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1.
Int J Artif Organs ; : 3913988241268000, 2024 Aug 21.
Artículo en Inglés | MEDLINE | ID: mdl-39166435

RESUMEN

Thromboembolic complications still arise on blood contacting surfaces. Surface charge and topography influence the subsequent deposition of proteins and platelets, potentially leading to thrombi. Research showed a correlation of surface charge and nanoscale roughness, and a negative surface charge as well as a smooth surface finish are associated with lower thrombogenicity. The aim of this study was to compare the platelet adhesion on titanium with different nanoscale roughnesses and to examine if those roughness variations caused a change in surface charge. Titanium samples were polished and roughened to four different nanoscale roughness levels. Platelet adhesion (covered surface area (CSA), N = 8) was tested in flow chambers with human whole blood using fluorescence imaging. ζ-potential was measured over a broad range of pH-values and interpolated to obtain the ζ-potential for pHBlood (7.4). Platelet adhesion tests were evaluated in terms of p-values and the Wilcoxon test effect size and the trend of the ζ-potential at pHBlood and the CSA was compared. Ra-values ranged between 35 (polished) and 156 nm. Regarding platelet adhesion, the polished sample showed the lowest mean CSA with a medium or strong effect size compared to the roughened samples. The interpolated ζ-potentials for pHBlood follow a similar trend as the CSA, with the lowest ζ-potential measured for the polished surface. These findings suggest that the decreasing ζ-potential due to lower nanoscale roughness might be an additional explanation for the improved hemocompatibility besides the smoother topography.

2.
Heliyon ; 10(5): e26550, 2024 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-38463800

RESUMEN

Microfluidic blood flow models have been instrumental to study the functions of blood platelets in hemostasis and arterial thrombosis. However, they are not suited to investigate the interactions of platelets with the foreign surfaces of medical devices such as stents, mainly because of the dimensions and geometry of the microfluidic channels. Indeed, the channels of microfluidic chips are usually rectangular and rarely exceed 50 to 100 µm in height, impairing the insertion of clinically used stents. To fill this gap, we have developed an original macrofluidic flow system, which precisely reproduces the size and geometry of human vessels and therefore represents a biomimetic perfectly suited to insert a clinical stent and study its interplay with blood cells. The system is a circular closed loop incorporating a macrofluidic flow chamber made of silicone elastomer, which can mimic the exact dimensions of any human vessel, including the coronary, carotid or femoral artery. These flow chambers allow the perfect insertion of stents as they are implanted in patients. Perfusion of whole blood anticoagulated with hirudin through the device at relevant flow rates allows one to observe the specific accumulation of fluorescently labeled platelets on the stent surface using video-microscopy. Scanning electron microscopy revealed the formation of very large thrombi composed of tightly packed activated platelets on the stents.

3.
Thromb Res ; 234: 134-141, 2024 02.
Artículo en Inglés | MEDLINE | ID: mdl-38218110

RESUMEN

AIM: To investigate the role of pentraxin 3 (PTX3) in atherosclerotic disease progression and plaque destabilization, as well as in coronary restenosis after directional coronary atherectomy (DCA). MATERIALS AND METHODS: PTX3 contents of early and advanced atherosclerotic lesions of the aorta obtained at autopsy were determined by ELISA and Western blot. Also, coronary plaques of patients with acute coronary syndrome (ACS) or stable angina pectoris (SAP) obtained by DCA were analyzed by immunohistochemistry for PTX3. The effects of PTX3 on smooth muscle cells (SMCs) and thrombogenesis were investigated with cultured human coronary artery SMCs and a flow chamber system, respectively. RESULTS: Advanced atherosclerotic lesions contained a significantly larger amount of PTX3 than early lesions (ELISA: 9.96 ± 2.77 ng/100 mg tissue, n = 8 vs 0.24 ± 0.18 ng/100 mg tissue, n = 6, P = 0.0097). Also, ACS plaques contained a significantly larger amount of PTX3 than SAP plaques (PTX3 immunohistochemistry-positive area percentage: 2.88 ± 0.53 %, n = 22 vs 0.67 ± 0.27 %, n = 23, P = 0.0009). Curiously, the patients who would remain free of post-DCA restenosis (n = 19) had plaques with a significantly higher PTX3 immunohistochemistry-positive area percentage than those who would develop restenosis (n = 12) (2.32 ± 0.49 % vs 0.49 ± 0.17 %, P = 0.002). In the mechanistic part of the study, PTX3 inhibited SMC proliferation and migration. PTX3 also inhibited platelet thrombus formation in the condition simulating arterial blood flow. CONCLUSIONS: PTX3 is increased in advanced (vs early) atherosclerotic lesions and unstable (vs stable) coronary plaques. The inhibitory effects of PTX3 on SMCs and thrombogenesis suggest that intraplaque PTX3 might have atheroprotective effects.


