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Kronfeld, Klaus-Peter; Köhler, Michael; Ellinger, Thomas
Microfluidic synthesis and properties of thermoresponsive hydrogel core-shell particles. - In: Journal of composites science, ISSN 2504-477X, Bd. 8 (2024), 5, 162, S. 1-9

An approach is demonstrated for the generation of swellable core-shell particles in the sub-millimeter range using a one-step microfluidic method. Particles are made of an agarose gel core and a shell consisting of hydrogel based on crosslinked poly-(N-isopropylacrylamide) (PNIPAM). Solidification of the core was achieved by cooling below the sol-gel temperature, while the shell was cured by photoinitiated co-polymerization. The shell of the particles is reversibly thermoresponsive; it contracts upon heating, releasing water, and becomes hydrophobic. The transition temperature as well as the stability of the particles are mainly affected by the shell monomer composition, while they are less affected by the type of the core material. Such composite particles remain swellable after drying.



https://doi.org/10.3390/jcs8050162
Saupe, Mario; Wiedemeier, Stefan; Gastrock, Gunter; Römer, Robert; Lemke, Karen
Flexible toolbox of high-precision microfluidic modules for versatile droplet-based applications. - In: Micromachines, ISSN 2072-666X, Bd. 15 (2024), 2, 250, S. 1-19

Although the enormous potential of droplet-based microfluidics has been successfully demonstrated in the past two decades for medical, pharmaceutical, and academic applications, its inherent potential has not been fully exploited until now. Nevertheless, the cultivation of biological cells and 3D cell structures like spheroids and organoids, located in serially arranged droplets in micro-channels, has a range of benefits compared to established cultivation techniques based on, e.g., microplates and microchips. To exploit the enormous potential of the droplet-based cell cultivation technique, a number of basic functions have to be fulfilled. In this paper, we describe microfluidic modules to realize the following basic functions with high precision: (i) droplet generation, (ii) mixing of cell suspensions and cell culture media in the droplets, (iii) droplet content detection, and (iv) active fluid injection into serially arranged droplets. The robustness of the functionality of the Two-Fluid Probe is further investigated regarding its droplet generation using different flow rates. Advantages and disadvantages in comparison to chip-based solutions are discussed. New chip-based modules like the gradient, the piezo valve-based conditioning, the analysis, and the microscopy module are characterized in detail and their high-precision functionalities are demonstrated. These microfluidic modules are micro-machined, and as the surfaces of their micro-channels are plasma-treated, we are able to perform cell cultivation experiments using any kind of cell culture media, but without needing to use surfactants. This is even more considerable when droplets are used to investigate cell cultures like stem cells or cancer cells as cell suspensions, as 3D cell structures, or as tissue fragments over days or even weeks for versatile applications.



https://doi.org/10.3390/mi15020250
Szántó, Géza; Pritzke, Pia; Kluitmann, Jonas; Köhler, Michael; Csáki, Andrea; Fritzsche, Wolfgang; Csarnovics, István; Bonyár, Attila
Optimization of the bulk refractive index sensitivity of silver nanoprisms. - In: Advanced optical materials, ISSN 2195-1071, Bd. 12 (2024), 15, 2302967, S. 1-11

The sensitivity and optical properties of silver nanoprisms (triangular plates with round-truncated corners) are investigated in this paper. Results of boundary element method simulations are compared with experimental results and literature data. Based on electron microscopy images of the synthesized nanoprisms, a single-particle model is set up for simulations with three running parameters: edge length, thickness, and roundness (defined as the radius of the circumscribed circle divided by the edge length). These geometric parameters can be optimized during chemical synthesis to create sensors with improved sensitivity. The effect of biomolecular layers is also investigated. As a novel approach to improve the agreement between the simulated and experimentally measured extinction spectra, the single-particle model is extended to consider the variation of the prisms' parameters in the form of distributions. The resulting extinction cross-section spectra correspond well with the experimental data. The calculated bulk refractive index sensitivity is 670 nm/RIU (RIU stands for refractive index unit) for the single particle model (length = 150 nm, thickness = 10 nm, and roundness = 0.1), while (690 ± 5) nm/RIU for the extended model. The presented model and obtained relations between sensitivity and geometry can be effectively used to design and optimize the fabrication technologies for silver nanoprism-based sensing applications.



https://doi.org/10.1002/adom.202302967
Köhler, Michael; Ehrhardt, Linda; Günther, Mike; Böhme, Manfred; Cao-Riehmer, Jialan
Low abundant bacteria reflect soil specificity - analysis of bacterial communities from archaeological investigation of pre-industrial saline ash deposits of Bad Dürrenberg (Germany). - In: Environments, ISSN 2076-3298, Bd. 11 (2024), 3, 42, S. 1-20

