Complex of hydrogel with magnetic immobilized GOD for temperature controlling fiber optic glucose sensor

• P(NIPAAm-co-AAm)-GOD complex was prepared and characterized.
• The complex has “on-off” effect for catalysis to glucose oxidation.
• A temperature controlling glucose sensor based on the complex was developed.
• This sensor has good properties and can detect glucose in real samples.

A fiber optic glucose biosensor based on Poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAAm-co-AAm))-magnetic-immobilized glucose oxidase (GOD) complex (PMIGC)was fabricated to perform the controllable detection of glucose by changing temperature. The complex was prepared by combining P(NIPAAm-co-AAm) with GOD immobilized on Fe3O4@SiO2(F)@meso-SiO2 nanoparticles using in-situ complex method. Since P(NIPAAm-co-AAm) has the lower critical solution temperature (LCST) of 36 °C, at the temperature above LCST, P(NIPAAm-co-AAm) shrank and PMIGC could not catalyze the oxidation of glucose. At the temperature below LCST, P(NIPAAm-co-AAm) swelled and catalysis occurred. Because of this temperature sensing characteristics of PMIGC, the temperature controllable detection of glucose can be carried out by the biosensor. The optimal detection conditions for this biosensor were achieved with pH6.5, 35 °C and 12 mg of GOD amount. At 25 °C, a good linear relationship between ϕ, the phase delay change of the sensor head, and the glucose concentration in the range of 50–700 mg/dL (2.78–38.89 mmol/L) was observed, the detection limit was 8.33 mg/dL (0.46 mmol/L) (S/N = 3). This linear graph can be defined by the equation of y = 0.01463 + 0.0003313x, R2 = 0.9914. The biosensor has the characteristics of good repeatability and selectivity, and can be used for the glucose detection in practical samples.