Process for the preparation of modified electrodes, electrodes prepared with said process, and enzymatic biosensors comprising said electrodes

Abstract

A process is described for the preparation of modified electrodes useful for the measurement of analytes in biological fluids, comprising the deposition of Prussian blue on screen printed electrodes, and the modified electrodes prepared via said process; the enzymatic electrodes and the biosensors comprising said modified electrodes and the method for the determination of analytes in biological fluids which uses said modified electrodes are also described.

1 .- 16 . (canceled) 
     
     
         17 . A screen printed electrode modified with Prussian blue prepared by a process, which comprises:
 sequential deposition on the working electrode surface of said screen printed electrode of a solution comprising the and at least one surface-active agent in an appropriate solvent and a solution comprising the ferrocyanide (II) or ferricyanide (III) ion and at least one surface-active agent in an appropriate solvent, said solutions having concentrations such as to obtain the formation of Prussian blue directly on the surface of the working electrode; wherein said solutions have equal concentration of between 20 mM and 2 M, and are deposited in equal volume of between 100 nL and 4 μL for an electrode surface between 0.314 mm 2  and 3.14 cm 2 ;   after mixing of the two solutions, the mixture is left to rest for a period of between 2 minutes and 2 hours; the working electrode surface is then washed with a washing solution; the electrode thus modified are left dried at a temperature between 50° C. and 200° C.;   wherein said screen printed electrode has not undergone pre-treatment before said sequential deposition of the solutions; and   wherein the quantity of Prussian blue deposited is between 10 and 200 nmol/cm 2      
     
     
         18 . The screen printed electrode as claimed in  claim 17 , wherein the quantity of Prussian blue is 100 nmol/cm 2 . 
     
     
         19 . An enzymatic electrode comprising the screen printed electrode modified as defined in  claim 17  and a suitable enzyme immobilised on said electrode, chosen so that a product thereof can be oxidised or reduced electrochemically on said modified electrode. 
     
     
         20 . The enzymatic electrode as claimed in  claim 19 , wherein said enzyme is the enzyme glucose oxidase. 
     
     
         21 . An enzymatic biosensor comprising the enzymatic electrode as defined in  claims 19  as the working electrode, a reference electrode, a counter-electrode if necessary and a cell for receiving the biological fluid to be analysed, so that the latter can come into contact with the enzyme immobilised on said enzymatic electrode. 
     
     
         22 . The biosensor according to  claim 21 , comprising said screen printed electrode and said reference electrode as the sole electrodes. 
     
     
         23 . A method for determination of the quantity of an analyte in a biological fluid comprising the application of an appropriate potential value between an enzymatic electrode as defined in  claim 19  and a reference electrode included in the an enzymatic biosensor a counter-electrode if necessary and a cell for receiving the biological fluid to be analyzed so that the latter can come into contact with the enzyme immobilised on said enzymatic electrode, and reading of the current signal generated. 
     
     
         24 . The method as claimed in  claim 23 , wherein said analyte is glucose and said potential applied is between −250 and +200 mV. 
     
     
         25 . The method as claimed in  claim 24 , wherein said potential applied is equal to −50 mV.