Publications by authors named "Andreas Baer"

4 Publications

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On the control of dispersion interactions between biological membranes and protein coated biointerfaces.

J Colloid Interface Sci 2021 Mar 11;598:464-473. Epub 2021 Mar 11.

PULS Group, Department of Physics and Interdisciplinary Center for Nanostructured Films, Friedrich-Alexander-Universität Erlangen-Nürnberg, IZNF, Cauerstrasse 3, 91058 Erlangen, Germany; Division of Physical Chemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia. Electronic address:

Hypothesis: Interaction of cellular membranes with biointerfaces is of vital importance for a number of medical devices and implants. Adhesiveness of these surfaces and cells is often regulated by depositing a layer of bovine serum albumin (BSA) or other protein coatings. However, anomalously large separations between phospholipid membranes and the biointerfaces in various conditions and buffers have been observed, which could not be understood using available theoretical arguments.

Methods: Using the Lifshitz theory, we here evaluate the distance-dependent Hamaker coefficient describing the dispersion interaction between a biointerface and a membrane to understand the relative positioning of two surfaces. Our theoretical modeling is supported by experiments where the biointerface is represented by a glass substrate with deposited BSA and protein layers. These biointerfaces are allowed to interact with giant unilamellar vesicles decorated with polyethylene glycol (PEG) using PEG lipids to mimic cellular membranes and their pericellular coat.

Results: We demonstrate that careful treatment of the van der Waals interactions is critical for explaining the lack of adhesiveness of the membranes with protein-decorated biointerfaces. We show that BSA alone indeed passivates the glass, but depositing an additional protein layer on the surface BSA, or producing multiple layers of proteins and BSA results in repulsive dispersion forces responsible for 100 nm large equilibrium separations between the two surfaces.
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http://dx.doi.org/10.1016/j.jcis.2021.02.078DOI Listing
March 2021

Structural characterization of an ionic liquid in bulk and in nano-confined environment using data from MD simulations.

Data Brief 2020 Feb 23;28:104794. Epub 2019 Nov 23.

Group for Computational Life Sciences, Department of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, 10000, Zagreb, Croatia.

This article contains data on structural characterization of the [C2Mim][NTf2] in bulk and in nano-confined environment obtained using MD simulations. These data supplement those presented in the paper "Insights from Molecular Dynamics Simulations on Structural Organization and Diffusive Dynamics of an Ionic Liquid at Solid and Vacuum Interfaces" [1], where force fields with three different charge methods and three charge scaling factors were used for the analysis of the IL in the bulk, at the interface with the vacuum and the IL film in the contact with a hydroxylated alumina surface. Here, we present details on the construction of the model systems in an extended detailed methods section. Furthermore, for best parametrization, structural and dynamic properties of IL in different environment are studied with certain features presented herein.
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http://dx.doi.org/10.1016/j.dib.2019.104794DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6909096PMC
February 2020

Insights from molecular dynamics simulations on structural organization and diffusive dynamics of an ionic liquid at solid and vacuum interfaces.

J Colloid Interface Sci 2019 Oct 6;553:350-363. Epub 2019 Jun 6.

Group of Computational Life Sciences, Department of Physical Chemistry, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia; PULS Group, Center for Nanostructured Films, Department of Physics, FAU Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany. Electronic address:

Hypothesis: A reliable modelling approach is required for simultaneous characterisation of static and dynamic properties of bulk and interfacial ionic liquids (ILs). This is a prerequisite for a successful investigation of experimentally inaccessible, yet important properties, including those that change significantly with the distance from both vacuum and solid interfaces.

Simulations: We perform molecular dynamics simulations of bulk [CMim][NTf], and thick IL films in contact with vacuum and hydroxylated sapphire surface, using the charge methods CHelpG, RESP-HF and RESP-B3LYP with charge scaling factors 1.0, 0.9 and 0.85.

Findings: By determining and employing appropriate system sizes and simulations lengths, and by benchmarking against self-diffusion coefficients, surface tension, X-ray reflectivity, and structural data, we identify RESP-HF/0.9 as the best non-polarizable force field for this IL. We use this optimal parametrisation to predict novel physical properties of confined IL films. First we fully characterise the internal configurations and orientations of IL molecules relative to, and as a function of the distance from the solid and vacuum interfaces. Second, we evaluate densities together with mobilities in-plane and normal to the interfaces and find that strong correlations between the IL's stratification and diffusive transport in the interfacial layers persist for several nanometres deep into IL films.
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http://dx.doi.org/10.1016/j.jcis.2019.06.017DOI Listing
October 2019

Resection of Ileoinguinal and Ileohypogastric Nerves Combined with Gluing in Modified Lichtenstein Repair.

Surg Technol Int 2015 May;26:143-8

Department of Colorectal and Hernia Surgery, Lukaskrankenhaus Neuss GmbH, Academic Teaching Hospital of Heinrich Heine University, Düsseldorf, Germany.

We conducted a cohort trial to investigate the relevance of resection of the ilioinguinal and iliohypogastric nerves in combination with mesh fixation with BioGlue™ (CryoLife® Inc., Kennsaw, Georgia) in modified Lichtenstein repair to the development of chronic pain and hernia recurrence.1 In all, 430 patients underwent Lichtenstein repair. In 247 patients the mesh was fixed by means of glue, and in 183 patients it was fixed with conventional sutures. In all cases the inguinal nerves N. ilioinguinalis and N. iliohypogastricus were located and resected after identification to prevent nerve reaction to the mesh. The pain intensity was measured with a numeric analogous scale (NAS) 24 hours after surgery. All complications were recorded with a follow-up of up to 5 years. There was a significantly lower pain intensity level in the gluing group compared with the suture group 24 hours after surgery (0.016 t test). The level was 3.8±2.4 in bilateral hernia and 3.3±2.1 in unilateral hernia in the gluing group. It was 4.7±3.3 in unilateral and 3.7±2.2 in bilateral hernia in the suture group. The cut-suture time was lower in the gluing group. There were no severe pain syndromes (NAS≥4) in the gluing group and only 1.1% in the suture group. There was a higher incidence of non-bacterial wound infections in the gluing group (3.6%) than in the suture group (1.1%). The rate of recurrence after 5 years amounted to 2.0% in the gluing group and 2.2% in the suture group. The technique of using BioGlue™ for mesh fixation combined with systematic nerve dissection reduces acute and chronic postoperative pain after modified Lichtenstein repair. Only 2 of 430 patients suffered from severe chronic pain. Combined gluing and systematic resection of the inguinal nerves is more comfortable than standard Lichtenstein repair.
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May 2015