Six soil samples from three layers of an archaeological investigation profile from a pre-industrial ash deposit place have been investigated by NGS analyses of 16 S rRNA. The three pairs of sample originate from top soil (internal reference), from an intermediate ash layer and from a lower ash layer, formed about two centuries ago. In addition to general abundant bacteria, special genera known as halophilic or alkaline-tolerant have been found as expected from the history of the place and from the measured pH-value and conductivity measurements. The close relations between samples of pairs and the differences between the three soil layers are clearly indicated by abundance correlation and PCA-diagrams. Comparative PCA correlation plots including samples from an archaeological excavation site dedicated to pre-industrial coal mining illustrate the high distinguishability of investigated soils. These relations are particular clearly shown when lower abundant bacteria are regarded. The investigations are a further example for the “ecological memory of soil” reflecting the strong human impact on this pre-industrial embossed place.



https://doi.org/10.3390/environments11030042
Jaster, Jonas; Dreßler, Elias; Geitner, Robert; Groß, Gregor Alexander
Synthesis and spectroscopic characterization of furan-2-carbaldehyde-d. - In: Molbank, ISSN 1422-8599, Bd. 2023 (2023), 2, M1654, S. 1-9

Here, we present a protocol for the one-step synthesis of the title compound in quantitative yield using adapted Vilsmeier conditions. The product was characterized by 1H-,2H-,13C-NMR-, as well as IR and Raman spectroscopy. Spectral data are given in detail.



https://doi.org/10.3390/M1654
Köhler, Michael; Ehrhardt, Linda; Cao-Riehmer, Jialan; Möller, Frances; Schüler, Tim; Günther, Mike
Beta-diversity enhancement by archaeological structures: bacterial communities of an historical tannery area of the city of Jena (Germany) reflect the ancient human impact. - In: Ecologies, ISSN 2673-4133, Bd. 4 (2023), 2, S. 325-343

Soil samples taken during archaeological investigations of a historical tannery area in the eastern suburb of the medieval city of Jena have been investigated by 16S r-RNA gene profiling. The analyses supplied a large spectrum of interesting bacteria, among them Patescibacteria, Methylomirabilota, Asgardarchaeota, Zixibacteria, Sideroxydans and Sulfurifustis. Samples taken from soil inside the residues of large vats show large differences in comparison to the environmental soil. The PCAs for different abundance classes clearly reflect the higher similarity between the bacterial communities of the outside-vat soils in comparison with three of the inside-vat soil communities. Two of the in-side vat soils are distinguishable from the other samples by separate use of each abundance class, but classes of lower abundance are better applicable than the highly abundant bacteria for distinguishing the sampling sites by PCA, in general. This effect could be interpreted by the assumption that less abundant types in the 16S r-RNA data tend to be more related to an earlier state of soil development than the more abundant and might be, therefore, better suited for conclusions on the state of the soils in an earlier local situation. In addition, the analyses allowed identification of specific features of each single sampling site. In one site specifically, DNA hints of animal residue-related bacteria were found. Obviously, the special situation in the in-site vat soils contributes to the diversity of the place, and enhances its Beta-diversity. Very high abundancies of several ammonia-metabolizing and of sulphur compound-oxidizing genera in the metagenomics data can be interpreted as an echo of the former tannery activities using urine and processing keratin-rich animal materials. In summary, it can be concluded that the 16S r-RNA analysis of such archaeological places can supply a lot of data related to ancient human impacts, representing a kind of “ecological memory of soil”.



https://doi.org/10.3390/ecologies4020021
Tsierkezos, Nikos; Freiberger, Emma; Ritter, Uwe; Krischok, Stefan; Ullmann, Fabian; Köhler, Michael
Application of nitrogen-doped multi-walled carbon nanotubes decorated with gold nanoparticles in biosensing. - In: Journal of solid state electrochemistry, ISSN 1433-0768, Bd. 27 (2023), 10, S. 2645-2658

Novel films consisting of nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) were fabricated by means of chemical vapor deposition technique and decorated with gold nanoparticles (AuNPs) possessing diameter of 14.0 nm. Electron optical microscopy analysis reveals that decoration of N-MWCNTs with AuNPs does not have any influence on their bamboo-shaped configuration. The electrochemical response of fabricated composite films, further denoted as N-MWCNTs/AuNPs, towards oxidation of dopamine (DA) to dopamine-o-quinone (DAQ) in the presence of ascorbic acid (AA) and uric acid (UA) was probed in real pig serum by means of cyclic voltammetry (CV) and square wave voltammetry (SWV). The findings demonstrate that N-MWCNTs/AuNPs exhibit slightly greater electrochemical response and sensitivity towards DA/DAQ compared to unmodified N-MWCNTs. It is, consequently, obvious that AuNPs improve significantly the electrochemical response and detection ability of N-MWCNTs. The electrochemical response of N-MWCNTs/AuNPs towards DA/DAQ seems to be significantly greater compared to that of conventional electrodes, such as platinum and glassy carbon. The findings reveal that N-MWCNTs/AuNPs could serve as powerful analytical sensor enabling analysis of DA in real serum samples.



