Fabrication and characterization of a surface plasmon resonance based fiber optic sensor using gel entrapment technique for the detection of low glucose concentration

In this paper we report the fabrication and characterization of a surface plasmon resonance (SPR) based fiber optic sensor, working on wavelength interrogation method, to measure the low glucose concentration (similar to the human blood) in aqueous fluid. The sensing probe is prepared by coating of films of silver and silicon on the optical fiber core followed by immobilization of enzyme (glucose oxidase) using gel entrapment method. Experimental results on SPR spectra show a blue shift in the resonance wavelength on increase in the concentration of the glucose in samples. Further, the sensitivity of the sensor decreases as the concentration of the glucose increases whereas the detection accuracy is almost independent of the glucose concentration. In addition, for 80 mg/dL glucose concentration, the influence of pH of the sample on the performance of the sensor has been studied in terms of sensitivity and detection accuracy. The results show that the optimum working pH range for the sensor is around pH 7 (close to blood pH 7.4). The sensor operates in the glucose concentration range of 0–260 mg/dL. Since the optimum performance and operating range of the sensor fall in the physiological range of human blood glucose it may find application in biomedical sciences. The other advantages are high sensitivity, glucose selectivity, stability and short response time of the sensor.