Entropic repulsion of cholesterol-containing layers counteracts bioadhesion.

Control of adhesion is a striking feature of living matter that is of particular interest regarding technological translation1-3. We discovered that entropic repulsion caused by interfacial orientational fluctuations of cholesterol layers restricts protein adsorption and bacterial adhesion. Moreover, we found that intrinsically adhesive wax ester layers become similarly antibioadhesive when containing small quantities (under 10 wt%) of cholesterol. Wetting, adsorption and adhesion experiments, as well as atomistic simulations, showed that repulsive characteristics depend on the specific molecular structure of cholesterol that encodes a finely balanced fluctuating reorientation at the interface of unconstrained supramolecular assemblies: layers of cholesterol analogues differing only in minute molecular variations showed markedly different interfacial mobility and no antiadhesive effects. Also, orientationally fixed cholesterol layers did not resist bioadhesion. Our insights provide a conceptually new physicochemical perspective on biointerfaces and may guide future material design in regulation of adhesion.

Engineering Bacterial Shape Using Soft Matter Microchambers.

This article describes the design and fabrication of microchambers that are used for the study of bacterial cells. The design allows for the confinement and precise manipulation of bacterial cell shape. The application of fluorescent dyes and fluorescent proteins enables the precise analysis of the localization of biomolecules within confined bacterial cell. This article also outlines three methods to engineer cell shape from a filamentous cell type and from spheroplasts without a cell wall using soft lithography-based technologies. © 2018 by John Wiley & Sons, Inc.

Post-column infusion of internal standard quantification for liquid chromatography-electrospray ionization-tandem mass spectrometry analysis - Pharmaceuticals in urine as example approach.

Liquid chromatography with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) technique is gaining more and more attraction as the method of choice for multi-sample analysis. However, it is strongly susceptible to the influence of matrix components. Matrix effects are the main source of substantial losses in detection sensitivity and have to be compensated via complex quantification methods In this work, we introduce a sophisticated quantification method for the LC-ESI-MS/MS analysis of 16 substances in urine samples using a single continuously post-column infused internal standard (PCI-IS) for matrix effect correction. The performance of the introduced technique was proven by the simultaneous quantification using internal standards. Our results demonstrate that a single post-column infused internal standard suffices to analyze multiple target analytes. The introduced method is a new approach to analyze complex matrices and represents a powerful alternative to the classic internal standard methodology. The proposed technique significantly reduces the required steps for sample preparation, costs of additional stable isotopically-labeled internal standards, and self-induced matrix effects.

Evaluation of the matrix effect of different sample matrices for 33 pharmaceuticals by post-column infusion.

Matrix effects that occur during quantitative measurement by liquid chromatography mass spectrometry specifically when using electrospray ionization are a widely recognized phenomenon. Sample matrix compounds affect the ionization process of the target analytes, lead to a low signal response, and flawed analytical results. How these matrix compounds directly influence the ionization process has not yet been completely understood. In the present study, we determined the matrix effect for 33 pharmaceutical substances in sample extracts of urine, plasma and wastewater. Most of the investigated substances were subject to a signal suppression effect. Only for a small subset of the compounds we detected a signal enhancement effect. We investigated the matrix effect profiles in detail to disentangle the influence of different matrices and to correlate the impact of specific components and groups of the analyzed extract in suppressing or enhancing effects in the profile. Most signal suppression effects were detected in the first half of the chromatographic run-time for the matrix extracts of urine and wastewater. The observed effects are caused by high mass flow of salts and other diverse matrix components that were contained in high concentrations in those biological matrices. We also found signal suppression in the matrix effect profile of plasma samples over a wide time range during the chromatographic separation that were associated with a high content of triglycerides of diverse carbohydrate chain lengths. Here, we provide a broader picture of how 33 substances were influenced during analysis. Our results imply that a high number of the investigated substances had comparable effects of matrix compounds, despite differences in their chemical structure.