Comprehensive analysis of cytokine adsorption properties of polymethyl methacrylate (PMMA) membrane material

Advances in Renal Replacement Therapy: The Role of Polymethyl Methacrylate Membranes in Acute Critically Ill Patients

BACKGROUND

Polymethyl methacrylate (PMMA) membranes are increasingly recognized for their effectiveness in treating acute kidney injury (AKI) due to their strong adsorption capabilities, particularly for inflammatory mediators like β2-microglobulin and IL-6. These membranes ensure mechanical stability and chemical inertness, minimizing adverse reactions during blood filtration.

SUMMARY

In acute conditions such as sepsis and acute respiratory distress syndrome (ARDS), PMMA membranes show promising findings. In sepsis, they may help reduce multiorgan failure by modulating immune responses, although further research is needed to confirm their routine use. For ARDS, PMMA membranes could mitigate "cytokine storms" by adsorbing key cytokines, improving oxygenation and hemodynamic stability, which may reduce ICU stays and reliance on mechanical ventilation. Monitoring biomarkers like IL-6, TNF-α is critical for tracking efficacy and tailoring therapy to individual needs. In chronic conditions, such as hemodialysis for chronic kidney disease, PMMA membranes help lower oxidative stress and β2-microglobulin levels, reducing complications such as amyloidosis. By decreasing oxidative damage, they provide long-term protective benefits for dialysis patients.

KEY MESSAGE

While these advantages are notable, large-scale studies are needed to establish PMMA's efficacy, refine treatment protocols, and confirm its broader role in acute and chronic disease management. The potential of PMMA membranes highlights their value, but standardized clinical evidence is necessary for widespread adoption.

Enhanced Bioactive Compound Absorption on PMMA Microwell Plates via Fine Controlling Air Plasma Treatment Time for Disease Diagnosis Applications

Microwell plates absorb bioactive compounds and are commonly used for disease prediction, diagnosis, and monitoring. Chemical absorption is more effective than physical absorption for stabilizing these compounds. This study systematically investigates the fundamental mechanisms of air plasma-induced surface modifications in poly(methyl methacrylate) (PMMA), focusing on carboxyl group formation kinetics, morphological evolution, and optical property changes. Air plasma treatment enhances the hydrophilicity and surface roughness of the PMMA plates. Light transmission remains comparable to untreated plates for 10 min treatment durations. Treatment for 3 min significantly increases the large-molecular-weight carboxyl compounds, with minimal loss after wash buffer rinsing. Thus, a 3 min air plasma treatment optimally enhances PMMA microwell plates for effective bioactive compound absorption.

Investigation of Inflammatory Reduction During Extracorporeal Membrane Oxygenation Using a Novel Cytokine Adsorption Column: A Rat Model Study

Background: Cardiopulmonary bypass (CPB) and extracorporeal membrane oxygenation (ECMO) are widely used. Previous methods to reduce inflammation have shown inconsistent results. We developed a cytokine adsorption column using polymethyl methacrylate (PMMA) and investigated its anti-inflammatory effects during ECMO. Materials and Methods: Male Sprague-Dawley rats were divided into three groups (seven rats in each group): SHAM, ECMO, and ECMO with PMMA (PMMA group). Experiments comprised 180 min of cannulation only in the SHAM group and 60 min of ECMO followed by 120 min of observation in the ECMO and PMMA groups. PMMA adsorption was conducted from 30 min after ECMO initiation to completion in the PMMA group. Blood parameters and cytokines were measured during experiments. Lung tissues were collected after the experiment for evaluation of tissue edema. Results: The PMMA group showed significantly lower levels of tumor necrosis factor alpha (TNF-α) and interleukin(IL)-6 compared to the ECMO group at 120 min after completing ECMO. However, there were no significant differences in IL-10 levels between the ECMO group and the PMMA group at the same time points. Lung edema incidence was significantly lower in the PMMA group. Conclusions: The PMMA column effectively suppressed systemic inflammatory reactions during ECMO.

