A fluorescence assay for dissolved oxygen using sol-gel encapsulated myoglobin and an analogy to the inner filter effect

In this study, we were interested in how the limit of detection for dissolved oxygen (DO) measurements in water would be affected when absorbances were translated into fluorescence intensities of a dye through a process analogous to the inner filter effect. The DO measurements were made through the oxygenation of deoxy-myoglobin trapped in a sol-gel matrix. First, the encapsulated myoglobin is reduced from met-myoglobin to deoxy-myoglobin by bathing the gel in a dithionite solution. Then, the gel is introduced to the sample of dissolved oxygen in water. Dissolved oxygen reacts with deoxy-myoglobin to give oxy-myoglobin. The observed spectroscopic changes are indicative of dissolved oxygen in water. In our system, the fluorescent dye, brilliant sulfaflavine, absorbs light at 430 nm and emits radiation at 520 nm. The excitation light for the dye is passed through the myoglobin-containing gel. The emission of the fluorescent dye changes as the absorbance of the myogoobin at 430 nm changes in response to dissolved oxygen in water. Theoretically, the change in fluorescence should be larger than the corresponding change in absorbance. From this work, it was concluded that the detection limit for dissolved air measurements could be enhanced through fluorescence provided that the sol-gels had long enough exposure to the water samples.