Silver nanoparticles exert concentration‐dependent influences on biofilm development and architecture

Abstract

Objectives:To investigate the impact of silver nanoparticles (AgNPs) on the biofilm growth and architecture.Materials and methods: Silver nitrate was reduced by d-maltose to prepare AgNPs in the presence of ammonia and sodium hydroxide. The physicochemical properties of AgNPs were characterized by transmission electron microscopy, ultraviolet-visible spectroscopy and inductively coupled plasma mass spectrometry. The development of biofilm with and without AgNPs was explored by crystal violet stain. The structures of mature biofilm were visually studied by confocal laser scanning microscopy and scanning electron microscopy. Bacterial cell, polysaccharide and protein within biofilm were assessed quantitatively by colony-counting method, phenol-sulphuric acid method and Bradford assay, respectively. Results:The spherical AgNPs (about 30 nm) were successfully synthesized. The effect of AgNPs on Pseudomonas aeruginosa biofilm development was concentrationdependent. Biofilm was more resistant to AgNPs than planktonic cells. Low doses of AgNPs exposure remarkably delayed the growth cycle of biofilm, whereas high concentration (18 μg/mL) of AgNPs fully prevented biofilm development. The analysis of biofilm architecture at the mature stage demonstrated that AgNPs exposure at all concentration led to significant decrease of cell viability within treated biofilms.However, sublethal doses of AgNPs increased the production of both polysaccharide and protein compared to control, which significantly changed the biofilm structure.Conclusions: AgNPs exert concentration-dependent influences on biofilm development and structure, which provides new insight into the role of concentration played in the interaction between antibacterial nanoparticles and biofilm, especially, an ignored sublethal concentration associated with potential unintended consequences.

Subinhibitory Concentrations of Biogenic Silver Nanoparticles Affect Motility and Biofilm Formation in Pseudomonas aeruginosa

“… Guo et al. (2019) observed that subinhibitory doses of AgNPs enhanced polysaccharide and protein production in P. aeruginosa CCM 3955 compared with the control, significantly altering biofilm structure.…”

“…Silver nanoparticles (AgNPs) are one of the most widely studied nanomaterials ( Guo et al., 2019 ; Kawish et al., 2020 ; Saeed et al., 2020 ) because of their chemical stability, malleability, flexibility, high electrical and thermal conductivity, catalytic activity, relatively low cost, and, mainly, potent antimicrobial action ( Durán et al., 2019 ). These unique properties have led AgNPs to find application in the medical industry (wound dressing, surgical instrument, and bone prosthesis production), textile industry (garment production), food industry (food packaging, countertop, and cutting board materials), and wastewater treatment ( McNamara and Tofail, 2017 ; Gadkari et al., 2018 ).…”

Antibacterial and antibiofilm potential of silver nanoparticles against antibiotic-sensitive and multidrug-resistant Pseudomonas aeruginosa strains

“…2) [88,89]. When bacteria is treated with AgNPs, morphological changes are revealed in biofilm's architecture, such as uneven cell surface, suggesting cell lysis [70], relevant morphological damages in the cell wall, membrane corrugation damage, changes in membrane polarization and/or permeability [90], and distinct EPS-matrix formation surrounding the bacterial strains [91]. Moreover, electrostatic interactions between AgNPs and bacterial membranes cause them to rupture, so that AgNPs can penetrate into the mature biofilm [86,92].…”

“…Used as post-treatment therapy, AgNPs were able to reduce P. aeruginosa CCM 3955 biofilm viability by 46.28%, 65.50%, and 92.43% and reduce biomass by 5.69%, 37.87%, and 67.52%, after treatment with concentrations at 2, 6, and 12 μg/mL, respectively [91]. Singh et al [69] evaluated the antibiofilm activity of AgNPs produced from Cannabis sativa against P. aeruginosa PA01 and as a result showed a decrease in biofilm's viability at a concentration at 50 μg/mL.…”

Silk Polymers and Nanoparticles: A Powerful Combination for the Design of Versatile Biomaterials

“…However, the widespread use of these powerful molecules has led to the apparition of antibiotic-resistant bacterial strains. Silver NPs have broad spectrum activity against gram positive and gram negative bacteria (Agnihotri et al, 2014 ), biofilms (Guo et al, 2019 ), multidrug resistant bacteria (Lara et al, 2010a ), fungi (Kim et al, 2009 ; Chudasama et al, 2011 ), and even some virus (Lara et al, 2010b ). The antibacterial action of silver NPs is dependent on their size and shape (Choi and Hu, 2008 ).…”