Osmium-Polymer Modified Carbon Nanotube Paste Electrode for Detection of Sucrose and Fructose

The aim of the work was the modification of a carbon nanotube paste electrode with a highly original osmium-polymer hydrogel for the development of a new amperometric biosensor for detection of sucrose and fructose. The biosensor for sucrose is based on the activity of the enzymes invertase and fructose dehydrogenase (FDH) immobilized into a carbon nanotube paste (CNTP) electrode properly modified with the Os-polymer. A second biosensor, for fructose only, is constructed containing inactive invertase and used for detection of fructose and for signal subtraction. The biosensors exhibit a detection limit for sucrose of 2 uM and for fructose of 1 uM, linearity up to 5 mM for both biosensors, high sensitivity (1.98 uA·cm−2·mM for sucrose and 1.95 uA·cm−2·mM for fructose), a good reproducibility (RSD = 2.5% for sucrose and 2.1% for fructose), fast response time (8 s for sucrose and 4 s for fructose) and a stability of about 4 months for both biosensors when stored under wet conditions at 4°C. Finally, the biosensors were applied for specific determi- nation of sucrose and fructose in several commercial fruit juice samples and validated with a commercial spectropho- tometric enzymatic kit.