Abstract:The biological mechanism of trabecular bone with its complex three-dimensional microstructure and the interaction between micro-environment and osteoblasts have been studied and applied in the field of bone repair, reconstruction and bone regeneration. However, previous research lack the simulation of the real environment of bone trabecula in vivo, especially the lack of accurate quantification of trabecular microstructure and the research and application of bone regeneration under the condition of interaction with microenvironment. In this study, a new method is used to analyze and construct the three-dimensional environment of trabecular bone. Three-dimensional cancellous bone model and geometric features analysis were conducted by using Mimics and Rhino software based on Micro CT of rabbit proximal femoral cancellous bone scan. Bionic trabecular structure was analyzed and constructed by using Stirling formula and 3D printed trabecular bone structure. The comparison on trabeculae area and structure similarity analysis between cancellous bone samples and bionic cancellous bone show that bionic cancellous bone has extremely high similarity (more than 95%) with natural cancellous bone structure. In vitro experiments of bionic bone trabecular can construct a good microenvironment for cell growth. In sum, the proposed method provides a useful tool for manufacturing a more realistic physiological structure for clinical research and application for tissue engineering.

Abstract:Genetic modification of biological scaffold to enhance angiogenesis is an effective method for bone regeneration. In this study, a 3D-PLGA/nHAp scaffold containing pdgfb-expressing lentiviral vectors to enhance angiogenesis for calvarial critical bone defect repair was designed. The modified scaffolds (LVpdgfb/ PLGA/nHAp) could continuously release bioactive LV-pdgfb particles for up to 5 days in vitro. In scaffold implanted critical calvarial bone defect mouse model, how the genetically modified 3D scaffolds affect the angiogenesis and bone formation was studied by two-photon and photoacoustic imaging, microCT and histomophological methods. Eight weeks post-implantation, blood vessel areas in LV-pdgfb/PLGA/nHAp scaffolds were significantly higher than in PLGA/nHAp scaffolds at each observed time point. In accordance with the angiogenesis process, microCT analysis indicated that the repairment of the critical-calvarial defects in LV-pdgfb/PLGA/nHAp group dramatically improved compared to the other groups, including bone mineral density (BMD), the ratio of bone volume to tissue volume (BV/TV), trabecular number (Tb.N). In this study, we verified and compared the application of two state of the art non-invasive in vivo imaging techniques in imaging of neo-vasculature inducing in 3D bone artifact, and demonstrated that lentivirus-mediated pdgf-b gene modified scaffolds could be a promising tool to build vascularized tissue engineering bone to repair a large bone defects in murine model.

Abstract:In this paper, the rheology and printability of the PS@Ag/PDMS conductive paste were studied. The PS@Ag/PDMS conductive paste was fabricated by mixing the shell-core structured PS@Ag (silver nanoparticles coated on the polystyrene microspheres surfaces) hybrid conductive fillers with liquid polydimethylsiloxane (PDMS) prepolymer and its curing agent. The sandwiched flexible strain sensors of PDMS-PS@Ag/PDMSPDMS were fabricated by embedding the PS@Ag/PDMS composites in two PDMS encapsulated layers using printing technology and spinning coating process. The real-time monitoring results of the sandwiched flexible strain sensors in human body motions show that the relative changes of resistance of the flexible strain sensor in elbow joint and knee joint flexion-extension cycles can reach 0.75 and 0.50 respectively. The sensors show high stretchability, sensitivity and signal uniformity, which have great potentials in the application of human body motion monitoring.

Abstract:To more accurately control the morphologies of self-assembled layers of titanium dioxide nanotubes (TNT), 10 turns of high pressure torsion (HPT) was applied to pure titanium to refine the grain size from 13 μm to 135 nm and then two-step electrochemical anodization (30 V, DC, 16 and 6 h) was used to produce TNT layers on these two substrates. Optical microscopy, transmission electron microscopy, scanning electron microscopy and wettability testing showed that grain refinement induced by HPT processing leads to thicker TNT layers with more homogeneous diameters, changed surface morphology and increased aqueous contact angle. The reason why two-step anodization increased the quality of anodized TNT layers and the underlying mechanism for how refined grain size influenced the morphologies and wettability of TNT layers were discussed.

Abstract:Antarctic krill as the dominant prey in the Southern Ocean has astonishing standing biomass. As a new source of chitosan, the unpolluted environment and the huge biomass stock would improve the quality of chitosan for biomedical application. In this study, Antarctic krill shrimp shells were used to extract chitosan by chemical method. The reacting condition in decalcification, deproteinization and deacetylation was optimized. The prepared chitosan extracted from Antarctic krill showed bright white powder, and the degree of deacetylationreached to 90.6%, with the molecular weight around 123 kDa and ash content around 0.095%. In hemostasis evaluation, Antarctic krill chitosan showed significantly superior hemostatic effect to other sources of commercialized chitosan, indicating its great prospects for hemostatic application.

Abstract:Small RNAs are essential regulators for T cell development, differentiation and functions. However, it is hard to deliver small RNAs into primary T cells by conventional transfection methods. Here, we reported that amphiphilic PBA-grafted PEI1.8k (PEI-PBA) nanovector facilitates the primary T cell-targeted RNA delivery miRNAthrough recognition of sialic groups on cell membrane of the T lymphocytes. CCK-8 (cell counting kit-8) and CFSE (5,6-carboxyfluorescein diacetate, succinimidyl ester) assay showed that the administration of PEI-PBA did not cause significant cell toxicity or abnormal proliferation. Meanwhile, the flowcytometry showed the average intake of miRNA was increased to 18.43% in the anti-CD3/CD28 activated CD3+ (cluster of differentiation 3) T lymphocytes by PEI-PBA in human, but not mouse. The results showed that PEI-PBA nano-system had effective delivery of small RNAs in human primary T cells without toxcity.

Abstract:Three-dimensional printing is a new raised technology, which can be used to control the shape of the scaffold and its inside structure. This technology has great potential in building tissue engineering scaffold, which can fulfill the requirement of personalized medicine. In recent years, Bio-3D printing technology has attracted more and more researchers’ attention, which breaks through the limitation of low spatial resolution of traditional tissue engineering technology, and can precisely control the distribution of cells in scaffold material, cell survival of the microenvironment, to provide a true three-dimensional balanced growth environment, making complex tissue and organ repair and in vitro reconstruction. This review introduces the three-dimensional bioprinting technology and the construction of bioinks, as well as the application in tissue and organ regeneration.