Colorimetric Immunosensor by Aggregation of Photochemically Functionalized Gold Nanoparticles

Abstract

A colorimetric immunosensor based on local surface plasmon resonance by gold nanoparticles is presented, and its application for the detection of human immunoglobulin G (IgG) is demonstrated. The color change of the colloidal solution is produced by nanoparticle aggregation, a process that can be tuned by the presence of the analyte once the nanoparticles are functionalized. In comparison to common functionalization techniques, the procedure described here is simpler, low-cost, and effective in binding antibodies upright on the gold surface. The dose–response curve is similar to that resulting in typical immunoassay platforms and is satisfactorily described by the proposed theoretical model. Human IgG at concentration levels of few hundreds of nanograms per milliliter can be detected by eyes within a few minutes, thereby making the colorimetric immunosensor proposed here a powerful tool in several areas, with urine test in medical diagnostics being the most immediate.

Direct quantification of surface coverage of antibody in IgG-Gold nanoparticles conjugates

“…Alternatively, antibody coverage was quantified by ELISA using the corresponding antigen labeled by HRP [11,18]. Antibody coverage to AuNP can also be quantified from the LSPR peak shift caused by antibody-induced changes in the local refractive index (RI) [24,25]. Though this approach provides a direct quantification of the adsorbed antibody, it requires accurate knowledge of proteins' RI at the nanoparticles surface which in turn depends on the surface coverage, protein orientation and water content [26][27][28].…”

Ultrasensitive antibody-aptamer plasmonic biosensor for malaria biomarker detection in whole blood

“…As previously shown, beside oriented antibodies, the surface functionalization adopted in this work leads also to their close packed distribution both on AuNPs 52,53 and flat surfaces 68 . In this way, not only the interacting area of the biosensor is fully exploited thereby obtaining high sensitivity and low LOD, but also the specificity is inherently warranted by the presence of the antibodies (and even more increased in our scheme by the presence of the aptamers).…”

Role of gold nanoparticles in advanced biomedical applications

“…In similar fashion, effective immuno-sensing was also performed using gold nanoparticles. 256,257 The formation of an immune complex caused aggregation of the nanoparticles, which was used to determine analyte levels through UV-vis spectroscopy.…”