Objective:To investigate the effects of shear stress magnitude and exposure time on the damage of blood component erythrocytes and von willebrand factor (VWF) based on microfluidic technology.Methods:A blood shear platform was built based on a microfluidic chip, samples were prepared under different shear stress magnitudes and exposure time lengths, free hemoglobin assay experiments were performed on blood samples, the hemolysis indices of different samples were measured, and the relative molecular masses of different samples of VWF were analyzed by immunoblotting and chemiluminescence imaging.Results:The quantitative relationships between the hemolysis index and the degradation rate of high relative molecular mass VWF with shear stress and exposure time followed the power function model well.Conclusions:The microfluidic experimental platform has the advantages of a precise and controllable internal microenvironment and easy and rapid detection, which can be used for the quantitative study of blood damage patterns.

Objective To study von Willebrand factor(VWF) damage based on a novel Maglev Taylor-Couette blood-shearing device. Methods The magnetic levitation (maglev) Taylor-Couette blood-shearing device was designed, and the blood-shearing platform was built. Fresh porcine blood was tested in circulation loop for 1 hour at laminar flow state. VWF damage was assessed by analyzing sample through Western blot and enzyme-linked immunosorbent assay. Results With the increase of exposure time and shear stress, a large number of high molecular weight VWF multimers were degraded into low molecular weight VWF. The maximum rate of degradation was 569%. When the shear stress increased from 18 Pa to 55 Pa, the ratio of VWF-Rco to VWF-Ag decreased from 45.7% to 32.8%. ConclusionsCompared with initial sample, the VWF damage was mainly manifested by the decrease of high molecular weight VWF and the decrease of VWF activity, and VWF-Ag did not change significantly. The novel maglev Taylor-Couette blood-shearing device can quantitatively control the flow parameters (exposure time and shear stress), and be used for blood damage research in vitro, thus providing references for the design and optimization of extracorporeal membrane oxygenation and blood pump.

Objective: To investigate the epidemiological and clinical characteristics of 91 cases of dengue fever outbreak in Jiangxi Province in 2019, and to strengthen the management and prevention of dengue fever. Methods: The clinical data, laboratory results and etiology tests of 91 patients with dengue fever from the Ninth Hospital of Nanchang, Zhangshu People′s Hospital, Fengcheng People′s Hospital and Nanchang County People′s Hospital from July 31, 2019 to September 27, 2019 were retrospectively collected. The t test was used for continuous variables and chi-square test was used for categorical variables. Results: A total of 91 dengue fever patients were reviewed. The patients age ranged from 4 to 87 years old, and the majority were adult patients. Most patients were farmers and they all had mosquito-biting history. Local cases were the major source of this outbreak. The incubation time was (5.19±2.96) days. All patients had fever over 38 ℃. Thirty-eight (41.8%) patients developed rashes, mainly distributed on the limbs and trunk, and 15 patients (16.5%) developed myalgia and fatigue. The incidence of rashes in patients admitted in September was 15.9% (7/44), which was significantly lower than 68.1% (32/47) in July and August (χ²=25.262, P<0.01). The incidence of headache in patients admitted in September was 27.3%(12/44), which was significantly lower than 78.7% (37/47) in July and August (χ² =24.206, P<0.01). Among the 91 patients, 64 (70.3%) patients had white blood cell counts less than 4×10⁹/L, 14(15.4%) patients had platelet counts less than 50×10⁹/L. The positive rate of dengue non-structural protein 1 (NS1) antigen was 100.0%(37/37), the positive rates of dengue antibody IgM and IgG were 50.0%(11/22) and 13.6%(3/22), respectively. Among the 113 serum samples tested for dengue virus RNA, 106 were identified with dengue virus type-1 and two were dengue virus type-2. In 22 patients who received tests within 7 days, the positive rate of NS1 antigen was 100.0% (22/22), the IgM and IgG positive rates were 50.0%(11/22) and 13.6% (3/22), respectively, and 19 patients were infected with dengue type-1. Among the IgM antibody positive cases, the onset days before sampling was (5.09±1.64) days, longer than that of IgM antibody negative cases ((2.82±1.83) days), with statistical significance (t=3.063, P=0.007). The onset time before sampling in dengue virus RNA-positive group was (3.53±1.87) days, which was shorter than that of RNA-negative group ((6.67±0.58) days), and the difference was statistically significant (t=2.839, P=0.013). Conclusions The dengue fever outbreak cases in Jiangxi Province in 2019 have typical clinical manifestations of dengue fever. Using the NS1 antigen test, IgM and IgG antibody tests and real-time fluorescent quantitative polymerase chain reaction for dengue virus genotyping during early onset of the disease can assistant clinicians in clinical management, controlling infectious source and stopping disease transmission.