Department of Food Processing Technology and Management
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Item TOWARDS MIMICKING THE FETAL LIVER NICHE: THE INFLUENCE OF ELASTICITY AND OXYGEN TENSION ON HEMATOPOIETIC STEM/PROGENITOR CELLS CULTURED IN 3D FIBRIN HYDROGELS(MDPI, 2020-09-02) Christian, Garcia-Abrego; Samantha, Zaunz; Burak, Toprakhisar; Ramesh, Subramani; Olivier, Deschaume; Stijn, Jooken; Manmohan, Bajaj; Herman, Ramon; Catherine, Verfaillie; Carmen, Bartic; Jennifer, PattersonHematopoietic stem/progenitor cells (HSPCs) are responsible for the generation of blood cells throughout life. It is believed that, in addition to soluble cytokines and niche cells, biophysical cues like elasticity and oxygen tension are responsible for the orchestration of stem cell fate. Although several studies have examined the effects of bone marrow (BM) niche elasticity on HSPC behavior, no study has yet investigated the effects of the elasticity of other niche sites like the fetal liver (FL), where HSPCs expand more extensively. In this study, we evaluated the effect of matrix stiffness values similar to those of the FL on BM-derived HSPC expansion. We first characterized the elastic modulus of murine FL tissue at embryonic day E14.5. Fibrin hydrogels with similar stiffness values as the FL (soft hydrogels) were compared with stiffer fibrin hydrogels (hard hydrogels) and with suspension culture. We evaluated the expansion of total nucleated cells (TNCs), Lin−/cKit+cells, HSPCs (Lin−/Sca+/cKit+ (LSK) cells), and hematopoietic stem cells (HSCs: LSK- Signaling Lymphocyte Activated Molecule (LSK-SLAM) cells) when cultured in 5% O2 (hypoxia) or in normoxia. After 10 days, there was a significant expansion of TNCs and LSK cells in all culture conditions at both levels of oxygen tension. LSK cells expanded more in suspension culture than in both fibrin hydrogels, whereas TNCs expanded more in suspension culture and in soft hydrogels than in hard hydrogels, particularly in normoxia. The number of LSK-SLAM cells was maintained in suspension culture and in the soft hydrogels but not in the hard hydrogels. Our results indicate that both suspension culture and fibrin hydrogels allow for the expansion of HSPCs and more differentiated progeny whereas stiff environments may compromise LSK-SLAM cell expansion. This suggests that further research using softer hydrogels with stiffness values closer to the FL niche is warranted.Item THE INFLUENCE OF SWELLING ON LOCAL ELASTIC PROPERTIES OF POLYACRYLAMIDE HYDROGELS(Open Science Framework, 2017) Ramesh, Subramani; Alicia, Izquierdo-Alvarez; Pinaki, Bhattacharya; Mathieu, Meerts; Paula, Moldenaers; Herman, Ramon; Hans Van, OosterwyckPolyacrylamide (PAM)hydrogelsarecommonly usedas soft cell culture substrates for cell mechanical and mechanobiological studiesbecause oftheir tunable stiffness,easeof handling, transparent natureand surface functionalization to promote cell adhesion. The dependence of bulk rheological and local elastic properties (for example, as assessed by means of Atomic Force Microscopyor AFM) of PAM hydrogels onmonomer and cross-linkerconcentrationsand on polymerization temperature havebeen extensively investigated.PAM hydrogels are known to swell, which may affect their elastic properties and therefore may complicate the interpretation ofcell culturingexperiments because of a lack of control of substrate stiffness. Direct measurements of the effect of swelling on PAM elastic properties are scarce. We report here, for the first time, the direct observation of swelling (by measuring the volumetric swelling ratio) and its influence onlocal elastic properties, as measuredby AFM. Bulk rheological measurements were performed as well to enable the comparison between local and global elastic properties during and after hydrogel polymerization. Four PAM hydrogel compositions were considered,with corresponding storage shear moduliof 4530 Pa(termed stiffest), 2900 Pa(stiff), 538 Pa(soft)and 260 Pa(softest) as measured immediately after polymerization. These values as well as values obtained during hydrogel polymerization were found to be in good agreement with the local elastic moduli derived from AFM and assuming hydrogel incompressibility. After polymerization, the hydrogels were subjected to swelling conditions over six days in phosphate buffered salineand swelling ratios and local elastic moduli were measured each day.Additional short term measurements (at 0, 3, 6, 9, 12 and 24 hours) were performed for the soft and softest gelsto study their swelling kinetics in more detail. Swelling ratio and local elastic modulus did not change with time for the stiffest and stiff gels, while for the soft and softest gels substantialchanges between Day 0 and Day 1were found for both swelling ratio (21.6%and 133% increase for soft and softest gel respectively) and local elastic modulus (33.7%and 33.3% decrease for soft and softest gel respectively). Experimental data werefurther analysed theoretically by combining models of ideal elastomeric gels