Extracorporeal albumin dialysis

Application of Nanoparticles as Novel Adsorbents in Blood Purification Strategies

BACKGROUND

Blood purification therapy for patients overloaded with metabolic toxins or drugs still needs improvement. Blood purification therapies, such as in hemodialysis or peritoneal dialysis can profit from a combined application with nanoparticles.

SUMMARY

In this review, the published literature is analyzed with respect to nanomaterials that have been customized and functionalized as nano-adsorbents during blood purification therapy. Liposomes possess a distinct combined structure composed of a hydrophobic lipid bilayer and a hydrophilic core. The liposomes which have enzymes in their aqueous core or obtain specific surface modifications of the lipid bilayer can offer appreciated advantages. Preclinical and clinical experiments with such modified liposomes show that they are highly efficient and generally safe. They may serve as indirect and direct adsorption materials both in hemodialysis and peritoneal dialysis treatment for patients with renal or hepatic failure. Apart from dialysis, nanoparticles made of specially designed metal and activated carbon have also been utilized to enhance the removal of solutes during hemoadsorption. Results are a superior adsorption capacity and good hemocompatibility shown during the treatment of patients with toxication or end-stage renal disease. In summary, nanomaterials are promising tools for improving the treatment efficacy of organ failure or toxication.

KEY MESSAGES

(i) The pH-transmembrane liposomes and enzyme-loaded liposomes are two representatives of liposomes with modified aqueous inner core which have been put into practice in dialysis. (ii) Unmodified or physiochemically modified liposomal bilayers are ideal binders for lipophilic protein-bound uremic toxins or cholestatic solutes, thus liposome-supported dialysis could become the next-generation hemodialysis treatment of artificial liver support system. (iii) Novel nano-based sorbents featuring large surface area, high adsorption capacity and decent biocompatibility have shown promise in the treatment of uremia, hyperbilirubinemia, intoxication, and sepsis. (vi) A major challenge of production lies in avoiding changes in physical and chemical properties induced by manufacturing and sterilizing procedures.

Linoleic acid-modified liposomes for the removal of protein-bound toxins: An in vitro study

INTRODUCTION

Protein-bound uremic toxins (PBUTs) and liver failure-related cholestatic solutes are associated with adverse outcomes in patients with chronic kidney disease (CKD) and liver failure, respectively, and are not easily removed by traditional dialysis therapies. We constructed linoleic acid-modified liposomes (LA-liposomes) as indirect adsorbent in the dialysate, and evaluated their effects on the clearance of the representative PBUTs and cholestatic solutes.

METHODS

The LA-liposomes were prepared by the thin-film hydration method. The binding rates of liposomes and protein-bound solutes were detected by the ultrafiltration column. The in vitro dialysis experiments were performed using both non-current and current devices to assay the clearing efficiency of the dialysate supported by LA-liposomes.

RESULTS

The LA-liposomes exhibited good binding properties to the PBUTs, bilirubin and bile acids. The LA-liposome dialysate showed higher solute reduction rates of the representative PBUTs and cholestatic solutes than the traditional dialysate or dialysate supported by the unmodified plain liposomes. Also, albumin binding of the PBUTs was significantly inhibited by the addition of linoleic acid (LA), and the removal efficiency of PBUTs was greatly enhanced by the combination of indirect adsorbent LA-liposomes and LA as the competitive displacer.

CONCLUSION

LA-liposomes were efficient in the clearance of the representative PBUTs and liver failure-related solutes. Moreover, the combination of indirect adsorbent LA-liposomes and competitive displacer suggested a potential application for the extremely highly-bound solutes.

Improving the clearance of protein-bound uremic toxins using cationic liposomes as an adsorbent in dialysate

