ObjectiveTo review the research progress of novel cross-linking methods applied in bio-derived materials. MethodsThe literature about the latest progress in the cross-linking methods of bio-derived materials was reviewed and analyzed. ResultsThe novel cross-linking methods of the bio-derived materials can be divided into chemical methods, physical methods, and biological methods, whose available application and cross-linking properties are greatly depended on their mechanisms. So proper methods should be developed to meet the various application requirements of the materials. A series of studies shows the feasibility and availability of the cross-linked bio-derived materials in the repair and reconstruction of the tissue. ConclusionBio-derived materials modified by novel cross-linking methods are proved to obtain excellent biocompatibility and tissue repair ability, better mechanical properties and degradation properties, and so on. Those methods provide researchers more choices to cross-linking materials, which are help to obtain the clinical tissue engineering products.
ObjectiveTo prepare polyurethane (PU) microspheres and evaluate its physicochemical properties and biocompatibility for biomedical applications in vitro. MethodsThe PU microspheres were prepared by self-emulsification procedure at the emulsification rates of 1 000, 2 000, 3 000, and 4 000 r/min. The molecular structure was tested by Fourier transform infrared spectrometer and the surface and interior morphology of PU microspheres were observed by scanning electron microscopy (SEM). PU microspheres prepared at best emulsification rate were selected for the subsequent experiment. The human umbilical vein endothelial cells (HUVECs) were cultured and seeded on the materials, then cell morphology and adhesion status were observed by calcein-acetoxymethylester/pyridine iodide (Calcein-AM/PI) staining. The cells were cultured in the H-DMEM containing 10%FBS with additional 1% phenol (group A), in the extracts of PU prepared according to GB/T 16886.12 standard (group B), and in H-DMEM containing 10%FBS (group C), respectively. Cell counting kit 8 (CCK-8) assay was used to detect the cell viability. The blood compatibility experiments were used to evaluate the blood compatibility, the PU extracts as experimental group, stroke-physiological saline solution as negative control group, and distilled water as positive control group. The hemolytic rate was calculated. ResultsThe SEM results of PU microspheres at the emulsification rate of 2 000 r/min showed better morphology and size. The microstructure of the PU was rough on the surface and porous inside. The Calcein-AM/PI staining showed that the HUVECs attached to the PU tightly and nearly all cells were stained by green. CCK-8 assays demonstrated that group B and group C presented a significantly higher cell proliferative activity than group A (P<0.05), indicating low cytotoxicity of the PU. The absorbance value was 0.864±0.002 in positive control group and was 0.015±0.001 in negative control group. The hemolysis rate of the PU extracts was 0.39%±0.07% (<5%), indicating no hemolysis. ConclusionThe PU microspheres are successfully prepared by self-emulsification. The scaffold can obviously promote cell attachments and proliferation and shows low cytotoxicity and favorable blood compatibility, so it might be an ideal filler for soft tissue.