Asunto(s)
Síndrome Coronario Agudo , Aterosclerosis , Enfermedad de la Arteria Coronaria , Placa Aterosclerótica , Componente Amiloide P Sérico , Trombosis , Humanos , Proteína C-Reactiva/análisis , Trombosis/etiología , Trombosis/prevención & control , Progresión de la Enfermedad
4.
Sensors (Basel) ; 23(23)2023 Nov 30.
Artículo en Inglés | MEDLINE | ID: mdl-38067919

RESUMEN

Optical sensors excel in performance but face efficacy challenges when submerged due to potential surface colonization, leading to signal deviation. This necessitates robust solutions for sustained accuracy. Protein and microorganism adsorption on solid surfaces is crucial in antibiofilm studies, contributing to conditioning film and biofilm formation. Most studies focus on surface characteristics (hydrophilicity, roughness, charge, and composition) individually for their adhesion impact. In this work, we tested four materials: silica, titanium dioxide, aluminum oxide, and parylene C. Bovine Serum Albumin (BSA) served as the biofouling conditioning model, assessed with X-ray photoelectron spectroscopy (XPS). Its effect on microorganism adhesion (modeled with functionalized microbeads) was quantified using a shear stress flow chamber. Surface features and adhesion properties were correlated via Principal Component Analysis (PCA). Protein adsorption is influenced by nanoscale roughness, hydrophilicity, and likely correlated with superficial electron distribution and bond nature. Conditioning films alter the surface interaction with microbeads, affecting hydrophilicity and local charge distribution. Silica shows a significant increase in microbead adhesion, while parylene C exhibits a moderate increase, and titanium dioxide shows reduced adhesion. Alumina demonstrates notable stability, with the conditioning film minimally impacting adhesion, which remains low.


Asunto(s)
Óxido de Aluminio , Dióxido de Silicio , Óxido de Aluminio/química , Dióxido de Silicio/química , Propiedades de Superficie , Albúmina Sérica Bovina/química , Titanio/química , Adsorción
5.
Biotechnol Bioeng ; 120(12): 3518-3528, 2023 12.
Artículo en Inglés | MEDLINE | ID: mdl-37641171

RESUMEN

Terrestrial cyanobacteria grow as phototrophic biofilms and offer a wide spectrum of interesting products. For cultivation of phototrophic biofilms different reactor concepts have been developed in the last years. One of the main influencing factors is the surface material and the adhesion strength of the chosen production strain. In this work a flow chamber was developed, in which, in combination with optical coherence tomography and computational fluid dynamics simulation, an easy analysis of adhesion forces between different biofilms and varied surface materials is possible. Hereby, differences between two cyanobacteria strains and two surface materials were shown. With longer cultivation time of biofilms adhesion increased in all experiments. Additionally, the content of extracellular polymeric substances was analyzed and its role in surface adhesion was evaluated. To test the comparability of obtained results from the flow chamber with other methods, analogous experiments were conducted with a rotational rheometer, which proved to be successful. Thus, with the presented flow chamber an easy to implement method for analysis of biofilm adhesion was developed, which can be used in future research for determination of suitable combinations of microorganisms with cultivation surfaces on lab scale in advance of larger processes.


