Dialysis Apparatus Research Articles

Equilibration of precipitants in a counter-diffusion apparatus for protein crystallization.

A cost-effective capillary dialysis apparatus (Toledo Capillary Box, TCB) developed for biomacromolecule crystal growth in microgravity and unit gravity environments can provide slow equilibration between the precipitant reservoir and capillary solutions, nurturing growth of neutron-diffraction-quality crystals. Under microgravity conditions, mass transfer of precipitants and biomacro-mol-ecules occurs under diffusion-controlled conditions, promoting slow growth and suppressing defect formation. The equilibration of common precipitants (polyethyl-ene glycol and salts such as ammonium sulfate) between capillary and reservoir solutions was measured for capillaries oriented horizontally or vertically with respect to the gravitational field at unit gravity. Precipitants equilibrated less rapidly in the vertical orientation when capillary solution densities were lower than those of the reservoir solutions. A plug filled with agarose gel was introduced in the TCB apparatus for salt precipitants since salts often exhibit relatively high free diffusion. Equilibration of the capillaries with reservoir solutions was significantly delayed for many of the salt precipitants tested. Analytical and semi-analytical models allow the prediction of precipitant equilibration of capillary and reservoir solutions under diffusion-controlled transport and show good agreement with experimental results.

ИОНОПЕРЕНОС ПРИ КОНВЕКТИВНО – ДИФФУЗИОННОМ РАЗДЕЛЕНИИ ПОТОКОВ

Model problems on the separation of charge-carrying components into two streams using a membrane in a cell of a dialysis apparatus are considered. For a brighter detection of the separation effect, the components are taken such that they differ markedly from each other in the mass of ions and diffusion coefficients. The convective-diffusion process of transition of ions through membranes with different physical features that create resistance to the transition is considered. As a result of the solution, the potential and component distributions were obtained in the cell volume of the dialysis apparatus as a function of time. It was shown that a quasi-equilibrium state is established relatively quickly in the capillary and the membrane, which determines the ratio of the flow rates of the components in the cell channels.

Using computational fluid dynamic for hemodialysis air chamber design modification.

Design modification is a main step in developing machines and artificial organ. A new dialysis apparatus air chamber detects clot formation and interruption of blood refining circuit. Due to using enough anticoagulant, thrombosis may occur because of vortex formed by turbulent flow. Turbulent blood flow causes to endothelial injury thus supporting the formation of a thrombus. Computational fluid dynamics can estimate the flow velocity and turbulence distribution and it can be used as applicable tool to design diagnosis and modifying. In this paper CFD simulation used to find the high turbulent intensity region within the chamber and an optimization method is adopted based on the geometry changing and trying the simulation results. The turbulent intensity is chosen as a criterion to achieving to an optimized condition. Finally, a best geometry is derived for the chamber entrance by this process and modified prototype is manufactured. This refined chamber maintains on the dialysis machine and tested for several patients with different blood characteristics. The results show that no more clot formation has been observed in this new designed chamber.

HLM-beads: Rapid Assessment of Nonspecific Binding to Human Liver Microsomes Using Magnetizable Beads

In early drug development, drug-drug interaction risk is routinely assessed using human liver microsomes (HLMs). Nonspecific binding of drugs to HLMs can affect the determination of accurate enzyme parameters (Km, Ki, KI). Previously, we described a novel in vitro model consisting of HLMs bound to magnetizable beads [HLM-magnetizable-beads system (HLM-beads)]. The HLM-beads enable rapid separation of HLMs from incubation media by applying a magnetic field. Here, HLM-beads were further characterized and evaluated as a tool to assess HLM nonspecific binding of small molecules. The free fractions (fu,mic) of 13 compounds (chosen based on their pKa values) were determined using HLM-beads under three HLM concentrations (0.025, 0.50, and 1.0 mg/ml) and compared with those determined by equilibrium dialysis. Most fu,mic values obtained using HLM-beads were within 0.5- to 2-fold of the values determined using equilibrium dialysis. The highest fold difference were observed for high binders itraconazole and BIRT2584 (1.9- to 2.9-fold), as the pronounced adsorption of these compounds to the equilibrium dialysis apparatus interfered with their fu,mic determination. Correlation and linear regression analysis of the fu,mic values generated using HLM-beads and equilibrium dialysis was conducted. Overall, a good correlation of fu,mic values obtained by the two methods were observed, as the r and R2 values from correlational analysis and linear regression analysis were >0.9 and >0.89, respectively. These studies demonstrate that HLM-beads can produce comparable fu,mic values as determined by equilibrium dialysis while reducing the time required for this type of study from hours to only 10 minutes and compound apparatus adsorption. SIGNIFICANCE STATEMENT: This work introduces a new method of rapidly assessing nonspecific microsomal binding using human liver microsomes bound to magnetizable beads.

