Fluorescence glucose monitoring based on transduction of enzymatically-driven pH changes within microcapsules
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abstract
This work explores a novel approach to transducing changes in glucose concentration by fluorescence sensing of local microscale changes in pH resulting from the enzyme-catalyzed oxidation of glucose within small reaction vessels. Synthetic and natural polyelectrolytes were used to fabricate biocompatible microcapsules (5 m mean diameter) using acid-dissolvable melamine formaldehyde (MF) templates. The resulting microcapsules had a cationic internal matrix comprising chitosan, poly(vinyl sulfate), and MF oligomers, which was used to electrostatically absorb anionic glucose oxidase (GOx) labeled with a pH-sensitive dye (pyrene 8-hydroxy-1,4,6-trisulfonylchloride). The ratiometric variation of excitation spectra in response to changes in pH was monitored as a function of glucose concentration. In vitro tests of the sensors in buffered solutions proved that internal pH changes resulting from the GOx-catalyzed glucose oxidation could be observed in response to sequential additions of glucose in the physiological region of interest (0-30 mM). The preliminary results demonstrate potential for this sensing approach, warranting further experimentation for validation of sensor function and reversibility. A potential application of these sensors is for minimally-invasive monitoring of glucose by diabetics by implantation in the dermis of the skin ("smart tattoos"). Copyright 2006 American Scientific Publishers. All rights reserved.
