An enzyme Biosensor Based on Organic Transistors for Recognizing α-Amino Acid Enantiomers

The chiral recognition of α-amino acids has attracted considerable interest because different enantiomeric amino acids show differences in their biological behavior and pharmacological activity. An organic electrochemical transistor (OECT)-based biosensor modified with L-amino acid oxidases (L-AAODX) was fabricated and successfully used as a biosensor for enantioselectively discriminating α-amino acids, such as D/L-tryptophan (D/L-Trp), D/L-tyrosine (D/L-Tyr) and D/L-phenylalanine (L-Phe) with high performance because L-AAODX selectively catalyzed the oxidation of L-Trp, L-Tyr, and L-Phe along with the amplification of OECT. The biosensor showed a sensitivity of 19.67 μA/μM with a LOD of 10 nM (S/N > 3) over the range of 10 nM to 30 μM for L-Trp, 16.71 μA/μM with a LOD of 2 nM (S/N >3) over the range of 2 nM to 30 μM for L-Tyr and 15.51 μA/μM with a LOD of 10 nM (S/N > 3) over the range of 30 nM to 30 μM for L-Phe. Furthermore, the biosensor can both be used for the chiral recognition of Trp, Tyr and Phe, and distinguish L-amino acids from its interferences (e.g., Glu, UA, L-Asp, L-Lys and L-Glu) and common metal ions (K+, Na+ and Fe3+).