Effective clearance of uremic toxins using functionalised silicon Nanoporous membranes.

In-house fabricated silicon nanoporous membranes (SNMs), functionalized for efficient clearance of uremic toxins, can lead to compact and portable dialysis systems. Efficacy of 15nm thick SNMs, with average pore diameter of 8nm, was tested for dialysis of two uremic toxins - urea and creatinine using custom made teflon apparatus of 2, 10 and 30ml. The apparatus consisted of two reservoirs, with the cis containing the uremic fluid, and the trans containing the dialysate. Peristalsis was found to enhance the clearance rate by a factor of four as compared to unstirred condition. Functionalisation of the SNMs reduced protein binding, and surface binding of urea from 23% to negligible values. A lateral array of nine SNMs and a new design for the dialysis apparatus, increased the clearance rate by a factor of twelve from that of the single SNM. The arrays cleared about 42% of urea and 48% of creatinine from 30ml of diluted serum samples, in 15min. Periodic replacement of the trans fluid cleared about 81% of high concentration uremic toxins from the cis reservoir in 45 mins. The SNM arrays are stable, reproducible, and with the superior clearance rates for urea and creatinine, they have the potential to be used as membranes for portable hemodialysers.

Automated Polymer Purification Using Dialysis.

The automated dialysis of polymers in synthetic robots is described as a first approach for the purification of polymers using an automated protocol. For this purpose, a dialysis apparatus was installed within a synthesis robot. Therein, the polymer solution could be transferred automatically into the dialysis tube. Afterwards, a permanent running dialysis could be started, enabling the removal of residual monomer. Purification efficiency was studied using chromatography and NMR spectroscopy, showing that the automated dialysis requires less solvent and is faster compared to the classical manual approach.

P1249SEVERE HEMODYNAMIC INSTABILITY DURING DIALYSIS - DRY, STUNNED OR ALLERGIC? STATE OF THE ART ECHOCARDIOGRAPHY COMBINED WITH SIMULTANEOUS LUNG ULTRASOUND