with a poroelastic swelling kinetics model, which confirmed the validity of observed trends with respect to literature data. The results demonstrate that swelling can have an important effect on PAM elastic properties and must be taken into account when using PAM as a cell culture substrate, particularly for PAM gels with low monomer and cross-linker concentrationsItem IMMERSED BOUNDARY MODELS FOR QUANTIFYING FLOW-INDUCED MECHANICAL STIMULI ON STEM CELLS SEEDED ON 3D SCAFFOLDS IN PERFUSION BIOREACTORS(PLOS Computational Biology, 2016-09-22) Yann, Guyot; Bart, Smeets; Tim, Odenthal; Ramesh, Subramani; Frank P, Luyten; Herman, Ramon; Ioannis, Papantoniou; Liesbet, GerisPerfusion bioreactors regulate flow conditions in order to provide cells with oxygen, nutrients and flow-associated mechanical stimuli. Locally, these flow conditions can vary depending on the scaffold geometry, cellular confluency and amount of extra cellular matrix deposition. In this study, a novel application of the immersed boundary method was introduced in order to represent a detailed deformable cell attached to a 3D scaffold inside a perfusion bioreactor and exposed to microscopic flow. The immersed boundary model permits the prediction of mechanical effects of the local flow conditions on the cell. Incorporating stiffness values measured with atomic force microscopy and micro-flow boundary conditions obtained from computational fluid dynamics simulations on the entire scaffold, we compared cell deformation, cortical tension, normal and shear pressure between different cell shapes and locations. We observed a large effect of the precise cell location on the local shear stress and we predicted flow-induced cortical tensions in the order of 5 pN/μm, at the lower end of the range reported in literature. The proposed method provides an interesting tool to study perfusion bioreactors processes down to the level of the individual cell’s micro-environment, which can further aid in the achievement of robust bioprocess control for regenerative medicine applications.Item TWO DISTINCT FLUORESCENT QUANTUM CLUSTERS OF GOLD STARTING FROM METALLIC NANOPARTICLES BY PH-DEPENDENT LIGAND ETCHING(Springer Link, 2008) Madathumpady, Abubaker Habeeb Muhammed; Subramani, Ramesh; Sudarson, Sekhar Sinha; Samir Kumar, Pal; Thalappil, PradeepTwo fluorescent quantum clusters of gold, namely Au25 and Au8, have been synthesized from mercaptosuccinic acid-protected gold nanoparticles of 4–5 nm core diameter by etching with excess glutathione. While etching at pH ∼3 yielded Au25, that at pH 7–8 yielded Au8. This is the first report of the synthesis of two quantum clusters starting from a single precursor. This simple method makes it possible to synthesize well-defined clusters in gram quantities. Since these clusters are highly fluorescent and are highly biocompatible due to their low metallic content, they can be used for diagnostic applications.Item SPATIOTEMPORAL ANALYSES OF CELLULAR TRACTIONS DESCRIBE SUBCELLULAR EFFECT OF SUBSTRATE STIFFNESS AND COATING(Springer Link, 2019) Alicia, Izquierdo-Álvarez; Diego A, Vargas; Álvaro, Jorge-Peñas; Ramesh, Subramani; Marie-Mo, Vaeyens; Hans Van, OosterwyckCells interplay with their environment through mechanical and chemical interactions. To characterize this interplay, endothelial cells were cultured on polyacrylamide hydrogels of varying stiffness, coated with either fibronectin or collagen. We developed a novel analysis technique, complementary to traction force microscopy, to characterize the spatiotemporal evolution of cellular tractions: We identified subpopulations of tractions, termed traction foci, and tracked their magnitude and lifetime. Each focus consists of tractions associated with a local single peak of maximal traction. Individual foci were spread over a larger area in cells cultured on collagen relative to those on fibronectin and exerted higher tractions on stiffer hydrogels. We found that the trends with which forces increased with increasing hydrogel stiffness were different for foci and whole-cell measurements. These differences were explained by the number of foci and their average strength. While on fibronectin multiple short-lived weak foci contributed up to 30% to the total traction on hydrogels with intermediate stiffness, short-lived foci in such a number were not observed on collagen despite the higher tractions. Our approach allows for the use of existing traction force microscopy data to gain insight at the subcellular scale without molecular probes or spatial constraining of cellular tractions.Item ASSESSING POLLUTANT SORPTION EFFICIENCY OF MODIFIED AND UNMODIFIED BIOCHAR WITH BACILLUS CEREUS ON CONTAMINATED LAKE WATER: IMPLICATIONS FOR ORYZA SATIVA SEEDLING AND ARTEMIA FRANCISCANA LARVAE VIABILITY(Springer Link, 2023-10-02) Mathiyazhagan, Narayanan; Ramesh, Subramani; Sabariswaran, KandasamyThis study evaluated the efficacy of biochar in removing pollutants from a polluted lake. Biochar, both with and without Bacillus cereus, was assessed for its sorption