Comparison of Pre-dilution and Post-dilution Methods on Cytokine Clearance Using Polymethylmethacrylate (PMMA) Membrane Hemofilters in Continuous Hemodiafiltration

In Japan, the post-dilution method is preferred to maintain the dialysis efficiency of low molecular weight substances in continuous hemodiafiltration (CHDF). In contrast, the pre-dilution method is preferable to ensure a stable filter lifetime, especially for membranes with cytokine absorptive characteristics that are at high risk of membrane coagulation. However, the impact of the dilution method on the removal performance of adsorptive membranes for cytokines remains unclear. This study aimed to investigate the effect of different dilution methods on the adsorption clearance of cytokine on polymethylmethacrylate (PMMA) membranes by in vitro experiments. Bovine albumin, interleukin (IL)-6, and creatinine were added to phosphate-buffered saline to achieve final concentrations of 3.5 g/dL, 1000 pg/mL, and 10 mg/dL, respectively. The test solution was passed through the 1.8 m2 PMMA membrane hemofilter at a flow rate of 100 mL/min in a single-pass system. The dialysate/filtration flow rates used were 2.5/2.5, 5.0/5.0, and 7.5/7.5 mL/min for each pre- and post-dilution method. Samples were collected seven times from pre- and post-hemofilter every minute, 10 min after the start of CHDF. Samples were frozen and stored, and the concentration of IL-6 was measured by enzyme-linked immunosorbent assay (ELISA), and clearance was calculated. Creatinine clearance increased with an increasing flow rate in pre- and post-dilution, while IL-6 clearance was less affected by flow rate. IL-6 clearance was 35.5 mL/min (32.1-39.6) for pre-dilution and 37.1 mL/min (33.8-41.1) for post-dilution in the 2.5/2.5 setting, and 34.2 mL/min (28.8-36.2) for pre-dilution and 32.4 mL/min (32.4-37.4) for post-dilution in the 5.0/5.0 setting. The dilution methods showed no significant differences. Moreover, in the 7.5/7.5 setting, clearance was 29.5 mL/min (27.7-37.2) for pre-dilution and 39.9 mL/min (37.8-41.5) for post-dilution (P<0.001); however, all clearance values were higher than theoretical values expected from filtration removal. In conclusion, the cytokine removal characteristics of the PMMA membrane hemofilter were not largely affected by the dilution method, and IL-6 clearance could be fully demonstrated even in the pre-dilution method.

A Retrospective Study on the Start and End of Continuous Hemodialysis Using a Polymethylmethacrylate Hemofilter for Severe Acute Pancreatitis

Objective We previously reported the successful outcomes in severe acute pancreatitis (SAP) after continuous hemodialysis using a polymethylmethacrylate hemofilter (PMMA-CHD). The present study makes informative suggestions regarding the initiation and termination of PMMA-CHD. Methods We retrospectively studied 63 patients with SAP admitted to the intensive care unit between January 1, 2011, and December 31, 2022, including 30 who received PMMA-CHD therapy for renal dysfunction. Statistical significance was evaluated using a multiple logistic regression analysis for severity scores, prognostic factor scores in the Japanese severity criteria, the Kidney Disease: Improving Global Outcomes (KDIGO) stage, and the lung injury score (LIS). Results At the onset of blood purification therapy using PMMA-CHD, a significant increase in the KDIGO stage was shown, with a cutoff value of 2.0. The prognostic factor score and LIS at the start of blood purification therapy were significantly high, with a cutoff value of 3.0. Analyses of severity scores, the KDIGO stage, and the LIS before the start of PMMA-CHD were also increased significantly, with cutoff values of +2.0, +1.0, and +3.0, respectively. Furthermore, on analyses of improvements in values after starting PMMA-CHD, the value of KDIGO staging significantly decreased, and the cutoff value was -2.0. The prognostic factor score was also significantly decreased, with a cutoff value of -2.0. Conclusion Prognostic factor scores of the Japanese severity criteria and LIS, as well as the KDIGO stage, are valuable indicators for determining the start and end of PMMA-CHD therapy.