Asunto(s)
Biopelículas , Cianobacterias , Matriz Extracelular de Sustancias Poliméricas , Hidrodinámica
6.
Thromb Res ; 229: 99-106, 2023 09.
Artículo en Inglés | MEDLINE | ID: mdl-37421684

RESUMEN

It is crucial for hemostasis that platelets are rapidly recruited to the site of vascular injury by the adhesive ligand von Willebrand factor (VWF) multimers. The metalloproteinase ADAMTS13 regulates this hemostatic activity by proteolytically reducing the size of VWF and its proteolytic kinetics has been investigated by biochemical and single-molecule biophysical methods. However, how ADAMTS13 cleaves VWF in flowing blood remains poorly defined. To investigate the force-induced VWF cleavage, VWF A1A2A3 tridomains were immobilized and subjected to hydrodynamic forces in the presence of ADAMTS13. We demonstrated that the cleavage of VWF A1A2A3 by ADAMTS13 exhibited biphasic kinetics governed by shear stress, but not shear rate. By fitting data to the single-molecule Michaelis-Menten equation, the proteolytic constant kcat of ADAMTS13 had two distinct states. The mean proteolytic constant of the fast state (kcat-fast) was 0.005 ± 0.001 s-1, which is >10-fold faster than the slow state (kcat-slow = 0.0005 ± 0.0001 s-1). Furthermore, proteolytic constants of both states were regulated by shear stress in a biphasic manner, independent of the solution viscosity, indicating that the proteolytic activity of ADAMTS13 was regulated by hydrodynamic force. The findings provide new insights into the mechanism underlying ADAMTS13 cleaving VWF under flowing blood.


Asunto(s)
Hemostasis , Factor de von Willebrand , Plaquetas , Proteína ADAMTS13
7.
Biomolecules ; 13(4)2023 03 24.
Artículo en Inglés | MEDLINE | ID: mdl-37189336

RESUMEN

MAdCAM-1 binds to integrin α4ß7, which mediates the rolling and arrest of circulating lymphocytes upon the vascular endothelia during lymphocytic homing. The calcium response by adhered lymphocytes is a critical event for lymphocyte activation and subsequent arrest and migration under flow. However, whether the interaction of integrin α4ß7 /MAdCAM-1 can effectively trigger the calcium response of lymphocytes remains unclear, as well as whether the fluid force affects the calcium response. In this study, we explore the mechanical regulation of integrin α4ß7-induced calcium signaling under flow. Flou-4 AM was used to examine the calcium response under real-time fluorescence microscopy when cells were firmly adhered to a parallel plate flow chamber. The interaction between integrin α4ß7 and MAdCAM-1 was found to effectively trigger calcium signaling in firmly adhered RPMI 8226 cells. Meanwhile, increasing fluid shear stress accelerated the cytosolic calcium response and enhanced signaling intensity. Additionally, the calcium signaling of RPMI 8226 activated by integrin α4ß7 originated from extracellular calcium influx instead of cytoplasmic calcium release, and the signaling transduction of integrin α4ß7 was involved in Kindlin-3. These findings shed new light on the mechano-chemical mechanism of calcium signaling in RPMI 8226 cells induced by integrin α4ß7.


