Strategy to Immobilize Peptide Probe Selected through In Vitro Ribosome Display for Electrochemical Aptasensor Application

In this study, we demonstrated an electrochemical aptasensor for calmodulin (CaM) detection and the peptide sequence (YWDKIKDFIGG) is obtained from in vitro ribosome display selection. To immobilize this peptide probe on the electrode surface, cystine was incorporated at the end of this peptide sequence. After a maleimide-functionalized poly(3,4-ethylenedioxythiophene), poly(EODT-MI), film was electropolymerized on the electrode, the peptide probe was immobilized through thiol–ene conjugation with the cystine end. Four peptides with different linkers were used for the binding test of bovine serum albumin and CaM using a quartz crystal microbalance. The zwitterionic linker EKEKEKEKEKEK provided good antifouling properties and the highest CaM binding. Furthermore, the immobilization of the peptide with this zwitterionic linker resulted in a minimal increase in the electrochemical impedance. By immobilizing the peptide with the selected zwitterionic linker, we successfully demonstrated an electrochemical aptasensor with a linear detection range for CaM from 0.01 to 10 mg/L and a detection limit of 0.001 mg/L.