Abstract Background and Aims Intradialytic hypotension is a fairly common and serious adverse phenomenon. Associated comorbidities include e.g. heart failure, hypovolemia, allergic reactions with the dialysis apparatus and electrolyte disturbancies. Excessive ultrafiltration may explain later onset hypotension, but early-onset hemodynamic collapse remains poorly understood. Preventive interventions may include incremental dialysis, increasing dry weight, increasing dialysis time and changing dialysis membranes/apparatus. This study combines Echocardiography (Echo) and Lung Ultrasound (LUS) for hemodynamic phenotyping of patients with severe, early onset intra-dialytic hypotension. The aim is to figure out possible preventive strategies depending on underlying abnormalities. Method We enrolled dialysis patients with a symptomatic decrease in systolic arterial pressure < 90 mmHg requiring norepinephrine during the first 60 minutes of at least two consecutive dialysis sessions in our dialysis department. Echo + LUS was done simultaneously to everyone at baseline, i.e. BEFORE dialysis begun, and later at onset of a hypotension episode during dialysis. Patients with active bleeding or any other obvious temporary etiology for hypotension were excluded. Echo concentrated especially on volemic state and filling pressures, while LUS evaluated the lungs and pleurae for signs of pulmonary congestion. Cardiac structure and function (e.g. valves, ejection fraction) was also evaluated. Results Between 1.10.2019 - 31.12.2019 10 patients were enrolled. All patients eventually required norepinephrine despite fluid challenge. No patients had signs or symptoms of an allergic reaction, such as urticaria or stridor/obstructive respiration, nor significant electrolyte disturbancies. 5/10 patients had severe systolic cardiac dysfunction at baseline (LVEF < 30 %) and these 5 patients also simultaneously showed signs of congestion and fluid overload on ultrasound. On the contrary, the other 5/10 patients without severe cardiac failure all had low left-sided filling pressures and a collapsed inferior vena cava on Echo ALREADY at baseline, i.e. before initiation of dialysis. All of these hypovolemic patients had an excellent residual diuresis (> 1500ml/d). All 10 patients in this study showed a significant drop in body volume measurement (BVM) -curves and left-sided filling pressures on Echo prior to onset of hypotension. Of the 5 patients with severe cardiac dysfunction, 2/5 were transmitted into palliative care without dialysis, while 3/5 could be managed without future norepinephrine by longer, more frequent dialysis sessions using more convective and less diffusive dialysis. Of the latter 5 “dry” patients without severe cardiac dysfunction, 3/5 had no more hypotensive episodes after increasing dry weight and using incremental dialysis programs, and the remaining 2 dry patients could be completely switched off dialysis due to vivid residual function. 3/5 of the “dry patients” had a baseline pulse pressure > 120 mmHg and 3 had coronary artery disease, both possibly predisposing to diastolic under-filling. No patients in this study presented with significant myocardial stunning, defined as a > 10 % decrease in LVEF compared to baseline. Conclusion Severe, intra-dialytic hypotension requiring vasopressors may be prevented by individual tailoring of dialysis prescription. Ultrasound may help phenotyping patients requiring different dialysis strategies, including stopping dialysis entirely. Stunning and allergic reactions seemed rare. At baseline, patients seemed to be mainly 1) either over-dialyzed (hypovolemic or hypo-osmotic) or 2) having significant cardiac disease, naturally requiring quite opposite preventive strategies. A decrease in left ventricular preload furthermore occurred in all patients at onset of hypotension, suggesting crossover of a patient-specific preload threshold.

Development of an Accident Reproduction Simulator System Using a Hemodialysis Extracorporeal Circulation System

Background:Accidents that occur during dialysis treatment are notified to the medical staff via alarms raised by the dialysis apparatus. Similar to such real accidents, apparatus activation or accidents can be reproduced by simulating a treatment situation. An alarm that corresponds to such accidents can be utilized in the simulation model.Objectives:The aim of this study was to create an extracorporeal circulation system (hereinafter, the circulation system) for dialysis machines so that it sets off five types of alarms for: 1) decreased arterial pressure, 2) increased arterial pressure, 3) decreased venous pressure, 4) increased venous pressure, and 5) blood leakage, according to the five types of accidents chosen based on their frequency of occurrence and the degree of severity.Materials and Methods:In order to verify the alarm from the dialysis apparatus connected to the circulation system and the accident corresponding to it, an evaluation of the alarm for its reproducibility of an accident was performed under normal treatment circumstances. The method involved testing whether the dialysis apparatus raised the desired alarm from the moment of control of the circulation system, and measuring the time it took until the desired alarm was activated. This was tested on five main models from four dialyzer manufacturers that are currently used in Japan.Results:The results of the tests demonstrated successful activation of the alarms by the dialysis apparatus, which were appropriate for each of the five types of accidents. The time between the control of the circulatory system to the alarm signal was as follows, 1) venous pressure lower limit alarm: 7 seconds; 2) venous pressure lower limit: 8 seconds; 3) venous pressure upper limit: 7 seconds; 4) venous pressure lower limit alarm: 2 seconds; and 5) blood leakage alarm: 19 seconds. All alarms were set off in under 20 seconds.Conclusions:Thus, we can conclude that a simulator system using an extracorporeal circulation system can be set to different models of dialyzers, and that the reproduced treatment scenarios can be used for simulation training.

