Middle molecules and small-molecular-weight proteins in ESRD: properties and strategies for their removal

Advances in uremic toxin detection and monitoring in the management of chronic kidney disease progression to end-stage renal disease

Patients with end-stage kidney disease (ESKD) rely on dialysis to remove toxins and stay alive. However, hemodialysis alone is insufficient to completely remove all/major uremic toxins, resulting in the accumulation of specific toxins over time. The complexity of uremic toxins and their varying clearance rates across different dialysis modalities poses significant challenges, and innovative approaches such as microfluidics, biomarker discovery, and point-of-care testing are being investigated. This review explores recent advances in the qualitative and quantitative analysis of uremic toxins and highlights the use of innovative methods, particularly label-mediated and label-free surface-enhanced Raman spectroscopy, primarily for qualitative detection. The ability to analyze uremic toxins can optimize hemodialysis settings for more efficient toxin removal. Integration of multiple omics disciplines will also help identify biomarkers and understand the pathogenesis of ESKD, provide deeper understanding of uremic toxin profiling, and offer insights for improving hemodialysis programs. This review also highlights the importance of early detection and improved understanding of chronic kidney disease to improve patient outcomes.

Lifting the Veil: Characteristics, Clinical Significance, and Application of β-2-Microglobulin as Biomarkers and Its Detection with Biosensors

Because β-2-microglobulin (β₂M) is a surface protein that is present on most nucleated cells, it plays a key role in the human immune system and the kidney glomeruli to regulate homeostasis. The primary clinical significance of β₂M is in dialysis-related amyloidosis, a complication of end-stage renal disease caused by a gradual accumulation of β₂M in the blood. Therefore, the function of β₂M in kidney-related diseases has been extensively studied to evaluate its glomerular and tubular functions. Because increased β₂M shedding due to rapid cell turnover may indicate other underlying medical conditions, the possibility to use β₂M as a versatile biomarker rose in prominence across multiple disciplines for various applications. Therefore, this work has reviewed the recent use of β₂M to detect various diseases and its progress as a biomarker. While the use of state-of-the-art β₂M detection requires sophisticated tools, high maintenance, and labor cost, this work also has reported the use of biosensor to quantify β₂M over the past decade. It is hoped that a portable and highly efficient β₂M biosensor device will soon be incorporated in point-of-care testing to provide safe, rapid, and reliable test results.

Mass Transport in High-Flux Hemodialysis: Application of Engineering Principles to Clinical Prescription

An understanding of the processes underlying mass transfer is paramount for the attainment of adequate solute removal in the dialytic treatment of patients with kidney failure. In this review, engineering principles are applied to characterize the physical mechanisms behind the two major modes of mass transfer during hemodialysis, namely diffusion and convection. The manner in which flow rate, dialyzer geometry, and membrane microstructure affect these processes is discussed, with concepts such as boundary layers, effective membrane diffusivity, and sieving coefficients highlighted as critical considerations. The objective is to improve clinicians' understanding of these concepts as important factors influencing the prescription and delivery of hemodialysis therapy.

Lab-on-a-chip Dielectrophoretic Manipulation of Beta-2 Microglobulin for Toxin Removal in An Artificial Kidney

Background:

This paper presents a fundamental study of protein manipulation under the influence of dielectrophoretic (DEP) force for a lab-on-a-chip platform.

Objective:

Protein manipulation is dependent on the polarisation factor of protein when exposed to an electric field. Therefore the objective of this work is a microfluidic device and measurement system are used to characterise the human beta-2 microglobulin (β2M) protein via lateral attractive forces and vertical repulsive forces by means of DEP responses.

Method:

The manipulation of the β2M protein was conducted using a microfluidic platform with a tapered DEP microelectrode and the protein concentration was quantified based on a biochemical interaction using an Enzyme-Linked Immunosolvent Assay (ELISA). The protein distribution has been analysed based on the β2M concentration for each microfluidic outlet.

Results:

At 300 kHz, the protein experienced a negative DEP (nDEP) with of 83.3% protein distribution on the middle microchannel. In contrast, the protein experienced a positive DEP (pDEP) at 1.2 MHz with of 78.7% of protein on the left and right sides of the microchannel.

Conclusion:

This is concept proved that the tapered DEP microelectrode is capable of manipulating a β2M via particle polarisation, hence making it suitable to be utilised for purifying proteins in biomedical application.

Hemodialysis is associated with higher serum FGF23 level when compared with peritoneal dialysis

BACKGROUND

Considering the growing relevance of fibroblast growth factor-23 (FGF23) and increased cardiovascular mortality in dialysis population, an analysis was performed to assess the influence of dialysis modality (peritoneal dialysis and hemodialysis) on level of FGF23.

METHODS

A cross-sectional study was performed in 80 continuous ambulatory peritoneal dialysis (CAPD) and 65 hemodialysis (HD) patients without residual renal function. Levels of calcium, phosphate, parathyroid hormone and FGF23 were measured, and their correlations were analyzed. Data on demographics, dialysis modality and FGF23 level were also analyzed.

RESULTS

A significant correlation was found between FGF23 and serum calcium, serum phosphate and dialysis vintage in dialysis patients. Level of FGF23 was significantly higher in hemodialysis patients than that in peritoneal dialysis population. Multivariable regression revealed that, compared to CAPD, hemodialysis was found to be a predictor for higher FGF23 level, which was independent of serum calcium and phosphate level (P < 0.05).

