Properties of membranes used for hemodialysis therapy

Ionic Liquids as Tools to Incorporate Pharmaceutical Ingredients into Biopolymer-Based Drug Delivery Systems

This mini-review focuses on the various roles that ionic liquids (ILs) play in the development and applications of biopolymer-based drug delivery systems (DDSs). Biopolymers are particularly attractive as drug delivery matrices due to their biocompatibility, low immunogenicity, biodegradability, and strength, whereas ILs can assist the formation of drug delivery systems. In this work, we showcase the different strategies that were explored using ILs in biopolymer-based DDSs, including impregnation of active pharmaceutical ingredients (APIs)-ILs into biopolymeric materials, employment of the ILs to simplify the process of making the biopolymer-based DDSs, and using the ILs either as dopants or as anchoring agents.

Functional Properties of Grapefruit Seed Extract Embedded Blend Membranes of Poly(vinyl alcohol)/Starch: Potential Application for Antiviral Activity in Food Safety to Fight Against COVID-19

The poly(vinyl alcohol) (PVA) and starch-based polymeric films with a ratio of 2:8 were prepared using solution casting followed by a solvent evaporation method. Four types of membranes with varied concentrations of grapefruit seed extract (GSE) i.e., 2.5-10 wt% was incorporated in the films. The prepared membranes were assessed for transparency test, mechanical properties, surface morphology, permeability test for O2, and antimicrobial properties. The PVA/starch-10% GSE loaded film showed excellent mechanical properties showing highest 1344 ± 0.7% elongation at break but poor optical transparency with 53.8% to 68.61%. The Scanning Electron Microscopic study reveals the good compatibility between the PVA, Starch, and GSE. The gas permeability test reveals that the prepared films have shown good resistance to the O2 permeability 0.0326-0.316 Barrer at 20 kg/cm2 feed pressure for the prepared membranes showing excellent performance. By adding the little amount of GSE into the PVA/starch blend membranes showed promising antimicrobial efficacy against MNV-1. For 4 h. incubation, PVA/starch blend membranes containing 2.5%, 5%, and 10% GSE caused MNV-1 reductions of 0.92, 1.89, and 2.27 log PFU/ml, respectively. Similarly, after 24 h, the 5% and 10% GSE membranes reduced MNV-1 titers by 1.90 and 3.26 log PFU/ml, respectively. Antimicrobial tests have shown excellent performance to resist microorganisms. The water uptake capacity of the membrane is found 72% for the PVA/starch pristine membrane and is reduced to 32% for the 10% GSE embedded membrane. Since the current pandemic situation due to COVID-19 occurred by SARSCOV2, the prepared GSE incorporated polymeric blend films are the rays of hope in the packaging of food stuff.

Dialysis Membranes for Acute Kidney Injury

Mortality and morbidity rates among critically ill septic patients having acute kidney injury (AKI) are very high, considering the total number of deaths after their admission. Inappropriate selection of the type of continuous renal replacement therapy and inadequate therapy become the immediate causes of these issues. Dialysis is a commonly used treatment intended to prolong the life of AKI patients. Dialysis membranes, which are the core of dialysis treatment, must be properly selected to ensure fair treatment to the patients. The accumulation of certain types of molecules must be dealt with using the right membrane. Whether it is low-flux, high-flux, or adsorptive type, the dialysis membrane should be chosen depending on the condition of the patients. The selection of dialysis membranes should also be based on their effect on the treatment outcomes and well-being. All these options are needed to serve the patients of different clinical settings. The use of dialysis membranes is not restricted to conventional haemodialysis, but rather they can be employed in haemoperfusion, haemofiltration, haemodiafiltration, or a combination of any two of them. This review focuses in-depth on different types of dialysis membranes, their characteristics, and approaches in addressing the issues encountered in patients having AKI with sepsis and/or multiorgan failure in intensive care units.

In silico ordinary differential equation/partial differential equation hemodialysis model estimates methadone removal during dialysis

Background

There is a need to have a model to study methadone’s losses during hemodialysis to provide informed methadone dose recommendations for the practitioner.

