Controlling the Binding Efficiency of Surface Confined Antibodies through the Design of Mixed Self-Assembled Monolayers

A plethora of different electronic and optoelectronic devices have been developed lately, for biosensing applications (e.g., label-free, fast, and easier to operate) based on a detecting interface accommodating the biorecognition elements, anchored by thiolate self-assembled monolayers (SAMs) on a gold surface. Here, a surface plasmon resonance (SPR) characterization of anti-p24 anchored on different SAMs is performed to investigate the effect of the SAM structure on the antibodies' packing efficiency and the sensors' analytical figures of merit. Notably, the mixed SAM deposited from a solution 10:1 of 3-mercaptopropionic acid and 11-mercaptoundecanoic acid (11MUA) is compared to that resulting from a solution 10:1 of ad hoc synthesized N-(2-hydroxyethyl)-3-mercaptopropanamide (NMPA)/11MUA. Despite the improvement in the anti-p24 surface coverage registered using the 11MUA/NMPA SAM, the latter produces a significant decrease in the antibodies' binding efficiency against human immunodeficiency virus p24 protein. To provide a molecular rationale behind the SPR data, density functional theory calculations are also undertaken. A comprehensive physical view of the main competing phenomena affecting the biorecognition events at a biofunctionalized gold detecting interface is represented here.