potential. The treated water samples were analyzed for toxicity using Oryza sativa and Artemia franciscana larvae. The lake water exceeded permissible limits for pH, turbidity, dissolved oxygen (DO), chemical oxygen demand (COD), biological oxygen demand (BOD), and various metals. The 10-day biosorption study with different treatment groups (MB, UMB, MBB, UMBB, and BC) revealed that the MBB group exhibited remarkable pollutant sorption potential. It achieved pollutant removal percentages of 33.35% for Cd, 15.73% for As, 26.21% for Cr, 32.72% for Pb, 32.81% for Zn, 23.58% for Cu, 5.44% for Cl, 22.01% for Ni, 28.2% for Hg, and 4.19% for SO42−. MBB-treated lake water showed no toxicity, confirming pollutant removal by metal-tolerant Bacillus cereus in modified biochar.Item 3D NANOMANIPULATION: DESIGN AND APPLICATIONS OF FUNCTIONAL NANOSTRUCTURED BIO-MATERIALS(IOP Science, 2020) Lega P V; Orlov A P; Frolov A V; Subramani R; Irzhak A V; Koledov V V; Smolovich A M; Shelyakov A VRecent progress in the development of the new functional materials opens up exciting possibilities for designing reconfigurable micro- and nano-structures and for operating mechanical nanotools which are controlled by external fields or heat. The nanotools such as nanotweezers with an active layer thickness of about several tenths of nm, and whose overall size is of the order of 1 µm can be applied to different micro- and nanoobjects. The present report gives an overview of the application of mechanical nanotools in 3D nanomanipulation of bio-nano objects such as micro biofibers DNA etc. The future prospects of mechanical bottom up nanomanipulation for biomedical technology, food technology are discussed.Item TWO-DIMENSIONAL NETWORK STABILITY OF NUCLEOBASES AND AMINO ACIDS ON GRAPHITE UNDER AMBIENT CONDITIONS: ADENINE, L-SERINE AND L-TYROSINE(Royal Society of Chemistry, 2010-03-09) Ilko, Bald; Sigrid, Weigelt; Xiaojing, Ma; Pengyang, Xie; Ramesh, Subramani; Mingdong, Dong; Chen, Wang; Wael, Mamdouh; Jianguo, Wang; Flemming, BesenbacherWe have investigated the stability of two-dimensional self-assembled molecular networks formed upon co-adsorption of the DNA base, adenine, with each of the amino acids, L-serine and L-tyrosine, on a highly oriented pyrolytic graphite (HOPG) surface by drop-casting from a water solution. L-serine and L-tyrosine were chosen as model systems due to their different interaction with the solvent molecules and the graphite substrate, which is reflected in a high and low solubility in water, respectively, compared with adenine. Combined scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations show that the self-assembly process is mainly driven by the formation of strong adenine–adenine hydrogen bonds. We find that pure adenine networks are energetically more stable than networks built up of either pure L-serine, pure L-tyrosine or combinations of adenine with L-serine or L-tyrosine, and that only pure adenine networks are stable enough to be observable by STM under ambient conditions.Item BUILDING LAYER-BY-LAYER 3D SUPRAMOLECULAR NANOSTRUCTURES AT THE TEREPHTHALIC ACID/STEARIC ACID INTERFACE(Royal Society of Chemistry, 2011-07-14) Yinli, Li; Lei, Liu; Ramesh, Subramani; Yunxiang, Pan; Bo, Liu; Yanlian, Yang; Chen, Wang; Wael, Mamdouh; Flemming, Besenbacher; Mingdong, DongBy using the layer-by-layer deposition method, we build three dimensional (3D) supramolecular nanostructures by stacking small molecular species on top of the first buffer layer, which can be utilized to fabricate novel 3D supramolecular functional nanostructures.Item GREEN SYNTHESIZED SILVER NANOPARTICLES: TOXICITY AGAINST POECILIA RETICULATA FISHES AND CERIODAPHNIA CORNUTA CRUSTACEANS(Springer Link, 2016-11-30) Ramachandran, Ishwarya; Baskaralingam, Vaseeharan; Sathappan, Shanthi; Subramani, Ramesh; Pitchaimani, Manogari,; Kannan, Dhanalakshmi; Sekar, Vijayakumar; Giovanni, BenelliRecently, the green synthesis of silver nanoparticles gained increasing attention due to interesting properties for optical, antimicrobial and pest control applications. However, their toxicity against micro-crustaceans and fishes has been scarcely explored, while most of the research efforts focused on mosquito control with the green-synthesized nanocomposites. In this study, we investigated the toxic effects of AgNO3, Cissus quadrangularis (Cq)-synthesized AgNPs and Cq extract in two different study models, the larvae of Poecilia reticulata fishes and adults of the micro-crustacean Ceriodaphnia cornuta. In both species, AgNO3 and Cq-AgNPs showed high mortality rates even if tested at very low doses. Molecular analysis revealed high DNA damages induced by Cq-AgNPs on both aquatic organisms. Furthermore, light microscopy studies evidenced lesions in the gills and vacuolization in the gills and in the abdomen of P. reticulata larvae. Overall, our research pointed out that the exposure of aquatic organisms to AgNO3 or green-fabricated AgNPs can damage fishes and crustaceans, posing noteworthy risks to the aquatic ecosystems.