Chemical Sensor for Haemodialysis Application

The water used to supply a haemodialysis center requires particular mode of treatment in order to achieve the best technical, economic and therapeutic distribution. Dialysis patients come in contact weekly with a large amount of water through the dialysis apparatus. It is therefore essential that this solution has a high quality and purity in terms of proper electrolyte composition, low concentration or absence of organic and inorganic chemical pollutants, low concentration or absence of bacteria, yeasts, fungi and endotoxins. The chemical and microbiological quality of water intended for medical and biomedical treatments, such as haemodialysis, is generally defined on the basis of a plurality of international reference standards (ASTM International standards D1193 and D5196; International Pharmacopoeia and European Pharmacopoeia CAP / NCCLS 1988). In this work the authors have designed an electrochemical device used to characterize pure and ultrapure water for biomedical applications (Patent: TO2014A000765). The results obtained show a good ability of the device in the discrimination of different bacteria and of their concentration (CFU); Pseudomonas and E-coli have been here tested.

A High-Throughput Cell-Based Method to Predict the Unbound Drug Fraction in the Brain

Optimization of drug efficacy in the brain requires understanding of the local exposure to unbound drug at the site of action. This relies on measurements of the unbound drug fraction (fu,brain), which currently requires access to brain tissue. Here, we present a novel methodology using homogenates of cultured cells for rapid estimation of fu,brain. In our setup, drug binding to human embryonic kidney cell (HEK293) homogenate was measured in a small-scale dialysis apparatus. To increase throughput, we combined drugs into cassettes for simultaneous measurement of multiple compounds. Our method estimated fu,brain with an average error of 1.9-fold. We propose that our simple method can be used as an inexpensive, easily available and high-throughput alternative to brain tissues excised from laboratory animals. Thereby, estimates of unbound drug exposure can now be implemented at a much earlier stage of the drug discovery process, when molecular property changes are easier to make.

Establishment of a Blood Purification System for Renal Failure Rats Using Small‐Size Dialyzer Membranes

Hemodialysis techniques for small animals have not been established because no small dialysis apparatus has been available. We recently developed a small-size dialyzer and established an appropriate blood purification system for small animals. To confirm the appropriate dialysate flow rate, bovine blood was dialyzed for 60 min at a fixed blood flow rate of 1.0 mL/min and variable dialysate flow rates. Blood urea nitrogen and creatinine levels decreased significantly at a dialysate flow rate of 5 mL/min (from 13.7 ± 0.2 to 10.3 ± 1.2 mg/dL and 1.07 ± 0.15 to 0.61 ± 0.12 mg/dL, respectively, P < 0.05). To determine the appropriate in vivo conditions, extracorporeal circulation was performed in anesthetized male Sprague-Dawley rats at a dialysate flow rate of 0.0 mL/min, for 240 min, and at variable blood flow rates. Extracorporeal circulation was successful at a blood flow rate of 1.0 mL/min, but not 1.5 mL/min. To establish in vivo hemodialysis conditions, we used the animal model of end stage renal failure. Sprague-Dawley rats were fed a 0.75% adenine-containing diet for 3 weeks, after which they received hemodialysis for 120 min at a dialysate and blood flow rate of 5.0 and 1.0 mL/min, respectively. There were no significant changes in systolic blood pressure or heart rate during dialysis. Thus, this blood purification system can be safely used for small animals at a dialysate flow rate of 5.0 mL/min and a blood flow rate of 1.0 mL/min. This system provides a basis for further research on hemodialysis therapy.

My Addiction: The Artificial Kidney, The Rise and Fall of Dialysis

My Addiction: The Artificial Kidney, The Rise and Fall of Dialysis

Rate constants for drug release from micellar solutions of non-ionic surfactants.

The release of weak acid from micellar solutions containing different concentrations of two structurally related non-ionic surfactants was estimated using a dynamic dialysis apparatus. In all cases the effect of the surfactant was to reduce the amount of weak acid transferred. The data have been subjected to compartmental analysis using non-linear regression analysis. Rate constants for exchange cross the dialysis membrane were independent of surfactant concentration. As surfactant concentration increased the rate constants for transfer from the non-micellar region did not show a marked change.

The binding of bupivacaine to maternal and foetal plasma proteins.

