Search Results (5)

Deep hot dry rock (HDR) geothermal energy is a widespread and sustainable renewable energy that could be extracted for the decarbonisation of electricity generation. Measurements are essential for hydraulic fracturing in HDR monitoring, which can be used for assessing the current state and predicting the future performance of geothermal systems. However, a major challenge is that it is difficult to implement hydraulic fracturing for HDR under high-temperature and high-pressure (HTHP) conditions. Similarly, it is hard to conduct laboratory-scale hydraulic fracturing experiments under HTHP due to the sealing failure of injection pipes in boreholes. Therefore, in this paper, we proposed a novel sealing technique by using a wedge-shaped structure for sealing injection pipes under HTHP environments. By conducting numerical simulations and experimental verifications, we discovered that (1) compression stress should be applied on the seal to achieve pre-sealing. Specifically, a compression displacement of between 2 mm and 6 mm is suggested. (2) Copper material with good ductility, high-temperature bearing performance, and excellent thermal expansion is preferred for manufacturing the seal components. (3) Heating-induced thermal expansion of sealing is conducive to re-sealing rocks. Full article

One key application of organ-on-chip systems is the examination of drug transport and absorption through native cell barriers such the blood–brain barrier. To overcome previous hurdles related to the transferability of existing static cell cultivation protocols and polydimethylsiloxane (PDMS) as the construction material, a chip platform with key innovations for practical use in drug-permeation testing is presented. First, the design allows for the transfer of barrier-forming tissue into the microfluidic system after cells have been seeded on porous polymer or Si3N4 membranes. From this, we can follow highly reproducible models and cultivation protocols established for static drug testing, from coating the membrane to seeding the cells and cell analysis. Second, the perfusion system is a microscopable glass chip with two fluid compartments with transparent embedded electrodes separated by the membrane. The reversible closure in a clamping adapter requires only a very thin PDMS sealing with negligible liquid contact, thereby eliminating well-known disadvantages of PDMS, such as its limited usability in the quantitative measurements of hydrophobic drug molecule concentrations. Equipped with tissue transfer capabilities, perfusion chamber inertness and air bubble trapping, and supplemented with automated fluid control, the presented system is a promising platform for studying established in vitro models of tissue barriers under reproducible microfluidic perfusion conditions. Full article

Aims: Irreversible electroporation is an ablation technique being adapted for the treatment of atrial fibrillation. Currently, there are many differences reported in the in vitro and pre-clinical literature for the effective voltage threshold for ablation. The aim of this study is a direct comparison of different cell types within the cardiovascular system and identification of optimal voltage thresholds for selective cell ablation. Methods: Monophasic voltage pulses were delivered in a cuvette suspension model. Cell viability and live–dead measurements of three different neuronal lines, cardiomyocytes, and cardiac fibroblasts were assessed under different voltage conditions. The immediate effects of voltage and the evolution of cell death was measured at three different time points post ablation. Results: All neuronal and atrial cardiomyocyte lines showed cell viability of less than 20% at an electric field of 1000 V/cm when at least 30 pulses were applied with no significant difference amongst them. In contrast, cardiac fibroblasts showed an optimal threshold at 1250 V/cm with a minimum of 50 pulses. Cell death overtime showed an immediate or delayed cell death with a proportion of cell membranes re-sealing after three hours but no significant difference was observed between treatments after 24 h. Conclusions: The present data suggest that understanding the optimal threshold of irreversible electroporation is vital for achieving a safe ablation modality without any side-effect in nearby cells. Moreover, the evolution of cell death post electroporation is key to obtaining a full understanding of the effects of IRE and selection of an optimal ablation threshold. Full article

In Part I, by using ³¹P-NMR spectroscopy, we have shown that isolated granum and stroma thylakoid membranes (TMs), in addition to the bilayer, display two isotropic phases and an inverted hexagonal (H_II) phase; saturation transfer experiments and selective effects of lipase and thermal treatments have shown that these phases arise from distinct, yet interconnectable structural entities. To obtain information on the functional roles and origin of the different lipid phases, here we performed spectroscopic measurements and inspected the ultrastructure of these TM fragments. Circular dichroism, 77 K fluorescence emission spectroscopy, and variable chlorophyll-a fluorescence measurements revealed only minor lipase- or thermally induced changes in the photosynthetic machinery. Electrochromic absorbance transients showed that the TM fragments were re-sealed, and the vesicles largely retained their impermeabilities after lipase treatments—in line with the low susceptibility of the bilayer against the same treatment, as reflected by our ³¹P-NMR spectroscopy. Signatures of H_II-phase could not be discerned with small-angle X-ray scattering—but traces of H_II structures, without long-range order, were found by freeze-fracture electron microscopy (FF-EM) and cryo-electron tomography (CET). EM and CET images also revealed the presence of small vesicles and fusion of membrane particles, which might account for one of the isotropic phases. Interaction of VDE (violaxanthin de-epoxidase, detected by Western blot technique in both membrane fragments) with TM lipids might account for the other isotropic phase. In general, non-bilayer lipids are proposed to play role in the self-assembly of the highly organized yet dynamic TM network in chloroplasts. Full article

By permeabilizing the cell membrane with ultrasound and facilitating the uptake of iron oxide nanoparticles, the magneto-sonoporation (MSP) technique can be used to instantaneously label transplantable cells (like stem cells) to be visualized via magnetic resonance imaging in vivo. However, the effects of MSP on cells are still largely unexplored. Here, we applied MSP to the widely applicable adipose-derived stem cells (ASCs) for the first time and investigated its effects on the biology of those cells. Upon optimization, MSP allowed us to achieve a consistent nanoparticle uptake (in the range of 10 pg/cell) and a complete membrane resealing in few minutes. Surprisingly, this treatment altered the metabolic activity of cells and induced their differentiation towards an osteoblastic profile, as demonstrated by an increased expression of osteogenic genes and morphological changes. Histological evidence of osteogenic tissue development was collected also in 3D hydrogel constructs. These results point to a novel role of MSP in remote biophysical stimulation of cells with focus application in bone tissue repair. Full article