Silver nanoparticles–chitosan composites activity against resistant bacteria: tolerance and biofilm inhibition

• Published in: Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology 2021-08, Vol.23 (8), p.196-196, Article 196
• Main Authors: dos Santos, Eduarda Melquiades Pirette, Martins, Carla Castelo Branco, de Oliveira Santos, João Victor, da Silva, Wagner Roberto Cirilo, Silva, Sidicleia Bezerra Costa, Pelagio-Flores, Miguel Angel, Galembeck, André, Cavalcanti, Isabella Macário Ferro
• Format: Article
• Language: English
• Subjects: Absorption spectra; American Type Culture Collection; Ascorbic acid; Bacteria; Bactericidal activity; Biofilms; Characterization and Evaluation of Materials; Chemistry and Materials Science; Chitosan; Clinical isolates; Exopolysaccharides; Inorganic Chemistry; Lasers; Materials Science; Minimum inhibitory concentration; Morphology; Multidrug resistance; Nanoparticles; Nanotechnology; Optical Devices; Optics; Particulate composites; Photonics; Physical Chemistry; Reducing agents; Research Paper; Scanning transmission electron microscopy; Silver; Slime; Transmission electron microscopy
• ISSN: 1388-0764; 1572-896X
• DOI: 10.1007/s11051-021-05314-1

This study aimed to evaluate the effectiveness of silver nanoparticles–chitosan composites (AgNPs) with different morphologies and particle size distributions against resistant bacteria and biofilm formation. Four different samples were prepared by a two-step procedure using sodium borohydride and ascorbic acid as reducing agents and characterized by UV–Vis absorption spectra, scanning transmission electron microscopy. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the AgNPs were determined according to the Clinical and Laboratory Standards Institute (CLSI) against clinical isolates multidrug-resistant and strains of the American Type Culture Collection (ATCC). An assay was performed to determine the MICs during 20 successive bacteria exposures to AgNPs to investigate whether AgNPs induce tolerance in bacteria. The antibiofilm activities of AgNPs were also evaluated by determining the minimum biofilm inhibitory concentration (MBIC). The spherical AgNPs present diameters ranging from 9.3 to 62.4 nm, and some samples also have rod-, oval-, and triangle-shaped nanoparticles. The MIC and MBC values ranged from 0.8 to 25 μg/mL and 3.1 to 50 μg/mL, respectively. Smaller and spherical AgNPs exhibited the highest activity, but all the AgNPs developed in this study exhibit bactericidal activity. There was no significant MIC increase after 20 passages to the AgNPs. Regarding the antibiofilm activity, MBICs ranged from 12.5 to 50 μg/mL. Again, smaller and spherical nanoparticles presented the best results with phenotypic inhibition of production of slime or exopolysaccharide (EPS) matrix. Thus, it was concluded that AgNPs have a promising potential against resistant bacteria and bacteria that grow on biofilms without inducing tolerance.