title: Development of a highly enantioselective capacitive immunosensor for the detection of alpha-amino acids.
abstract: 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.
authors.affiliation: Department of Chemistry, Fudan University, Shanghai 200433, People's Republic of China.
authors.forename: Song
authors.initials: S
authors.lastname: Zhang
authors.forename: Jingjing
authors.initials: J
authors.lastname: Ding
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.forename: Jilie
authors.initials: J
authors.lastname: Kong
authors.forename: Oliver
authors.initials: O
authors.lastname: Hofstetter
mesh_terms: D000596:Amino Acids / Q000032:analysis*; D015374:Biosensing Techniques; D006241:Haptens; D010649:Phenylalanine / Q000031:analogs & derivatives; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D006241:Haptens; C009722:4-aminophenylalanine; D010649:Phenylalanine