University of Twente Student Theses


The development of single layer hollow fibers based on PES and PVP K90 for outside-in dialysis.

Weening, N.A. (2023) The development of single layer hollow fibers based on PES and PVP K90 for outside-in dialysis.

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Abstract:Chronic kidney disease (CKD) has emerged as a significant contributor to human suffering and mortality in the 21st century. Alarmingly, it stands out as one of the few diseases experiencing an increasing mortality rate in the modern era. With the prevalence of unhealthy lifestyle habits in modern society, it is estimated that there will be a notable rise in the number of individuals affected by chronic kidney disease (CKD). The ideal treatment for these patients would be a kidney transplantation. However, due to limited availability of donor kidneys or compatibility issues, such as blood type mismatch, pose significant challenges. As a result, the majority of patients require alternative therapies to sustain their lives. A therapy often used as kidney replacement is hemodialysis. Hemodialysis makes use of an external filtering device capable of filtering the patients’ blood from toxins which would otherwise accumulate within the patient’s body. Currently, the patient’s blood flows through the fibers that lie within this filtering device, while dialysis solution flows outside of these fibers in the opposite direction. Because of this counter-current flow, the toxins diffuse out of the blood into the dialysis solution through the semi-permeable fiber membrane. The filtered blood is returned to the body. This therapy, however, has multiple downsides. Hemodialysis involves a 3 times per week, 4-hour long session which is not able to remove all toxins from the blood. In addition, the fibers experience blood clotting within the fibers, affecting the filtration capacity. Furthermore, there is a risk of elution of membrane material, specifically polyvinylpyrrolidone (PVP), which can result in structural changes within the membrane. Additionally, the introduction of PVP into the patient’s bloodstream may lead to potential health complications. One solution which is currently studied, is the use of outside-in fibers. For outside-in fibers, the dialysis solution flows through the lumen of the fibers, whereas the blood flows through the inter-fiber space, preventing blood clotting of the fibers and increasing the efficiency of the fibers. Multiple outside-in fibers have already been produced and tested with success at the Advanced Organ and bioengineering Therapeutics faculty. Previously, the outside-in fibers were made using a 7 wt.% PVP K90 solution from Sigma-Aldrich. However, with new supplier BASF for the PVP K90, it has been a challenge to successfully fabricate outside-in fibers. It was found that the molecular weight of the new PVP K90 (MW ≈ 1000.000 - 1500.000 Da) is significantly higher than the previously used PVP K90 (MW ≈ 360.000 Da). To compensate for this increase in molecular weight, outside-in fibers were fabricated using 5.6 wt.%, which did not result in the preferred mechanical and structural properties due to high viscosity of the solution. In this study, a 4 wt.% PVP K90 solution is used to fabricate, characterize and test outside-in fibers using this new PVP K90, comparing them to the previously made 5.6 wt.% PVP K90 (Sigma-Aldrich) fibers and the commercial fibers used for FX high-flux dialyzers of Fresenius. Multiple outside-in fibers were prepared and it has been possible to find methods to directly change the fiber structure and mechanical properties of these new 4 wt.% PVP K90 (BASF) fibers. The fibers with the most promising mechanical properties and structure have been analyzed further by measuring the water permeance and the toxin removal. The water permeance measured was approximately 20 ± 5 L m−2h −1 bar−1 after a 4000 ppm sodium hypochlorite treatment of 2h. The creatinine removal using spiked plasma (0.1mg/mL) had a value of approximately 1630 ± 171 after 4h. The dialysanse calculated had a value of approximately 395 mL m−2 min−1 . The water permeance and the removal of these 4 wt.% PVP K90 fibers were in the range of the commercial FX high-flux dialyzers, as well as the previously made 5.6 wt.% PVP K90 from Sigma-Aldrich fibers. Additionally, this study does give insight in how to manipulate the mechanical and structural properties of these fibers to eventually be able to produce outside-in fibers with excellent toxin removal.
Item Type:Essay (Bachelor)
Faculty:TNW: Science and Technology
Subject:35 chemistry
Programme:Biomedical Technology BSc (56226)
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