Objective To study the effect of preparation conditions for small-diameter polyurethane(PU) vascular graft on microstructure and mechanical properties. Methods The small-diameter microporous PU artificial vascular grafts were prepared by dipping and leaching method. The dimension and microstructure were controlled by changing mold diameter, PU materials, salt sizes, salt to polymer ratio, times of dipping layers etc. The mechanical properties of PU grafts including radical compliance, water permeability, longitudinal strength, burst strength, and suture tearing strength were measured and the effect of the graft dimension and microstructure on their properties were studied. Results The internal diameter of grafts prepared was 2-4 mm depending on mold diameter. The wall thickness was 0.6-1.2 mmafter dipping 4-8 layers. The density was 0.23-0.49 g/cm3. The pore was 42-95 μm in diameter. The porosity was 56%80%. The radical compliance was 1.2%-7.4%·13.3 kPa-1 and higher compliances could be obtained by using moreelastic polyurethane, higher salt to polymer ratio, longer diameter and less wall thickness. The water permeability, mainly depending on salt to polymer ratio,diameter, and wall thickness, was 0.29-12.44 g／(cm2·min). The longitudinal strength was 1.55-4.36 MPa correlating with tensile strength of polyurethane and salt to polymer ratio. The burst strength was 60-300 kPa also depending on tensile strength of polyurethane and salt to polymer ratio. The suture tearing strength was 19.5-96.2 N／cm2 depending on tensile strength of polyurethanebut not on the angle of tearing and graft axial directions. The compliance and water permeability of Chronoflex grafts were higher than those of PCU1500 grafts, but longitudinal strength, burst strength, and suture tearing strength of PCU1500 grafts were better than those of Chronoflex grafts. Conclusion Small-diameter grafts with proper pore sizes, porosity, matching compliance can be obtained by selecting PU materials and optimizing the preparation conditions.
The link between micro- and macro-parameters for radiation interactions that take place in living biological systems is described in this paper. Meanwhile recent progress and development in microdosimetry and nanodosimetry are introduced, including the methods to measure and calculate these micro- or nano-parameters. The relationship between radiobiology and physical quantities in microdosimetry and nanodosimetry was presented. Both the current problems on their applications in radiation protection and radiotherapy and the future development direction are proposed.
Mechanical properties and biological evaluation of buffalo horn material were examined in this study. The effects of sampling position of buffalo horn on mechanical properties were investigated with uniaxial tension and micron indentation tests. Meanwhile, the variation of element contents in different parts of buffalo horn was determined with elemental analysis, and the microstructure of the horn was measured with scanning electron microscopy. In addition, biological evaluation of buffalo horn was studied with hemolytic test, erythrocyte morphology, platelet and erythrocyte count, and implantation into mouse. Results showed that the buffalo horn had good mechanical properties and mechanical characteristic values of it gradually increased along with the growth direction of the horn, which may be closely related to its microstructure and element content of C, N, and S in different parts of the buffalo horn. On the other hand, because the buffalo horn does not have toxicity, it therefore does not cause hemolysis of erythrocyte and has a good affinity with it. Buffalo horn has good histocompatibility but meanwhile it may induce the platelet adhesion and aggregation. Even so, it does not continue to rise to induce a large number of platelet to aggregate with resulting blood clotting. Therefore, the buffalo horn material has been proved to possess good blood compatibility according to the preliminary evaluation.
In order to improve the interfacial bonding strength of hydroxyapatite/polyurethane implanted material and dispersion of hydroxyapatite in the polyurethane matrix, we in the present study synthesized nano-hydroxyapatite/polyurethane composites by in situ polymerization. We then characterized and analyzed the fracture morphology, thermal stability, glass transition temperature and mechanical properties. We seeded MG63 cells on composites to evaluate the cytocompatibility of the composites. In situ polymerization could improve the interfacial bonding strength, ameliorate dispersion of hydroxyapatite in the properties of the composites. After adding 20 wt% hydroxyapatite into the polyurethane, the thermal stability was improved and the glass transition temperatures were increased. The tensile strength and maximum elongation were 6.83 MPa and 861.17%, respectively. Compared with those of pure polyurethane the tensile strength and maximum elongation increased by 236.45% and 143.30%, respectively. The composites were helpful for cell adhesion and proliferation in cultivation.
Objective To summarize the influence of microstructure on performance of triply-periodic minimal surface (TPMS) bone scaffolds. Methods The relevant literature on the microstructure of TPMS bone scaffolds both domestically and internationally in recent years was widely reviewed, and the research progress in the imfluence of microstructure on the performance of bone scaffolds was summarized. Results The microstructure characteristics of TPMS bone scaffolds, such as pore shape, porosity, pore size, curvature, specific surface area, and tortuosity, exert a profound influence on bone scaffold performance. By finely adjusting the above parameters, it becomes feasible to substantially optimize the structural mechanical characteristics of the scaffold, thereby effectively preempting the occurrence of stress shielding phenomena. Concurrently, the manipulation of these parameters can also optimize the scaffold’s biological performance, facilitating cell adhesion, proliferation, and growth, while facilitating the ingrowth and permeation of bone tissue. Ultimately, the ideal bone fusion results will obtain. Conclusion The microstructure significantly and substantially influences the performance of TPMS bone scaffolds. By deeply exploring the characteristics of these microstructure effects on the performance of bone scaffolds, the design of bone scaffolds can be further optimized to better match specific implantation regions.