Assessment of the Quorum Sensing Inhibition Activity of a Non-Toxic Chitosan in an N-Acyl Homoserine Lactone (AHL)-Based Escherichia coli Biosensor

Abstract

New approaches to deal with drug-resistant pathogenic bacteria are urgent. We studied the antibacterial effect of chitosans against an Escherichia coli quorum sensing biosensor reporter strain and selected a non-toxic chitosan to evaluate its quorum sensing (QS) inhibition activity and its effect on bacterial aggregation. To this end, chitosans of varying degree of acetylation (DA) (12 to 69%) and molecular weight (Mw) (29 to 288 kDa) were studied. Only chitosans of low DA (~12%) inhibited bacterial growth, regardless of their Mw. A chitosan with medium degree of polymerization (named MDP) DA30, with experimental DA 42% and Mw 115 kDa was selected for further QS inhibition and scanning electron microscopy (SEM) imaging studies. MDP DA30 chitosan exhibited QS inhibition activity in an inverse dose-dependent manner (≤12.5 µg/mL). SEM images revealed that this chitosan, when added at low concentration (≤30.6 µg/mL), induced substantial bacterial aggregation, whereas at high concentration (234.3 µg/mL), it did not. Aggregation explains the QS inhibition activity as the consequence of retardation of the diffusion of N-acylated homoserine lactones (AHLs).

Covalently and ionically, dually crosslinked chitosan nanoparticles block quorum sensing and affect bacterial cell growth on a cell-density dependent manner

“…Figure S7A and B). In the same assays, we also observed cell aggregates in the presenec of the NPs (Figure S8), in agreement with previous studies 42,65,66 .…”

“…PC-NPs displayed a QQ activity that is comparable to those of the ionically crosslinked IC-NPs and raw CS preparations characterized earlier by our group (Table I) 42,65,66 . Interestingly, the QQ activity of the dually crosslinked CC-NPs was much lower (Table I), further attesting to the significance of the new fabrication method reported here.…”

A Truncated Galectin-3 Isolated from Skin Mucus of Atlantic Salmon Salmo salar Binds to and Modulates the Proteome of the Gram-Negative Bacteria Moritella viscosa

“…There was an increased optical density in the presence of galectin-3C at later time points (Figure 6), this could be explained by the formation of aggregates (Figure 7). This is in accordance with findings in a study of chitosan introduced aggregates of Escherichia coli [32]. Low concentrations of chitosan give abrupt increase in optical density in the Escherichia coli growth curve, but measurement of green fluorescence (from the bacterial strain's green fluorescent protein (GFP)) amount indicates that there are fewer rather than more bacteria present than in the control samples.…”

“…Low concentrations of chitosan give abrupt increase in optical density in the Escherichia coli growth curve, but measurement of green fluorescence (from the bacterial strain's green fluorescent protein (GFP)) amount indicates that there are fewer rather than more bacteria present than in the control samples. Scanning electron microscopy shows bacterial aggregates in samples with abrupt optical density increases, but not in control samples or at chitosan concentrations where no sudden increases in optical density was observed [32]. In the presence of lactose the bacteria grew slower, in accordance with the known inhibition of bacterial growth of carbohydrates due to hyperosmotic extracellular fluid and in accordance with a previous study showing no oxidative production of acid for the bacteria in the presence of lactose [33].…”

Characterisation of chitosan molecular weight distribution by multi-detection asymmetric flow-field flow fractionation (AF4) and SEC

“…Many of its material and biological properties are intimately related or linked to the molecular weight (MW) of the polymer. Examples are its biodegradability, its potential to interact with the mucosal surfaces, its hemostatic, antimicrobial and anticholesterolemic properties as well as the material properties derived from its polymeric nature such as formation of hydrogels, supramolecular particles (complexes), nanoparticles, and scaffold materials among others [1][2][3][4][5][6][7][8][9][10]. Chitosan-based biomaterials have also become well-established drug, gene and protein delivery platforms, particularly for biologics (e.g.…”