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Construction and application of the amperometric uric acid biosensors based on the covalent immobilization of uricase by different strategies
Tvorynska, Sofiia ; Barek, J. ; Josypčuk, Bohdan
In this work, a promising combination of a biosensor based on the\nenzymatic mini-reactor with the detection principle of four-electron\nreduction of the consumed oxygen at highly negative potential has\nbeen developed for uric acid determination using flow injection\nanalysis. The construction of the biosensor provides a spatial\nsegregation of the biorecognition (uricase-based mini-reactor) and\ndetection (tubular detector of silver solid amalgam (TD-p-AgSA))\nparts. To find out the most appropriate enzyme immobilization\nprotocol, three different strategies of the covalent attachment for\nuricase from Bacillus fastidiosus have been compared. It was found\nthat the biosensor with the mini-reactor based on the covalent\nattachment of uricase via glutaraldehyde to -NH2 functionalized\nmesoporous silica powder MCM-41 showed extremely high stability\n(>1 year) and reusability (at least 600 measurements) The biosensor's\npractical applicability was confirmed by successful determination\nof uric acid in human urine.
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Behavior of Metallothioneins and Phytochelatins at Mercury and Amalgam Electrodes
Šestáková, Ivana ; Navrátil, Tomáš ; Josypčuk, Bohdan
The presence of cysteine residues in molecules of metallothioneins or phytochelatins is crucial for their electrochemical behavior. At mercury electrodes, the reduction of\ntetracoordinated Cd and Zn in molecule of mamamalian MT is observed in solution of pH 8- 8.5, whereas with lowering pH or at presence of excessive ions, signals of differently coordinated or free metal ions appear. Such changes were confirmed on model complexes with phytochelatin PC2 .Using amalgam electrodes CuSAE or AgSAE for voltammetry of metallothioneins or phytochelatins, their Cu or Ag complexes are formed on the electrode surface, which could be with limitations - employed for the analytical purposes.
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