Dual sensitivity enhancement in gold nanoparticle-based lateral flow immunoassay for visual detection of carcinoembryonic antigen.

In this work, we presented the development of cost-effective dual sensitivity enhancement in gold nanoparticle-based lateral flow test strip for detection of carcinoembryonic antigen. On the one hand, we employed protein G as a host matrix for oriented immobilization of antibodies within the nitrocellulose membrane. On the other hand, we utilized gold enhancement approach to visualize the final signals effectively. Primary examinations revealed that the smaller sized nanoparticles have greater signal enhancement compared to bigger ones. So, mono-dispersed gold nanoparticles with average diameters of 11.40 ± 1.40 nm were utilized as tags. The measurement of fluorescent intensity of FITC-tagged secondary antibody attached to the polyclonal antibody, in the presence/absence of protein G as a host matrix on microplate wells, showed the successful oriented immobilization of antibodies via the host matrix. The FESEM images confirmed the attachment and growth of nanoparticles within the porous nitrocellulose membrane, after gold enhancement. Finally, under the optimized conditions, the developed strip could quantify the standard values of target within 2-50 ng/mL range with a limit of detection of 0.35 ng/mL. This strategy enabled the reduction of antibody consumption from a conventional amount of 0.6 µg/strip down to 0.012 µg/strip. The serum samples containing carcinoembryonic antigen were also successfully analyzed by the developed strip with a visual detection limit of 10 ng/mL, which confirms favorable characteristics of the developed test strip for point-of-care applications.