In this paper, by using ethyl silicate, ethanol and fluorescence indicator as the precursors, the multifunctional optic
biosensing (MOBS) film containing cholesterol oxidase and the fluorescence indicator was prepared by sol-gel method.
This biosensing film has both the function of biocatalyst and oxygen biosensing and can be used as the effective
biosensing materials for fiber optic cholesterol sensor. The fiber optical cholesterol sensor based on fluorescence
quenching was designed and fabricated using lock-in amplifying technology to realize the detection of cholesterol
concentration. The experimental results showed that the best precursor proportion in volume ratio is: ethyl silicate:
ethanol: 0.01 M HCl = 5: 8: 1.6. The drying rate of the sol could be controlled by using formamide as the controlling
drier. When 16% of formamide were added in the mixing system, the cracks of the film could be reduced greatly and the
immobilization of cholesterol oxidase and the fluorescence indicator could be improved effectively. A linear relationship
between phase delay φ and the cholesterol concentration was observed in the range of 100 to 500 mg/dL. Since the
cholesterol concentration is in the range of 140 to 200 mg/dL in the blood of healthy people, it will be possible for the
sensor to be used in clinical detection. The biosensor with MOBS film has the response time of about 30 s, which is
rather fast for a biosensor, and the relative deviation of ±5.03%. This biosensor also has good stability.