A scalable route to quaternary ammonium-functionalized AgCl colloidal antimicrobials inhibiting food pathogenic bacteria and biofilms
Diellza Bajrami, Syed Imdadul Hossain, Alexia Barbarossa, Maria Chiara Sportelli, Rosaria Anna Picca, Luigi Gentile, Francesco Mastrolonardo, Antonio Rosato, Alessia Carocci, Nicola Antonio Colabufo, Boris Mizaikoff, Nicola Cioffi
Abstract
This study explores how a simple argentometric titration-like approach could be evolved into a versatile, scalable, fast, and robust strategy for the production of AgCl/quaternary ammonium compounds (QACs) colloidal nanoantimicrobials (NAMs). These systems, which are green, stable, cost-effective, and reproducible are found to be effective against a wide range of food pathogenic bacteria and biofilms. The option of a large-scale production for such colloidal suspensions was explored via the use of a peristaltic pump. The use of various types of biosafe QACs and a wide range of solvents including aqueous and organic ones renders this system green and versatile. Nanocolloids were characterized using UV–Vis, X-ray photoelectron and Fourier transform infrared (FTIR) spectroscopies. Their morphology and crystalline nature were investigated by transmission electron microscopy (TEM) and selected area diffraction pattern (SAED). Nanoparticle (NP) size distribution and hydrodynamic radius were measured by dynamic light scattering (DLS), while the ζ-potential was found to be highly positive, thus indicating significant colloidal stability and antimicrobial activity. In fact, the higher the NP surface charge, the stronger was their bioactivity. Furthermore, the antibacterial and antibiofilm effects of the as-prepared NCs were tested against Gram-positive bacteria, such as Staphylococcus aureus (ATCC 29213) and Listeria monocytogenes, and Gram-negative bacteria, such as Escherichia coli (ATCC 25922) and Pseudomonas aeruginosa (ATCC 27853) . The results clearly indicate that AgCl/QACs provide pronounced antibiofilm activity with long-term bacteriostatic effects against foodborne pathogenic bacteria rendering them an ideal choice for active food packaging systems.