Abstract The binding of bupivacaine to maternal and foetal plasma proteins has been investigated using a three-compartment dialysis apparatus, in which maternal and foetal plasma could be examined simultaneously. Maternal protein bound approximately twice as much bupivacaine as foetal protein per gram of protein at drug concentrations in the range 0·05 to 5·0 μg/ml. Over the same range of concentrations, 92–78% of bupivacaine was bound to maternal plasma protein but only 35–31% was bound to human albumin indicating that other proteins are involved in the binding of the drug to plasma proteins.

RELATIVE BLOOD VOLUME BASED BIOFEEDBACK DURING HAEMODIALYSIS

Intra-dialytic hypotension is the most frequently occurring complication during haemodialysis and can lead to serious complications. Devices that continuously and non-invasively monitor relative blood volume (RBV) changes during HD are being advocated as a tool to maintain an adequate volume of the intravascular compartment in order to avoid dialysis hypotension. Nowadays, most manufacturers have incorporated a RBV monitor in their dialysis apparatus and two manufacturers have designed biofeedback devices that control intra-dialytic RBV changes. The goal of RBV based biofeedback systems is to prevent a severe or abrupt decrease in blood volume in order to prevent the development of dialysis hypotension. Biofeedback technologies can diminish the severity and/or frequency of dialysis hypotension. At present, however, a completely symptom-free HD is not a reality. The major reasons for this are patient characteristics such as cardiovascular co-morbidity and high UF rates and a lack of understanding of the relation between RBV changes and blood pressure/cardiovascular stability.

Alginate‐coated chitosan membrane for guided tissue regeneration

AbstractChitosan membranes were first prepared by a thermally induced phase separation method and then alginate was coated on one side of the membranes by a modified dialysis apparatus to prepare alginate/chitosan membranes (A/C membranes). Electron spectroscopy for chemical analysis (ESCA), scanning electron microscope, and contact angle measurements were conducted to evaluate the surface characteristics. The mechanical strength, degradation behavior, and cell adhesion test were performed to evaluate the feasibility of using A/C membrane in guided tissue regeneration applications. The results revealed that alginates could effectively be coated onto the chitosan membrane. As observed in ESCA results, the N‐atomic emission peak was decreased from originally 6.2% on the untreated chitosan surface to 2% on the alginate‐treated surface. The contact angle decreased on the alginate‐modified side substantially, compared with the untreated side (from 88.4° to 34.2°). The A/C membrane had a higher water content of 71.8% in comparison to the chitosan membrane of 61.8%. Consequently, A/C membrane became stiffer and had a higher Young's modulus and strength. After a 30‐day in vitro shaking test, the weight of membranes was degraded to about 75% from the original. The 3T3 fibroblast cells showed less adhesion to alginate‐modified side as compared to the untreated chitosan‐side in cell adhesion test. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4528–4534, 2006

A Heavy Metal Biotrap for Wastewater Remediation Using Poly-γ-Glutamic Acid

Poly-gamma-glutamic acid (gamma-PGA) obtained from Bacillus licheniformis ATCC 9945 was evaluated as a potential biosorbent material for use in the removal of heavy metals from aqueous solution. Copper (Cu(2+)) was chosen as the model heavy metal used in these studies since it is extensively used by electroplating and other industries, has been the model for many other similar studies, and can be easily assayed through a number of convenient methods. Cu(2+)-gamma-PGA binding parameters under varying conditions of pH, temperature, ionic strength, and in the presence of other heavy metal ions were determined for the purified biopolymer using a specially designed dialysis apparatus. Applying the Langmuir adsorption isotherm model showed that gamma-PGA had a copper capacity approaching 77.9 mg/g and a binding constant of 32 mg/L (0.5 mM) at pH 4.0 and 25 degrees C. Cu(2+)-gamma-PGA adsorption was relatively temperature independent between 7 and 40 degrees C, while an increase in ionic strength led to a decrease in metal ion binding. Cd(2+) and Zn(2+) ions compete with Cu(2+) for binding sites on the gamma-PGA biopolymer. Metal uptake by gamma-PGA was further tested using a tangential flow filtration apparatus in a diafiltration mode in which metal was continually processed through a dilute solution of gamma-PGA without allowing for equilibrium to be established. The circulating polymer solution was able to complex metal as well as successfully prevent passage of unbound copper ions present in solution through the membrane. Using 500 mL of a 0.2% gamma-PGA solution, up to 97% of a 50 mg/L copper sulfate solution processed at a flow rate of 115 mL/min was retained by the polymer. For a 10 mg/L solution of Cu(2+) as copper sulfate, filtrate concentrations of Cu(2+) never rose above 0.6 mg/L while processing 2.5 L of dilute copper sulfate.

