Colloidal carbon particles as a new label for rapid immunochemical test methods: quantitative computer image analysis of results.

Colloidal carbon particles can serve as label in sol particle immunoassays. The universal applicability of these particles in qualitative and (semi)quantitative immunoassays has been demonstrated. Sol particle and/or dipstick immunoassays, not yet optimized in terms of sensitivity, are discussed. The colloidal label has been used successfully in a mouse immunoglobulin isotyping kit. Human serum albumin spotted onto nitrocellulose in a concentration range of 7.8 to 1000 ng could be detected using anti-albumin antibody absorbed onto colloidal carbon particles. It was also possible to perform a competitive assay with this conjugate for a concentration range of free human serum albumin varying from 0.25 to 6.75 micrograms. The Kunitz-type trypsin inhibitor from soybean was determined by a colloidal carbon based immunoassay in a range of 2.5 to 160 ng. In this assay, free and colloidal carbon-bound inhibitor competed for binding specific antibodies spotted onto a nitrocellulose membrane. An image- and data-processing procedure has been developed that enables a rapid and simple quantification of colloidal carbon sol particle immunoassays. The average grey level of a spot is taken as a measure for quantitative purposes. This so-called Sol-particle Image Processed ImmunoAssay (SIPIA) procedure is equally well applicable to assays using other colloidal particles.

Urea removal by means of direct binding.

The availability of more efficient means for the removal of metabolic waste products, especially urea, from dialysates, body fluids or the gastrointestinal tract, is a key to new and simpler ways of treatment of renal failure patients. A research program of Organon Teknika in cooperation with AKZO Chemie has resulted in development of a new sorbent in which the active element is the ninhydrin entity. This product irreversibly binds urea under mild conditions without formation of side products. Also creatinine is bound. The sorbent proves to be non-toxic, non-pyrogenic, stable, insoluble and resistant against acid and sterilization procedures. In combination with amongst others a sorbent for phosphate and potassium developed earlier, the urea sorbent can be applied in dialysate regeneration. In vitro experiments show that for dialyses of four hours duration less than one kg of urea sorbent can be sufficient. Also other applications, e.g., oral use are mentioned.

Capabilities of the Redy cartridge for regeneration of hemofiltrate.

Capabilities of the Redy cartridge for hemofiltrate regeneration were tested. Electrolytes, creatinine, BUN, uric acid, acid-base, glucose, heparin, fluoride and amino acids were measured in the cartridge inflow and outflow (V = 70 ml/min) over a four-hour period. There was complete adsorption of potassium, calcium, magnesium, creatinine, BUN, uric acid, phosphate and heparin. Sodium ions, hydrogen ions, fluoride ions and possibly other trace elements are released by the cartridge. Amino acid absorption is almost complete if the amino acids are aromatic, have two or more N-atoms or if they have S-atoms. When using hemofiltrate after sorbent regeneration for reinfusion to the patient, one has to consider electrolyte substitution (i.e., K, Ca, Mg), sodium balance, trace element metabolism, acid-base problems, amino-acid profiles and ammonia overload.

Regeneration of dialysate.

Large amounts (250 liters) of dialysate fluid are needed for dialysis of patients with chronic kidney diseases. A reduction of these amounts is obtainable by regeneration. With the Redy system, in which urea is decomposed by the enzyme urease, only 5.5 liters of dialysate is used. Other systems depending solely on sorption of urea still need excessive amounts of sorbents and no alternative, in the form of stable chemical binding, is available. If, therefore, further reduction of dialysate volume is desired, the problem of urea removal must be solved.

A hemoperfusion column based on activated carbon granules coated with an ultrathin membrane of cellulose acetate.

A hemoperfusion system has been developed which makes use of activated carbon encapsulated with cellulose acetate. Studies have revealed that there are no stagnant flow regions in the column, there is minimal particle release and the coating is 30 A thick. The relationships between pore size, pore volume and surface area have been examined. Twenty-five patients in grade IV coma have been treated with the column for treatment of drug overdose or agricultural chemical poisoning; the clinical course of one meprobamate-poisoned patient is described in detail.