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Zeußel, Lisa; Chowdhary, Shefali; Wu, Haocheng; Kumar, Vipan; Singh, Sukhdeep
Sustainable harnessing of waste polycarbonate for synthesizing activated furans to generate Stenhouse adducts on polymer surface. - In: Chemistry, ISSN 1861-471X, Bd. 19 (2024), 13, e202400369, S. 1-11

Plastics are versatile materials, offering lightweight, durable, and affordable solutions across various industries. However, their non-degradable nature poses challenges by end of their life. This study presented an innovative carbonyl extraction method to utilize waste poly(bisphenol A carbonate) (PC) as reaction precursor to synthesis of activated furan as precursor for photoswitchable Stenhouse adducts. This innovative chemical strategy not only generated N,N’-functionalized barbiturates but also provided an eco-friendly and cost-effective alternative to traditional synthesis methods. The method presented hereby not only promotes sustainability by repurposing waste polycarbonate as carbonyl equivalent under green conditions but also yielded reusable bisphenol A (BPA). Furthermore, the derived activated furans exhibited their functionality by forming colored donor-acceptor Stenhouse adducts (DASAs) on aminated polymer surfaces. This work demonstrated a transition from a linear plastics economy toward a circular one, highlighting the potential of plastic waste as a resource for creating materials with improved properties.
Zeußel, Lisa; Schober, Andreas; Ullmann, Fabian; Krischok, Stefan; Heinrich, Doris; Singh, Sukhdeep
Visible-light-assisted donor-acceptor-Stenhouse-adduct-based reversible photoswitching on a laser-structurable OrmoComp substrate. - In: ACS applied polymer materials, ISSN 2637-6105, Bd. 5 (2023), 10, S. 8631-8640

Laser-assisted nanolithography of commercially available photoresists is offering a limitless designing opportunity in the micro- and nanostructuring of 3D organotypic cell culture scaffolds. Among them, chemically functionalized OrmoComp has shown promising improvement in cell adhesion that paves the way to assemble cellular entities on a desirable geometry. Establishing a photoswitchable chemistry on the OrmoComp surface may offer an additional degree of freedom to manipulate the surface chemistry locally and selectively. We have established the methods for functionalization of the photopolymerized OrmoComp surface with visible-light-switchable donor-acceptor Stenhouse adducts. Unlike other polymers, a photopolymerized OrmoComp surface appears to be optimal for reversible photothermal switching, offering the possibility to influence surface properties like absorption and hydrophilicity tremendously. Light-assisted chemical modulation between colored triene-2-ol and colorless cyclopentenone can be achieved to a size region as narrow as 20 μm. Thermal reversion to the original triene-2-ol state can be analyzed spectroscopically and observed with the naked eye.
Zeußel, Lisa; Singh, Sukhdeep
Meldrum’s acid furfural conjugate MAFC: a new entry as chromogenic sensor for specific amine identification. - In: Molecules, ISSN 1420-3049, Bd. 28 (2023), 18, 6627, S. 1-17

Bioactive amines are highly relevant for clinical and industrial application to ensure the metabolic status of a biological process. Apart from this, generally, amine identification is a key step in various bioorganic processes ranging from protein chemistry to biomaterial fabrication. However, many amines have a negative impact on the environment and the excess intake of amines can have tremendous adverse health effects. Thus, easy, fast, sensitive, and reliable sensing methods for amine identification are strongly searched for. In the past few years, Meldrum’s acid furfural conjugate (MAFC) has been extensively explored as a starting material for the synthesis of photoswitchable donor-acceptor Stenhouse adducts (DASA). DASA formation hereby results from the rapid reaction of MAFC with primary and secondary amines, which has so far been demonstrated through numerous publications for different applications. The linear form of the MAFC-based DASA exhibits intense pink coloration due to its linear conjugated triene-2-ol conformation, which has inspired researchers to use this easy synthesizable molecule as an optical sensor for primary, secondary, and biogenic amines. Due to its new entry into amine identification, a collection of the literature exclusively on MAFC is demanded. In this mini review, we intend to present the state-of-the-art of MAFC as an optical molecular sensor in hopes to motivate researchers to find even more applications of MAFC-based sensors and methods that pave the way to their usage in medicinal applications.
Mai, Patrick; Hampl, Jörg; Bača, Martin; Brauer, Dana; Singh, Sukhdeep; Weise, Frank; Borowiec, Justyna; Schmidt, André; Küstner, Johanna Merle; Klett, Maren; Gebinoga, Michael; Schroeder, Insa S.; Markert, Udo R.; Glahn, Felix; Schumann, Berit; Eckstein, Diana; Schober, Andreas
MatriGrid® based biological morphologies: tools for 3D cell culturing. - In: Bioengineering, ISSN 2306-5354, Bd. 9 (2022), 5, 220, S. 1-41

