Fabrication of an electrochemical EGFR immunosensor using BSA-templated Pb nanocluster as a biocompatible signaling probe

Detection of epidermal growth factor receptor (EGFR) is of paramount importance in medical sciences, since it has significant application in cancer diagnosis, drug development, and therapy monitoring1. In this work we introduce a new probe for the development of a sensitive, and selective sandwich-type electrochemical EGFR immunosensor. To design the immunsensor, we employed streptavidin-coated magnetic beads (MB) as a platform for immobilization of the biotinylated primary antibody (Ab1), and utilized a newly synthesized bovine serum albumin (BSA)-templated Pb nanocluster (PbNC@BSA), conjugated to secondary antibody (Ab2), as a signaling probe. After sandwiching the target protein between primary and secondary Ab, we dissolved PbNC@BSA into an acid, and recorded square wave anodic stripping voltammetric (SWASV) signal of the Pb ions as an analytical signal for quantification of the EGFR. The immunosensor responded linearly towards EGFR within the range of 0.4 ng/mL to 35 ng/mL, with a detection limit of 8 pg/mL. The immunosensor showed a good sensitivity, selectivity, stability, and reproducibility, and proved suitable for direct measurement of EGFR in human serum samples. We also used the as-synthesizd PbNC@BSA as a fluorescence label for in vitro bioimaging of cancerous HeLa and non-cancerous HUVEC cells. In addition, we investigated cytotoxicity of PbNC@BSA to cancerous and healthy cells, the results of which show that PbNC@BSA has considerable cytotoxicity to cancerous cells while exhibits subtle cytotoxicity to healthy cells. Thus, PbNC@BSA as a metal-based signaling probe is a biocompatible fluorescent probe for live cell imaging, with possible theraputic applications.