CONCLUSIONS

These findings demonstrate that FGF23 levels are significantly higher in hemodialysis patients than that in peritoneal dialysis patients. We demonstrate an important association between dialysis modality (HD vs CAPD) and higher FGF23, independent of classical determinants (serum calcium and phosphate level).

Cytochrome P450-endogenous substrates metabolism is reduced in patients with a multiple organ dysfunction after coronary artery bypass grafting

Aim: To evaluate endogenous toxic substrates and liver monooxygenase function in cardiosurgical patients with multiple organ dysfunction syndrome (MODS). Methods: 45 patients with MODS and 34 patients with an uneventful postoperative period were studied. The endogenous substrates were quantified with blood middle molecules (MM). Liver monooxygenase function was evaluated with antipyrine (AP) pharmacokinetics. Results: On the first postoperative day, MODS patients were characterized by high concentration of toxic substrates (MM: +43.8%) and a significant decrease in liver monooxygenase function (AP clearance: −44%), while controls patients had a mild increase in endogenous substrates and a slight depression in monooxygenase function. On the 3rd–4th postoperative day, in the main group, endogenous substrates increased (MM: +53.1%), while in the control group toxic substrates decreased (MM: +6.9%). In both groups, an increase in liver monooxygenase function was noticed. Major differences were observed on the 10th–12th postoperative day. In the main group, toxic substrates remained elevated (MM: +37.5%) and monooxygenase function was depressed (AP clearance: −45.4%), while in the control group endogenous substrates and monooxygenase function were equal to the baseline. The correlation analysis showed a negative relationship between AP pharmacokinetics and endogenous substrates. Conclusion: Slowdown in liver microsomal oxidation is one of the main reasons for the accumulation of endogenous toxic substrates in MODS cardiac patients.

Bottom-up nanotechnology: the human nephron filter

Over one million patients worldwide have end-stage renal disease and require dialysis or kidney transplantation. Despite the availability of these forms of renal replacement therapy for nearly four decades, mortality and morbidity are high and patients often have a poor quality of life. We have developed a human nephron filter (HNF) utilizing bottom-up nanotechnology that would eventually make feasible a continuously functioning, wearable or implantable artificial kidney. The device consists of two membranes operating in series within one device cartridge. The first membrane mimics the function of the glomerulus, using convective transport to generate a plasma ultra filtrate, which contains all solutes approaching the molecular weight of albumin. The second membrane mimics the function of the renal tubules, selectively reclaiming designated solutes to maintain body homeostasis. No dialysis solution is used in this device. The HNF has been computer modeled, and operating 12 hour per day, 7 days per week the HNF provides the equivalent of 30 ml/min glomerular filtration rate (compared to half that amount for conventional thrice-weekly hemodialysis). The HNF system, by eliminating dialysate and utilizing a novel membrane system created through applied nanotechnology, represents a breakthrough in renal replacement therapy based on the functioning of native kidneys. The enhanced solute removal and wearable design should substantially improve patient outcomes and quality of life.

The Human Nephron Filter: Toward a Continuously Functioning, Implantable Artificial Nephron System

BACKGROUND

Nearly 900,000 patients worldwide have end-stage renal disease and require dialysis or kidney transplantation, and this number is expected to more than double by 2010, placing considerable stress on healthcare systems throughout the world. Despite the availability of these forms of renal replacement therapy for nearly four decades, mortality and morbidity is high and patients often have a poor quality of life.

METHODS

We have developed a human nephron filter (HNF) utilizing nanotechnology that would eventually make feasible a continuously functioning, implantable artificial kidney. The device consists of two membranes operating in series within one device cartridge. The first membrane mimics the function of the glomerulus, while the second membrane mimics the function of the renal tubules.

FINDINGS

The device has been computer-modeled and operating 12 h/day, 7 days/week, the HNF provides the equivalent of 30 ml/min glomerular filtration rate (compared to half that amount for conventional thrice weekly hemodialysis).

CONCLUSIONS

The HNF system, by eliminating dialysate and utilizing a novel membrane system created through applied nanotechnology may represent a breakthrough in renal replacement therapy based on the functioning of native kidneys. The enhanced solute removal and wearable design should substantially improve patient outcomes and quality of life.

Continuously functioning artificial nephron system: The promise of nanotechnology

Nearly 900,000 patients worldwide have end-stage renal disease and require dialysis or kidney transplantation. Despite the availability of these forms of renal replacement therapy for nearly four decades, mortality and morbidity are high and patients often have a poor quality of life. We have developed a human nephron filter (HNF) utilizing nanotechnology that would eventually make feasible a continuously functioning, wearable or implantable artificial kidney. The device consists of two membranes operating in series within one device cartridge. The first membrane mimics the function of the glomerulus, using convective transport to generate a plasma ultrafiltrate containing all solutes approaching the molecular weight of albumin. The second membrane mimics the function of the renal tubules, selectively reclaiming designated solutes to maintain body homeostasis. No dialysis solution is used in this device. The HNF has been computer-modeled, and operating 12 hr per day, 7 days per week the HNF provides the equivalent of 30 mL/min glomerular filtration rate (compared to half that amount for conventional thrice-weekly hemodialysis). Animal studies should begin in the next 1 to 2 years, and clinical trials would then follow 1 to 2 years subsequent. The HNF system, by eliminating dialysate and utilizing a novel membrane system created through applied nanotechnology, represents a breakthrough in renal replacement therapy based on the functioning of native kidneys. The enhanced solute removal and wearable design should substantially improve patient outcomes and quality of life.