| 1. |
- Ahmerkamp, Soeren, et al.
(författare)
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Simultaneous visualization of flow fields and oxygen concentrations to unravel transport and metabolic processes in biological systems
- 2022
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Ingår i: CELL REPORTS METHODS. - : Elsevier. - 2667-2375. ; 2:5
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Tidskriftsartikel (refereegranskat)abstract
- From individual cells to whole organisms, O-2 transport unfolds across micrometer- tomillimeter-length scales and can change within milliseconds in response to fluid flows and organismal behavior. The spatiotemporal complexity of these processes makes the accurate assessment of O-2 dynamics via currently availablemethods difficult or unreliable. Here, we present "sensPIV,'' a method to simultaneously measure O-2 concentrations and flow fields. By tracking O-2-sensitive microparticles in flow using imaging technologies that allow for instantaneous referencing, wemeasuredO(2) transportwithin (1) microfluidic devices, (2) sinkingmodel aggregates, and (3) complex colony-forming corals. Through the use of sensPIV, we find that corals use ciliarymovement to link zones of photosynthetic O-2 production to zones of O-2 consumption. SensPIV can potentially be extendable to study flow-organism interactions across many life-science and engineering applications.
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| 2. |
- Botte, Ermes, et al.
(författare)
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Size-related variability of oxygen consumption rates in individual human hepatic cells
- 2024
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry. - 1473-0197 .- 1473-0189.
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Tidskriftsartikel (refereegranskat)abstract
- Accurate descriptions of the variability in single-cell oxygen consumption and its size-dependency are key to establishingmore robust tissue models. By combining microfabricated devices with multiparameter identification algorithms, wedemonstrate that single human hepatocytes exhibit an oxygen level-dependent consumption rate and that their maximaloxygen consumption rate is significantly lower than that of typical hepatic cell cultures. Moreover, we found that clusters oftwo or more cells competing for a limited oxygen supply reduced their maximal consumption rate, highlighting their abilityto adapt to local resource availability and the presence of nearby cells. We used our approach to characterize the covarianceof size and oxygen consumption rate within a cell population, showing that size matters, since oxygen metabolism covarieslognormally with cell size. Our study paves the way for linking the metabolic activity of single human hepatocytes to theirtissue- or organ-level metabolism and describing its size-related variability through scaling laws.
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| 3. |
- Cui, Yuan, 1995-, et al.
(författare)
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Combined measurement of oxygen respiration and dry mass in single diatom cells
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Oxygen (O₂) is a universal proxy for biological metabolism and is widely used to track cellular energy expenditure under steady-state conditions or external disturbances. Thus O₂ metabolism has been an important factor in studying unifying ecosystem theories, such as the metabolic scaling theory, indicating that metabolic rates scale to a certain power of an organism's mass, spanning over 21 orders of magnitude. In many biological systems, this interspecific exponent is close to 3/4, a relationship known as Kleiber's law. Understanding the metabolic scaling of microorganisms is crucial for predicting their ecological roles and responses to environmental changes. However, measuring the O₂ metabolism of individual microorganisms has been challenging due to technical limitations, restricting high-throughput investigations of cell-to-cell heterogeneity. This study investigates the metabolic scaling of three diatom species - Thalassiosira rotula (T. rotula), Ditylum brightwellii (D. brightwellii), and Coscinodiscus species (Coscinodiscus sp.) - by employing a micro-respiration chamber and advanced imaging techniques. The micro-respiration chamber is made of glass and consist of gas-tight microwells with immobilized O₂-sensitive optodes to isolate single cells and measure their respiration. The optical properties of the chamber enable for combining O₂ respiration measurements with quantitative phase imaging (QPI), a non-invasive microscopy technique that measures cellular dry mass through optical path differences (OPD). We quantified respiration rates and dry mass for individual cells, uncovering interspecific and distinct intraspecific metabolic scaling patterns. Among the three measured species, T. rotula and Coscinodiscus sp. exhibited smaller intraspecific scaling exponents than D. brightwellii, highlighting the influence of morphological and physiological traits on metabolic efficiency. The interspecific scaling pattern aligned with the general metabolic scaling theory, supporting the 3/4 scaling exponent expected by theory. These proof of concept results demonstrate the feasibility of integrating respiration and dry mass measurements into scaling framework for single-cells, and highlights the importance of conducting further species-specific analyses to account for unique morphological and physiological traits that can influence metabolic rates. Our study thus provides a foundation for future research into the effect of environmental impacts on the metabolic scaling of marine diatoms, essential phytoplankton species within marine biogeochemical cycles.
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| 4. |
- Cui, Yuan, 1995-, et al.
