Abstract
In this work, we studied the antimicrobial properties of a nanocomposite system based on a lactose-substituted chitosan and silver nanoparticles: Chitlac-nAg. Twofold serial dilutions of the colloidal Chitlac-nAg solution were both tested on Streptococcus mitis, Streptococcus mutans, and Streptococcus oralis planktonic phase and biofilm growth mode as well as on saliva samples. The minimum inhibitory and bactericidal concentrations of Chitlac-nAg were evaluated together with its effect on sessile cell viability, as well as both on biofilm formation and on preformed biofilm. In respect to the planktonic bacteria, Chitlac-nAg showed an inhibitory/bactericidal effect against all streptococcal strains at 0.1% (v/v), except for S. mitis ATCC 6249 that was inhibited at one step less. On preformed biofilm, Chitlac-nAg at a value of 0.2%, was able to inhibit the bacterial growth on the supernatant phase as well as on the mature biofilm. For S. mitis ATCC 6249, the biofilm inhibitory concentration of Chitlac-nAg was 0.1%. At sub-inhibitory concentrations, the Streptococcal strains adhesion capability on a polystyrene surface showed a general reduction following a concentration-dependent-way; a similar effect was obtained for the metabolic biofilm activity. From these results, Chitlac-nAg seems to be a promising antibacterial and antibiofilm agent able to hinder plaque formation.
Highlights
Biofilm is characterized by microbial communities that are organized as a network of cell-to-cell interactions [1]
We investigated the antimicrobial properties of Chitlac-nAg, on planktonic and sessile phases of oral Streptococci
In respect to the planktonic bacteria, the Chitlac-nAg showed an interesting bactericidal effect against all streptococcal strains at 0.1% (v/v) and this value represented the minimum inhibitory concentration, except for S. mitis ATCC 6249 that was inhibited at one step less
Summary
Biofilm is characterized by microbial communities that are organized as a network of cell-to-cell interactions [1]. S. oralis, are the initial colonizers of tooth surface due to their ability to recognize and adhere to the receptors on the acquired pellicle coating the oral surfaces [1] Their ability to co-aggregate and induce specific cell-cell interaction between genetically distinct microorganisms is crucial to form mature oral biofilm [1]. Silver ions induce the inactivation of critical physiological functions such as cell wall synthesis, membrane transport, nucleic acid (RNA and DNA) synthesis and translation, protein folding and function, and electron transport [13,14,16] For these reasons “nanosilver” has gained popularity in consumer products. We investigated the antimicrobial properties of Chitlac-nAg, on planktonic and sessile phases of oral Streptococci Both free-living cells and in formation and mature biofilms of S. mitis, S. mutans, and S. oralis were analyzed. The effect of Chitlac-nAg was studied on saliva samples, both on planktonic and sessile growth mode
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