Aim

To build a one-dimensional (1-D), hollow-fiber geometry, ordinary differential equation (ODE) and partial differential equation (PDE) countercurrent hemodialyzer model (ODE/PDE model).

Methodology

We conducted a cross-sectional study in silico that evaluated eleven hemodialysis patients. Patients received a ceiling dose of methadone hydrochloride 30 mg/day. Outcome measures included: the total amount of methadone removed during dialysis; methadone’s overall intradialytic mass transfer rate coefficient, k_m; and, methadone’s removal rate, j_ME. Each metric was measured at dialysate flow rates of 250 mL/min and 800 mL/min.

Results

The ODE/PDE model revealed a significant increase in the change of methadone’s mass transfer with increased dialysate flow rate, %Δk_m=18.56, P=0.02, N=11. The total amount of methadone mass transferred across the dialyzer membrane with high dialysate flow rate significantly increased (0.042±0.016 versus 0.052±0.019 mg/kg, P=0.02, N=11). This was accompanied by a small significant increase in methadone’s mass transfer rate (0.113±0.002 versus 0.014±0.002 mg/kg/h, P=0.02, N=11). The ODE/PDE model accurately predicted methadone’s removal during dialysis. The absolute value of the prediction errors for methadone’s extraction and throughput were less than 2%.

Conclusion

ODE/PDE modeling of methadone’s hemodialysis is a new approach to study methadone’s removal, in particular, and opioid removal, in general, in patients with end-stage renal disease on hemodialysis. ODE/PDE modeling accurately quantified the fundamental phenomena of methadone’s mass transfer during hemodialysis. This methodology may lead to development of optimally designed intradialytic opioid treatment protocols, and allow dynamic monitoring of outflow plasma opioid concentrations for model predictive control during dialysis in humans.

Optimization of the convection volume in online post-dilution haemodiafiltration: practical and technical issues

In post-dilution online haemodiafiltration (ol-HDF), a relationship has been demonstrated between the magnitude of the convection volume and survival. However, to achieve high convection volumes (>22 L per session) detailed notion of its determining factors is highly desirable. This manuscript summarizes practical problems and pitfalls that were encountered during the quest for high convection volumes. Specifically, it addresses issues such as type of vascular access, needles, blood flow rate, recirculation, filtration fraction, anticoagulation and dialysers. Finally, five of the main HDF systems in Europe are briefly described as far as HDF prescription and optimization of the convection volume is concerned.

γ-Alumina modification with long chain carboxylic acid surface nanocrystals for biocompatible polysulfone nanocomposites

High performance polysulfone/γ-alumina biocompatible nanocomposites are reported for the first time and the effects of γ-alumina surface modification are explored. We show that some fatty acids chemisorb over the surface of γ-alumina forming nanosized self-assembled structures. These structures present thermal transitions at high temperatures, 100 °C higher than the melting temperatures of the pure acids, and are further shifted about 50 °C in the presence of polysulfone. The chemistry involved in the chemisorption is mild and green meeting the stringent bio sanitary protocols for biocompatible devices. It has been found that the self-assembled structures increase mechanical strength by about 20% despite the foreseeable lack of strong particle-matrix interactions, which manifests as small variations in both the glass transition temperature and the Young's modulus. Electron microscopy observation of fractured surfaces has revealed that some acids induce an extended region of influence around the nanoparticles and this fact has been used to explain the enhancement of mechanical strength.

Improved management of intradialytic hypotension (IDH) using vitamin E-bonded polysulfone membrane dialyzer

BACKGROUND

Intradialytic hypotension (IDH) is a common clinical trait in hemodialysis (HD) which is caused by poor biocompatibility of the dialyzer membrane. Aiming to improve IDH, vitamin E-bonded polysulfone dialyzer (VPS-H) was evaluated in a pilot study.

METHODS

Eight IDH patients on standard HD were switched from their conventional high-flux dialyzers to VPS-H, and intradialytic blood pressure (BP) was monitored regularly for 10 months.

