On the role of intermolecular interactions in stabilizing AuNP@Ampicillin nano-antibiotics

Abstract

The fight against antibiotic resistance has become a major public health issue in recent years. In this context, nano-antibiotics composed of gold nanoparticles with antibiotics grafted on their surface often exhibit outstanding properties, sometimes even bypassing bacterial resistance mechanisms. Among these nano-antibiotics, gold nanoparticles/ampicillin hybrid systems (AuNPs@Ampicillin) are very effective. However, despite their very promising antibacterial properties, very little information concerning their atomic-scale structure is reported in the literature. In the present paper, the structure and energetics of AuNPs@Ampicillin nano-antibiotics have been investigated using first-principles numerical simulations through the study of the ampicillin adsorption on the three low Miller index facets Au(111), Au(100) and Au(110) of the AuNPs as a function of both the antibiotics coverage and its protonation state. Intermolecular interactions were found to be very stabilizing for coverages compatible with experimental data. An optimal coverage zone has been determined, in which the combination of a favorable gold surface-antibiotics interaction and of stabilizing intermolecular interactions can lead to an overall stabilization of the nano-antibiotics. As regards the mechanism of action of the nano-antibiotics, this study has confirmed that the active site of the free antibiotic is exposed to the solvent when the antibiotic is grafted onto the gold nanoparticle.