scholarly journals Cultivation of hierarchical 3D scaffolds inside a perfusion bioreactor: scaffold design and finite-element analysis of fluid flow

2021 ◽  
Vol 3 (12) ◽  
Author(s):  
Kaylie Sampson ◽  
Songmi Koo ◽  
Carter Gadola ◽  
Anastasiia Vasiukhina ◽  
Aditya Singh ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Perfusion Bioreactor ◽  
Osteoporotic Bone ◽  
Scaffold Design ◽  
Culture Dish ◽  
Element Analysis ◽  
3D Scaffolds ◽  
Tissue Culture Dish ◽  
Thermally Induced ◽  
Bone Nonunion

AbstractThe use of porous 3D scaffolds for the repair of bone nonunion and osteoporotic bone is currently an area of great interest. Using a combination of thermally-induced phase separation (TIPS) and 3D-plotting (3DP), we have generated hierarchical 3DP/TIPS scaffolds made of poly(lactic-co-glycolic acid) (PLGA) and nanohydroxyapatite (nHA). A full factorial design of experiments was conducted, in which the PLGA and nHA compositions were varied between 6‒12% w/v and 10‒40% w/w, respectively, totaling 16 scaffold formulations with an overall porosity ranging between 87%‒93%. These formulations included an optimal scaffold design identified in our previous study. The internal structures of the scaffolds were examined using scanning electron microscopy and microcomputed tomography. Our optimal scaffold was seeded with MC3T3-E1 murine preosteoblastic cells and subjected to cell culture inside a tissue culture dish and a perfusion bioreactor. The results were compared to those of a commercial CellCeram™ scaffold with a composition of 40% β-tricalcium phosphate and 60% hydroxyapatite (β-TCP/HA). Media flow within the macrochannels of 3DP/TIPS scaffolds was modeled in COMSOL software in order to fine tune the wall shear stress. CyQUANT DNA assay was performed to assess cell proliferation. The normalized number of cells for the optimal scaffold was more than twofold that of CellCeram™ scaffold after two weeks of culture inside the bioreactor. Despite the substantial variability in the results, the observed improvement in cell proliferation upon culture inside the perfusion bioreactor (vs. static culture) demonstrated the role of macrochannels in making the 3DP/TIPS scaffolds a promising candidate for scaffold-based tissue engineering.

scholarly journals An Improved Transwell Design for Microelectrode Ion-Flux Measurements

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 273
Author(s):  
Boris Buchroithner ◽  
Pavel Spurný ◽  
Sandra Mayr ◽  
Johannes Heitz ◽  
Dmitry Sivun ◽  
...  
Keyword(s):  
Umbilical Vein ◽  
Cell Monolayer ◽  
Three Dimensional ◽  
Cellular Membrane ◽  
Ion Flux ◽  
Direct Access ◽  
Cell Contact ◽  
Culture Dish ◽  
Tissue Culture Dish ◽  
Transwell System

The microelectrode ion flux estimation (MIFE) is a powerful, non-invasive electrophysiological method for cellular membrane transport studies. Usually, the MIFE measurements are performed in a tissue culture dish or directly with tissues (roots, parts of the plants, and cell tissues). Here, we present a transwell system that allows for MIFE measurements on a cell monolayer. We introduce a measurement window in the transwell insert membrane, which provides direct access for the cells to the media in the upper and lower compartment of the transwell system and allows direct cell-to-cell contact coculture. Three-dimensional multiphoton lithography (MPL) was used to construct a 3D grid structure for cell support in the measurement window. The optimal polymer grid constant was found for implementation in transwell MIFE measurements. We showed that human umbilical vein endothelial cells (HUVECs) efficiently grow and maintain their physiological response on top of the polymer structures.

Heat Transfer and Thermal Stress Analysis of an Optoelectronic Package

1991 ◽  
Vol 113 (3) ◽  
pp. 258-262 ◽  
Author(s):  
J. G. Stack ◽  
M. S. Acarlar
Keyword(s):  
Heat Transfer ◽  
Thermal Management ◽  
Power Dissipation ◽  
Point Of View ◽  
Optical Data ◽  
Data Link ◽  
Element Analysis ◽  
Thermally Induced ◽  
Temperature Changes ◽  
Induced Stresses

The reliability and life of an Optical Data Link transmitter are inversely related to the temperature of the LED. It is therefore critical to have efficient packaging from the point of view of thermal management. For the ODL® 200H devices, it is also necessary to ensure that all package seals remain hermetic throughout the stringent military temperature range requirements of −65 to +150°C. For these devices, finite element analysis was used to study both the thermal paths due to LED power dissipation and the thermally induced stresses in the hermetic joints due to ambient temperature changes

scholarly journals Thermo-hydro-mechanical coupling analysis of a thermo-active diaphragm wall

