Antibody Conjugated Gold Nanoparticles for Detection of Small Amounts of Antigen Based on Surface Plasmon Resonance (SPR) Spectra

In this paper, a fast and sensitive localized surface plasmon resonance (LSPR) based biosensor was developed and the optimization of gold – antibody conjugates through investigation of different parameters were performed. Gold nanoparticles (AuNPs) with a size of ~20 nm were synthesized via chemical reduction of HAuCl4 with trisodium citrate as reducing and stabilizing agent. The impacts of pH of gold colloids and antibody concentrations on conjugation of electrostatically absorbed antibodies on the AuNPs surface were evaluated. The diverse amounts of antigens were added to the selected gold – antibody conjugate and the calibration curve and limit of detection of the system were successfully obtained. The UV Vis and DLS outputs were utilized to prove the efficiency and repeatability of the system. As a result, the designed biosensor shows a convincing LOD of 400 ng/ml of antigen. It is suggested that electrostatic absorption strategy of AuNPs with negative charge to the positively charged antibodies can be an efficient methodology. Results showed an effective LSPR system for detection of small amounts of antigen in short time as well as with high accuracy.