Comparative analyses of adsorbed circulating proteins in the PMMA and PES hemodiafilters in patients on predilution online hemodiafiltration

Acute and chronic inflammation are common in patients with end-stage kidney disease (ESKD). So, the adsorption of pro-inflammatory cytokines by the hollow fiber of the dialysis membrane has been expected to modify the inflammatory dysregulation in ESKD patients. However, it remains to be determined in detail what molecules of fiber materials can preferably adsorb proteins from the circulating circuit. We aimed this study to analyze directly the adsorbed proteins in the polymethyl methacrylate (PMMA) and polyethersulfone (PES) membranes in patients on predilution online hemodiafiltration (OL-HDF). To compare the adsorbed proteins in the PMMA and PES hemodiafilters membrane, we initially performed predilution OL-HDF using the PES (MFX-25Seco) membrane while then switched to the PMMA (PMF™-A) membrane under the same condition in three patients. We extracted proteins from the collected hemodiafilters by extraction, then SDS-PAGE of the extracted sample, protein isolation, in-gel tryptic digestion, and nano-LC MS/MS analyses. The concentrations of adsorbed proteins from the PMMA and PES membrane extracts were 35.6±7.9 μg/μL and 26.1±9.2 μg/μL. SDS-PAGE analysis revealed distinct variations of adsorbed proteins mainly in the molecular weight between 10 to 25 kDa. By tryptic gel digestion and mass spectrometric analysis, the PMMA membrane exhibited higher adsorptions of β2 microglobulin, dermcidin, retinol-binding protein-4, and lambda-1 light chain than those from the PES membrane. In contrast, amyloid A-1 protein was adsorbed more potently in the PES membrane. Western blot analyses revealed that the PMMA membrane adsorbed interleukin-6 (IL-6) approximately 5 to 118 times compared to the PES membrane. These findings suggest that PMMA-based OL-HDF therapy may be useful in controlling inflammatory status in ESKD patients.

COVID-19: The Dysregulated Response to Infection - Why Consider Polymethylmethacrylate Membrane in Hemodialysis Patients?

Since SARS-CoV-2 spread through China at the end of 2019, COVID-19 has been probably the most difficult challenge in the last decades for healthcare systems all around the world, still representing a danger for fragile patients with different comorbidities. Chronic dialysis patients affected by COVID-19 experienced severe disease with a higher mortality rate compared to the general population. Morbidity and mortality of this severe acute respiratory syndrome depend on both acute respiratory failure and systemic immunological involvement with consequent inflammation-mediated injury. Indeed, the most important determining factor of COVID-19 severity is the strength of the so-called "cytokine storm" associated with SARS-CoV-2 infection. Therefore, this severe infection varies clinically from an asymptomatic condition to a generalized and violent inflammatory response and acute respiratory distress syndrome, with consequent pulmonary interstitial edema and a high risk of multi-organ failure. The use of extracorporeal therapies targeting cytokine clearance to improve patients' outcomes has been widely debated, especially in end-stage kidney disease's patients on maintenance dialysis or in individuals affected by acute kidney injury admitted to intensive care units. Different studies were conducted to demonstrate how specific dialyzers could decrease the COVID-19 inflammatory state. The aim of this narrative review was to summarize main studies about this topic, focusing primarily on the role of polymethylmethacrylate dialyzer and underlining pros and cons of this sorbent.

Blood Purification in Patients with Sepsis Associated with Acute Kidney Injury: A Narrative Review

Sepsis leads to organ dysfunction. Acute kidney injury, a common type of organ dysfunction, is associated with a high mortality rate in patients with sepsis. Kidney replacement therapy can correct the metabolic, electrolyte, and fluid imbalances caused by acute kidney injury. While this therapy can improve outcomes, evidence of its beneficial effects is lacking. Herein, we review the indications for blood purification therapy, including kidney replacement therapy, and the current knowledge regarding acute kidney injury in terms of renal and non-renal indications. While renal indications have been well-documented, indications for blood purification therapy in sepsis (non-renal indications) remain controversial. Excessive inflammation is an important factor in the development of sepsis; blood purification therapy has been shown to reduce inflammatory mediators and improve hemodynamic instability. Given the pathophysiology of sepsis, blood purification therapy may decrease mortality rates in these patients. Further trials are needed in order to establish the effectiveness of blood purification therapy for sepsis.

