▎ 摘　　要

Direct electrochemistry of phenylalanine dehydrogenase (PDH) immobilized on graphene oxide nanosheets (GO)-chitosan film was investigated for detecting phenylketonuria (PKU). A graphene based L-phenylalanine (L-Phe) biosensor was developed using a PDH-GO-chitosan based nanocomposite. The catalytic enzyme electrode retained its biocatalytic activity, exhibited a surface confined, reversible proton and electron transfer reaction, and had excellent stability, bioactivity, sensitivity and accuracy. Electroanalytical study of the bioelectrode was performed to characterize the biosensor response. The results showed that PDH-GO-chitosan nanocomposite film can be used for highly sensitive and accurate determination of L-phe. The biosensor exhibited a wider linearity range from 500 nM to 15 mM of L-Phe with the detection limit of 416 nM and much higher sensitivity as compared with other L-Phe monitoring biosensors. The enzyme electrode reached steady state current and its sensitivity was 15.04 mA. M(-1)cm(-2). The enzyme electrode retained its excellent electrocatalytic activity (83%) after one month of storage in 4 degrees C (n= 5).