Artificial kidney: Challenges and opportunities

This review aims to present the developments occurring in the field of artificial organs and particularly focuses on the presentation of developments in artificial kidneys. The challenges for biomedical engineering involved in overcoming the potential difficulties are showcased, as well as the importance of interdisciplinary collaboration in this marriage of medicine and technology. In this review, modern artificial kidneys and the research efforts trying to provide and promise artificial kidneys are presented. But what are the problems faced by each technology and to what extent is the effort enough to date?

Bio-inspired self-pumping microfluidic device for cleaning of urea using reduced graphene oxide (rGO) modified polymeric nanohybrid membrane

In vitro technology facilitates the replication of in vivo tissues more accurately than conventional cell-based artificial organs, enabling researchers to mimic both the structural and functional characteristics of natural systems. Here, we demonstrate a novel spiral-shaped self-pumping microfluidic device for the cleaning of urea by incorporating reduced graphene oxide (rGO) modified a Polyethersulfone (PES) nanohybrid membrane for efficient filtration capacity. The spiral-shaped microfluidic chip is a two-layer configuration of polymethyl methacrylate (PMMA) integrated with the modified filtration membrane. In essence, the device replicates the main features of the kidney (Glomerulus), i.e., a nano-porous membrane modified with reduced graphene oxide to separate the sample fluid from the upper layer and collect the biomolecule-free fluid through the bottom of the device. We have achieved a cleaning efficiency of 97.94 ± 0.6 % using this spiral shaped microfluidic system. The spiral-shaped microfluidic device integrated with nanohybrid membrane has potential for organ-on-a-chips applications.

Application of mathematical analysis on dialysis

Hemodialysis is a blood purification method based on solute removal by diffusion and incorporates filtration to improve the efficiency of water removal and removal of high molecular weight substances. It is now a well-established treatment, due to the improved performance of dialyzers. This review outlines the development process of dialyzers, focusing on the application based on the mathematical analysis. First, phenomena occurring in the vicinity of the dialysis membrane are explained using a film model for diffusion and a gel polarization model for filtration. Then, currently established dialyzer designs are introduced using mathematical analysis. Furthermore, the design of dialyzers to promote internal filtration, the designs of hemodiafilters suitable for online hemodiafiltration (HDF), and the design of compact dialyzer for are also presented.

Current Status and Future of Artificial Kidney in Humans

The number of patients needing renal replacement therapy (RRT) is increasing rapidly with an increase in lifestyle diseases such as diabetes, hypertension, and metabolic syndrome. Kidney transplantation, whenever feasible, is the most preferred mode of RRT. However, there is a growing shortage of donor kidneys for transplantation. While dialysis is partially able to perform the filtration and excretion function of the kidneys, it is still not able to perform the other renal tubular and endocrine functions of a normal kidney and has quality-of-life issues with significant long-term morbidity. The need of the hour is to develop an ideal artificial kidney that would be wearable or implantable and would be able to perform the complete excretory, filtration, tubular, endocrine, and metabolic functions of the kidney while preserving the quality of life and minimizing complications. In this review, we discuss the characteristics of an ideal artificial kidney, the challenges of developing such a device, a brief description of the past and current work on this topic, and what the artificial kidney of the future should look like.

Circuit haemodynamics during non-citrate and regional citrate continuous renal replacement, and impact of blood flow on filter life

BACKGROUND

During continuous renal replacement therapy (CRRT) with regional citrate anticoagulation (RCA), blood flow (Qb) might affect vascular access dysfunction (AD) and, thereby, circuit life.

METHODS

Circuit life and circuit haemodynamics were studied in three intensive care units (ICUs) by analysing hemofilter device data (Prismaflex^®, Baxter, Chicago, IL). The three sites shared similar RCA protocols but differed in Qb (120-130 vs 150-200 mL/h). Non-RCA circuits were compared with RCA circuits in which the impact of Qb was also assessed.