https://doi.org/10.1007/s10008-023-05562-2
Xie, Ting; Ehrhardt, Linda; Günther, Mike; Köhler, Michael; Cao-Riehmer, Jialan
Current to biomass: media optimization and strain selection from cathode-associated microbial communities in a two-chamber electro-cultivation reactor. - In: Environments, ISSN 2076-3298, Bd. 10 (2023), 6, 97, S. 1-19

Cathode-associated microbial communities (caMCs) are the functional key elements in the conversion of excess electrical energy into biomass. In this study, we investigated the development of electrochemical caMCs based on two-chamber microbial electrolytic cells (MECs) after optimization of media composition. Microbial communities obtained from a historical soil sample were inoculated into the cathode chamber of MECs. The inorganic medium with (A) carbon dioxide in air or (B) 100 mM sodium bicarbonate as carbon source was used in the absence of any organic carbon source. After 12 days of operation, the experimental results showed that (1) the bacterial community in group B exhibited lush growth and (2) a single strain TX168 Epilithonimonas bovis isolated from group A indicated electrochemical activity and synthesized large volumes of biomass using sodium bicarbonate. We also analyzed the caMCs of the MECs and reference samples without electro-cultivation using 16S rRNA gene sequencing. The results showed that the caMCs of MECs in groups A and B were dominated by the genera Acinetobacter and Pseudomonas. The caMCs were further inoculated and cultured on different agars to isolate specific electroactive bacterial strains. Overall, our study highlights the possibility of converting excess energy into biomass by electro-cultivation and the importance of selecting appropriate media to enrich specific microbial communities and single strains in MECs.



https://doi.org/10.3390/environments10060097
Maz&ptbov;etyt&ptbov;e, Raminta; Kronfeld, Klaus-Peter; Köhler, Michael
Five-level structural hierarchy: microfluidically supported synthesis of core-shell microparticles containing nested set of dispersed metal and polymer micro and nanoparticles. - In: Particle & particle systems characterization, ISSN 1521-4117, Bd. 14 (2023), 10, 2300030, S. 1-13

This study presents the development of a hierarchical design concept for the synthesis of multi-scale polymer particles with up to five levels of organization. The synthesis of core-shell microparticles containing nested sets of dispersed metal and polymer micro- and nanoparticles is achieved through in situ photopolymerization using a double co-axial capillaries microfluidic device. The flow rates of the carrier, shell, and core phases are optimized to control particle size and result in stable core-shell particles with well-dispersed three-level composites in the shell matrix. The robustness and reversibility of these core-shell particles are demonstrated through five cycles of drying and re-swelling, showing that the size and structure of core-shell particles remain unchanged. Additionally, the permeability and mobility of dye molecules within the shell matrix are tested and showed that different molecular weight dyes have different penetration times. This study highlights the potential of microfluidics as a powerful tool for the controlled and precise synthesis of complex structured materials and demonstrates the versatility and potential of these core-shell particles for sensing applications as particle-based surface-enhanced Raman scattering (SERS).



https://doi.org/10.1002/ppsc.202300030
Hadzich, Antonella; Flores, Santiago; Masucci, Ashley E.; Gomez, Enrique D.; Groß, Gregor Alexander
NMR and GPC analysis of alkyd resins: influence of synthesis method, vegetable oil and polyol content. - In: Polymers, ISSN 2073-4360, Bd. 15 (2023), 9, 1993, S. 1-14

Alkyd resins are oil-based polymers that have been widely used for generations in the surface coating industry and beyond. Characterization of these resins is of high importance to understand the influence of its components on its behavior, compatibility with other resins, and final quality to ensure high durability. Here, NMR spectroscopy and GPC were used for characterizing differences in the chemical structure, molecular distribution, and dispersity between oil-based and fatty acid-based alkyd polymers made from sacha inchi and linseed oils. Sancha inchi (Plukentia volubilis L.) is a fruit-bearing plant native to South America and the Caribbean, and has a rich unsaturated fatty acid content. The effect of vegetable oil and polyol selection on the synthesis of alkyd resins for coating applications was analyzed. The influence of two different synthesis methods, monoglyceride and fatty acid processes, was also compared. Important structural differences were observed using NMR: one-dimensional spectra revealed the degree of unsaturated fatty acid chains along the polyester backbone, whereas, 2D NMR experiments facilitated chemical shift assignments of all signals. GPC analysis suggested that alkyd resins with homogeneous and high molecular weights can be obtained with the fatty acid process, and that resins containing pentaerythritol may have uniform chain lengths.



https://doi.org/10.3390/polym15091993

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