Asunto(s)
Calcio , Integrinas , Calcio/metabolismo , Señalización del Calcio , Integrinas/metabolismo , Linfocitos/metabolismo , Fenómenos Mecánicos , Humanos
8.
Environ Monit Assess ; 195(6): 669, 2023 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-37184777

RESUMEN

Microplastics (MPs) in the environment typically age. However, the influence of aged MPs on the adsorption of antibiotics in soil remains unknown. In this study, the adsorption behavior of trimethoprim (TMP) on soil and soil containing aged polyamide (PA) was investigated using batch and stirred flow chamber experiments. The adsorption of TMP on the tested soil with and without PA was fast, with the ka values ranging from 50.5 to 55.6 L (mg min)-1. The adsorption of TMP on aged PA was more than 20 times larger than that on the tested soil, which resulted in an "enrichment effect." Furthermore, aged PA altered the pH of the reaction system, thereby enhancing the adsorption of TMP. Consequently, the Kd values of TMP for soil, soil containing 5%, and 10% aged PA were 5.64, 12.38, and 23.65 L kg-1, respectively. The effect of aged PA on the adsorption of TMP on soil depended on pH values. However, TMP adsorption on soil containing 10% aged PA was constantly higher (p < 0.01) than that on soil with NaCl concentrations ranging from 0 to 50 mmol L-1. These findings provide new insights into the effect of environmental MPs on the fate and transport of antibiotics in soil environments.


Asunto(s)
Microplásticos , Trimetoprim , Trimetoprim/análisis , Suelo , Plásticos , Nylons , Adsorción , Monitoreo del Ambiente , Antibacterianos/análisis
9.
Front Med Technol ; 5: 1149594, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37092024

RESUMEN

Background: Stent is widely regarded as the main treatment for curing cardiovascular diseases such as stenosis. Previous research has revealed that the damage of endothelial cells (EC), i.e., the components of endothelium, during stent implantation, could lead to severe complications, such as restenosis. To prevent restenosis, enhancements have been made to surface biocompatibility to accelerate the stent endothelialization process. Anodization on the Ni-Ti is a simple and efficient surface modification method to improve the biocompatibility of the Ni-Ti stent surfaces by enhancing the surface hydrophilicity, leading to an increase in the EC activities. The EC activity is known to be affected by the blood flow. Flow change by stent structure may result in EC dysfunctions, thereby leading to restenosis. It is thus essential to investigate the EC activities resulting from the anodization on the Ni-Ti surface under flow conditions. Objective: To study the influence of the endothelialization process on the Ni-Ti stent surface through anodization. The EC attachment and morphology on the anodized stent strut were observed under both with and without the flow conditions. Method: A parallel plate flow chamber was designed to generate a constant wall shear stress (WSS) to study the flow effect on the EC behavior. The hydrophilicity of the Ni-Ti stent strut surface was enhanced by a TiO2 layer fabricated via anodization. The EC distribution on the surface of the anodized nitinol stent strut was observed after 24 h of static (without flow) and flow exposure (with flow) experiment. Results: Under the static condition, the EC density on the surface of the anodized Ni-Ti stent strut was higher compared with the control. Under the flow condition, the enhancement of the EC density on the surface of the stent strut with anodization was reduced. The EC demonstrates a long and thin spindle-shaped morphology under the flow condition. Conclusion: Unlike the static condition, the EC is demonstrating a long and thin morphology in response to the flow under the flow condition. By improving the surface hydrophilicity, the anodization could enhance the EC migration onto the strut surface, and subsequently, accelerate the Ni-Ti stent endothelialization process. The improvement of the surface hydrophilicity is lower under the flow conditions when compared with the static conditions.

10.
Methods Mol Biol ; 2626: 277-289, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-36715910

RESUMEN

The Drosophila egg chamber is a powerful system to study epithelial cell collective migration and polarized basement membrane secretion. A strength of this system is the ability to capture these dynamic processes in ex vivo organ culture using high-resolution live imaging. Ex vivo culture also allows acute pharmacological or labeling treatments, extending the versatility of the system. However, many current ex vivo egg chamber culture setups do not permit easy medium exchange, preventing researchers from following individual egg chambers through multiple treatments. Here we present a method to immobilize egg chambers in an easy-to-construct flow chamber that permits imaging of the same egg chamber through repeated solution exchanges. This will allow researchers to take greater advantage of the wide variety of available pharmacological perturbations and other treatments like dyes to study dynamic processes in the egg chamber.