Role of the CD40-CD40 Ligand Pathway in Cardiovascular Events, Neurological Alterations, and Other Clinical Complications of Chronic Hemodialysis Patients: Protective Role of Adsorptive Membranes

Despite the recent advances in dialysis technology, mortality rate of chronic uremic patients still remains excessively high: of note, in comparison to age- and sex-matched healthy controls, this frail population shows a higher incidence of infections, cancer, cognitive decline, and, in particular, major adverse cardiovascular events (MACE) that represent nowadays the first cause of mortality. Several traditional and nontraditional factors contribute to this increased risk for MACE and accelerated cellular senescence: among these, inflammation has been shown to play a key role. The costimulatory pathway CD40-CD40 Ligand (CD40L) is harmfully activated during inflammation and uremia-associated clinical complications: in particular, the soluble form of CD40L (sCD40L) can bind to the CD40 receptor triggering a cascade of detrimental pathways in immune and nonimmune cells. In this narrative review, we summarize the current concepts of the biological role of the CD40-CD40L pathway in uremia-associated organ dysfunction, focusing on the above-described main causes of mortality. Moreover, we discuss the interaction of the CD40-CD40L pathway with extracellular vesicles, microparticles recently identified as new uremic toxins. The biological effects of sCD40L in MACE, cognitive decline, infections, and cancer will be also briefly commented. Last, based on recent studies and ongoing clinical trials, we herein describe the modulatory activity of adsorptive dialysis membranes in polymethylmethacrylate on CD40-CD40L detrimental activation.

Enhancing Immune Protection in Hemodialysis Patients: Role of the Polymethyl Methacrylate Membrane

End-stage renal disease (ESRD) is characterized by deep disorders in both innate and adaptive immune systems that imply unbalance deactivation and immunosuppression. The central, widely recognized factors responsible for this immune dysregulation are uremia, uremic toxin retention, hemodialysis membrane biocompatibility, and related cardiovascular complications. Recently, several studies strengthened the concept that dialysis membranes are not considered as a simple diffusive/adsorptive device but as a platform to personalize a dialysis approach to improve the quality of life of ESRD patients. Therefore, understanding of the molecules associated with altered immune response is crucial and could lead to therapeutically intervention or adaptation of the dialysis procedure itself for the management of immunological dysfunction of ESRD patients. The polymethyl methacrylate (PMMA)-based membrane is characterized by a symmetrical structure with large-sized pores, providing a better hydrophobic and cationic adsorption capacity compared to the other synthetic membranes. Together with hydrophobic interactions, the high adsorption rate of cytokines (i.e., IL-6) can also be enhanced by the size of nano-pores placed on the membrane surface. PMMA membranes exhibit adsorptive properties for a large amount of uremic toxins including p-cresol and indoxyl sulfate, as well as β2-microglobulin characterized by higher molecular weight, maintaining the diffusive clearance of small molecules like urea with a great biocompatibility. Besides exerting a strong anti-inflammatory effects in line with the improvement of immune responses in patients undergoing dialysis, PMMA also plays a role in modulating adaptive immune response, i.e., can clear blood from soluble CD40, a natural antagonist of the CD40/CD40L signaling that acts inhibiting immunoglobulin production by B cells. This review provides an overview of the main concepts and current understanding of immune dysfunction in hemodialysis and summarizes the recent findings regarding PMMA-based dialysis as potential strategy to restore immune balance in ESRD patients.

Evaluation of the Effect of the PMMA Dialysis Membrane on the Level of Inflammation in Patients on Hemodialysis

INTRODUCTION

The inflammation syndrome is typical for chronic kidney disease (CKD) and increases with the progression of CKD. It is extremely important to monitor the markers of inflammation in patients with CKD, as there is a clear relationship between the level of inflammation and mortality in these patients. Currently, there is no single approach to the treatment of chronic inflammation in patients with CKD.

