Construction of CS/BSA multilayers for electrochemical recognition of tryptophan enantiomers

Ultra stable and reproducible electrochemical chiral interface ((CS/BSA)1.5/GCE) based on chitosan (CS) and bovine serum albumin (BSA) was fabricated using layer-by-layer (LbL) self-assembly technique. Its structure and properties were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and electrochemical methods. Snowflake like morphology was observed on the (CS/BSA)1.5 films using SEM. Interestingly, the (CS/BSA)1.5 chiral interface achieved chiral recognition of D-Trp and L-Trp via contact angle measurements. Under optimized experimental conditions, differential pulse voltammetry (DPV) results showed that the peak current ratio of D-Trp to L-Trp (ID/IL) was 3.83 at (CS/BSA)1.5/GCE (glass carbon electrode). In addition, there was a good linear relationship between the peak current and Trp enantiomer concentration in the range of 0.005–0.15 mM. Our study shows the (CS/BSA)1.5/GCE can be used to quickly determine the ratio of enantiomers in non-racemic Trp mixture solutions, which is of great significance for the chiral recognition in non-racemic mixtures of chiral compounds.