A new method to evaluate the local clearance at different annular rings inside hemodialyzers.

Recent research indicated that the dialysate flow distribution inside a hemodialyzer was not uniform ("channeling" of the dialysate flows). However, effect of the channeling on the solute clearance has not been directly and quantitatively examined. In this report, a novel experiment approach is presented to test the hypothesis that hollow fibers in different regions within a given hemodialyzer may contribute differently to the solute clearance. Water solution with urea (molecular weight 60) and creatinine (molecular weight 113) were made as "blood," and pure water was used as dialysate. Two high flux dialyzers, dialyzer A (cellulose triacetate) and dialyzer B (polyethersulfone), were used in this study. The hollow fiber potting area at the blood inlet of a dialyzer was divided into equal area concentric rings. In each experiment, only one of the rings was open for blood flow, and the other rings were blocked by epoxy. The "blood" was pumped at 120 ml/min while the dialysate flow rate (Qd) varied at 500, 800, and 1,000 ml/min, respectively. The solute clearance with a specific ring open (local clearance) was determined by measuring solute (urea/creatinine) concentration at the "blood" inlet and outlet. For dialyzer A, local clearance of urea and creatinine were significantly higher in the outer ring than in the inner ring. With increasing Qd, local solute clearance increased significantly for all rings. For dialyzer B, at any given Qd, solutes local clearance also increased from the inner to outer rings. In comparison, the effect of increasing Qd on solute clearance was greater for dialyzer B than for dialyzer A. In conclusion, using the new experimental method, the authors quantitatively evaluated the solute clearance contributed by the hollow fibers at different locations (concentric rings) in dialyzers. Hollow fibers at different locations did contribute differently to the solute clearance, which may be caused by the channeling of dialysate flow. A careful design of the dialyzer to minimize the channeling is needed.

Microfiltration isolation of human urinary exosomes for characterization by MS.

PURPOSE: The purpose of this study was to address the hypothesis that small vesicular urinary particles known as exosomes could be selectively microfiltered using low protein-binding size exclusion filters, thereby simplifying their use in clinical biomarker discovery studies. EXPERIMENTAL DESIGN: We characterized a microfiltration approach using a low protein binding, hydrophilized polyvinylidene difluoride membrane to easily and efficiently isolate urinary exosomes from fresh, room temperature or 4°C urine, with a simultaneous depletion of abundant urinary proteins. Using LC-MS, immunoblot analysis, and electron microscopy methods, we demonstrate this method to isolate intact exosomes and thereby enrich for a low abundant urinary proteome. RESULTS: In comparison to other standard methods of exosome isolation including ultracentrifugation and nanofiltration, we demonstrate equivalent enrichment of the exosome proteome with reduced co-purification of abundant urinary proteins. CONCLUSION AND CLINICAL RELEVANCE: In conclusion, we demonstrate a microfiltration isolation method that preserves the exosome structure, reduces contamination from higher abundant urinary proteins, and can be easily implemented into mass spectrometry analysis for biomarker discovery efforts or incorporation into routine clinical laboratory applications to yield higher sample throughput.

The multidisciplinary approach to develop artificial organs.

This paper presents the author's perspective of how artificial organ development has evolved in the past 35 years into a multidisciplinary effort. Examples are taken from the fields of hemodialysis, oxygenators, and affinity immunoadsorption devices. Development of the multidisciplinary approach to develop dialysis and oxygenation membranes has been significantly advanced by private and governmental collaboration and conferences that gathered together chemists, physicians, engineers, and fluid dynamics experts. Lengthy delays occurred in artificial organ development when such interdisciplinary collaborations did not take place.

A new isoelectric focusing gel for two-dimensional electrophoresis constructed in microporous hollow fiber membranes.

We describe the preparation of IEF tube gels inside a nonwetting microporous plastic tubing. The gel in the tube need not be extruded after the first dimension separation. Instead, the porous structure of the tubes is made wettable, and the proteins are electrophoresed "through-the-wall" into the second dimension PAGE gel. Commercial ampholytes and reagents are suitable for the procedure. A useful p/ range of 4.5-9.5 can be obtained when p/ 3-10 ampholyte mixtures are used. Because of the high surface area of the porous material, precautions must be exercised to reduce oxygen inhibition during polymerization and dehydration of the gel during storage and use. A sheath device is described that satisfies these requirements. The plastic tubes can be disposed of by incineration and pose no biohazard.