Regular articleA temperature-triggered fiber optic biosensor based on hydrogel-magnetic immobilized enzyme complex for sequential determination of cholesterol and glucose

•Hydrogen-magnetic immobilized GOD complex was prepared.•A fiber optic sensor based on PMIGC and COD was developed.•The sensor can detect cholesterol and glucose sequentially.•The sensor has good properties and can be used for real samples.

This work described a temperature-triggered fiber optic biosensor for sequential detection of cholesterol and glucose based on poly(N-isopropylacrylamide)-co-acrylamide)(P(NIPAAm-co-AAm))-magnetic immobilized glucose oxidase(GOD) complex (PMIGC) and magnetic immobilized cholesterol oxidase (COD). At 38 °C, the sensor will selectively detect cholesterol concentration with the detection range of 25-250 mg/dL since P(NIPAAm-co-AAm) is known to shrink above its lower critical solution temperature (LCST) of 36 °C, and will separate GOD from analytes so that PMIGC has no catalysis effect on glucose. When the temperature was switched to 25 °C (below LCST), PMIGC could catalyze the oxidation of glucose since GOD will be exposed to analytes due to the swell of P(NIPAAm-co-AAm). This sensor can be used for the detection of glucose with the detection range of 50-700 mg/dL. The optimal detection conditions for cholesterol were achieved with pH 7.0, 40 °C and 10 mg COD (in 75 mg carrier), and those for glucose were achieved with pH6.5, 35 °C and 12 mg GOD (in 90 mg carrier). The biosensor proposed is shown to have outstanding repeatability, selectivity and yield satisfactory detection results on practical samples.

Graphical abstractDownload high-res image (110KB)Download full-size imageA fiber optic biosensor was developed to perform the sequential detection of cholesterol and glucose at different temperature (38 °C and 25 °C)