Determination of glucose levels using a functionalized hydrogel-optical fiber biosensor: toward continuous monitoring of blood glucose in vivo.

Glucose-selective optical sensors were fabricated by incorporating 3-phenylboronic acid and a tertiary amine, dimethylaminopropylacrylamide, into a hydrogel matrix. Determination of glucose in solution is based on the glucose-induced contraction of the hydrogel. The gel was fabricated on the end of an optical fiber, and the optical length was measured by an interferometric technique. Previously it was found the gel could be tuned for enhanced glucose sensitivity and selectivity by varying the 3-phenylboronic acid/tertiary amine ratio. The properties of the responsive hydrogel as a glucose sensor were determined in more detail with respect to swelling kinetics and equilibrium swelling degree. Temperature effects, size variation, molecular interference, and reversibility were addressed. Results showed there was a good degree of reversibility, both for equilibrium swelling and swelling kinetics. Fabricated hydrogel sensors with slight differences in size yielded an overlapping relative response indicating an excellent degree of sensor reproducibility. The sensor proved to be temperature-dependent; by increasing the temperature from 25 to 37 degrees C, the swelling was about 4-fold more rapid, and a concomitant decrease in equilibrium swelling was seen. Identified interference from other analytes with determination of glucose was used a basis for selecting ethylenediaminetetraacetic acid (EDTA) as an anticoagulant for in vitro determination of glucose concentration in blood plasma. Glucose measurements performed in blood plasma were promising, showing that the sensor is capable of measuring physiological glucose levels in blood with a minimal effect from interfering molecules. The obtained results indicate that the developed sensor is a candidate for continuous monitoring of glucose in blood.