Array-based titanium dioxide biosensors for ratiometric determination of glucose, glutamate and urea.

A novel optical array-based titanium dioxide (TiO(2)) biosensor combining with simple vapor deposition method was developed to simultaneously determine multianlaytes including glucose, urea and glutamate in serum samples. Carboxy seminaphthorhodamine-1-dextran (SNARF-1-dextran), serving as a single-molecule fluorescent probe, was co-immobilized with different enzymes including urease, glucose dehydrogenase (GDH), and glutamate dehydrogenase (GLDH) for determination of urea, glucose and glutamate simultaneously. The SNARF-1-dextran was a useful pH sensitive dye and the fluorescence ratio at 585 and 630 nm was used to characterize the change in solution pH. Atomic force microscopic (AFM) and scanning electron microscopy (SEM) images showed that TiO(2) is a crack-free stable sol-gel material, which can effectively trap enzymes in the sol-gel-derived matrices prepared by vapor deposition method. The surface morphology of the sol-gel-derived TiO(2) films changed significantly after the immobilization of macromolecules and enzymes. The array-based TiO(2) biosensors show good analytical performance on the simultaneous determination of multiple samples for multianalytes without obvious cross-interference. The analytical ranges of the three analytes in water samples were between 0.01 and 10 mM and limit of detections (LODs) were in the range 2.4-5.5 microM. In addition, satisfactory dynamic ranges of 2-3 orders of magnitude with LODs of 3.1-7.8 microM in serum samples were obtained. These results demonstrate the first report of combining a sol-gel-derived TiO(2) array biosensor with SNARF-1-dextran for ratiometric determination of multianalytes simultaneously and provide a viable alternative to current silica technology for the fabrication of array-based optical biosensors.