RESULTS

About 3,981,906 min of circuit pressures were analysed in 2568 circuits in 567 patients. High-Qb RCA was associated with more extreme pressures, and greater AD (IRR 3.7 (1.93-7.08) as well as reduced filter life 21.1 (10.2-42.6) vs 27.0 (14.8-41.6) h). AD in high-Qb RCA circuits was associated with a 49% reduction in filter life, versus 24% reduction in low-Qb RCA, associated with a rise in the rate of increase in transfilter pressure.

CONCLUSIONS

High-Qb RCA-CRRT was associated with greater access dysfunction, earlier filter loss and increased haemodynamic impacts of access dysfunction, suggesting low-Qb RCA-CRRT may improve circuit mechanics, function and longevity.

Preliminary safety study of the Automated Wearable Artificial Kidney (AWAK) in Peritoneal Dialysis patients

BACKGROUND

Regeneration of peritoneal dialysis (PD) fluid using sorbent technology can provide flexibility and improve quality of life. This study examined the safety and efficacy of the automated wearable artificial kidney (AWAK) device in PD patients.

METHODS

This pilot study included prevalent PD patients from a single center in Singapore between 2016 and 2018. Participants underwent up to nine AWAK therapies over 72 h and were followed up for 1 month. Primary outcomes were serious adverse events (SAEs) and completion of nine therapies without device deficiency. Secondary outcomes were weekly peritoneal Kt/V _urea, solutes clearance and adverse events (AEs).

RESULTS

Twenty-one patients were screened and 15 were included in the study. Device alterations were required to overcome issues including flow occlusions initially, which resulted in three cohorts (n = 2, 2 and 11 respectively). No SAEs were observed during the study and at the follow-ups. Common AEs were abdominal pain/discomfort (60%) and bloatedness (47%). The median estimated peritoneal weekly Kt/V _urea was 3.0 (interquartile range: 2.2-4.8). There were significant reductions in pre- and post-study median serum urea (20.8 vs. 14.9 mmol/L; p = 0.001), creatinine (976.0 vs. 667.5 µmol/L; p = 0.001), phosphate (1.7 vs. 1.5 mmol/L; p = 0.03), and β2-microglobulin (29114.0 vs. 26339.0 µg/L; p = 0.048). Fluid reabsorption occurred among patients with residual kidney function. However, median body weights were not significantly different pre- and post-study (66.4 vs. 65.7 kg; p = 0.83).

CONCLUSIONS

This preliminary study demonstrated that no SAEs were observed with the AWAK-PD device; however, 60% of participants developed abdominal pain/discomfort. Further device enhancements are needed to improve ultrafiltration and reduce AEs.

Between two stools? Pharmacologists nominated for Nobel prizes in "physiology or medicine" and "chemistry" 1901-1950 with a focus on John Jacob Abel (1857-1938)

Since the early stages of its academic professionalization, pharmacology has been an interdisciplinary field strongly influenced by the natural sciences. Using the Nobel Prize as a lens to study the history of pharmacology, this article analyzes nominations of pharmacologists for two Nobel Prize categories, namely “chemistry” and “physiology or medicine” from 1901 to 1950. Who were they? Why were they proposed, and what do the Nobel dossiers say about excellence in pharmacology and research trends? This paper highlights the evaluation of “shortlisted” candidates, i.e., those candidates who were of particular interest for the members of the Nobel Committee in physiology or medicine. We focus on the US scholar John Jacob Abel (1857–1938), repeatedly referred to as the “Founder of American Pharmacology.” Nominated 17 times in both categories, Abel was praised by his nominators for both basic research as well as for his influential positions as editor and his work as chair at Johns Hopkins University. The Abel nominations were evaluated for the Nobel Committee in chemistry by the Swedish professor of chemistry and pharmaceutics Einar Hammarsten (1889–1968), particularly interested in Abel’s work on hormones in the adrenal glands and in the pituitary gland. Eventually, Hammarsten did not view Abel’s work prizeworthy, partly because other scholars had done—according to Hammarsten—more important discoveries in the same fields. In conclusion, analyses of Nobel Prize nominations help us to better understand various meanings of excellence in pharmacology during the twentieth century and beyond.

