BSA‐templated Pb Nanocluster as a Biocompatible Signaling Probe for Electrochemical EGFR Immunosensing

We report here a new electrochemical probe for the development of a sensitive, and selective sandwich‐type electrochemical immunosensor for the detection of epidermal growth factor receptor (EGFR). The probe is a newly synthesized bovine serum albumin (BSA)‐templated Pb nanocluster (Pb_NC@BSA). For fabrication of the immunosensor, we employed streptavidin‐coated magnetic beads (MB) as a platform for immobilization of the biotinylated primary antibody (Ab₁), and utilized the Pb_NC@BSA conjugated to secondary antibody (Ab₂) as a signaling probe. After sandwiching the target protein between Ab₁ and Ab₂, we dissolved Pb_NC@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 displayed good sensitivity, selectivity, stability, and reproducibility, and proved suitable for direct measurement of EGFR in human serum samples. Moreover, we used the as‐synthesized Pb_NC@BSA as a fluorescence label for in vitro cell viability analysis as well as bioimaging of cancerous HeLa and non‐cancerous HUVEC cells. Pb_NC@BSA exhibited low cytotoxicity and high biocompatibility in living cells, and was a suitable fluorescent probe for live cell imaging, with potential therapeutic applications.