A potentiometric biosensor for determination of trypsin is described based on current-controlled reagent delivery. A polymeric membrane protamine-sensitive electrode with dinonylnaphthalene sulfonate as cation exchanger is used for in site generation of protamine. Diffusion of protamine across the polymeric membrane can be controlled precisely by applying an external current. The hydrolysis catalyzed with trypsin in sample solution decreases the concentration of free protamine released at the sample-membrane interface and facilitates the stripping of protamine out of the membrane surface via the ion-exchange process with sodium ions from the sample solution, thus decreasing the membrane potential, by which the protease can be sensed potentiometrically. The influences of anodic current amplitude, current pulse duration and protamine concentration in the inner filling solution on the membrane potential response have been studied. Under optimum conditions, the proposed protamine-sensitive electrode is useful for continuous and reversible detection of trypsin over the concentration range of 0.5-5 U mL-1 with a detection limit of 0.3 U mL-1. The proposed detection strategy provides a rapid and reagentless way for detection of protease activities and offers great potential in the homogeneous immunoassays using proteases as labels.
Publication date: July 2013Source:Journal of Solid State Chemistry, Volume 203 Author(s): S. Kumar , K. Singh , M. Miclau , Ch. Simon , C. Martin , A. Maignan The change from antiferromagnetism induced ferroelectricity to spin glass ferroelectric relaxor has been studied along the ... more
Publication date: July 2013Source:Journal of Solid State Chemistry, Volume 203 Author(s): Brian B. Kitchen , Nina Verdal , Terrence J. Udovic , John J. Rush , Michael R. Hartman , Daniel J. DeVries To investigate the previously reported low-temperature phase transition in rubidium ... more
Publication date: July 2013Source:Journal of Solid State Chemistry, Volume 203 Author(s): T. Sasikala , L. Rama Moorthy , A. Mohan Babu , T. Srinivasa Rao The present work reports the absorption, photoluminescence and decay properties of singly doped Dy3+ and co-doped Dy3+/Tm3+ ions ... more
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