METHODS

This was a prospective open cohort study. We studied 31 patients on hemodialysis from March 1, 2020, to August 1, 2021, in 2 Moscow clinics (No. 7 and S.P. Botkin). Inclusion criteria for patients in the study were an adequate dialysis according to the KT/V index ≥1.4, absence of an active inflammatory process or infections, age over 18 years, standard hemodialysis regimen of 3 times per week, at least 4 h, levels of interleukin-6 (IL-6), IL-8, and C-reactive protein (CRP) above the reference values. Patients were transferred from hemodialysis performed using a standard polysulfone (PS) membrane to a polymethylmethacrylate (PMMA) membrane (Filtryzer BK-2.1F). For dialysis treatment in patients, blood flow rates of 250-350 mL/min were used, and the flow rate of the dialysis solution was set at 500 mL/min. The control group consisted of 19 patients, with similar inclusion parameters, who continued their treatment with hemodialysis using a PS membrane. The aim of the research was to study the effect of the dialysis membrane (Filtryzer BK-2.1F) on the level of inflammation in routine practice compared to a PS membrane. Adverse events were monitored.

RESULTS

By the end of the study, after 12 months, the levels of cytokines significantly decreased only in patients who had treatment with PMMA membrane, starting from the 3rd month of treatment, and became close to normal levels: IL-6 from 16.9 ± 8.0 to 8.5 ± 4.8 pg/mL (p ≤ 0.0001); IL-8 from 78.5 ± 11.4 to 43.6 ± 11.6 pg/mL (p ≤ 0.0001); and CRP from 10.33 ± 2.83 to 6.15 ± 1.57 mg/L (p ≤ 0.0001). Values of inflammation markers did not change in control group.

CONCLUSION

In our study, we demonstrated for the first time a significant reduction in the level of inflammation in patients on standard hemodialysis in routine practice due to the use of PMMA membranes.

Rationale for sequential extracorporeal therapy (SET) in sepsis

Sepsis and septic shock remain drivers for morbidity and mortality in critical illness. The clinical picture of patients presenting with these syndromes evolves rapidly and may be characterised by: (a) microbial host invasion, (b) establishment of an infection focus, (c) opsonisation of bacterial products (e.g. lipopolysaccharide), (d) recognition of pathogens resulting in an immune response, (e) cellular and humoral effects of circulating pathogen and pathogen products, (f) immunodysregulation and endocrine effects of cytokines, (g) endothelial and organ damage, and (h) organ crosstalk and multiple organ dysfunction. Each step may be a potential target for a specific therapeutic approach. At various stages, extracorporeal therapies may target circulating molecules for removal. In sequence, we could consider: (a) pathogen removal from the circulation with affinity binders and cartridges (specific), (b) circulating endotoxin removal by haemoperfusion with polymyxin B adsorbers (specific), (c) cytokine removal by haemoperfusion with sorbent cartridges or adsorbing membranes (non-specific), (d) extracorporeal organ support with different techniques for respiratory and cardiac support (CO₂ removal or extracorporeal membrane oxygenation), and renal support (haemofiltration, haemodialysis, or ultrafiltration). The sequence of events and the use of different techniques at different points for specific targets will likely require trials with endpoints other than mortality. Instead, the primary objectives should be to achieve the desired action by using extracorporeal therapy at a specific point.

A Larger Membrane Area Increases Cytokine Removal in Polymethyl Methacrylate Hemofilters

Blood purification is performed to control cytokines in critically ill patients. The relationship between the clearance (CL) and the membrane area during adsorption is not clear. We hypothesized that the CL increases with the hydrophobic area when hydrophobic binding contributes to cytokine adsorption. We investigated the relationship between the hemofilter membrane area and the CL of the high mobility group box 1 protein (HMGB-1) and interleukin-6 (IL-6). We performed experimental hemofiltration in vitro using polymethyl methacrylate membranes CH-1.8W (1.8 m²) and CH-1.0N (1.0 m²), as well as polysulfone membrane NV-18X (1.8 m²). After adding 100 mg of HMGB1 or 10 μg of IL-6 into the test solution, experimental hemofiltration was conducted for 360 min in a closed-loop circulation system, and the same amount of HMGB1 and IL-6 was added after 180 min. With CH-1.8W and CH-1.0N, both HMGB-1 and IL-6 showed a rapid concentration decrease of more than 70% at 180 min and 360 min after the re-addition. At 15 min, the CL of HMGB-1 was CH-1.8W: 28.4 and CH-1.0N: 19.8, and that of IL-6 was CH-1.8W: 41.1 and CH-1.0N: 25.4. CH-1.8W and CH-1.0N removed HMGB1 and IL-6 by adsorption and CH-1.8W was superior in CL, which increased with a greater membrane area.