Controlled synthesis of icosahedral gold nanocrystals, and their self-assembly with an ionic liquid for enhanced immunosensing of squamous cell carcinoma antigen

Icosahedral gold nanocrystals (AuNCs) were synthesized by using the ionic liquid (IL) 1-(10-bromodecyl)-3-methyl-imidazolium bromide as a morphology-controlling reagent. The novel IL 1,3-di-(3-mercaptopropyl)-imidazolium bromide was employed as a bifunctional monomer to integrate the AuNCs onto the surface of a glassy carbon electrode (GCE) modified with gold nanoparticles. After interaction with thioglycolic acid (TGA) and activation of the carboxy groups, the antibody against squamous cell carcinoma antigen was immobilized on the modified GCE. Residual active sites were blocked with bovine serum albumin. The new materials and the steps for immunosensor fabrication were fully characterized. The reduction in peak current (using hexacyanoferrate as an electrochemical probe) due to the recognition of SCCA is linearly related to the SCCA concentration in the 0.02 to 10 ng mL −1 concentration range. The detection limit is as low as 12.6 pg mL −1 (at an S/N ratio of 3). The assay was applied to the quantitation of SCCA in human serum samples. The accuracy was validated by comparison with an ELISA method. The two methods displayed excellent consistency. Icosahedral gold nanocrystals were self-assembled onto a gold nanoparticle modified glassy carbon electrode surface by using 1,3-di-(3-mercaptopropyl)-imidazolium bromide ionic liquid as a linker. Antibody for squamous cell carcinoma antigen was immobilized onto the gold nanocrystal based interface to fabricate an immunosensor.