385 research outputs found
SEM2: Introducing mechanics in cell and tissue modeling using coarse-grained homogeneous particle dynamics
No full textModeling multiscale mechanics in shape-shifting engineered tissues, such as organoids and organs-on-chip, is both important and challenging. In fact, it is difficult to model relevant tissue-level large non-linear deformations mediated by discrete cell-level behaviors, such as migration and proliferation. One approach to solve this problem is subcellular element modeling (SEM), where ensembles of coarse-grained particles interacting via empirically defined potentials are used to model individual cells while preserving cell rheology. However, an explicit treatment of multiscale mechanics in SEM was missing. Here, we incorporated analyses and visualizations of particle level stress and strain in the open-source software SEM++ to create a new framework that we call subcellular element modeling and mechanics or SEM2. To demonstrate SEM2, we provide a detailed mechanics treatment of classical SEM simulations including single-cell creep, migration, and proliferation. We also introduce an additional force to control nuclear positioning during migration and proliferation. Finally, we show how SEM2 can be used to model proliferation in engineered cell culture platforms such as organoids and organs-on-chip. For every scenario, we present the analysis of cell emergent behaviors as offered by SEM++ and examples of stress or strain distributions that are possible with SEM2. Throughout the study, we only used first-principles literature values or parametric studies, so we left to the Discussion a qualitative comparison of our insights with recently published results. The code for SEM2 is available on GitHub at https://github.com/Synthetic-Physiology-Lab/sem2
Određivanje antioksidativnog kapaciteta u vinu, farmaceutskim proizvodima i sokovima na modificiranom biosenzoru s lakazom
No full textA simple and highly sensitive electrochemical biosensor based on laccase immobilized onto a gold nanoparticle/graphene nanoplatelet-modified screen-printed carbon electrode (AuNP/GNPl/SPCE) was developed for the determination of hydroquinone (HQ) and other polyphenolic compounds. The biosensor shows excellent electro-catalytic activity towards oxidation of hydroquinone at a potential of -0.05 V (vs Ag/AgCl, 3M KCl) in phosphate buffer as supporting electrolyte (0.1 M, pH 7.0) using hydrodynamic amperometry. Analytical characteristics uncover that the AuNPs/GNPls/SPCE comprises a wide linear range for the dependence of the signal on hydroquinone concentrations from 4 to 130 μM with a detection limit (3σ) of 1.5 μM. The repeatability (5 measurements, 100 μM hydroquinone) is ±2 % and the reproducibility (5 biosensors, 100 μM hydroquinone) is ±3 %. Interference studies of most common compounds with the determination of hydroquinone demonstrated negligible effects. Finally, the biosensor and the analytical method were applied to the determination of phenolic antioxidant capacity (AOC) in wine and blueberry syrup based on Trolox (6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid) and hydroquinone equivalents. The results were evaluated by using their calibration curves which were satisfactory and agreed well with the results obtained by the reference method Trolox Equivalent Antioxidant Capacity assay (TEAC-Assay).Za određivanje hidrokinona (HQ) i drugih fenolnih spojeva razvijen je jednostavan i vrlo osjetljiv elektrokemijski biosenzor na bazi lakaze, imobilizirane na nanočestice zlata u grafenskoj tinti modificiranoj sa 2D grafenskim nanopločicama, u obliku sitotiskane ugljične elektrode (AuNP / GNPl / SPCE). Biosenzor pokazuje izvrsnu elektrokatalitičku aktivnost prema oksidaciji hidrokinona pri potencijalu od -0,05 V (vs Ag / AgCl, 3M KCl) u fosfatnom puferu (0,1 M, pH 7,0) kod mjerenja metodom hidrodinamičke amperometrije. Analitička svojstva otkrivaju da AuNPs / GNPls / SPCE širok linearni odziv s povećanjem koncentracije hidrokinona od 4 do 130 μM, s granicom detekcije (3σ) od 1,5 uM. Ponovljivost (5 mjerenja, 100 μM hidrokinona) je ± 2%, a reproducibilnost (5 biosenzora, 100 μM hidrokinona) je ± 3%. Interferencijska ispitivanja za određivanje hidrokinona u prisutnosti različith spojeva pokazala su minimalne smetnje. Konačno, biosenzor i analitička metoda primijenjeni su za određivanje fenolnog antioksidacijskog kapaciteta (AOC) u vinu, sirupu od borovnice i farmaceutskim proizvodima iskazanog preko ekvivalentata standarda Troloxa (6-hidroksi-2,5,7,8-tetrametilkroman-2-karboksilne kiseline) i hidrokinona. Rezultati su ocijenjeni korištenjem kalibracijskih krivulja koje su dobro korelirale s rezultatima dobivenim primjenom referentne metode “Trolox Equivalent Antioxidant Capacity assay” (TEAC-Assay)