Recent trends in 3D cell culturing has placed organotypic tissue models at another level. Now, not only is the microenvironment at the cynosure of this research, but rather, microscopic geometrical parameters are also decisive for mimicking a tissue model. Over the years, technologies such as micromachining, 3D printing, and hydrogels are making the foundation of this field. However, mimicking the topography of a particular tissue-relevant substrate can be achieved relatively simply with so-called template or morphology transfer techniques. Over the last 15 years, in one such research venture, we have been investigating a micro thermoforming technique as a facile tool for generating bioinspired topographies. We call them MatriGrid®s. In this research account, we summarize our learning outcome from this technique in terms of the influence of 3D micro morphologies on different cell cultures that we have tested in our laboratory. An integral part of this research is the evolution of unavoidable aspects such as possible label-free sensing and fluidic automatization. The development in the research field is also documented in this account.
Bača, Martin; Brauer, Dana; Klett, Maren; Fernekorn, Uta; Singh, Sukhdeep; Hampl, Jörg; Groß, Gregor Alexander; Mai, Patrick; Friedel, Karin; Schober, Andreas
Automated analysis of acetaminophen toxicity on 3D HepaRG cell culture in microbioreactor. - In: Bioengineering, ISSN 2306-5354, Bd. 9 (2022), 5, 196, S. 1-16

Real-time monitoring of bioanalytes in organotypic cell cultivation devices is a major research challenge in establishing stand-alone diagnostic systems. Presently, no general technical facility is available that offers a plug-in system for bioanalytics in diversely available organotypic culture models. Therefore, each analytical device has to be tuned according to the microfluidic and interface environment of the 3D in vitro system. Herein, we report the design and function of a 3D automated culture and analysis device (3D-ACAD) which actively perfuses a custom-made 3D microbioreactor, samples the culture medium and simultaneously performs capillary-based flow ELISA. A microstructured MatriGrid® has been explored as a 3D scaffold for culturing HepaRG cells, with albumin investigated as a bioanalytical marker using flow ELISA. We investigated the effect of acetaminophen (APAP) on the albumin secretion of HepaRG cells over 96 h and compared this with the albumin secretion of 2D monolayer HepaRG cultures. Automated on-line monitoring of albumin secretion in the 3D in vitro mode revealed that the application of hepatotoxic drug-like APAP results in decreased albumin secretion. Furthermore, a higher sensitivity of the HepaRG cell culture in the automated 3D-ACAD system to APAP was observed compared to HepaRG cells cultivated as a monolayer. The results support the use of the 3D-ACAD model as a stand-alone device, working in real time and capable of analyzing the condition of the cell culture by measuring a functional analyte. Information obtained from our system is compared with conventional cell culture and plate ELISA, the results of which are presented herein.
Zeußel, Lisa; Hampl, Jörg; Weise, Frank; Singh, Sukhdeep; Schober, Andreas
Bio-inspired 3D micro structuring of a liver lobule via direct laser writing: a comparative study with SU-8 and SUEX. - In: Journal of laser applications, ISSN 1938-1387, Bd. 34 (2022), 1, 012007, S. 012007-1-012007-12

Real biological tissues show a great variety of different geometric morphologies with special features on different geometric scales. An interesting example is the liver lobule that is the basic subunit of a liver. The lobule is a quasihexagonal macroscopic structure with periodic like so-called sinusoidal elements with structural features on the micro- and macroscale made of proteins, cells, and fluids. Various tools from micromachining and nanotechnology have demonstrated their capabilities to construct micromorphologies precisely, but even the reconstruction of such a system in technical polymers is challenging. In this work, the rapidly evolving technique of multiphoton polymerization has been explored for the construction of a scaffold that mimics the micromorphology of the liver with high resolution and detail up to the millimeter scale. At the end, a highly complex fluidically perfusable structure was achieved and simulations showed that the occurring shear stress, fluid velocity, and stream lines are comparable to the native liver lobule. Hereby, the photoresists SU-8 and SUEX TDFS were compared in terms of their processability, achievable resolution, and suitability for the intended application. Our results have shown that SUEX needs lower writing velocities but is easier to process and achieves a considerable higher resolution than SU-8. The scaffold could provide a base frame with a geometrically defined morphology for hepatic cells to adhere to, which could act as a starting point for cells to build new liver tissue for further integration in more complex systems.
Zeußel, Lisa; Aziz, Carlos; Schober, Andreas; Singh, Sukhdeep
pH-dependent selective colorimetric detection of proline and hydroxyproline with Meldrum's acid-furfural conjugate. - In: Chemosensors, ISSN 2227-9040, Bd. 9 (2021), 12, 343, S. 1-13

