Heike Böhm

Desmosine-Inspired Cross-Linkers for Hyaluronan Hydrogels

We designed bioinspired cross-linkers based on desmosine, the cross-linker in natural elastin, to prepare hydrogels with thiolated hyaluronic acid. These short, rigid cross-linkers are based on pyridinium salts (as in desmosine) and can connect two polymer backbones. Generally, the obtained semi-synthetic hydrogels are form-stable, can withstand repeated stress, have a large linear-elastic range, and show strain stiffening behavior typical for biopolymer networks. In addition, it is possible to introduce a positive charge to the core of the cross-linker without affecting the gelation efficiency, or consequently the network connectivity. However, the mechanical properties strongly depend on the charge of the cross-linker. The properties of the presented hydrogels can thus be tuned in a range important for engineering of soft tissues by controlling the cross-linking density and the charge of the cross-linker.

Charged Triazole Cross-Linkers for Hyaluronan-Based Hybrid Hydrogels

Polyelectrolyte hydrogels play an important role in tissue engineering and can be produced from natural polymers, such as the glycosaminoglycan hyaluronan. In order to control charge density and mechanical properties of hyaluronan-based hydrogels, we developed cross-linkers with a neutral or positively charged triazole core with different lengths of spacer arms and two terminal maleimide groups. These cross-linkers react with thiolated hyaluronan in a fast, stoichiometric thio-Michael addition. Introducing a positive charge on the core of the cross-linker enabled us to compare hydrogels with the same interconnectivity, but a different charge density. Positively charged cross-linkers form stiffer hydrogels relatively independent of the size of the cross-linker, whereas neutral cross-linkers only form stable hydrogels at small spacer lengths. These novel cross-linkers provide a platform to tune the hydrogel network charge and thus the mechanical properties of the network. In addition, they might offer a wide range of applications especially in bioprinting for precise design of hydrogels.

Surface-Mediated Priming During In Vitro Generation of Monocyte-Derived Dendritic Cells

Ex vivo‐generated human dendritic cells (DC) are most commonly generated from monocytes using standard cell culture dishes. To elucidate the effect of the plastic surface during the differentiation process, we compared a standard adhesive plastic dish with four different mainly non‐adherent surfaces. Untouched monocytes were cultured for 3 days in the presence of IL‐4 and GM‐CSF. Time‐lapse videos were recorded, and the phenotype of the cells was analysed by flow cytometry. The cytokine profiles were analysed using a 25‐plex cytokine assay. The use of non‐adherent surfaces led to a significant reduction in expression of CD14 and CD38, and a significant increase in expression of CD86 compared to standard culture dishes. Expression levels of DC‐SIGN and PD‐L2 were reduced significantly on cells cultured on non‐adherent surfaces. The cytokine production was independent on the surface used. The surface‐mediated priming should therefore be considered when aiming to induce specific immune responses. This is especially important with regard to DC‐based immunotherapy, where an adjustment of the surface during the DC generation process might have highly beneficial effects.

Correction: Hyaluronsäuregele zur Druckregulierung in der Glaukomtherapie

Correction: Ophthalmologe 2017 https://doi.org/10.1007/s00347-017-0602-z Sehr geehrter Leser, sehr geehrte Leserin, leider wurde der oben genannte Beitrag online zunachst mit fehlerhaftem deutschen Titel veroffentlicht. Wir bitten, den korrekten Titel Hyaluronsauregele zur Druckregulierung in der Glaukomtherapie zu berucksichtigen und den Fehler zu entschuldigen. Die RedaktionCorrection:Ophthalmologe 2017 https://doi.org/10.1007/s00347-017-0602-z Sehr geehrter Leser,sehr geehrte Leserin,leider wurde der oben genannte Beitrag online zunächst mit fehlerhaftem deutschen Titel veröffentlicht. Wir bitten, den korrekten Titel Hyaluronsäuregele zur Druckregulierung in der Glaukomtherapie zu berücksichtigen und den Fehler zu entschuldigen.Die Redaktion

A new assay for single nucleotide polymorphism analysis based on displacement reactions in PNA–DNA double helices

In this article, we describe a new method for single nucleotide polymorphism analysis using the displacement reaction of the DNA in a PNA–DNA double helix by the target DNA. Thereby, the probe consists of a TMR-labeled PNA and a Cy5-labeled DNA forming a FRET system. Due to the displacement of the labeled DNA strand by the target DNA, the FRET is invalidated and the fluorescence of the donor dye (TMR) increases. Investigations of the exchange reaction show that increasing salt concentration and temperature accelerate the exchange rate.