An investigation of the interactions between an E. coli bacterial quorum sensing biosensor and chitosan-based nanocapsules

Abstract

Highlights Chitosan-coated nanocapsules, but not nanoemulsions, influence the -potential of E.coli  A fixed number of nanocapsules binds and promotes aggregation of bacteria  In silico simulations agree closely with experimental results  Chitosan-coated nanocapsules attenuate the bacterial quorum sensing response § These authors contributed equally to this publication * Author for correspondence Colloids and Surfaces B: Biointerfaces 149 (2017) 358-368 AbstractWe examined the interaction between chitosan-based nanocapsules (NC), with average hydrodynamic diameter ~114-155 nm, polydispersity ~0.127, and -potential ~+50 mV, and an E. coli bacterial quorum sensing reporter strain. Dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) allowed full characterization and assessment of the absolute concentration of NC per unit volume in suspension. By centrifugation, DLS, and NTA, we determined experimentally a "stoichiometric" ratio of ~80 NC/bacterium. By SEM it was possible to image the aggregation between NC and bacteria. Moreover, we developed a custom in silico platform to simulate the behavior of particles with diameters of 150 nm and -potential of +50 mV on the bacterial surface. We computed the detailed force interactions between NC-NC and NC-bacteria and found that a maximum number of 145 particles might interact at the bacterial surface. Additionally, we found that the "stoichiometric" ratio of NC and bacteria has a strong influence on the bacterial behavior and influences the quorum sensing response, particularly due to the aggregation driven by NC.

Chitosan nanoencapsulation of flavonoids enhances their quorum sensing and biofilm formation inhibitory activities against an E.coli Top 10 biosensor

“…An interpretation to this effect can be offered in line with previous studies carried out in our laboratory showing that unloaded chitosan-based nanocapsules obtained from the same chitosan sample as in the present study and under an identical preparation protocol, at specific number ratios of nanocapsules/bacterium inhibit the relative QS response in a very similar way as we report here. This has been attributed to the aggregation exerted by the capsules on the E. coli bacteria, the result of electrostatic interactions [52]. Since in our experiments the dose of flavonoids was controlled not by the actual concentration loaded in the capsules, but by the total amount of added formulations, our results therefore, concur with the mentioned previous findings.…”

“…A combination of both physicochemical and biological analysis was used to investigate the effects of free and chitosan-based nanocapsules loaded with baicalein and quercetin against a bioengineered E.coli Top 10 biosensor and MDCK-C7 mammalian cells. The chitosan (DA 42%) used in this study, does not have antibacterial activity and, therefore, it is best suited for producing nanocapsules for bacterial quorum sensing studies [52]. The physicochemical characteristics of the nanoformulations in terms of size, zeta potential, encapsulation efficiency (Table 1) and stability in biological media (Figure 1) concurred closely with those of previous reports [25,54].…”

“…To account for the enhanced inhibition observed when the flavonoids were loaded in the nanocapsules, we can argue that there is a local delivery effect, that it is enhanced at low concentrations. In our previous study, we showed that 100% of the chitosan nanocapsules bind to E. coli Top 10, when they are dosed at low concentrations, below the optimal "stoichiometric" nanocapsule/bacterium binding point [52]. It is also conceivable, that under such scenario, the nanocapsules release their payloads in a sustained and controlled manner.…”

“…We investigated the influence of applying different concentrations of both free and chitosannanoencapsulated baicalein and quercetin on the relative growth and the relative quorum sensing of the transformed E. coli Top 10 biosensor strain that expresses GFP production only under the influence external 3OC6HSL [51][52][53]. A close inspection of Figure 2 reveals that free baicalein (Figure 2i-a) did not have any substantive inhibitory effects on the QS response of the bacteria.…”

Revestimento Com Filmes Comestíveis À Base De Quitosana E Glicerol Para Extensão Da Vida De Prateleira De Morangos

“…Uma de suas particularidades é sua propriedade antibacteriana, já conhecida frente alguns tipos de bactérias, como Escherichia coli e Staphylococcus aureus [4][5][6] . Uma das explicações para tal propriedade é que, além de alterar a permeabilidade da membrana celular da bactéria, ao impedir a troca gasosa entre interior e exterior da célula, também causa disfunção celular ao romper a membrana 2,5,7 .…”