Asunto(s)
Proteínas de Drosophila , Drosophila , Animales , Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Movimiento Celular , Diagnóstico por Imagen , Membrana Basal/metabolismo , Proteínas de Drosophila/metabolismo , Oogénesis
11.
Platelets ; 34(1): 2157805, 2023 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-36631918

RESUMEN

Pharmacological inhibition of the platelet ADP-receptor P2Y12 is a cornerstone in the prevention of atherothrombotic events in adult patients with acute coronary syndrome (ACS). Thienopyridines such as clopidogrel and prasugrel exert their antithrombotic effect by means of active metabolites that irreversibly inhibit P2Y12. Due to the short half-life of these metabolites, a subpopulation of ADP-responsive platelets will form in between dosing. With increased platelet turnover rate or poor patient compliance, the fraction of ADP-responsive platelets will increase, potentially increasing the risk for new thrombotic events. In contrast, the reversible P2Y12 inhibition produced by direct-acting ADP blockers such as ticagrelor and cangrelor inhibit the entire platelet population. In this study, we evaluated the impact of these pharmacological differences on thrombus formation in an ex vivo flow chamber model. A customized image analysis pipeline was used for automatized, large-scale identification and tracking of single platelets incorporated into the thrombus, enabling quantitative analysis of the relative contribution of inhibited and uninhibited platelets to thrombus growth and consolidation. Comparative experiments were conducted using the irreversible and reversible P2Y12 inhibitors prasugrel active metabolite (PAM) and ticagrelor, respectively. Our results show that PAM inhibited thrombus platelet recruitment more gradually than ticagrelor, with a slower onset of inhibition. Further, we show that the presence of a small fraction (<10%) of uninhibited platelets did not abrogate the antithrombotic effect of PAM to any significant extent. Finally, we demonstrate a gradual enrichment of inhibited platelets in the thrombus shell due to selective recruitment of inhibited platelets to the thrombus periphery.


Asunto(s)
Síndrome Coronario Agudo , Inhibidores de Agregación Plaquetaria , Antagonistas del Receptor Purinérgico P2Y , Trombosis , Humanos , Síndrome Coronario Agudo/tratamiento farmacológico , Plaquetas/metabolismo , Fibrinolíticos/uso terapéutico , Inhibidores de Agregación Plaquetaria/uso terapéutico , Clorhidrato de Prasugrel/farmacología , Clorhidrato de Prasugrel/uso terapéutico , Antagonistas del Receptor Purinérgico P2Y/uso terapéutico , Receptores Purinérgicos P2Y12/metabolismo , Trombosis/tratamiento farmacológico , Trombosis/metabolismo , Ticagrelor/farmacología , Ticagrelor/uso terapéutico
12.
Methods Mol Biol ; 2600: 81-90, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-36587091

RESUMEN

Endothelial cell response to shear stress from the flowing blood plays an important role in diseases such as atherosclerosis. It is therefore essential to study how different flow regimes, including both atheroprotective laminar flow and atheropromoting disturbed flow, impact endothelial cell function. Shear stress effects can be studied in vitro using a variety of techniques, each with their own advantages and disadvantages. In this chapter, we describe how to use a parallel plate flow chamber to study the impact of both laminar and disturbed flow on endothelial cell monolayers.


Asunto(s)
Aterosclerosis , Células Endoteliales , Humanos , Células Endoteliales/fisiología , Endotelio Vascular/fisiología , Estrés Mecánico , Células Cultivadas
13.
Front Immunol ; 13: 1016361, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-36275645