Fabrication of a porous polymer membrane enzyme reactor and its enzymatic kinetics study in an artificial kidney model

A porous polymer membrane-based d-amino acid oxidase (DAAO) reactor was developed that mimicked enzymatic activity in a renal ischemia model. Using glycidyl methacrylate as a biocompatible reactive monomer, poly(styrene-glycidyl methacrylate) was synthesized via a reversible addition fragment chain transfer polymerization technique. The prepared porous polymer membrane was used as a support to effectively immobilize DAAO. Compared to DAAO modified on nonporous polymer membrane and free DAAO in solution, the constructed porous polymer membrane-based DAAO enzyme reactor displayed 3-fold and 19-fold increase in enzymolysis efficiency, respectively. In addition, a chiral ligand exchange capillary electrophoresis system for DAAO was used to study DAAO enzymatic kinetics with d,l-methionine as the substrate. The proposed porous polymer membrane-based enzyme reactor showed excellent performance both on reproducibility and stability. Moreover, the enzyme reactor was successfully applied to mimic DAAO activity in a renal ischemia model. These results demonstrated that the enzyme could be efficiently immobilized onto a porous polymer membrane as an enzyme reactor and has great potential in mimicking the enzymatic activity in kidney.

Urea removal strategies for dialysate regeneration in a wearable artificial kidney

The availability of a wearable artificial kidney (WAK) that provides dialysis outside the hospital would be an important advancement for dialysis patients. The concept of a WAK is based on regeneration of a small volume of dialysate in a closed-loop. Removal of urea, the primary waste product of nitrogen metabolism, is the major challenge for the realization of a WAK since it is a molecule with low reactivity that is difficult to adsorb while it is the waste solute with the highest daily molar production. Currently, no efficient urea removal technology is available that allows for miniaturization of the WAK to a size and weight that is acceptable for patients to carry. Several urea removal strategies have been explored, including enzymatic hydrolysis by urease, electro-oxidation and sorbent systems. However, thus far, these methods have toxic side effects, limited removal capacity or slow removal kinetics. This review discusses different urea removal strategies for application in a wearable dialysis device, from both a chemical and a medical perspective.

Progress in the Development and Challenges for the Use of Artificial Kidneys and Wearable Dialysis Devices

Background

Renal transplantation is the treatment of choice for chronic kidney disease (CKD) patients, but the shortage of kidneys and the disabling medical conditions these patients suffer from make dialysis essential for most of them. Since dialysis drastically affects the patients' lifestyle, there are great expectations for the development of wearable artificial kidneys, although their use is currently impeded by major concerns about safety. On the other hand, dialysis patients with hemodynamic instability do not usually tolerate intermittent dialysis therapy because of their inability to adapt to a changing scenario of unforeseen events. Thus, the development of novel wearable dialysis devices and the improvement of clinical tolerance will need contributions from new branches of engineering such as artificial intelligence (AI) and machine learning (ML) for the real-time analysis of equipment alarms, dialysis parameters, and patient-related data with a real-time feedback response. These technologies are endowed with abilities normally associated with human intelligence such as learning, problem solving, human speech understanding, or planning and decision-making. Examples of common applications of AI are visual perception (computer vision), speech recognition, and language translation. In this review, we discuss recent progresses in the area of dialysis and challenges for the use of AI in the development of artificial kidneys.

Summary and Key Messages

Emerging technologies derived from AI, ML, electronics, and robotics will offer great opportunities for dialysis therapy, but much innovation is needed before we achieve a smart dialysis machine able to analyze and understand changes in patient homeostasis and to respond appropriately in real time. Great efforts are being made in the fields of tissue engineering and regenerative medicine to provide alternative cell-based approaches for the treatment of renal failure, including bioartificial renal systems and the implantation of bioengineered kidney constructs.

