Development of a device for chemiluminescence determination of superoxide generated inside a dialysis hollow-fiber membrane.

Reactive oxygen species (ROS) generated during hemodialysis treatment cause dialysis complications because of the high reactivity of ROS. To prevent dialysis complications caused by oxidative stress, it is important to evaluate the generation and dismutation of ROS during hemodialysis treatment. In this study, our aim was to develop a device to determine superoxide (O(2)(-)) generated inside a dialysis hollow fiber, and also to examine whether this device could detect O(2)(-) separated from plasma using hollow fibers. Experimental apparatus was set up so that hypoxanthine (HX) solution flowed inside the hollow fibers and 2-methyl-6-p-methoxyphenylethynyl-imidazopyrazinone (MPEC) solution flowed outside the hollow fibers. Then, xanthine oxidase (XOD) solution was added to the HX solution to generate O(2)(-), and chemiluminescence resulting from the reaction of O(2)(-) with MPEC was measured with an optical fiber. Chemiluminescence intensity was measured at different HX concentrations, and the peak area of relative luminescence intensity yielded a first-order correlation with the HX concentration. Based on the relationship between HX and O(2)(-) concentrations determined by the cytochrome c reduction method, the relative luminescence intensity measured by this device was linearly dependent on the O(2)(-) concentration inside the hollow fibers. After modifications were made to the device, XOD solution injection into plasma including HX resulted in an increase in the relative luminescence intensity. We concluded that this novel device based on chemiluminescence is capable of determining aqueous O(2)(-) generated inside a hollow fiber and also of detecting O(2)(-) in plasma.

Fluorescence enhancement of fluorescein isothiocyanate-labeled protein a caused by affinity binding with immunoglobulin g in bovine plasma.

Fluorescence enhancement of fluorescein isothiocyanate-labeled protein A (FITC-protein A) caused by the binding with immunoglobulin G (IgG) in bovine plasma was studied. FITC-protein A was immobilized onto a glass surface by covalent bonds. An increase in fluorescence intensity was dependent on IgG concentration ranging from 20 to 78 µg/mL in both phosphate buffer saline and bovine plasma. This method requires no separation procedure, and the reaction time is less than 15 min. A fluorescence enhancement assay by the affinity binding of fluorescence-labeled reagent is thus available for the rapid determination of biomolecules in plasma.

Electrical oscillation at a water/octanol interface in a hydrophobic container.

The electrical potential oscillation at and the shape of the water/octanol interface were investigated using hydrophobic fluoroplastic containers. The interfacial potential between a water solution containing 1.5 mM sodium dodecyl sulfate (SDS) and an octanol solution containing 5 mM tetrabutylammonium chloride oscillated with an amplitude of 50-100 mV. The potential oscillation was also observed using a transparent fluoroplastic tube. The water/octanol interface shape was unchanged and no interfacial flow was observed during the oscillation. The interface shape was convex toward the octanol phase for 1.5 mM SDS, meaning that SDS adsorption to the wall was suppressed by the hydrophobic container. Therefore, the octanol system in a hydrophobic container enabled us to elucidate the electrical oscillation without any influence from the wall effect.

Evaluation of dialyzer jacket structure and hollow-fiber dialysis membranes to achieve high dialysis performance.

The objective of this study was to determine the optimum dialyzer jacket structure and hollow-fiber dialysis membrane, both of which are indispensable factors for achieving high dialysis performance, by clarifying the relationship between the dialysis performance and the flow of dialysate and blood in a hollow-fiber dialyzer. We evaluated the clearance, dialysate, and blood flow for four commercially available hollow-fiber dialyzers, namely, the APS-15S, APS-15SA, TS-1.6UL, and CX-1.6U. To evaluate dialysate and blood flow, we measured the residence-time distribution of dialysate and blood flow of these dialyzers by the pulse-response method. We also determined the clearances of urea, creatinine, vitamin B(12), and lysozyme to evaluate the dialysis performance of these dialyzers. While the baffle and taper structures allow effective supply of dialysate into the dialyzer jacket, the hollow-fiber shape, inner diameter, and packing density significantly influence the dialysate flow. In dialyzers with long taper-holding slits, the slit area is a key design parameter for achieving optimum dialysate flow. Similarly, the blood flow is significantly influenced by the structure of the inflowing and outflowing blood ports at the header of a dialyzer, and the shape and inner diameter of the hollow fibers. Hollow fibers with smaller inner diameters cause an increase in blood pressure, which causes blood to enter the hollow fibers more easily. The hollow-fiber shape hardly affects the blood flow. While improved dialysate and blood flow cause higher clearance of low molecular-weight substances, higher membrane area and pure-water permeability accelerate internal filtration, thereby causing an increase in the clearance of large molecular-weight substances.