RESUMEN

Endothelial cells (ECs) can present antigens to circulating effector memory T cells (TEM) and to regulatory T cells (T regs), triggering antigen-specific extravasation at specific sites where foreign antigens are introduced, e.g. by infection or transplantation. We model human antigen-induced transendothelial migration (TEM) using presentation of superantigen by cultured human dermal microvascular (HDM)ECs to isolated resting human peripheral blood T cell subpopulations or to T effector cells activated in vitro. T cell receptor (TCR)-mediated cytokine synthesis, a common assay of T cell activation by antigen, is modulated by antigen-independent signals provided by various positive or negative costimulator proteins (the latter known as checkpoint inhibitors) expressed by antigen presenting cells, including ECs. We report here that some EC-expressed costimulators also modulate TCR-TEM, but effects differ between TEM and cytokine production and among some T cell types. Blocking EC LFA-3 interactions with TEM CD2 boosts TEM but reduces cytokine production. Blocking EC ICOS-L interactions with TEM CD28 (but not ICOS) reduces both responses but these involve distinct CD28-induced signals. Activated CD4+ T effector cells no longer undergo TCR-TEM. Engagement of T cell CD28 by EC ICOS-L increases TCR-TEM by activated CD8 effectors while engagement of OX40 promotes TCR-TEM by activated CD4 T regs. B7-H3 mostly affects TEM of resting TEM and some checkpoint inhibitors affect cytokine synthesis or TEM depending upon subtype. Our data suggest that blockade or mimicry of costimulators/checkpoint inhibitors in vivo, clinically used to modulate immune responses, may act in part by modulating T cell homing.


Asunto(s)
Antígenos CD28 , Células Endoteliales , Humanos , Células Endoteliales/metabolismo , Memoria Inmunológica , Receptores de Antígenos de Linfocitos T/metabolismo , Superantígenos , Interleucina-2 , Antígenos CD58
14.
Molecules ; 27(17)2022 Sep 04.
Artículo en Inglés | MEDLINE | ID: mdl-36080463

RESUMEN

The aim of this study was to minimize the risk of life-threatening thromboembolism in the ventricle through the use of a new biomimetic heart valve based on metal-polymer composites. Finite volume element simulations of blood adhesion to the material were carried out, encompassing radial flow and the cone and plane test together with determination of the effect of boundary conditions. Both tilt-disc and bicuspid valves do not have optimized blood flow due to their design based on rigid valve materials (leaflet made of pyrolytic carbon). The main objective was the development of materials with specific properties dedicated to contact with blood. Materials were evaluated by dynamic tests using blood, concentrates, and whole human blood. Hemostability tests under hydrodynamic conditions were related to the mechanical properties of thin-film materials obtained from tribological tests. The quality of the coatings was high enough to avoid damage to the coating even as they were exposed up to maximum loading. Analysis towards blood concentrates of the hydrogenated carbon sample and the nitrogen-doped hydrogenated carbon sample revealed that the interaction of the coating with erythrocytes was the strongest. Hemocompatibility evaluation under hydrodynamic conditions confirmed very good properties of the developed coatings.


Asunto(s)
Prótesis Valvulares Cardíacas , Carbono , Humanos , Hidrodinámica , Nitrógeno
15.
Pharmaceutics ; 14(9)2022 Aug 31.
Artículo en Inglés | MEDLINE | ID: mdl-36145584

RESUMEN

Silicone-based medical devices composed of polydimethylsiloxane (PDMS) are widely used all over the human body (e.g., urinary stents and catheters, central venous catheters stents) with extreme clinical success. Nevertheless, their abiotic surfaces, being prone to microorganism colonization, are often involved in infection occurrence. Improving PDMS antimicrobial properties by surface functionalization with biosurfactants to prevent related infections has been the goal of different works, but studies that mimic the clinical use of these novel surfaces are missing. This work aims at the biofunctional assessment of PDMS functionalized with rhamnolipids (RLs), using translational tests that more closely mimic the clinical microenvironment. Rhamnolipids were covalently bonded to PDMS, and the obtained surfaces were characterized by contact angle modification assessment, ATR-FTIR analysis and atomic force microscopy imaging. Moreover, a parallel flow chamber was used to assess the Staphylococcus aureus antibiofilm activity of the obtained surfaces under dynamic conditions, and an in vitro characterization with human dermal fibroblast cells in both direct and indirect characterization assays, along with an in vivo subcutaneous implantation assay in the translational rabbit model, was performed. A 1.2 log reduction in S. aureus biofilm was observed after 24 h under flow dynamic conditions. Additionally, functionalized PDMS lessened cell adhesion upon direct contact, while supporting a cytocompatible profile, within an indirect assay. The adequacy of the biological response was further validated upon in vivo subcutaneous tissue implantation. An important step was taken towards biofunctional assessment of RLs-functionalized PDMS, reinforcing their suitability for medical device usage and infection prevention.