Carbon paste electrodes bulk-modified with carbon nanotubes and chemically oxidized carbon nanotubes for the determination of hydrogen peroxide
No full textCarbon paste electrodes (graphite/paraffin oil) bulk-modified with multiwalled carbon nanotubes (MWCNT) and chemically oxidized MWCNT (O-MWCNT) were used as sensors for the hydrodynamic chronoamperometric determination of hydrogen peroxide (H2O2). Experimental parameters, such as the type and pH of the supporting electrolyte or the working potential(s) applied were investigated in the batch arrangement
Low Cost Hydrogen Peroxide Sensor from Manganese Oxides Modified Pencil Graphite Electrode
No full textAbstractElectrodeposition of manganese oxides film onto the cheap pencil graphite electrode using potassium permanganate precursor provides the good alternative method of fabrication the low cost hydrogen peroxide sensor. Effect of deposition potential, deposition time and concentration of potassium permanganate were investigated. The modified electrode displayed electrocatalytic activity towards the oxidation of hydrogen peroxide in alkaline medium. Amperometric detection of hydrogen peroxide in ammonium buffer pH 9.0 is possible at the operation potential of +0.50V vs Ag/AgCl instead of over +0.80V vs Ag/AgCl with unmodified electrode. Linear concentration range between 0.50-138ppm of hydrogen peroxide was obtained with a detection limit of 0.28ppm
Atmosphere
No full textThe atmosphere is the receiver of many by-products of our society, such us products of combustion of fossil fuels and industrial manufacturing. The studies on chemical pathways of trace atmospheric species are often complexes since the life cycles of such species are linked to an elaborate system of chemical and physical processes. As a result, it is possible that
a perturbation in the concentration of one species leads to significant changes in quantity and lifetimes of other trace species; the feedback could also amplify or damp the original perturbation. Trace species can exhibit an enormous range of spatial and temporal variability, depending on their lifetime in the atmosphere. Relatively long-lived species are usually uniformly distributed: in this case strategically located sampling sites around the globe could be adequate to characterize their spatial distribution and temporal trend. As species lifetimes become shorter, their spatial and temporal distributions become more variable
Cyclodextrin-based potentiometric sensors for Metformin
No full text-Cyclodextrins ( -CDs) based polyvinylchloride (PVC) electrodes were fabricated and applied for potentiometric determination of Metformin (Mf). Matrix composition optimization was done referring the effect of type and content of -CDs, anionic sites and plasticizer. Electrodes incorporated with 2-hydroxypropyl- -CD as sensing ionophore, sodium tetrakis (4-florophenyl) borate (NaTFPB) as anionic site and o-nitrophenyloctyl ether (o-NPOE)
as electrode plasticizer showed the best electroanalytical performances. The fabricated electrodes worked satisfactorily in the concentration range from 10-6 to 10-2 mol L-1 with detection limit reaching 7×10-6 mol L-1 and fast response time of 8 s. The developed sensors possessed improved selectivity and have been successfully applied for the potentiometric
determination of Mf in pharmaceutical formulation. Comparison of the obtained results with those provided by reference method revealed adequate accuracy for control assay
Carbon electrode materials in the analysis of vitamins with antioxidant properties
