The influence of surface roughness on the damage of von Willebrand Factor under shear flow condition

In vitro comparative study of red blood cell and VWF damage on 3D printing biomaterials under different blood-contacting conditions

Mechanical circulatory support devices (MCSDs) are often associated with hemocompatible complications such as hemolysis and gastrointestinal bleeding when treating patients with end-stage heart failure. Shear stress and exposure time have been identified as the two most important mechanical factors causing blood damage. However, the materials of MCSDs may also induce blood damage when contacting with blood. In this study, the red blood cell and von Willebrand Factor (VWF) damage caused by four 3D printing biomaterials were investigated, including acrylic, PCISO, Somos EvoLVe 128, and stainless steel. A roller pump circulation experimental platform and a rotor blood-shearing experimental platform were constructed to mimic static and dynamic blood-contacting conditions of materials in MCSDs, respectively. Free hemoglobin assay and VWF molecular weight analysis were performed on the experimental blood samples. It indicated that different 3D printing materials and technology could induce different levels of damage to red blood cells and VWF, with acrylic causing the least damage under both static and dynamic conditions. In addition, it was found that blood damage measured for the same material differed on the two platforms. Therefore, a combination of static and dynamic experiments should be used to comprehensively investigate the effects of blood damage caused by the material. It can provide a reference for the design and evaluation of materials in different components of MCSDs.

A comprehensive comparison of the in vitro hemocompatibility of extracorporeal centrifugal blood pumps

Purpose: Blood damage has been associated with patients under temporary continuous-flow mechanical circulatory support. To evaluate the side effects caused by transit blood pumping, in vitro hemocompatibility testing for blood damage in pumps is considered a necessary reference before clinical trials. Methods: The hemocompatibility of five extracorporeal centrifugal blood pumps was investigated comprehensively, including four commercial pumps (the Abbott CentriMag, the Terumo Capiox, the Medos DP3, and the Medtronic BPX-80) and a pump in development (the magAssist MoyoAssist^®). In vitro, hemolysis was tested with heparinized porcine blood at nominal operating conditions (5 L/min, 160 mmHg) and extreme operating conditions (1 L/min, 290 mmHg) using a circulation flow loop. Hematology analyses concerning the blood cell counts and the degradation of high-molecular-weight von Willebrand factor (VWF) during 6-h circulation were also evaluated. Results: Comparing the in vitro hemocompatibility of blood pumps at different operations, the blood damage was significantly more severe at extreme operating conditions than that at nominal operating conditions. The performance of the five blood pumps was arranged in different orders at these two operating conditions. The results also demonstrated superior hemocompatibility of CentriMag and MoyoAssist^® at two operating conditions, with overall low blood damage at hemolysis level, blood cell counts, and degradation of high-molecular-weight VWF. It suggested that magnetic bearings have an advantage in hemocompatibility compared to the mechanical bearing of blood pumps. Conclusion: Involving multiple operating conditions of blood pumps in in vitro hemocompatibility evaluation will be helpful for clinical application. In addition, the magnetically levitated centrifugal blood pump MoyoAssist^® shows great potential in the future as it demonstrated good in vitro hemocompatibility.

Electrostatic Repulsive Features of Free-Standing Titanium Dioxide Nanotube-Based Membranes in Biofiltration Applications

This study presents the electrostatic repulsive features of electrochemically fabricated titanium dioxide nanotube (NT)-based membranes with different surface nanomorphologies in cross-flow biofiltration applications while maintaining a creatinine clearance above 90%. Although membranes exhibit antifouling behavior, their blood protein rejection can still be improved. Due to the electrostatically negative charge of the hexafluorotitanate moiety, the fabricated biocompatible, superhydrophilic, free-standing, and amorphous ceramic nanomembranes showed that about 20% of negatively charged 66 kDa blood albumin was rejected by the membrane with ∼100 nm pores. As the nanomorphology of the membrane was shifted from NTs to nanowires by varying fabrication parameters, pure water flux and bovine serum albumin (BSA) rejection performance were reduced, and the membrane did not lose its antifouling behavior. Herein, nanomembranes with different surface nanomorphologies were fabricated by a multi-step anodic oxidation process and characterized by scanning electron microscopy, atomic force microscopy, water contact angle analysis, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The membrane performance of samples was measured in 3D printed polyethylene terephthalate glycol flow cells replicating implantable artificial kidney models to determine their blood toxin removal and protein loss features. In collected urine mimicking samples, creatinine clearances and BSA rejections were measured by the spectrophotometric Jaffe method and high-performance liquid chromatography.

Investigation into the effect of the aspect ratio of cylindrical surface microstructure on von Willebrand factor damage

Hemorrhagic episodes in patients carrying mechanical circulatory support represent a severe clinical complication. These bleeding episodes may originate from a reduced functionality of von Willebrand factor (VWF), a multimer protein pertinent to form a hemostatic plug. The reduced functionality is due to increased loss of high molecular weight von Willebrand factor multimers (HMWM-VWF), a phenomenon that is facilitated by device-induced increases in shear stress to which VWF is exposed. However, in addition to the mechanics factors, VWF damage may also be affected by interface factors, including the properties of bulk material and the surface characteristics. In this study, the effect of cylindrical surface microstructure topography on VWF damage was investigated. In the 1 to 9 range, the high aspect ratio surface features were constructed on the polycarbonate (PC) films. The topographic surfaces were fabricated by 3D printing casting on a template. A roller pump circulation platform was built to conduct in vitro experiments. VWF antigen (VWF-Ag) and VWF ristocetin cofactor activity (VWF-Rico) on these topographic surfaces were quantified by enzyme-linked immunosorbent assay (ELISA), the loss of HMWM-VWF was quantified by immunoblotting. The lower loss of HMWM-VWF was observed on surfaces with high aspect ratio compared to the pristine PC templates and surfaces with low aspect ratio, while VWF-Ag was nearly unchanged. The topographical parameters found to significantly reduce the loss of HMWM-VWF were high aspect ratio structures of more than 5. The results signify that topographical manipulation of surfaces is a feasible approach for reducing the loss of HMWM-VWF.