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In this paper amperometric glucose biosensors based on titanium (Ti) electrode coated with Prussian blue (PB) layer and immobilized glucose oxidase (GOx) is reported. Several techniques of PB layer deposition and immobilization of GOx were applied in order to find the most optimal design of biosensor. PB layer was formed by electrochemical PB deposition on titanium electrode in FeCl 3 and K 3 [Fe(CN) 6 ] solution. GOx was immobilized on PB layer using two techniques: immobilization by electrochemical polymerization of pyrrole and fixation with vapor of glutaraldehyde. The designed biosensors displayed sensitivity toward glucose in the range from 0.19 to 3.87 μA cm −2 mM −1 .

Prussian blue (PB) is an electrochromic material, which can be used as a signal transducer in the formation of optical urea biosensors. The previous researches in electrochromic properties of PB demonstrated the optical PB response to ammonium ions, which occurs when ammonium ions are interacting with PB layer at a constant 0.2 V vs Ag|AgCl|KClsat potential. In this work PB optical dependence on ammonium ions concentration was applied in the formation of electrochromic urea biosensor. Biosensor was formed by modifying the optically transparent indium tin oxide (ITO) coated glass electrode (glass/ITO) with Prussian blue layer and immobilizing urease (glass/ITO/PB‐urease). Calibration curve showed the linear dependency (R2=0.995) between the change of maximal absorbance (ΔA) and urea concentration in concentration range varying from 3 mM to 30 mM. The highest sensitivity (4 ΔA M−1) of glass/ITO/PB‐urease biosensor is in the concentration range from 7 mM to 30 mM. It was determined that working principle of the glass/ITO/PB‐urease biosensor is not related to pH changes occurring during enzymatic hydrolysis of urea.