Immobilization of an esterase inhibitor on a porous hollow-fiber membrane by radiation-induced graft polymerization for developing a diagnostic tool for feline kidney diseases.

Removal of the major urinary protein, cauxin, a carboxylesterase, from cat urine is essential for distinguishing between physiological and abnormal proteinuria by a urine dipstick. We have previously developed a material for removing cauxin by using lens culinaris agglutinin (LCA) lectin which targets the N-linked oligosaccharides present in cauxin. To improve the affinity and specificity toward cauxin, we immobilized 1,1,1-trifluoro-3-(2-sulfanylethylsulfanyl) propane-2-one, an inhibitor of esterases, to a polymer chain grafted on to a porous hollow-fiber membrane by applying radiation-induced graft polymerization. Normal male urine was forced to permeate through the pores rimmed by the ligand-immobilized polymer chain. Cauxin could not be detected in the effluent from the membrane. The residence time of the urine across a membrane thickness of 1 mm was set at 7 s. The respective dynamic and equilibrium binding capacities of the membrane for cauxin were 2 and 3 mg/g. The developed cauxin-affinity membrane material was more effective for diagnosing cat kidney diseases than the LCA lectin tip.