Ultrasensitive electrochemical immunosensor via RAFT polymerization signal amplification for the detection of lung cancer biomarker

Abstract

Abstract Cytokeratin fragment antigen 21–1 (CYFRA21-1), a characteristic biomarker of non-small cell lung cancer (NSCLC), its abundance is closely related to the diagnosis and prognosis of the disease. Thus, an ultrasensitive electrochemical immunosensor for the detection of CYFRA21-1 was designed by exploiting reversible addition-fragmentation chain transfer (RAFT) polymerization signal amplification strategy. Briefly, graphene oxide (GO) was immobilized on a glassy carbon electrode (GCE) surface to bind a CYFRA21-1 primary antibody (Ab1) via an amide bond, allowing the analyte CYFRA21-1 to be selectively anchored to Ab1 by specific antigen-antibody interactions. Then, the chain transfer agent-conjugated a CYFRA21-1 secondary antibody was attached to the CYFRA21-1, forming a sandwich-like immunocomplex that can be linked to numerous monomers through RAFT polymerization. Accordingly, a high-density electroactive polymer chain was then grafted onto the immunocomplex, dramatically amplifying the electrochemical signal generated by the immobilized CYFRA21-1. Using the strategy, the current response increased linearly with the logarithm of the CYFRA21-1 concentration in the range of 0.5 fg mL−1 to 10 pg mL−1 (R2 = 0.998), with a low detection limit of 0.14 fg mL−1 (S/N = 3). Furthermore, the CYFRA21-1 concentrations in clinical serum samples analyzed by our method were consistent with those obtained by magnetic particle chemiluminescence assay (MPCA) method. Thus, owing to its high sensitivity, environmental benignity, and low cost, this strategy shows great potential for clinical diagnosis and analysis.