A cross-linking reagent is required to improve mechanical strength and degradation properties of biopolymers for tissue engineering. To find the optimal preparative method, we prepared diverse genipin-cross-linked chitosan/collagen scaffolds using different genipin concentrations and various cross-linking temperatures and cross-linking times. The compressive strength increased with the increasing of genipin concentration from 0.1 to 1.0%, but when concentration exceeded 1.0%, the compressive strength decreased. Similarly, the compressive strength increased with the increasing of temperature from 4 to 20°C, but when temperature reached 37°C, the compressive strength decreased. Showing a different trend from the above two factors, the effect of cross-linking time on the compressive strength had a single increasing tendency. The other results also demonstrated that the pore size, degradation rate and swelling ratio changed significantly with different cross-linking conditions. Based on our study, 1.0% genipin concentration, 20°C cross-linking temperature and longer cross-linking time are recommended.
The aim of this study was to investigate whether a surface coating with graphene could enhance the surface bioactivation of titanium alloys (Ti6Al4V) to further accelerate in vivo osteogenesis and osseointegration at the implant surface. In this study, a New Zealand white rabbit femoral condyle defect model was established. After 4, 12 and 24 weeks, biomechanical testing, micro-computed tomography (Micro-CT) analyses and histological observations were performed. At the highest push-out forces during the test, microstructure parameters, such as the bone volume/total volume fraction (BV/TV) and mineral apposition rate (MAR), of the new bone were significantly higher in the graphene-coated Ti6Al4V group (G-Ti6Al4V) than in the Ti6Al4V group (P < 0.05). Van Gieson (VG) staining showed that the G-Ti6Al4V group had more new bone formation than the Ti6Al4V group, and the G-Ti6Al4V group showed a closer fit between the bone and implant. In conclusion, graphene might be a novel type of nano-coating material for enhancing the surface biological activity of Ti-based alloy materials and may further promote in vivo osteogenesis and osseointegration.
Articular cartilage has a limited self-regenerative capacity. Thus, treatment of cartilage lesions is a major challenge. Tissue engineering using a variety of biomaterials is a promising solution to the problem of cartilage damage. In this in vitro study, we investigated the effect of the presence of cartilage-tissue chondroitin-sulfate (CS) in a fibrin scaffold on the differentiation of adipose-derived adult stem cells (ADAS cells) into chondrocytes. Isolated rabbit ADAS cells were cultured in fibrin matrices with and without CS for up to 14 days. ADAS cells differentiated into chondrocytes in both matrices, but cell proliferation, glycoaminoglycans content, and type II collagen expression were significantly higher in the fibrin-CS matrices than those in the fibrin matrices alone. Histological examination and scanning electronic microscopy revealed the fibrin-CS matrices exceeded in inducing differentiation of ADAS cells into chondrocytes in terms of tissue morphological characteristics. We concluded that the fibrin-CS matrices mimicking native cartilage extracellular matrix could act as a three-dimensional scaffold for cartilage tissue engineering and have the potential for promoting ADAS cells differentiation into chondrocytes. ß
The objective of this study was to investigate whether surface coating with graphene could enhance the surface bioactivation of PET-based artificial ligaments to accelerate graft-to-bone healing after anterior cruciate ligament reconstruction. In an in vitro study, the proliferation of MC3T3-E1 cells and their differentiation on the scaffolds were quantified via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and real-time polymerase chain reaction assays. The significantly higher optical-density values and transcription levels of osteoblast-specific genes indicated that graphene modification could promote the proliferation of MC3T3-E1 cells and accelerate their specific differentiation into osteogenic lineages on scaffolds. In an in vivo test, rabbits were used to establish an extra-articular graft-to-bone healing model. At 4, 8, and 12 weeks after surgery, biomechanical tests, microcomputed tomography analysis, and histological observations were performed. The final results demonstrated that the microstructural parameters, the average mineral apposition rate of the bone, and the biomechanical properties of the graphene-coated polyethylene terephthalate (PET)-based artificial ligament (G-PET-AL) group were significantly higher than those of the PET-AL graft group (P < 0.05). The results of Van Gieson staining indicated that in the G-PET-AL group, there was more newly formed bone than there was in the group in which nongraphene-coated PET-ALs were used. In conclusion, graphene exhibits considerable potential for enhancing the surface bioactivation of materials.
Abstract. The mechanisms responsible for the phenomenon of an accelerated speed of fracture healing in patients with traumatic brain injury (TBI) remain unclear. The present study was performed to test the hypothesis that TBI causes changes in calcitonin gene-related peptide (CGRP) levels in sera that enhance fracture healing. A standard closed femoral fracture was produced in rats, which were subjected to additional closed head trauma. The fracture healing was assessed 4 and 8 weeks later using micro-CT. Sera, brain tissues and muscles surrounding the fracture sites collected at 24, 48, 72 and 168 h after injury were used to detect the expression of CGRP using ELISA, immunohistochemistry and RT-PCR. Micro-CT demonstrated that fracture healing and mineralization in the TBI-fracture group occurred earlier compared to the fracture-only group. ELISA analysis revealed a high concentration of CGRP in the TBI-fracture group (P<0.05), and immunohistochemistry assay and RT-PCR analysis revealed a significant increase in CGRP in the brain and muscle of the TBI-fracture group at 168 h after fracture (P<0.001). Our results indicate that the mechanism for the enhancement of fracture-healing secondary to traumatic brain injury is correlated to the high levels of CGRP, which may be released from the brain tissue into the serum.
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