Synthesis and Characterization of Flat Sheet and Hollow Fiber Membranes for Filtration of Uremic Toxins in Dialysate

Abstract

End-stage renal disease (ESRD) is a highly prevalent disease affecting around 750k people in the United States alone. With over 60% of ESRD patients receiving hemodialysis, it remains the most common form of treatment. However, traditional hemodialysis restricts the lives of patients, necessitating frequent long sessions at dialysis clinics, while having a poor prognosis with a 42% 5-year survival rate. Portable dialysis systems are a solution which can provide continuous dialysis and promote patient autonomy. One major challenge for portable dialysis is the high volumes of dialysate consumed; 120 L of dialysate is needed for one hemodialysis session. To circumvent this challenge, we investigated polymeric materials for the continuous filtration of toxins out of a small volume of dialysate: a dialysate recycling system. Electrodecomposition is a method to remove urea from dialysate but is disrupted by the presence of glucose. Thus, we aimed to harness polymeric materials for size-exclusion filtration for the separation of urea and glucose. By analyzing the effect of polymer type, concentration, additives, thermal annealing, and synthesis temperature on membrane formation, we developed and optimized a cellulose acetate flat sheet membrane with a urea to glucose separation ratio of over 30. We then synthesized and analyzed the formation mechanisms of hollow fiber membranes with different polymer types, given their superior surface area to volume ratio compared to flat sheet membranes. We found that polyethersulfone membranes demonstrated specific qualities promising for dialysate filtration applications, such as multiple skin layers, polymer chain reorientation, and well-formed channeled macrovoids. These findings elucidate the mechanisms of polymer material formation while providing synthesis techniques for successful materials that can be incorporated into a dialysate recycling system in the future.