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.

The efficacy of chitosan (CS) to be used as drug delivery carrier has previously been reported. However, limited work has been pursued to produce stable and mucoadhesive CS electrosprayed particles for oral drug delivery, which is the aim of this study. Various CS types with different molecular weight (MW), degree of deacetylation (DD), and degree of polymerization (DP) were assessed. In addition, the effect of the solvent composition was also investigated. Results showed that stable CS electrosprayed particles can be produced by dissolving 3% w/v of low MW CS in mixtures of aqueous acetic acid and ethanol (50/50% v/v). The stable CS particles displayed diameters of approximately 1 μm as determined by dynamic light scattering. The zeta potential of these particles was found to be approximately 40 mV confirming the mucoadhesion properties of these CS electrosprayed particles and its potential to be used as drug delivery carrier.

Quorum sensing (QS) explains a type of bacterial cell-cell communication mediated by exocellular compounds that act as autoinducers (AIs). As such, QS can be considered the most primordial form of language. QS has profound implications for the control of many important traits (e.g. biofilm formation, secretion of virulence factors, etc.). Conceptually, the QS response can be split into its "listening" and "speaking" components, i.e. the power to sense AI levels vs. the ability to synthesize and release these molecules. By explaining the cell-density dependence of QS behavior as the consequence of the system's arrival to a threshold AI concentration, models of QS have traditionally assumed a salient role for the "QS speaking" module during bacterial cell-to-cell communication. In this paper, we have provided evidence that challenges this AI-centered view of QS and establishes LuxR-like activators at the center of QS. Our observation that highly coordinated, cell-density dependent responses can occur in the absence of AI production, implies that the ability to launch such responses is engrained within the "QS listening" module. Our data indicates that once a critical threshold of intracellular activator monomers in complex with AI is reached, a highly orchestrated QS response ensues. While displaying a clear cell-density dependence, such response does not strictly require the sensing of population levels by individual cells. We additionally show, both in vivo and in silico, that despite their synchronous nature, QS responses do not require that all the cells in the population participate in the response. Central to our analysis was the discovery that percolation theory (PT) can be used to mathematically describe QS responses. While groundbreaking, our results are in agreement with and integrate the latest conclusions reached in the field. We explain for the first time, the cell-density-dependent synchronicity of QS responses as the function of a single protein, the LuxR-like activator, capable of coordinating the temporal response of a population of cells in the absence of cell-to-cell communication. Being QS the most primordial form of speech, our results have important implications for the evolution of language in its ancient chemical form.Abbreviations: 3D = three dimensional, ac = threshold intracellular concentration of activator molecules, AHL = acyl-homoserine lactone, AHL f isch = N-(3-oxohexanoyl)-L-homoserine lactone, AHL viol = N-hexanoyl-DL-homoserine-lactone, AI = autoinducer, a.u. = arbitrary units, BMB = bromophenol blue, CA = trans-cinnamaldehyde, Fl = fluorescence intensity, FI/OD600 = density-normalized fluorescence intensity, GFP = green fluorescent protein, M w = molecular weight, PT = percolation theory, QS = quorum sensing, tc = percolation critical time, wt = wild type Quorum sensing (QS) explains a type of bacterial cell-to-cell communication mediated by exocellular chemical compounds that act as autoinducers (AIs). Since QS can be considered the most primordial form of language [1-6], unde...

Novel hybrid hydrogels were formed by adding chitosan (Ch) to phospholipids (P) self-assembled particles in lactic acid. The effect of the phospholipid concentration on the hydrogel properties was investigated and was observed to affect the rate of hydrogel formation and viscoelastic properties. A lower concentration of phospholipids (0.5% wt/v) in the mixture, facilitates faster network formation as observed by Dynamic Light Scattering, with lower elastic modulus than the hydrogels formed with higher phospholipid content. The nano-porous structure of Ch/P hydrogels, with a diameter of 260±20 nm, as observed by cryo-scanning electron microscopy, facilitated the penetration of water and swelling. Cell studies revealed suitable biocompatibility of the Ch/P hydrogels that can be used within life sciences applications.

conditions, complicated handling due to a large number of tubing connections, and the lack of compatibility with established laboratory infrastructure and bioassays. Performing experiments in desired cell culture microenvironments (2D or 3D model) possesses another additional challenge. The physiological relevance of a 3D microenvironment has been extensively studied elsewhere. [11,12] Recent studies show that, especially for clinically relevant processes, 2D cell culture systems have limitations as they result in abnormal phenotypes. [13] In addition to the biological issues, major technical hurdles exist with 2D cultivation in available microfluidic devices. These hurdles include immobilization of non-adherent cells such as cells derived from the hematopoietic system to prevent cell loss during medium exchange and detaching adherent cells from the chip for downstream analysis. Both procedures can substantially alter the inherent cell phenotype. [14,15] In comparison, 3D cell culture models gained significant relevance in the past years due to their biocompatibility, tissue like water content, high porosity, permeability, and in mimicking mechanical properties of the extracellular matrix resulting in a higher physiological relevance. [16] Despite its biological advantages, 3D cell culture hampers the combination of time-lapse data with endpoint measurements such as immunostainings as the hydrogel itself acts as a diffusion barrier. This diffusion barrier impedes supply with fresh nutrients, removal of waste products, and the implementation of efficient washing processes for endpoint staining protocols. In addition, embedding cells into macro 3D matrices complicates cell retrieval after cell cultivation as the hydrogel has to be removed enzymatically or chemically to release embedded cells. [17] In this work, we evaluate a new design of a macro-to-micro interface that can be used for simple and reliable control of microfluidic processes including comprehensive cell culture processes. The presented macro-to-micro interface overcomes significant technical challenges thereby making microfluidic cell culture procedures accessible for biological laboratories.By integrating a workflow that has been described previously, [6] we overcome mentioned limitations and are providing a valuable tool for cultivating single cells, cell-cell pairs, and low cell numbers in spherical hydrogel beads acting as a 3D microenvironment. At the same time, we combine time-lapse (fluorescence) microscopy data with endpoint measurements that provide A new design of a macro-to-micro interface that can be used for simple and reliable control of comprehensive microfluidic cell culture processes is introduced making microfluidic procedures easily accessible to biological laboratories. The novel macro-to-micro interface is evaluated by adapting a workflow for single-cell, cell pair, and cell cluster encapsulation into hydrogel beads acting as 3D microenvironment with subsequent long-term cultivation. For the first time, the coupling of single-cell...