Narrow Results

This study was designed to investigate the antioxidant and free radical scavenging capacities of arjunic acid, an aglycone obtained from the fruit of medicine Terminalia Fruit. Liver microsomes, mitochondria, and red blood cells (RBCs) were prepared from Wistar rats. The antioxidant capacity was determined by the inhibitory effect on lipid peroxidation, hydrogen peroxide induced RBCs hemolysis, and RBCs autoxidative hemolysis. The free radical scavenging activity was tested by DPPH method and 2′,7′-dichlorodihydrofluoresc in diacetate (DCFH₂-DA) assay. Ascorbic acid was chosen as the positive controls. Results showed that arjunic acid was a strong antioxidant and a free radical scavenger, more potent than ascorbic acid, in microsomes lipid peroxidation, DPPH, hydrogen peroxide induced RBCs hemolysis, and (DCFH₂-DA) assay (p < 0.05). However, no significant difference was observed in the RBCs autoxidative hemolysis assay (p > 0.05).

A manganese oxide contained coating was prepared on biodegradable AZ31B magnesium alloy to control the degradation of AZ31B and improve its biocompatibility. Morphology, composition, and corrosion resistance of the coating were studied. The SEM observations showed that the coating was approximately 4–6 μm in thickness with net-like microcracks. The XPS analysis indicated that the coating was mainly composed of MgO, Mg(OH)₂, MnO₂, Mn₂O₃, and Mn₃O₄. It was found that AZ31B with such coating showed better corrosion resistance in simulated blood plasma through electrochemical and immersion tests. The hemolytic assay indicated that the treated AZ31B had no hemolytic effect.

Low hemolysis is an important factor for axial blood pumps that has been used in patients with heart failure. The structure of impellers plays a key role in the hemolytic properties of axial blood pumps. Axial blood pumps with various structure impellers exhibit different hemolytic characteristic. In the present study, we aimed to investigate the type of impellers structures in axial blood pumps that contain the best low hemolytic properties. Also, it is expensive and time-consuming to validate the axial blood pump's hemolytic property by in vivo experiments. Therefore, in the present study, the numerical method was applied to analyze the hemolytic property in a blood pump. Specifically, the hemolysis of the pump was calculated by using a forward Euler approach based on the changes in shear stress and related exposure times along the particle trace lines. The different vane structures and rotational speed that affect hemolysis were analyzed and compared. The results showed that long–short alternant vanes exhibited the best hemolytic property which could be utilized in the optimization design of axial blood pumps.

Low hemolysis and hydraulic performance are important factors for an axial blood pump, which have been transplanted in patients with heart failure (HF). The distance and clearance between impeller and diffuser play a key role in hemolytic properties and hydraulic performances of axial blood pumps that were developed by our group inspired by the design features of HeartMate II. In the present study, we aimed to investigate the appropriate distance and clearance between impellers and diffusers of axial blood pumps, which contains the best low hemolytic property and hydraulic performance using the computational fluid dynamics (CFDs) approach. Specially, the hemolysis of the pump was calculated by using two different empirical power-law hemolytic blood damage models with two sets of parameters. The two hemolytic blood damage models with two sets of parameters were analyzed and compared. Further, the different distances and clearances between impellers and diffusers that affect hemolytic and hydraulic characteristics were also analyzed. The results showed that the pump with distance of 2mm and clearance of 0.2mm between impeller and diffuser exhibited the best hemolytic property and better hydraulic performance.

Hemolysis in blood-contacting devices severely affects the health of users, and computation fluid dynamics (CFD) simulation is a crucial method for hemolysis analysis. Medical equipment has high requirements for simulation accuracy. Modification of the turbulence model is one of the most effective ways to improve efficiency. In this study, we designed nozzle models to simulate hemolytic shear flow, varying the degree of shear flow through different nozzle orifice sizes. The study acquires microscopic flow results through Particle Image Velocimetry (PIV) experiments, and the Sparlart–Allmaras (S–A) model was modified based on the experimental results. In the study, we obtained the influence characteristics of the model coefficients on the simulation results and completed the accuracy correction. The results showed that the model coefficient $c_{b1}$ has the most significant effect on the simulation results. Correcting $c_{b1}$ to about 200% of the standard value can significantly improve the simulation accuracy, and the high shear flow intensity corresponds to a slightly lower correction value. The model modification eliminates the simulation error in the high-speed area, and the comparison results show that it is superior to the standard turbulence model.

In recent years, ventricular assist devices (VAD) have received a worldwide admissibility and have become the unrivalled tools for replacing a failed heart. Most of the newer generations of these devices, including second and third generations, are designed to produce non-pulsatile flow at constant rotational speed. Here, we have proposed the design of a VAD, which although is an axial flow type, is able to produce pulsatile flow; and this has come through by changing the rotational speed of the impeller of the pump. This pump, which has an output analogous to cardiac output, is able to produce a flow rate of approximately 6 L per minute. Designing of this pump is based on turbomachinery theories and applying computational fluid dynamics (CFD) methods. The proposed pattern of the changes of rotational speed is trapezoidal and consists of four phases. Studies of the shear stresses imposed on the blood within the pump have shown that there has been an acceptable margin of safety for this pump in terms of blood injuries such as hemolysis and thrombosis.

Artificial prostheses create non-physiologic flow conditions with stress forces that may induce blood cell damage, particularly hemolysis. Earlier computational fluid dynamics (CFD) prediction models based on a quantified power model showed significant discrepancies with actual hemolysis experiments. These models used the premise that shear stresses act as the primary force behind hemolysis. However, additional studies have suggested that extensional stresses play a more substantial role than previously thought and should be taken into account in hemolysis models. We compared extensional and shear stress flow fields within the contraction of a short capillary with sharp versus tapered entrances. The flow field was calculated with CFD to determine stress values, and hemolysis experiments with porcine red blood cells were performed to correlate the effects of extensional and shear stress on hemolysis. Our results support extensional stress as the primary mechanical force involved in hemolysis, with a threshold value of 1000 Pa under exposure time less than 0.060 ms.