16.
J Funct Biomater ; 13(3)2022 Jul 12.
Artículo en Inglés | MEDLINE | ID: mdl-35893460

RESUMEN

The vascular endothelial cells constitute the innermost layer. The cells are exposed to mechanical stress by the flow, causing them to express their functions. To elucidate the functions, methods involving seeding endothelial cells as a layer in a chamber were studied. The chambers are known as parallel plate, T-chamber, step, cone plate, and stretch. The stimulated functions or signals from endothelial cells by flows are extensively connected to other outer layers of arteries or organs. The coculture layer was developed in a chamber to investigate the interaction between smooth muscle cells in the middle layer of the blood vessel wall in vascular physiology and pathology. Additionally, the microfabrication technology used to create a chamber for a microfluidic device involves both mechanical and chemical stimulation of cells to show their dynamics in in vivo microenvironments. The purpose of this study is to summarize the blood flow (flow inducing) for the functions connecting to endothelial cells and blood vessels, and to find directions for future chamber and device developments for further understanding and application of vascular functions. The relationship between chamber design flow, cell layers, and microfluidics was studied.

17.
Front Microbiol ; 13: 842249, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35668754

RESUMEN

In technical fermentations, filamentous microorganisms are exposed to different forms of mechanical stress, among which shear stress is prevalent in turbulent broths. Whereas small-scale bioreactors allow for realistic turbulent flow field conditions, they are not well-suited to investigate the fungal response to shear stress in more detail, as they only reveal the integral effect of a highly dynamic stress stimulus. Therefore, the widely used model system for producing constant, but rather low shear forces, the parallel plate flow chamber, is extended in this work by adding a backward-facing step (BFS). The BFS induces vortex shedding in the wake of the step and brings out distinct areas of different shear stress levels at the bottom of the chamber where mycelia grow. This allows for a stress-dependent analysis of growing cells using a confocal laser-scanning microscope. As the real stress cannot be measured in the experiment, the wall shear stress is estimated numerically using computational fluid dynamics (CFD). As a first application of the experimental setup, the relative biomass concentration, the relative amount of secretory vesicles and the relative amount of the chosen product glucoamylase produced by the filamentous fungus Aspergillus niger were measured. The obtained area scans show homogeneous mycelia growth in areas of low stress and cloud-like patterns downstream of the predicted flow reattachment length where high shear stress dominates. Quantitative analysis of the time course suggests that the amount of available secretory vesicles inside of A. niger decreases when the shear stress is increased, despite that no significant differences in biomass production could be found. In contrast, the highest level of glucoamylase was reached for intermediate volumetric flow rates, i.e., levels of shear stress.

