The vessels in the microcirculation keep adjusting their structure to meet the functional requirements of the different tissues. A previously developed theoretical model can reproduce the process of vascular structural adaptation to help the study of the microcirculatory physiology. However, until now, such model lacks the appropriate methods for its parameter settings with subsequent limitation of further applications. This study proposed an improved quantum-behaved particle swarm optimization (QPSO) algorithm for setting the parameter values in this model. The optimization was performed on a real mesenteric microvascular network of rat. The results showed that the improved QPSO was superior to the standard particle swarm optimization, the standard QPSO and the previously reported Downhill algorithm. We conclude that the improved QPSO leads to a better agreement between mathematical simulation and animal experiment, rendering the model more reliable in future physiological studies.
Objective To prepare nano polypyrrole (PPy)/chitin composite membrane and observe their biocompatibility. Methods The nano PPy was synthesized by microemulsion polymerization, blended with chitosan and then formed membranes. The membranes were then modified by acetylation to get the experimental membranes (nano PPy/chitin composite membranes, group A). The chitosan membranes (group B) and chitin ones (group C) modified by acetylation acted as control. Scanning electron microscopy and FT-IR spectra were used to identify the nano PPy and the membranes of each group. And the conductivity of membranes of each group was measured. Schwann cells were co-cultured in vitro with each group membranes to observe the biocompatibility by inverted microscope observing, living cell staining, cell counting, and immunofluorescence staining. The lysozyme solution was used to evaluate the degradation of the membranes in vitro. Results The FT-IR spectra showed that the characteristic vibrational absorption peaks of C=C from nano PPy appeared at 1 543.4 cm–1 and 1 458.4 cm–1. Scanning electron microscopy observation revealed that the size of nano PPy particles was about 100-200 nm. The nano PPy particles were synthesized. It was successful to turn chitosan to chitin by the acetylation, which was investigated by FT-IR analysis of membranes in groups A and C. The characteristic peaks of the amide Ⅱ band around 1 562 cm–1 appeared after acetylated modification. Conductivity test showed that the conductivity of membranes in group A was about (1.259 2±0.005 7)×10–3 S/cm, while the conductivity of the membranes in groups B and C was not detected. The nano PPy particles uniformly distributed on the surface of membranes in group A were observed by scanning electron microscope; the membranes in control groups were smooth. As a result, the nano PPy/chitin composite membranes with electrical conductivity were obtained. The cultured Schwann cells were found to survive with good function by fluorescein diacetate live cell staining, soluble protein-100 immunofluorescence staining, and inverted microscope observing. The cell counting showed that the proliferation of Schwann cells after 2 days and 4 days of group A was more than that of the two control groups, and the differences were significant (P<0.05). It indicated that the nano PPy/chitin composite membranes had better ability of adhesion and proliferation than those of chitosan and chitin membranes. The degradation of membranesin vitro showed that the degradation rates of membranes in groups A and C were significantly higher than those in group B at all time points (P<0.05). In a word, the degradation performance of the membranes modified by acetylation was better than that of chitosan membranes under the same condition. Conclusion The nano PPy and chitosan can be blended and modified by acetylation successfully. Nano PPy/chitin composite membranes had electrical conductivity, degradability, and good biocompatibility in vitro.
Vena cava filter is a filter device designed to prevent pulmonary embolism caused by thrombus detached from lower limbs and pelvis. A new retrievable vena cava filter was designed in this study. To evaluate hemodynamic performance and thrombus capture efficiency after transplanting vena cava filter, numerical simulation of computational fluid dynamics was used to simulate hemodynamics and compare it with the commercialized Denali and Aegisy filters, and in vitro experimental test was performed to compare the thrombus capture effect. In this paper, the two-phase flow model of computational fluid dynamics software was used to analyze the outlet blood flow velocity, inlet-outlet pressure difference, wall shear stress on the wall of the filter, the area ratio of the high and low wall shear stress area and thrombus capture efficiency when the thrombus diameter was 5 mm, 10 mm, 15 mm and thrombus content was 10%, 20%, 30%, respectively. Meanwhile, the thrombus capture effects of the above three filters were also compared and evaluated by in vitro experimental data. The results showed that the Denali filter has minimal interference to blood flow after implantation, but has the worst capture effect on 5 mm small diameter thrombus; the Aegisy filter has the best effect on the trapping of thrombus with different diameters and concentrations, but the low wall shear stress area ratio is the largest; the new filter designed in this study has a good filtering and capture efficiency on small-diameter thrombus, and the area ratio of low wall shear stress which is prone to thrombosis is small. The low wall shear stress area of the Denali and Aegisy filters is relatively large, and the risk of thrombosis is high. Based on the above results, it is expected that the new vena cava filter designed in this paper can provide a reference for the design and clinical selection of new filters.