Development of a highly enantioselective capacitive immunosensor for the detection of alpha-amino acids.
This work describes a highly enantioselective and sensitive immunosensor for the detection of chiral amino acids based on capacitive measurement. The sensor was prepared by first binding mercaptoacetic acid to the surface of a gold electrode, followed by modification with tyramine utilizing carbodiimide activation. The hapten 4-amino-D-phenylalanine was then covalently immobilized onto the electrode by diazotization. Stereoselective binding of an anti-D-amino acid antibody to the hapten-modified sensor surface resulted in capacitance changes that were detected with high sensitivity by a potentiostatic step method. Using capacitance measurement, detection limits of 5 pg of antibody/mL were attained. The exquisite stereoselectivity of the antibody was also utilized in a competitive setup to quantitatively determine the concentration of the analyte d-phenylalanine in nonracemic samples containing both enantiomers of this amino acid. Trace impurities of d-phenylalanine as low as 0.001% could be detected.
Zhang
Song
S
Department of Chemistry, Fudan University, Shanghai 200433, People's Republic of China.
Ding
Jingjing
J
Liu
Ying
Y
Kong
Jilie
J
Hofstetter
Oliver
O
D000596:Amino Acids / Q000032:analysis*; D015374:Biosensing Techniques; D006241:Haptens; D010649:Phenylalanine / Q000031:analogs & derivatives; D013237:Stereoisomerism
D000596:Amino Acids; D006241:Haptens; C009722:4-aminophenylalanine; D010649:Phenylalanine