Nanotechnology, Science and Applications (Dec 2024)
The Substantial Role of Cell and Nanoparticle Surface Properties in the Antibacterial Potential of Spherical Silver Nanoparticles
Abstract
Marta Krychowiak-Maśnicka,1,* Weronika Paulina Wojciechowska,1,* Karolina Bogaj,1 Aleksandra Bielicka-Giełdoń,2 Ewa Czechowska,3 Magdalena Ziąbka,4 Magdalena Narajczyk,5 Anna Kawiak,6 Tomasz Mazur,7 Beata Szafranek,2 Aleksandra Królicka1 1University of Gdansk, Intercollegiate Faculty of Biotechnology, Laboratory of Biologically Active Compounds, Gdansk, Poland; 2University of Gdansk, Faculty of Chemistry, Gdansk, Poland; 3University of Gdansk, Intercollegiate Faculty of Biotechnology, Laboratory of Experimental and Translational Immunology, Gdansk, Poland; 4AGH University of Krakow, Faculty of Materials Science and Ceramics, Department of Ceramics and Refractories, Krakow, Poland; 5University of Gdansk, Faculty of Biology, Bioimaging Laboratory, Gdansk, Poland; 6University of Gdansk, Intercollegiate Faculty of Biotechnology, Laboratory of Plant Protection and Biotechnology, Gdansk, Poland; 7AGH University of Krakow, Academic Centre for Materials and Nanotechnology, Krakow, Poland*These authors contributed equally to this workCorrespondence: Marta Krychowiak-Maśnicka, Laboratory of Biologically Active Compounds, Intercollegiate Faculty of Biotechnology of the University of Gdansk and the Medical University of Gdansk, University of Gdansk, Abrahama 58, Gdansk, 80-307, Poland, Email [email protected]: Although it is well known that the size, shape, and surface chemistry affect the biological potential of silver nanoparticles (AgNPs), the published studies that have considered the influence of AgNP surface on antibacterial activity have not provided conclusive results. This is the first study whose objective was to determine the significance of the surface net charge of AgNPs on their antibacterial potential, attraction to bacterial cells, and cell envelope disruption, considering differences in bacterial surface properties.Methods: We evaluated five commercial AgNP colloids with identical size and shape but different surface ligands. We thoroughly characterized their physicochemical properties, including the zeta potential, hydrodynamic diameter, and polydispersity index, and determined the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC), along with silver absorption into bacterial cells. Moreover, we investigated structural changes in bacteria treated with AgNPs by using a crystal violet assay and electron microscopy.Results: The zeta potential of AgNPs ranged from − 47.6 to +68.5 mV, with a hydrodynamic diameter of 29– 87 nm and a polydispersity index of 0.349– 0.863. Bacterial susceptibility varied significantly (0.5 ≤ MIC ≤ 256 μg Ag/mL; 1 ≤ MBC ≤ 256 μg Ag/mL); we found the lowest susceptibility in bacteria with a cell wall or a polysaccharide capsule. The most active AgNPs (0.5 ≤ MIC ≤ 32 μg Ag/mL; 2 ≤ MBC ≤ 64 μg Ag/mL) had a moderate surface charge (− 21.5 and +14.9 mV). The antibacterial potential was unrelated to ion dissolution or cell envelope disruption, and bacterial cells absorbed less of the most active AgNPs (1.75– 7.65%).Conclusion: Contrary to previous reports, we found that a moderate surface charge is crucial for the antibacterial activity of AgNPs, and that a significant attraction of the nanoparticle to the cell surface reduces the antibacterial potential of AgNPs. These findings challenge the existing views on AgNP antibacterial mechanisms and interactions with bacterial cells. Keywords: human pathogen, ESKAPE, Klebsiella pneumoniae, cell envelope, ICP-OES, cell–nanoparticle interaction
