A Phenylketonuria Detecting System Constituted By Biosensor

Phenylketonuria (PKU) is an inherited metabolic disease that results in mental retardation and other neurological problems when treatment is not started within the first few weeks of life. The disease arises from the deficiency of a single enzyme, phenylalanine hydroxylase, which converts the essential amino acid, phenylalanine, to another amino acid, tyrosine. Failure of the conversion to take place results in a buildup of phenylalanine in the body that then damages the central nervous system. Two traditional methods to measure blood phenylalanine concentration, the Guthire test and fluorescent colorimetry, are all time-consuming and may not be easily adopted in our medical system. In this study, a precise and quick method using a biosensor device will be presented to detect the blood phenylalanine concentration in order to help control the disease. Biosensor play very important role in acquisition and processing of human medical information. It is becoming a new focus in biomedical field, and its rapid development will take place of traditional medical methods. The biosensor is composed of an ammonia electrode and a phenylalanine ammonia-lyase (PAL) coated hydrophobic gas-permeable membrane that separates the sample from the electrode internal solution. PAL catalyzes phenylalanine to ammonia, which result the potential change of the electrode. According to Nernst equation, the concentration of phenylalanine is determined by the potential measurement. To ensure optimal conditions, the detector contains a heating device, a magnetic stirrer, and a small refrigeration device. All of these devices are controlled by programmable controller. Liquid crystal touch screen communicated with programmable controller, provides a friendly man-machine interface, which make the operation more simple and convenient.The principle and preparation of the enzyme sensor is introduced. The composing of system, the hardware and software design are also presented. The advantages of the biosensor are: The lower limit of detection is 10-7 mol/L; Thelinear range is from 10-5 mol/L to 10-2 mol/L; Only ten minutes are needed to detect one sample; It only costs about 1/10 the price of a fluorescent colorimeter and easy to be widely available. By using this detecting instrument in clinical detection, Phenylketonuria can be diagnosed earlier, which is benefit for timely treatment. So its social utility is uncountable. The biosensor and detecting system can be adapted to other amino acid analysis and medical detection. So it is very valuable for biomedical detection and academy studies.