(författare)
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SlipO2Chip- single-cell respiration under tuneable environments
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In disciplines like toxicology and pharmacology, oxygen (O2) respiration is a universal metric for evaluating the effects of chemicals across various model systems, including mammalian and microalgal cells. However, for these cells the common practice is to segregate populations into control and exposure groups, which assumes direct equivalence in their responses and does not take into account cellular heterogeneity. This lack of resolution impedes our ability to precisely investigate differences among experimental groups in rare samples. To overcome this barrier, we introduce SlipO2Chip, an innovative microfluidic platform tailored for precisely quantifying single-cell O2 respiration in the coordinated absence and presence of chemical solutes. Constructed in glass, SlipO2Chip comprises a wet-etched channel plate on the top and a dry-etched microwell plate at the bottom. The microwells are coated with Pt(II) meso-Tetra(pentafluorophenyl)porphine (PtTFPP), an O2 sensing optode material and an O2-independent reference dye. A custom 3D-printed holder facilitates the controlled horizontal movement (‘slipping’) of the channel plate over the microwell plate, thereby establishing or disrupting the fluid path over microwells. Collectively, these design elements enable the immobilization of cells in microwells, their exposure to controlled fluid flows, the coordinated opening and closing of microwells and repeated measurements of single-cell O2 respiration. Uniquely, by sequentially executing opening and closing it becomes possible to measure single-cell respiration prior to and after exposure to chemical solutes. In a proof-of-concept application, we utilized SlipO2Chip to measure the impact of increasing exposures of the marine bacterial signal 2-heptyl-4-quinolone (HHQ) on the dark respiration of the diatom Ditylum brightwellii at single-cell resolution. Results revealed a dose-dependent decrease in per-cell O2 dark respiration, with a maximum reduction of 40.2% observed at HHQ concentrations exceeding 35.5 µM, and a half-maximal effective concentration (EC50) of 5.8 µM, consistent with that obtained via conventional bulk respiration methods. The ability of SlipO2Chip to sequentially assess the effects of chemical substances on single-cell O2 metabolism is advantageous for research where sample volumes are limited, such as clinical biopsies, studies involving rare microbial isolates, and toxicological studies wanting to address exposure effects while accounting for cell-to-cell variability.
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| 5. |
- Steininger, Fabian, et al.
(författare)
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Imaging Sample Acidification Triggered by Electrochemically Activated Polyaniline
- 2022
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 94:40, s. 13647-13651
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, we demonstrate 2D acidification of samples at environmental and physiological pH with an electrochemically activated polyaniline (PANI) mesh. A novel sensor–actuator concept is conceived for such a purpose. The sample is sandwiched between the PANI (actuator) and a planar pH optode (sensor) placed at a very close distance (∼0.50 mm). Upon application of a mild potential to the mesh, in contrast to previously reported acidification approaches, PANI releases a significant number of protons, causing an acid–base titration in the sample. This process is monitored in time and space by the pH optode, providing chemical imaging of the pH decrease along the dynamic titration via photographic acquisition. Acidification of samples at varying buffer capacity has been investigated: the higher the buffer capacity, the more time (and therefore proton charge) was needed to reach a pH of 4.5 or even lower. Also, the ability to map spatial differences in buffer capacity within a sample during the acid–base titration was unprecedentedly proven. The sensor–actuator concept could be used for monitoring certain analytes in samples that specifically require acidification pretreatment. Particularly, in combination with different optodes, dynamic mapping of concentration gradients will be accessible in complex environmental samples ranging from roots and sediments to bacterial aggregates.
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| 6. |
- Wiorek, Alexander, et al.
(författare)
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Imaging of CO2 and Dissolved Inorganic Carbon via Electrochemical Acidification–Optode Tandem
- 2023
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Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 8:7, s. 2843-2851
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Tidskriftsartikel (refereegranskat)abstract
- Dissolved inorganic carbon (DIC) is a key component of the global carbon cycle and plays a critical role in ocean acidification and proliferation of phototrophs. Its quantification at a high spatial resolution is essential for understanding various biogeochemical processes. We present an analytical method for 2D chemical imaging of DIC by combining a conventional CO2 optode with localized electrochemical acidification from a polyaniline (PANI)-coated stainless-steel mesh electrode. Initially, the optode response is governed by local concentrations of free CO2 in the sample, corresponding to the established carbonate equilibrium at the (unmodified) sample pH. Upon applying a mild potential-based polarization to the PANI mesh, protons are released into the sample, shifting the carbonate equilibrium toward CO2 conversion (>99%), which corresponds to the sample DIC. It is herein demonstrated that the CO2 optode–PANI tandem enables the mapping of free CO2 (before PANI activation) and DIC (after PANI activation) in complex samples, providing high 2D spatial resolution (approx. 400 μm). The significance of this method was proven by inspecting the carbonate chemistry of complex environmental systems, including the freshwater plant Vallisneria spiralis and lime-amended waterlogged soil. This work is expected to pave the way for new analytical strategies that combine chemical imaging with electrochemical actuators, aiming to enhance classical sensing approaches via in situ (and reagentless) sample treatment. Such tools may provide a better understanding of environmentally relevant pH-dependent analytes related to the carbon, nitrogen, and sulfur cycles.
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