Continuous Whole Blood Dialysis Based on Regenerated Dialysate Utilizing TiO2 Nanowire Photo-Electrochemical Oxidation and Protective Forward Osmotic Membrane

While a traditional 4-hour dialysis treatment uses up to 120L of fresh dialysate per session, a full-scale bench-top system was developed to remove clinically relevant amounts of uremic toxins in whole blood using only 0.5L of commercial dialysate solution over a 24-hour continuous dialysis process. Urea was removed by photoelectrochemical method through a UV/TiO2 nanowires array device connected to a Forward Osmosis (FO) membrane in a protected close loop, while other non-urea toxins were removed by Activated Carbon (AC) in the dialysate loop. Here we demonstrate a daily urea removal rate of 14.2g using 0.4m² of hemodialyzer membrane and 2.3m² FO membrane with 0.18m² TiO2 nanowires array in Photoelectrochemical Oxidative Urea Removal (POUR) unit. Other non-urea toxins represented by creatinine and phenylacetic acid with a daily removal rate of nearly 7g were achieved by 70g of AC absorbent in the dialysate loop. Urea, creatinine and phenylacetic acid were constantly infused to the saline solution with the speed of 15g/24h, 5.6g/24h and 1.4g/24h to simulate actual human toxins level. Urea is continuously removed in a 0.15M NaCl saline solution by the photo-oxidation reaction occurring on TiO2 nanowire surface with the presence of UV source and applied bias to enhance the electron-hole pair separation within the single crystal TiO2 nanowire. The POUR loop was also protected from the potential oxidative species generated from the photooxidation of urea by inline AC absorbent with real-time ORP and pH sensors, showing non-cytotoxicity to the blood loop. The FO membrane is also a key component to prevent small solute molecules from dialysate entering the POUR loop to lower its efficiency as well as forming harmful oxidative byproducts. Our results also showed a wide variety of treatment modes (ie. 4, 8, 12 hr daily times) by coupling different membrane components. More importantly, by eliminating the need for the external water source, our system offers possibilities of a variety of portable kidney dialysis treatment options for home, work and travel.