Study on Specific and Non-Specific Interactions Between BSA and Anti-BSA in Fluoroquinolone Antibiotic Solution by AFM

Most of the physiological activities of organisms are realized by protein-protein interactions (PPIs), which are one of the fundamental research fields in biomedicine. Investigation of micromechanical behaviour of proteins is important for understanding its biological functions. In this study, after the fabrication of self-assemble monolayers (SAMs), eight fluoroquinolone antibiotics were used as experimental subjects and their influence on the interactions between BSA and anti-BSA were investigated by atomic force microscopy (AFM). The Poisson distribution method was used to statistically calculate the adhesion forces obtained by AFM. The results showed that salified fluoroquinolone antibiotics could decrease the adhesion forces between BSA and anti-BSA, especially the non-specific interactions. In contrast, the non-salified fluoroquinolone antibiotics had no significant effect on PPIs between BSA and anti-BSA. The specific interaction notably changed at low (40 μg/mL) and high (200 μg/mL) concentrations of fluoroquinolone antibiotics. Together with AFM topographical analysis, this phenomenon was attributed to the pH reaching a value closer to the BSA isoelectric point and a higher ionic strength, which led to the reduction of antigen and antibody specific binding sites, respectively. These interpretations provide a foundation to better understand the mechanical behaviour of proteins.