mesenchymal stem cells(rBMSC).Following this,we prepare a mineralized bone suture(MBS)from MBC for non-weight bearing bone fixation,which then is tested on a rabbit median sternotomy model.It shows firm fixation of the rabbit sternum without causing discernible toxicity or inflammatory response.This study,by extending the mineralization to the organic solution system of highly concentrated counter-ions,develops a promising strategy to design and build targeted mineral-based composites.

Epidural Spinal Cord Stimulation Promotes Motor Functional Recovery by Enhancing Oligodendrocyte Survival and Differentiation and by Protecting Myelin after Spinal Cord Injury in Rats

Epidural spinal cord stimulation (ESCS) markedly improves motor and sensory function after spinal cord injury (SCI), but the underlying mechanisms are unclear.Here, we investigated whether ESCS affects oligodendrocyte differentiation and its cellular and molecular mechanisms in rats with SCI. ESCS improved hindlimb motor function at 7 days, 14 days, 21 days, and 28 days after SCI.ESCS also significantly increased the myelinated area at 28days, and reduced the number of apoptotic cells in the spinal white matter at 7 days. SCI decreased the expression of 20,30-cyclic-nucleotide 30-phosphodiesterase (CNPase,an oligodendrocyte marker) at 7 days and that of myelin basic protein at 28 days. ESCS significantly upregulated these markers and increased the percentage of Sox2/CNPase/DAPI-positive cells (newly differentiated oligodendrocytes) at 7 days. Recombinant human bone morphogenetic protein 4 (rh BMP4) markedly downregulated these factors after ESCS. Furthermore, ESCS significantly decreased BMP4 and p-Smad1/5/9 expression after SCI,and rh BMP4 reduced this effect of ESCS. These findings indicate that ESCS enhances the survival and differentiation of oligodendrocytes, protects myelin, and promotes motor functional recovery by inhibiting the BMP4-Smad1/5/9 signaling pathway after SCI.

Amorphous calcium magnesium phosphate nanocomposites with superior osteogenic activity for bone regeneration

The seek of bioactive materials for promoting bone regeneration is a challenging and longterm task.Functionalization with inorganic metal ions or drug molecules is considered effective strategies to improve the bioactivity of various existing biomaterials.Herein,amorphous calcium magnesium phosphate(ACMP)nanoparticles and simvastatin(SIM)-loaded ACMP(ACMP/SIM)nanocomposites were developed via a simple co-precipitation strategy.The physiochemical property of ACMP/SIM was explored using transmission electron microscope(TEM),Fourier transform infrared spectroscopy(FTIR),powder X-ray diffraction(XRD)and highperformance liquid chromatograph(HPLC),and the role of Mg^(2+) in the formation of ACMP/SIM was revealed using X-ray absorption near-edge structure(XANES).After that,the transformation process of ACMP/SIM in simulated body fluid(SBF)was also tracked to simulate and explore the in vivo mineralization performance of materials.We find that ACMP/SIM releases ions of Ca^(2+),Mg^(2+)and PO_(4)^(3),when it is immersed in SBF at 37℃,and a phase transformation occurred during which the initially amorphous ACMP turns into self-assembled hydroxyapatite(HAP).Furthermore,ACMP/SIM displays high cytocompatibility and promotes the proliferation and osteogenic differentiation of MC3T3-E1 cells.For the in vivo studies,lamellar ACMP/SIM/Collagen scaffolds with aligned pore structures were prepared and used to repair a rat defect model in calvaria.ACMP/SIM/Collagen scaffolds show a positive effect in promoting the regeneration of calvaria defect after 12weeks.The bioactive ACMP/SIM nanocomposites are promising as bone repair materials.Considering the facile preparation process and superior in vitro/vivo bioactivity,the as-prepared ACMP/SIM would be a potential candidate for bone related biomedical applications.