The effect of different molecular weight PEG additives on cellulose acetate asymmetric dialysis membrane performance

The influence of the different molecular weight polyethylene glycol (PEG) and the amount of PEG used in the dialysis membrane dope formulations was investigated. The three different types of PEG used are PEG 200, 400 and 600. The dialysis membrane performances were evaluated in terms of urea clearance using single layer dialysis apparatus at 37 °C with flow rate of 50 mL/min at the testing solution side whilst 100 mL/min at the other side. It was found that the presence of PEG 200 in the dialysis membrane enhanced the membrane performance exhibited by the high urea clearance and high urea permeability. In addition, the amount of PEG also affects dialysis membrane performance. High amounts of PEG greater than 10% do not improve the membranes performances. Human blood test revealed that dialysis membrane fabricated was biocompatible in terms of high removal rate of uremic toxic from human blood while preventing human protein to diffuse out from the blood side.

Measurement of relative blood volume changes during haemodialysis: merits and limitations

Dialysis hypotension is estimated to occur in 20% ofhaemodialysis (HD) sessions [1] and can lead to seriousvascular complications such as cerebral infarctionand cardiac and mesenteric ischaemia [2,3]. It maycontribute to chronic overhydration due to an inabilityto reach dry weight and may lead to under-dialysis[1,2,4]. Prevention of dialysis hypotension, therefore,is an important challenge to the dialysis staff. Theinitiating factor in the pathogenesis of dialysis hypo-tension is a decrease in blood volume which resultsfrom the imbalance between the ultrafiltration rate andthe plasma refilling rate [5]. Devices that continuouslyand non-invasively monitor relative blood volume(RBV) changes during HD are being advocated as atool to maintain an adequate volume of the intravas-cular compartment in order to avoid dialysis hypo-tension [6–8]. Nowadays, most manufacturers haveincorporated an RBV monitor in their dialysis appa-ratus, but evidence-based knowledge on how to use theRBV data in order to optimize the dialysis prescriptionof the individual patient is lacking. Moreover, there areconflicting data in the literature on the predictive valueof RBV changes for the occurrence of dialysis hypoten-sion. In this review, we will outline the pathophysio-logical response to ultrafiltration-induced reductionsinbloodvolume,evaluatetheRBVmeasuringmethods,discuss the relationship between RBV changes andbloodpressureanddiscussseveralfactorsthatinfluencethe validity of RBV measurements.

Development and validation of a 96-well equilibrium dialysis apparatus for measuring plasma protein binding

A 96-well equilibrium dialysis block was designed and constructed that is compatible with most standard 96-well format laboratory supplies and instruments. The unique design of the dialysis apparatus allows one to dispense and aspirate from either or both the sample and dialysate sides from the top of the apparatus, which is not possible with systems currently on the market. This feature permits the investigator to analyze a large number of samples, time points, or replicates in the same experiment. The novel alignment of the dialysis membrane vertically in the well maximizes the surface-to-volume ratio, eliminates problems associated with trapped air pockets, and allows one to add or remove samples independently or all at once. Furthermore, the design of the apparatus allows both the sample and dialysate sides of the dialysis well to be accessible by robotic systems, so assays can be readily automated. Teflon construction is used to minimize nonspecific binding of test samples to the apparatus. The device is reusable, easily assembled, and can be shaken in controlled temperature environments to decrease the time required to reach equilibrium as well as facilitate dissolution of test compounds. Plasma protein binding values obtained for 10 diverse compounds using standard dialysis equipment and the 96-well dialysis block validates this method.