Dalyadkins5605

In bone tissue engineering, a scaffold requires not only facilitating cell activity but also providing adequate mechanical support. One feasible approach to ensure it is to use modeling tools to design such a scaffold which is then built by additive manufacturing. In this study, curve interference was introduced to design porous scaffolds with gradient structures based on three lattice units (cubical, circular and spherical) which were then manufactured by selective laser sintering (SLS) with PA12/HA material. The mechanical properties of both uniform and graded porous scaffolds were analyzed based on numerical and experimental tests. The results show that the uniform cubical-pore scaffold as well as the gradient spherical-pore scaffold has the optimal mechanical property. Further, uniform and graded scaffolds exhibit distinct failure mechanism. The graded scaffold has a layer-by-layer failure feature while each layer of the uniform structure almost has the same degree of deformation. Additionally, the comparison between the numerical and experimental results shows a good agreement, validating that the proposed curve interference method coupled with SLS technology is suitable for implementing the design of scaffolds following expected performance.Resorbable biomaterials based on artificial extracellular matrices (aECM) represent promising scaffolds for the treatment of large bone defects. Here, we investigated various glycosaminoglycan (GAG) derivatives of varying sulfation degree with respect to their influence on in vivo bone healing. The materials used in this study consisted of GAG-coated degradable polycaprolactone-co-lactide (PCL). Critical size femur defects in rats were filled with autologous bone serving as positive control or the respective coated or uncoated PCL scaffolds. After 2 and 12 weeks, progress in the healing process was investigated by analyzing the new bone matrix formation, the collagen content and hydroxyapatite formation by using micro-computed tomography (μCT), biomechanical testing, nuclear magnetic resonance spectroscopy (NMR) and histology. check details The sulfated GAG coating contributed substantially to bone regeneration, increased collagen synthesis and initiated mineralization of the organic matrix. Most substantial collagen production was detected in scaffolds coated with chondroitin sulfate. Scaffolds coated with hypersulfated hyaluronan induced formation of new bone volume comparable to what was observed in the positive control. GAG differing in the sugar backbone and degree of sulfation modulate the healing process at different times, eventually leading to improved bone healing.Zn and its alloys are considered as a new class of biodegradable metals due to their moderate degradation rates and acceptable biocompatibility. However, inadequate mechanical properties limit their further applications, especially for cardiovascular stents. In this study, a novel biodegradable Zn-1.5Cu-1.5Ag (wt%) alloy with excellent mechanical properties was developed, and then its in vitro degradation and cytotoxicity were characterized. Microstructural characterization showed that hot extrusion produced a bimodal distribution of grain size and much finer secondary phase precipitates. The as-extruded alloy exhibited a satisfactory combination of strength and plasticity (yield strength 162.0 ± 2.94 MPa, ultimate tensile strength 220.3 ± 1.70 MPa and elongation 44.13 ± 1.09%). After being aged at room temperature for 8 months, its mechanical properties increased about 10%, implying its good anti-aging ability. The strain hardening exponent (n) calculated from true stress-strain curve showed that this alloy has evident strain hardening. Immersion tests in c-SBF solution revealed that this alloy has a moderate corrosion rate (48.6 ± 4.14 μm/year) and slightly localized corrosion behavior. Electrochemical tests showed that a weak passive film formed on surface during degradation, which has a limited protective effect. The cytotoxicity tests exhibited that this alloy possesses acceptable in vitro biocompatibility, which is comparable to pure Zn. According to the results of mechanical properties, corrosion behavior and cytotoxicity, the Zn-1.5Cu-1.5Ag alloy can be regarded as a potential candidate for cardiovascular stent applications.Herein, a mesoporous silica nanoparticle (MSN) based biocompatible, targeted and controlled drug delivery system has been synthesized for tumor tissue-specific drug delivery. Umbelliferone, a natural coumarin derivative was loaded into the pores of MSN and capped with pH-sensitive poly acrylic acid (PAA). For targeted delivery of umbelliferone in tumor tissue, folic acid (FA) was grafted onto the surface of drug-loaded and PAA-coated MSN. The successful construction of the nanohybrid (Umbe@MSN-PAA-FA) was confirmed by performing a series of characterization. The synthesized pH-responsive nanohybrid showed diameter of around 50 nm with overall negative surface charge and drug loading content of 12.56%. In vitro study showed that the nanohybrid caused significant cytotoxicity through the induction of both oxidative stress as well as mitochondrial damage in folate receptor over-expressed in human breast cancer cell, MCF-7 compared with free umbelliferone. In vivo study also exhibited that the nanohybrid effectively reduced tumor growth in tumor-bearing mice compared with free umbelliferone due to the enlarged bioavailability of the drug in tumor tissue. Besides, the nanohybrid did not exhibit any significant sign of systemic toxicity in other vital organs. Together, the study denoted that PAA and FA functionalized MSN controlled-drug delivery system could assist to increase the anticancer potential of umbelliferone.Biodegradable Zn alloys containing Fe suffer from a common problem that FeZn13 second phase particles are coarse. This problem roots thermodynamically from the negligible solid solubility of Fe in Zn and priority of FeZn13 solidification over Zn. In this paper, bottom circulating water-cooled casting method is successfully developed to significantly refine FeZn13 particles in Zn-0.3Fe alloy, owing to its cooling speed about 8 times of that of conventional casting. The second phase refinement alleviates brittleness of the alloy, increases the ultimate tensile strength by about 62%, and decreases electrochemical corrosion rate (CR) by about 19%, but immersion CR by only about 4% due to barrier effect of corrosion products. Viability of human umbilical vein endothelial cells maintains at a high level over 95% in 25-100% extracts. A great potential is shown for improving comprehensive properties of biodegradable Zn alloys without changing its chemical compositions through such a physical method.