18.
Int Urol Nephrol ; 54(10): 2695-2702, 2022 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-35366741

RESUMEN

BACKGROUND: Patients with end-stage renal disease (ESRD) receiving hemodialysis (HD) often experience bleeding. However, mechanisms behind this bleeding tendency are incompletely understood but may involve platelet dysfunction. We, therefore, studied platelet-dependent thrombus formation in flowing whole blood inside a microchip coated with collagen, and its association with circulating von Willebrand factor (VWF). METHODS: Blood samples were obtained in 22 patients before and after HD. The area under the 10 min flow pressure curve in a microchip (AUC10) reflecting total platelet thrombogenicity was measured, using the Total Thrombus-formation Analysis System (T-TAS01). AUC10 < 260 indicates platelet dysfunction. VWF activity and antigen in plasma were also assayed. RESULTS: VWF levels were moderately elevated and increased further after HD (P < 0.01 or lower). In contrast, AUC10 before and after HD was < 260 in 17/22 patients and < 130 in 15/22 patients, with no statistically significant difference in pre- vs post-HD measurements, indicating reduced platelet thrombogenicity, but with some variability as 5/22 patients showed normal platelet responsiveness. AUC10 and VWF activity or antigen levels in plasma were not correlated, either before or after HD. CONCLUSIONS: Most ESRD patients display moderate-to-severe platelet dysfunction as assessed by shear-induced platelet-dependent thrombus formation with T-TAS01. HD does not influence platelet function despite HD-induced elevations in VWF. T-TAS01 should be further evaluated as a tool in the assessment of bleeding risk in patients on HD.


Asunto(s)
Fallo Renal Crónico , Trombosis , Pruebas de Coagulación Sanguínea , Plaquetas , Humanos , Fallo Renal Crónico/complicaciones , Fallo Renal Crónico/terapia , Diálisis Renal/efectos adversos , Trombosis/etiología , Factor de von Willebrand
19.
Platelets ; 33(2): 273-277, 2022 Feb 17.
Artículo en Inglés | MEDLINE | ID: mdl-33554695

RESUMEN

Dual antiplatelet therapy (DAPT, aspirin, and a P2Y12 inhibitor) reduces thrombotic events in patients with coronary artery disease (CAD). The T-TAS PL assay uses arterial shear flow over collagen surface, better mimicking in vivo conditions compared to conventional agonist-based platelet function assays, to evaluate platelet function. Here, the platelet function in patients taking DAPT is evaluated with the T-TAS PL assay. In 57 patients with CAD, taking DAPT ≥7 days (n = 22 for clopidogrel, n = 15 for prasugrel, n = 20 for ticagrelor), T-TAS PL assessments were performed in duplicate, and expressed as area under the flow pressure curve within a 10-minute period (AUC10). The duplicate measurements were strongly correlated (r = 0.90, p < .001), with an intra-assay coefficient of variation (CV) of 11,5%. For clopidogrel, the median AUC10 was 11.5 (IQR5.9-41.8), for prasugrel 28.8 (IQR10.3-37.6), and for ticagrelor 8.9 (IQR 6.4-10.9). All measurements were below the AUC10 cutoff of 260 measured in healthy volunteers, suggesting excellent discrimination of DAPT-treated and untreated persons. The new T-TAS PL assay demonstrated complete discrimination of platelet function in patients on DAPT based on an established cutoff. Ticagrelor showed lower levels of platelet function and a more uniform response compared to prasugrel and clopidogrel.


Asunto(s)
Plaquetas/metabolismo , Pruebas de Función Plaquetaria/métodos , Trombosis/metabolismo , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad
20.
Biomolecules ; 11(11)2021 11 19.
Artículo en Inglés | MEDLINE | ID: mdl-34827725

RESUMEN

Microbial biofilms formed by pathogenic and antibiotic-resistant microorganisms represent a serious threat for public health in medicine and many industrial branches. Biofilms are involved in many persistent and chronic infections, the biofouling of water and food contamination. Therefore, current research is involved in the development of new treatment strategies. Biofilm is a complex system, and thus all aspects of the measurement and monitoring of its growth and eradication in various conditions, including static and dynamic flow, are issues of great importance. The antibiofilm character of rhamnolipid mixtures produced by four Pseudomonas aeruginosa strains was studied under different conditions. For this purpose, the biofilm of opportunistic pathogen Trichosporon cutaneum was used and treated under static conditions (microscope glass coverslip in a Petri dish) and under dynamic conditions (a single-channel flow cell). The results show that the biological activity of rhamnolipids depends both on their properties and on the conditions of the biofilm formation. Therefore, this aspect must be taken into account when planning the experimental or application design.


Asunto(s)
Basidiomycota , Glucolípidos , Biopelículas
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