Engineered Antifouling Peptides with Sarcosine Branches for Robust Electrochemical Detection of the HER2 Biomarker in Real Biological Samples

In complex biological matrices, the nonspecific adsorption phenomena occurring on the surfaces of electrochemical biosensors represent a considerable challenge for the precise detection of targets in heterogeneous biological samples. Furthermore, the presence of protein hydrolases in biofluids also affects the stability of biosensing devices utilizing natural proteins or peptides. It is therefore imperative to develop sensing devices capable of effectively minimizing such effects in real biological samples. Herein, we engineered a sarcosine branch-chain peptide (SBCP) with a strong antifouling capability to avoid biofouling and enhanced stability to resist hydrolysis by proteases. The peptide is composed of three sections: an anchoring sequence (CPPPP), an antifouling sequence (EK(Sar)EK(Sar)EK(Sar)EK(Sar)), and a recognition sequence (HLTVSPWY). An electrochemical biosensor was developed through the electrodeposition of poly(3,4-ethylenedioxythiophene) (PEDOT) incorporated with poly(norepinephrine) (PNE) on an electrode surface, followed by the electrodeposition of gold nanoparticles and the self-assembly of SBCP. The biosensor constructed using the SBCP containing a specific recognizing peptide sequence for the cancer biomarker human epidermal growth factor receptor 2 (HER2) was capable of sensitively detecting target HER2, within the concentration range of 1.0 pg mL^-1 to 1.0 μg mL^-1 and with a limit of detection of 0.37 pg mL^-1. Moreover, the biosensor demonstrated antifouling ability and the capacity to accurately detect the target in human serum, exhibiting a high degree of concordance with the assaying results of ELISA kits. These findings suggest that the biosensor based on the engineered peptides possesses promising potential for practical applications.