RESULTS

The results showed that hypotension of systolic BP (SBP), diastolic BP (DBP) and pulse pressure (PP) during the session were improved after changing the dialyzer. Notably, almost all the values recorded from 120 minutes into the session until the end of the treatment in the period between the second and tenth month after treatment were significantly different from the corresponding baseline values. Moreover, after 8 to 10 months, the SBP prior to a dialysis session was significantly reduced compared with baseline values. On the other hand, the pulse rate showed no difference throughout the study period.

CONCLUSIONS

This study provides early evidence of the beneficial role that vitamin E-bonded dialyzers may have in preventing IDH. Larger controlled trials are needed to confirm this original finding.

Conformational transitions of adsorbed proteins on surfaces of varying polarity

Combining a wide range of protein adsorption experiments (three globular proteins on eight well-defined homogeneous surfaces) with Monte Carlo simulations of lattice proteins at different concentrations and on surfaces of varying "polarity", we explore the extent and rheological behavior of adsorbed proteins as a function of substrate polarity, "on" rate constants (k(a)) and steric parameters (|A(1)|) from the random sequential adsorption model, and demonstrate a folding to unfolding transition upon adsorption. We show that model globular proteins (hen egg lysozyme, ribonuclease A, and insulin dimer) behave similarly with respect to adsorption. Experimentally, above a substrate wettability cos theta > 0.4 (where theta is the sessile contact angle of water on a substrate in air), the adsorbed mass, rigidity, and k(a) of the proteins are diminished, while the steric factor |A(1)| is increased, suggesting a lower packing density. To analyze these results, we have invoked computer simulations. We show that changing surface polarity has two profound effects. First, the amount adsorbed increases as the surfaces become more apolar. Further, the proteins become less stable as their adsorbed amount increased because they gain a large number of interprotein and protein-surface interactions. Finally, apolar surfaces served to reduce the unfolding free energy barriers, further facilitating the reorganizing of proteins on these surfaces. Thus, increasing the nonpolar nature of the surfaces resulted in a more rigid adsorbed layer, in good agreement with the experiments.

Acute effects of intermittent hemodialysis and sustained low-efficiency hemodialysis (SLED) on the pulmonary function of patients under mechanical ventilation

The effects of hemodialysis (HD) on pulmonary function are still controversial. The objective of this study was to evaluate the effect of intermittent hemodialysis (IHD) and sustained low-efficiency dialysis (SLED) on the respiratory mechanics of ICU patients under invasive mechanical ventilation. We prospectively studied 31 patients. Laboratory and respiratory evaluation (static and dynamic compliance and resistance) was performed pre- and post-HD. Forty HD sessions were studied and grouped in: SLED (n = 17; Qa = 200-250 mL/min, Qd = 300 mL/min) and IHD (n = 23; Qa = 250-300 mL/min, Qd = 500 mL/min). There was no difference between the groups according to age, gender, comorbidities, APACHE II, and cause of mechanical ventilation, but pre-HD, patients in the IHD group had higher levels of plasma creatinine (5.4 +/- 2.0 vs. 4.2 +/- 1.3 mg/dL, p = 0.048) and platelets (286 +/- 186 vs. 174 +/- 95 10(3)/mm(2), p = 0.032) and lower arterial pH (7.37 +/- 0.07 vs. 7.42 +/- 0.05, p = 0.02). The efficiency of the treatment was similar (p > 0.05) with both types of HD regarding fluid removal, urea reduction rate, and decrease in plasma creatinine. Pre-HD, the ventilatory conditions of both groups were similar (p > 0.05) except for pressure support ventilation and airflow resistance. There were no changes (pre- versus post-HD p > 0.05) induced either by IHD or SLED in the ratio PaO(2)/FiO(2) or in any measured ventilatory parameter. In conclusion, neither IHD nor SLED modifies the pulmonary function of patients under mechanical ventilation.

