An alternative covalent method for spike SARS-CoV-2 antibody immobilization on gold nanoparticles

An alternative method for immobilizing antibodies on the surface of gold nanoparticles (AuNPs) has been completed. AuNPs have been synthesized with ortho-hydroxybenzoic acid and immobilized with N-(3-Dimethylaminopropyl)-N’-ethyl carbodiimide hydrochloride/ N-Hydroxysuccinimide (AuNPs-EDC/NHS) and SARS-CoV-2 spike antibody (AuNPs-Ab). Ortho-hydroxybenzoic acid provides a carboxyl group for the surface modification of AuNPs. Thus, this method reduces one step of synthesis in covalent immobilization, which requires adding a carboxyl functional group on the surface of AuNPs. The results showed that after adding EDC/NHS and spike antibody SARS-CoV-2 the absorbance at UV-Vis did not decrease significantly, so the physical properties of AuNPs could be maintained. FTIR characterization showed the presence of ester belonging to EDC/NHS and amide covalent, meaning that the SARS-CoV-2 spike antibody was covalently bound to the AuNPs surface. TEM and FESEM images showed the morphology of AuNPs and AuNPs-Ab in spherical shapes. This alternative method offers a novel approach to immobilizing AuNPs for immunoassay applications.