Activated 2-furfural gives intense color formation when reacted with amines, due to a ring opening reaction cascade that furnishes a conjugated molecular system. Unique colorimetric characteristic of this reaction makes it an interesting candidate for developing chemosensors operating in visible range. Among many activated 2-furfural derivatives, Meldrum's acid furfural conjugate (MAFC) recently gained significant interest as colorimetric chemosensor. MAFC has been explored as selective chemosensor for detecting amines in solution, secondary amines on polymer surfaces and even nitrogen rich amino acids (AA) in aqueous solution. In this work, the pH dependency of MAFC-AA reaction is explored. It was found that proline gives an exceptionally fast colored reaction at pH 11, whereas at other pHs, no naked eye color product formation was observed. The reaction sequence including ring opening reaction upon nucleophilic addition of cyclic amine of proline resulting in a conjugated triene was confirmed by NMR titrations. The highly pH dependent reaction can e.g., potentially be used to detect proline presence in biological samples. An even more intense color formation takes place in the reaction of natural proline derivative 4-hydroxyproline. The detection limit of proline and 4-hydroxyproline with MAFC solution was found to be 11 [my]M and 6 [my)M respectively.
Zeußel, Lisa; Mai, Patrick; Sharma, Sanjay; Schober, Andreas; Ren, Shizhan; Singh, Sukhdeep
Colorimetric method for instant detection of lysine and arginine using novel Meldrum's acid-furfural conjugate. - In: ChemistrySelect, ISSN 2365-6549, Bd. 6 (2021), 27, S. 6834-6840

In the past few years Meldrum's acid furfural conjugate (MAFC) have been extensively explored as starting material for the synthesis of photo switchable donor acceptor stenhouse adducts (DASA). Hereby, we have explored the interaction of MAFC with various amino acids. To our surprise, nitrogen rich amino acids like lysine and arginine interact spontaneously with MAFC to give colored adduct immediately, whereas other amino acids, including nitrogen rich histidine, didn't show any coloration. Naked eye detection of lysine in benign solvent make this reagent an attractive new entry to the collection of chemosensors for the colorimetric detection of lysine and arginine. Intense coloration corresponds to the absorption at 514 nm under UV-Vis spectrometer. Lowest concentration of 100 m can be detected with UV-Vis spectrometer. NMR titrations reveals that the appearance of color is due to ring opening of a furfural that leads to the formation of conjugated triene species. Compared to previously reported chemosensors for lysine and arginine, MAFC offers advantages including simple synthesis, easy handling, high speed, low cost, good sensitivity/selectivity.
Marx-Blümel, Lisa; Marx, Christian; Weise, Frank; Frey, Jessica; Perner, Birgit; Schlingloff, Gregor; Lindig, Nora; Hampl, Jörg; Sonnemann, Jürgen; Brauer, Dana; Voigt, A.; Singh, Sukhdeep; Beck, B.; Jäger, Ute-Maria; Wang, Zhao Qi; Beck, James F.; Schober, Andreas
Biomimetic reconstruction of the hematopoietic stem cell niche for in vitro amplification of human hematopoietic stem cells. - In: PLOS ONE, ISSN 1932-6203, Bd. 15 (2020), 6, e0234638, insges. 17 S.
Marx-Blümel, Lisa; Frey, Jessica; Sonnemann, Jürgen; Schober, Andreas; Brauer, Dana; Schlingloff, Gregor; Singh, Sukhdeep; Hampl, Jörg; Weise, Frank; Lindig, Nora; Marx, Christian; Wang, Zhao-Qi; Perner, Birgit; Beck, James F.
Biomimetic reconstruction of tissue structures using the example of the hematopoietic stem cell niche for the in vitro amplification of human hematopoietic stem cells. - In: Bone marrow transplantation, ISSN 1476-5365, Bd. 54 (2019), S. 365-366