Probing chiral amino acids at sub-picomolar level based on bovine serum albumin enantioselective films coupled with silver-enhanced gold nanoparticles.

A novel electrochemical sensor with capability of probing chiral amino acids with gold nanoparticle (n-Au) labels using bovine serum albumin (BSA) as a chiral selector and subsequent signal amplification step by silver enhancement is introduced. The assay relies on the stereoselectivity of BSA embedded in ultrathin gamma-alumina sol-gel film coated on the surface of the glassy carbon electrode (GCE). The recognition to the n-Au-labeled L- or D-amino acids for BSA-GCE could be monitored by the differential pulse voltammetry (DPV), while the DPV signal was greatly amplified by the anchored silver atoms on the n-Au, leading to a new way of quantitatively analysis of chiral amino acids electrochemically at sub-picomolar level. With L-tryptophan as the probe solute, the linear concentration range was from 1.33 x 10(-12) to 1 x 10(-9)mol L(-1) and detection limit was 5 x 10(-13)mol L(-1). For tryptophan enantiomers, the enantioselectivity coefficient 2.3 was obtained.