Anionic and protein-bound uremic toxins, represented by indoxyl sulfate (IS), may be associated with cardiovascular outcomes and the progression of chronic kidney disease in cases of injured kidney function and are not easily cleared by traditional dialysis therapy. We fabricated cationic liposomes that were modified with polyethyleneimine (PEI), octadecylamine (Oct), and hexadecyl trimethyl ammonium bromide (CTAB), and evaluated the effects on the clearance of the representative protein-bound uremic toxins (PBUTs). The binding rate was obtained by ultrafiltration and in vitro dialysis was performed in a Rapid Equilibrium Dialysis (RED) device to assay the clearing efficiency of the dialysate supported by three types of cationic liposomes. The cationic liposomes showed a higher binding rate with IS (1.24-1.38 fold higher) and p-cresol (1.07-1.09 fold higher) than in the unmodified plain liposomes. The dialysate supported by cationic liposomes also exhibited better clearing efficiency for IS (PEI-20: 57.65 ± 1.74 %; Oct-5: 62.80 ± 0.69 %; CTAB-10: 66.54 ± 0.91 %; p < 0.05) and p-cresol (PEI-20: 67.05 ± 3.09 %; Oct-5: 79.26 ± 0.43 %; CTAB-5: 68.45 ± 1.72 %; p < 0.05) than for phosphate buffer saline (IS: 29.70 ± 2.38 %; p-cresol: 33.59 ± 3.44 %) or dialysate supported by bovine serum albumin (IS: 50.00 ± 4.01 %; p-cresol: 53.06 ± 0.97 %). In conclusion, cationic liposomes are efficient in the clearance of anionic PBUTs, and these modified liposomes suggest a potential application in blood purification.

Available extracorporeal treatments for poisoning: overview and limitations

Poisoning is a significant public health problem. In severe cases, extracorporeal treatments (ECTRs) may be required to prevent or reverse major toxicity. Available ECTRs include intermittent hemodialysis, sustained low-efficiency dialysis, intermittent hemofiltration and hemodiafiltration, continuous renal replacement therapy, hemoperfusion, therapeutic plasma exchange, exchange transfusion, peritoneal dialysis, albumin dialysis, cerebrospinal fluid exchange, and extracorporeal life support. The aim of this article was to provide an overview of the technical aspects, as well as the potential indications and limitations of the different ECTRs used for poisoned patients.

Artificial extracorporeal liver support therapy in patients with severe liver failure

Severe liver failure is common and carries a high mortality risk in patients with both acute and acute-on-chronic liver failure. The failing liver constitutes a medical emergency, and in many cases liver transplantation is the only definite treatment. Extracorporeal liver support can be employed as a strategy for bridging to transplantation or recovery. This article focuses on options for artificial (nonbiological) extracorporeal treatment: single-pass albumin dialysis, fractionated plasma separation and adsorption (Prometheus(®)) and the molecular adsorbent recirculatory system. Their different principles, potential advantages and indications are discussed. Despite proven biochemical efficacy, there are little data regarding clinical end points. Thus far, molecular adsorbent recirculatory system therapy in acute and acute-on-chronic liver failure showed no survival benefit compared with standard medical therapy. Prometheus therapy showed reduced mortality in subgroups of higher severity of disease compared with standard medical therapy. Nevertheless, the value of extracorporeal liver support remains to be corroborated by further clinical studies that include the optimal timing, mode, intensity and duration of this treatment.

Extracorporeal liver support therapy with Prometheus in patients with liver failure in the intensive care unit

Acute liver failure (ALF) and acute-on-chronic liver failure (AoCLF) are associated with a high mortality. In these patients an accumulation of both water-soluble and water-insoluble, protein-bound, metabolic waste products occurs. Conventional extracorporeal blood purification techniques based on diffusion and/or convection such as hemodialysis or hemofiltration may only eliminate small molecular weight, water-soluble compounds. In recent years, fractionated plasma separation and adsorption (FPSA) with the Prometheus system has been introduced for extracorporeal liver support therapy. To date, however, only limited data is available regarding the effect of this treatment on mortality and outcome of patients with advanced liver disease. Here we report on our experience with 23 patients with severe liver failure who were treated with Prometheus in our medical intensive care unit. Fourteen patients had AoCLF, and nine patients experienced ALF. The median bilirubin level at the start of Prometheus therapy was 30.5 mg/dL and the median Acute Physiology and Chronic Health Evaluation II (APACHE II) score was 26. During 40 individual treatment sessions lasting 5-6 h, Prometheus therapy reduced serum bilirubin levels from 23.7 mg/dL to 15.0 mg/dL (median values) (P < 0.001), and the overall survival was 26%. ALF patients had a better survival compared to AoCLF patients (44% vs. 22%; P = 0.022). Apart from one patient who developed hemodynamic instability during a treatment session, Prometheus therapy was well tolerated without relevant side-effects. In conclusion, extracorporeal liver support therapy with Prometheus is a novel and safe treatment option in patients with severe liver failure. In this series, patients with ALF showed a significantly better outcome with Prometheus therapy compared to AoCLF patients.