Sensitive immunosensing of squamous cell carcinoma antigen based on a nanocomposite of poly{3-amine-N-[3-(N-pyrrole)propyl]imidazole bromide} ionic liquid and gold nanoroots

Squamous cell carcinoma antigen (SCCA) is a good specific antigen for cancer diagnosis specifically for squamous cell carcinomas. In this study, 3-amine-N-[3-(N-pyrrole)propyl]imidazole bromide (APPIBr) ionic liquid was successfully synthesized and characterized by 1H NMR, HPLC-MS and FTIR. APPIBr ionic liquid is a unique functional material with a pyrrole moiety which can be polymerized by using electrochemical technique and an amine group for immobilizing biomolecules; thus, it is ideal for the fabrication of biosensors. Using chloroauric acid as precursor and N-dodecyl imidazole as functional monomer, gold nanoroots (AuNRs) were fabricated and characterized with TEM, SEM and XRD. An immunosensor was built on a glassy carbon electrode (GCE), through the steps of forming the poly(APPIBr)/AuNRs/GCE interface by electrodeposition of APPIBr, anti-SCCA immobilization, and several optimization steps to achieve a sensitive, accurate, precise, and selective anti-SCCA/poly(APPIBr)/AuNRs/GCE for the electrochemical immunosensing SCCA. It was found that poly(APPIBr)/AuNRs nanointerface can improve the sensing performance of the immunosensor. Under the optimized experimental conditions, there existed two linear regimes relating the peak current variation to the concentration of squamous cell carcinoma antigen in the range of 0.001-0.1 ng mL−1 and 0.1-5.0 ng mL−1. The detection limit was calculated to be 0.3 pg mL−1. The developed sensor was demonstrated its capability in quantitative analysis of squamous cell carcinoma antigen in human serum with recoveries of 97.3%, 102.4% and 107.4%.