Activity

In vivo experiments further demonstrate that the CS/HPC/nHA composite scaffold has a significant advantage in promoting bone formation in the bone defect area. All the results suggested that the CS/HPC/nHA scaffolds have great application prospect in bone tissue engineering.In general, cells are cultured and adapted to the in vitro rigidities of plastic or glass ranging between 1 and 10 GPa, which is very far from physiological values that are mostly in the kilopascal range. Stem cells however show a high sensitivity to the rigidity of their culture environment, which impacts their differentiation program. Here, we address the impact of rigidity on the long-term maintenance of pluripotency in human induced pluripotent stem cells (hiPSCs) to determine whether soft substrates could provide a new standard for hiPSC expansion and maintenance. To do this, we set up a fabrication process of polyacrylamide-based culture supports with a rigidity-decoupled surface chemistry. Soft elastic substrates with uniform and reproducible physicochemical properties were designed. The maintenance of pluripotency of two hiPSCs lines on substrates with stiffnesses ranging from 3 to 25 kPa was studied with an identical chemical coating consisting of a truncated recombinant vitronectin with defined surface density. Based on the analysis of cellular adhesion, survival, growth kinetics, three-dimensional distribution, and gene and protein expressions, we demonstrate that below 25 kPa hiPSCs do not maintain pluripotency on long-term culture, while pluripotency and self-renewal capacities are maintained above 25 kPa. In contrast to previous studies, no drift toward a specific germ line lineage was revealed. On soft substrates, cell colonies started to grow in three-dimensional (3D), suggesting that softness allows cells to limit contact with the synthetic matrix and to build their own microenvironment. These observations drastically limit the benefit of using standardized soft substrates to expand hiPSCs, at least with the current culture conditions. The development of a robust technology for the design of soft substrates nevertheless opens up perspectives to fine-tune physicochemical properties of the culture environment in addition to or in replacement of soluble growth factors to finely direct cell fate.Chitosan is a natural polycationic linear polysaccharide deacetylated from chitin. Glycol chitosan is a derivative of chitosan and has been extensively investigated in the biomaterials and hydrogel field for many bioengineering applications because of their unique material and biological properties. However, the molecular structure and network of glycol chitosan hydrogels remain unclear. Here, we explored the molecular structures and network of glycol chitosan with different protonation percentages by using full atomistic simulations. Hydrogel and xerogel models are constructed to understand the interactions between the water molecules and glycol chitosan chains. We calculated the radius of gyration and radial distribution function of hydrogel and xerogel models to understand the swelling behavior from molecular level. We find that when the pH is close to neutral and becomes basic, greater flexibility of glycol chitosan chains leads to a high swelling ratio. The slight contracting behavior of glycol chitosan chains and the dispersive distribution above 40% protonation can be interpreted to indicate a poor swelling ratio. The protonated amino groups inhibit the hydrogen-bond formation between water molecules and adjacent oxygen-containing groups of glycol chitosan main chains. selleck chemical On the other hand, the glycol groups of glycol chitosan are not affected by the electrostatic interaction, and the number of hydrogen bonds between glycol groups and water molecules does not vary with pH. The van der Waals interaction between glycol chitosan chains is dominant when the protonation percentages are lower than 40%, while the electrostatic interaction of amino groups is dominant when the protonation percentages are higher than 40%. Our results explain the effects of pH on the molecular structures of glycol chitosan and provide useful information regarding the design strategy of novel glycol chitosan and its derivatives for biomedical applications.The tumor microenvironment harbors essential components required for cancer progression including biochemical signals and mechanical cues. To study the effects of microenvironmental elements on Ewing’s sarcoma (ES) pathogenesis, we tissue-engineered an acellular three-dimensional (3D) bone tumor niche from electrospun poly(ε-caprolactone) (PCL) scaffolds that incorporate bone-like architecture, extracellular matrix (ECM), and mineralization. PCL-ECM constructs were generated by decellularizing PCL scaffolds harboring cultures of osteogenic human mesenchymal stem cells. The PCL-ECM constructs simulated in vivo-like tumor architecture and increased the proliferation of ES cells compared to PCL scaffolds alone. Compared to monolayer controls, 3D environments facilitated the downregulation of the canonical insulin-like growth factor 1 receptor (IGF-1R) signal cascade through mechanistic target of rapamycin (mTOR), both of which are targets of recent clinical trials. In addition to the downregulation of canonical IGF-1R signaling, 3D environments promoted a reduction in the clathrin-dependent nuclear localization and transcriptional activity of IGF-1R. In vitro drug testing revealed that 3D environments generated cell phenotypes that were resistant to mTOR inhibition and chemotherapy. Our versatile PCL-ECM constructs allow for the investigation of the roles of various microenvironmental elements in ES tumor growth, cancer cell morphology, and induction of resistant cell phenotypes.Unlike traditional broad-spectrum antibacterial agents, specifically targeted antimicrobial peptides (STAMPs) are difficult for bacteria to develop resistance to due to their unique membrane lytic mechanism. Additionally, STAMPs can maintain a normal ecological balance and provide long-term protection to the body. However, therapeutic applications of STAMPS are hindered by their weak activity and imperfect specificity, as well as lack of knowledge in understanding their structure-activity relationships. To investigate the effects of different parameters on the biological activities of STAMPs, a peptide sequence, WKKIWKDPGIKKWIK, was truncated, extended, and provided with an increased charge and altered amphipathicity. In addition, a novel template modification method for attaching a phage-displayed peptide, which recognized and bound to Escherichia coli (E. coli) cells, to the end of the sequence was introduced. Compared with the traditional template modification method, peptide 13, which contained a phage-displayed peptide at the C-terminus, exhibited superior narrow-spectrum antibacterial activity against E.