Determination of choline-containing phospholipids in serum with a fiber-optic biosensor

An optical fiber biosensor for choline-containing phospholipids monitoring in serum samples is described. Phospholipids are hydrolyzed by the enzyme phospholipase- D to choline which is analyzed with a fiber-optic biosensor based on choline oxidase and oxygen transduction. Several supports have been evaluated for enzyme immobilization. The optimum biosensing layer consists of the enzyme immobilized on a nylon membrane and placed onto an oxygen sensitive layer formed by a luminescent Ru(II) complex, tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II), dispersed in a silicone membrane. The performance of the biosensor has been optimized using a flow injection system. The linear dynamic range of the biosensing membranes is found to be 0.08–3.00 mg ml−1 phosphatidylcholine. Studies of the reproducibility, stability and interferences of the device, as well as the application of the sensor to measurements in serum samples, are reported.