No full textDisertační práce je zaměřena na elektrochemické stanovení klinicky významných antioxidantů (polyfenolů, vitamínu C a vitamínů rozpustných v tucích A a E). Z tohoto důvodu je celá práce rozdělena do tří základních celků. Jednotlivé celky obsahují teoretickou část, výsledky laboratorních pokusů a diskuzi. První část popisuje stanovení
celkového obsahu polyfenolických látek a celkovou antioxidační kapacitu u vybraných vzorků potravin pomocí amperometrického biosenzoru. Pozornost je věnována laboratorní přípravě zmíněného čidla, konstrukci elektrického převodníku, výběru biologicky aktivní složky, její imobilizaci na povrch pracovní elektrody a hledání optimálních podmínek pro měření. Využití tohoto elektrochemického biosenzoru je demonstrován na analýzách reálných vzorků. Druhá část je zaměřena na zlepšení citlivosti amperometrického stanovení
vitaminu C (kyselina askorbová), na uhlíkových pastových elektrodách modifikovaných uhlíkovými nano-trubičkami nebo mediátory oxidy kovů. Citlivost vitaminu C k vnějším vlivům a jeho přirozená degradace ve vzorku potravin lze právě účinně elektrochemicky monitorovat, což je popsáno v této kapitole. Závěrečná část popisuje možnosti elektrochemického stanovení lipofilních vitamínů v ryze vodných elektrolytech po předchozí extrakci do elektrodového materiálu. Důraz je kladen především na optimalizaci extrakce (výběr vhodné pastové
kapaliny, optimální obsah vybraného pojiva, nalezení vhodného organického rozpouštědla mísitelného s vodou, atd.), která bývá v elektrochemické analýze minimálně využívána.The dissertation is focused on electrochemical analysis of clinically important antioxidants (polyphenols, vitamin C and fat-soluble vitamins A and E). It is divided into three basic units. The individual sections contain a theoretical part, results of measured experiments and discussion. The first part describes an amperometric biosensor for the determination of total polyphenolic content and antioxidant capacity
of selected foods. The attention is paid to the laboratory preparation of biosensor, design of electrical transducer, selection biologically active component, its immobilization on the surface of the working electrode and searching the optimal conditions for measurement. The application of the electrochemical sensor is demonstrated in various analyzes of real samples. The second part focuses on improving the sensitivity in electrochemical determination of vitamin C (ascorbic acid) at carbon paste electrode modified by carbon nanotubes or metal oxide mediators. The research of the sensitivity of vitamin C to
external influences and its natural degradation in a food sample can also be electrochemically measured, which is also included in this chapter. The third final part is mainly dedicated to the determination of lipophilic vitamins in aqueous electrolytes after their extraction into electrode material. The emphasis is placed especially on the extraction of vitamins (selection of suitable paste liquid, the optimum paste liquid content, finding a suitable aqueous miscible organic
solvent for extraction, etc.) which is in electrochemical analysis minimally practiced.Fakulta chemicko-technologickáDokončená práce s úspěšnou obhajobo
Some New Approaches to the Characterization of the Carbon Paste Electrodes
No full textUhlíkové pastové elektrody mají dvě hlavní výhody: jejich povrch lze snadno reprodukovatelně obnovovat a dále, je možné je modifikovat v objemu za účelem získání specifických senzorů. Příprava těchto elektrod však závisí jednak na použitých materiálech, tedy na uhlíkovém prášku i na olejovém médiu, jednak na jejich vzájemném poměru. To umožňuje velikou variabilitu vlastností, současně ale otázka charakterizace těchto elektrod je velmi významná. Bylo zjištěno, že graf závislosti odporu elektrody na jejím složení je ve tvaru dvou protínajících se přímek. K vysvětlení této závislosti byl navržen, testován a diskutován model vycházející z představy těsně uspořádaných koulí (známé z krystalografie). Další způsob charakterizace těchto elektrod je založen na interpretaci cyklických voltamogramů nějakého dobře reverzibilního systému. Obě tyto metody jsou kompatibilní, navíc umožňují vysvětlení dalších jevů spojených s morfologií a se stárnutím těchto elektrod
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