Hong Mo

Studies on Crystal Morphology and Crystallization Kinetics of Polyamide 66 Filled with CaCO3 of Different Sizes and Size Distribution

In this study, two different sizes of calcium carbonates (CaCO3) were blended and filled into polyamide66 (PA66). The effect of CaCO3 on the crystallization behavior of PA66 is investigated by differential scanning calorimeter (DSC). The melting measurement results indicated PA66/CaCO3 composites have secondary crystallization phenomena, which means that the crystallization process is more complicated. The crystallization temperature of the efficient size distribution samples is lower than that of the single size distribution samples. The isothermal crystallization kinetics experimental results showed that PA66/CaCO3 has the heterogeneous nucleation process, while the pure PA66 has homogeneous nucleation process. Compared with the composites filled with single-size CaCO3, both the crystallization rate constant (K) and their Avrami exponents (n) of isothermal crystallization kinetics increase. The rheological measurement result shows that the shear viscosity of the efficient size distribution composites is lower than that of the single size distribution samples. The result can be used to explain that the experimental results of crystal morphology and crystallization. The lower viscosity of the system is, the harder nucleation, the easier crystal formation.

Novel triphosphorylation polyurethane nanoparticles for blood-contacting biomaterials' coating

Improving hemocompatibility of biomaterials and devices contacting the human blood has been the subject of intensive research. In this study, we synthesized a novel excellent blood compatible polyurethane/sodium triphosphate nanoparticle (PU/STPP). Characterization of polyurethane/sodium triphosphate (PU/STPP) nanoparticles was carried out by transmission electron microscopy (TEM), scanning electron microscopy (SEM), dynamic light scattering (DLS), nuclear magnetic resonance (NMR), and energy dispersive spectroscopy (EDS). Blood compatibility assessment of PU/STPP nanoparticles was performed by in vitro coagulation time, plasma clotting time, hemolysis rate, and red blood cell morphology tests. Cell compatibility evaluations of PU/STPP nanoparticles were obtained by MTT cell viability tests. The PU/STPP nanoparticles also were used to modify vascular prostheses with cosedimentation. Platelet adhesion tests showed that blood compatibility of vascular prostheses coated with PU/STPP nanoparticles is better than that of pure vascular prostheses.

Silver Nanoparticles Modified with Sodium Triphosphate: Antibacterial Activity, Hemocompatibility and Cytotoxicity

In this study, we report silver nanoparticles (Ag NPs) modified with sodium triphosphate (STTP) (Ag-STPP NPs) prepared by a simple surface modification and chemical reduction method. It was confirmed by 31P NMR spectroscopy that STPP was successfully introduced to the surface of Ag NPs. It was revealed by conductivity change measurements, bacterial growth kinetics and antibacterial efficiency tests that Ag-STPP NPs still retained the strong antibacterial ability. It was demonstrated by hemolysis assays, red blood cell morphology measurements, plasma recalcification time and in vitro clotting times that Ag-STPP NPs had improved hemocompatibility. It was also implied by cell viability measurements that Ag-STPP NPs possessed low cytotoxicity and high cytocompatibility. These findings, combined with the low-cost and ease of synthesis, make Ag-STPP NPs a promising candidate for biomedical applications.

Polyurethane/polyurethane nanoparticle-modified expanded poly(tetrafluoroethylene) vascular patches promote endothelialization: PU/PU NP-MODIFIED ePTFE VASCULAR PATCHES

Expanded poly(tetrafluoroethylene) (ePTFE) has been widely used as a vascular graft material due to the fact that it is durable, porous, flexible, and inert. However, ePTFE grafts easily induce thrombosis, calcification and neointimal hyperplasia in small-diameter (<6 mm) graft bypass surgeries and thus cause surgical failure. Therefore, it is necessary to improve the in vitro and in vivo performances of ePTFE grafts. In this work, we first prepared a polyurethane/polyurethane nanoparticles (PU/PU-NPs) composite film by a simple cosedimentation method. Compared with the pure PU film, the blood compatibility and the cell compatibility of the PU/PU-NPs composite film were significantly improved. Then, we constructed a PU/PU-NPs/ePTFE vascular patch (PPVP) by coating PU and PU-NPs onto the surface of an ePTFE graft. PU-NP modification endowed the ePTFE graft with the nanopatterned surface similar to the luminal surface of a blood vessel. PU NPs and the structural likeness of the surface synergistically optimized the overall performance, and thus improved the blood and cell compatibilities, effectively inhibited platelet adhesion, enhanced cell attachment and proliferation, and facilitated the formation of endothelial tissue-endothelialization. The abdominal artery patched with PPVP was not blocked and the endothelialization was achieved 30 days after the implantation. All the results taken together indicate that PPVP may be a promising alternative for a vascular patch.