Artificial Intelligence for the Artificial Kidney: Pointers to the Future of a Personalized Hemodialysis Therapy

Background

Current dialysis devices are not able to react when unexpected changes occur during dialysis treatment or to learn about experience for therapy personalization. Furthermore, great efforts are dedicated to develop miniaturized artificial kidneys to achieve a continuous and personalized dialysis therapy, in order to improve the patient's quality of life. These innovative dialysis devices will require a real-time monitoring of equipment alarms, dialysis parameters, and patient-related data to ensure patient safety and to allow instantaneous changes of the dialysis prescription for the assessment of their adequacy. The analysis and evaluation of the resulting large-scale data sets enters the realm of "big data" and will require real-time predictive models. These may come from the fields of machine learning and computational intelligence, both included in artificial intelligence, a branch of engineering involved with the creation of devices that simulate intelligent behavior. The incorporation of artificial intelligence should provide a fully new approach to data analysis, enabling future advances in personalized dialysis therapies. With the purpose to learn about the present and potential future impact on medicine from experts in artificial intelligence and machine learning, a scientific meeting was organized in the Hospital Universitari Bellvitge (L'Hospitalet, Barcelona). As an outcome of that meeting, the aim of this review is to investigate artificial intel ligence experiences on dialysis, with a focus on potential barriers, challenges, and prospects for future applications of these technologies.

Summary and Key Messages

Artificial intelligence research on dialysis is still in an early stage, and the main challenge relies on interpretability and/or comprehensibility of data models when applied to decision making. Artificial neural networks and medical decision support systems have been used to make predictions about anemia, total body water, or intradialysis hypotension and are promising approaches for the prescription and monitoring of hemodialysis therapy. Current dialysis machines are continuously improving due to innovative technological developments, but patient safety is still a key challenge. Real-time monitoring systems, coupled with automatic instantaneous biofeedback, will allow changing dialysis prescriptions continuously. The integration of vital sign monitoring with dialysis parameters will produce large data sets that will require the use of data analysis techniques, possibly from the area of machine learning, in order to make better decisions and increase the safety of patients.

Original article submission: Platelet stress accumulation analysis to predict thrombogenicity of an artificial kidney

An implantable artificial kidney using a hemofilter constructed from an array of silicon membranes to provide ultrafiltration requires a suitable blood flow path to ensure stable operation in vivo. Two types of flow paths distributing blood to the array of membranes were evaluated: parallel and serpentine. Computational fluid dynamics (CFD) simulations were used to guide the development of the blood flow paths. Pressure data from animal tests were used to obtain pulsatile flow conditions imposed in the transient simulations. A key consideration for stable operation in vivo is limiting platelet stress accumulation to avoid platelet activation and thrombus formation. Platelet stress exposure was evaluated by CFD particle tracking methods through the devices to provide distributions of platelet stress accumulation. The distributions of stress accumulation over the duration of a platelet lifetime for each device revealed that stress accumulation for the serpentine flow path exceeded levels expected to cause platelet activation while the accumulated stress for the parallel flow path was below expected activation levels.

Three-dimensional simulation of mass transfer in artificial kidneys

In this work, the three-dimensional velocity and concentration fields on both the blood and dialysate sides in an artificial kidney were simulated, taking into account the effects of the flow profiles induced by the inlet and outlet geometrical structures and the interaction between the flows of blood and dialysate. First, magnetic resonance imaging experiments were performed to validate the mathematical model. Second, the effects of the flow profiles induced by the blood and dialysate inlet and outlet geometrical structures on mass transfer were theoretically investigated. Third, the clearance of toxins was compared with the clearance value calculated by a simple model that is based on the ideal flow profiles on both the blood and dialysate sides. Our results show that as the blood flow rate increases, the flow field on the blood side becomes less uniform; however, as the dialysate flow rate increases, the flow field on the dialysate side becomes more uniform. The effect of the inlet and outlet geometrical structures of the dialysate side on the velocity and concentration fields is more significant than that of the blood side. Due to the effects of the flow profiles induced by the inlet and outlet geometrical structures, the true clearance of toxins is lower than the ideal clearance, especially when the dialysate flow rate is low or the blood flow rate is high. The results from this work are significant for the structural optimization of artificial kidneys and the accurate prediction of toxin clearance.