Predilution versus postdilution during continuous venovenous hemofiltration: a comparison of circuit thrombogenesis

During continuous venovenous hemofiltration, predilution can prolong circuit survival time, but the underlying mechanism has not been elucidated. The aim of the present study was to compare predilution with postdilution, with respect to circuit thrombogenesis. Eight critically ill patients were treated with both predilutional and postdilutional continuous venovenous hemofiltration in a crossover fashion. A filtration flow of 60 ml/min was used in both modes. We chose blood flows of 140 and 200 ml/min during predilution and postdilution, respectively, to keep the total flow through the hemofilter constant. Extracorporeal circuit pressures were measured hourly, and samples of blood and ultrafiltrate were collected at five different time points. Thrombin-antithrombin complexes and prothrombin fragments F1 + 2 were measured by ELISA, and platelet activation was assessed by flow cytometry. No signs of thrombin generation or platelet activation were found during either mode. During postdilution, baseline platelet count and maximal prefilter pressure had a linear relation, whereas both parameters were inversely related with circuit survival time. In summary, predilution and postdilution did not differ with respect to extracorporeal circuit thrombogenesis. During postdilution, baseline platelet count and maximal prefilter pressure were inversely related with circuit survival time.

Dialyzer membranes as determinants of the adequacy of dialysis

Hemodialysis membranes have undergone a gradual but substantial evolution over the past few decades. Classification of modern dialyzer membranes by chemical composition bears little relationship to their functional characteristics. The fundamental properties that determine the capacity of the membrane to remove solutes and fluids are its surface area, thickness, pore size, pore density, and potential to adsorb proteins. Dialyzer membrane performance is characterized clinically by its efficiency, defined as the potential to remove urea and presented as the mass-transfer area coefficient (KoA) and ultrafiltration coefficient (K(uf) ),defined as the potential to remove water adjusted for the transmembrane pressure. The parameter K(uf) usually, but not invariably, correlates with the membrane permeability, defined as the potential to remove middle molecules, with beta2-microglobulin being the currently popular marker. The sieving coefficient reflects the membrane potential to transport solutes by convection and is particularly useful for hemofiltration. Enhancing solute clearance is accomplished clinically by increasing blood and dialysate flow rates, strategies that also are applicable to middle molecules for highly permeable membranes. Novel designs of dialyzers include the optimization of fluid flow path geometry and increasing the membrane pore selectivity for solutes by using nanotechnology.

Pegylated interferon-alpha2a kinetics during experimental haemodialysis: impact of permeability and pore size of dialysers

BACKGROUND

Therapeutics in end-stage renal disease (ESRD) patients undergoing haemodialysis (HD) has to consider potential drug clearance during the dialysis procedure. Pegylated interferon-alpha (PEG-IFN-alpha), a middle-size protein drug active against viral hepatitis, allows convenient once-weekly dosing due to prolonged plasma half-life.

AIM

To investigate the impact of permeability and dialyser pore size on PEG-IFN-alpha blood levels during experimental HD.

METHODS

Polymethylmetacrylate (PMMA) membrane 1.6 m2 dialysers with three different permeabilities/pore sizes were selected.

RESULTS

A 40 kDa PEG-IFN-alpha2a (PEGASYS) was not cleared (< 5%) through low-flux/small pore size (25 A;B3A) and high-flux/middle-large pore size (60 A;BKP) dialysers, and was partially (approximately 15%) through intermediate permeability/large pore size (100 A;BKF) dialysers. In contrast, unmodified 17 kDa IFN-alpha2a(Roferon-A) was removed (65%-95%) through BKP or BKF, but not B3A, PMMA dialysers. Moreover, 12 kDa PEG-IFN-alpha2b(PegIntron) was cleared (40%-80%) through PMMA dialysers with pore sizes > or = 60 angstroms. When B3A or BKP were replaced every hour PEG-IFN-alpha2a plasma levels remained constant throughout three experimental-HD-sessions, but PEG-IFN-alpha2b was cleared partially every BKP replacement. Porosity differ among high-flux dialysers. Neither PEG-IFN-alpha2a nor PEG-IFN-alpha2b were removed after three HD sessions through (27/31/33 A) pore size polysulphone dialysers. Although PEG-IFN-alpha2a was not cleared through middle pore-size (43 A/AN69ST) polyacrylonitrile dialyser, PEG-IFN-alpha2b was partially removed.

CONCLUSIONS

The pharmacokinetics of Peg-IFN-alpha may vary in a patient on dialysis.