2018 ◽  
Vol 55 (5) ◽  
pp. 720-735 ◽  
Author(s):  
Yi Rui ◽  
Mei Yin
Keyword(s):  
New Technologies ◽  
Bending Moment ◽  
Diaphragm Wall ◽  
Elastic Model ◽  
Element Analysis ◽  
Thermally Induced ◽  
Mechanical Coupling ◽  
Reversal Effect ◽  
Earth Pressures ◽  
Geotechnical Aspect

Thermo-active diaphragm walls that combine load bearing ability with a ground source heat pump (GSHP) are considered to be one of the new technologies in geotechnical engineering. Despite the vast range of potential applications, current thermo-active diaphragm wall designs have very limited use from a geotechnical aspect. This paper investigates the wall–soil interaction behaviour of a thermo-active diaphragm wall by conducting a thermo-hydro-mechanical finite element analysis. The GSHP operates by circulating cold coolant into the thermo-active diaphragm wall during winter. Soil contraction and small changes in the earth pressures acting on the wall are observed. The strain reversal effect makes the soil stiffness increase when the wall moves in the unexcavated side direction, and hence gives different trends for long-term wall movements compared to the linear elastic model. The GSHP operation makes the wall move in a cyclic manner, and the seasonal variation is approximately 0.5–1 mm, caused by two factors: the thermal effects on the deformation of the diaphragm wall itself and the thermally induced volume change of the soil and pore water. In addition, it is found that the change in bending moment of the wall due to the seasonal GSHP cycle is caused mainly by the thermal differential across the wall during the winter, because the seasonal changes in earth pressures acting on the diaphragm wall are very limited.

Structure–property relation of porous poly (l-lactic acid) scaffolds fabricated using organic solvent mixtures and controlled cooling rates and its bio-compatibility with human adipose stem cells

2018 ◽  
Vol 33 (4) ◽  
pp. 397-415 ◽  
Author(s):  
Harish Chinnasami ◽  
Jeff Gimble ◽  
Ram V Devireddy
Keyword(s):  
Stem Cells ◽  
Cell Proliferation ◽  
Lactic Acid ◽  
Phase Separation ◽  
Mechanical Strength ◽  
Separation Method ◽  
Thermally Induced Phase Separation ◽  
Cooling Rates ◽  
Thermally Induced ◽  
Pore Sizes

Thermally induced phase separation method was used to make porous three-dimensional poly (l-lactic acid) scaffolds. The effect of imposed thermal profile during freezing of the poly (l-lactic acid) in dioxane solution on the scaffold was characterized by their micro-structure, porosity (%), pore sizes’ distribution, and mechanical strength. The porosity (%) decreased considerably with increasing concentrations of poly (l-lactic acid) in the solution, while a decreasing trend was observed with increasing cooling rates. The mechanical strength increases with increase in poly (l-lactic acid) concentration and also with increase in the cooling rate for both types of solvents. Therefore, mechanical strength was increased by higher cooling rates while the porosity (%) remained relatively consistent. Scaffolds made using higher concentrations of poly (l-lactic acid; 7% and 10% w/v) in solvent showed better mechanical strength which improved relatively with increasing cooling rates (1°C–40°C/min). This phenomenon of enhanced structural integrity with increasing cooling rates was more prominent in scaffolds made from higher initial poly (l-lactic acid) concentrations. Human adipose–derived stem cells were cultured on these scaffold (7% and 10% w/v) prepared by thermally induced phase separation at all cooling rates to measure the cell proliferation efficiency as a function of their micro-structural properties. Mean pore sizes played a crucial role in cell proliferation than percent porosity since all scaffolds were >88% porous. The viability percent of human adipose tissue–derived adult stem cells increased consistently with longer periods of culture. Thus, poly (l-lactic acid) scaffolds prepared by thermally controlled thermally induced phase separation method could be a prime candidate for making ex vivo tissue-engineered grafts for surgical implantation.

Abstract P383: 3D-collagen Matrix Enhanced Integrins And Matrix Metalloproteinases Expression In Cardiac Mesenchymal Cells

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Senthilkumar Muthusamy ◽  
Asha V Nath ◽  
Shilpa Ajit ◽  
Anil K PR
Keyword(s):  
Matrix Metalloproteinases ◽  
Adhesion Molecules ◽  
Type I Collagen ◽  
Collagen Matrix ◽  
Mesenchymal Cells ◽  
Pcr Analysis ◽  
Type I ◽  
Culture Dish ◽  
Tissue Culture Dish ◽  
3D Collagen

Introduction: Use of cardiac mesenchymal cells (CMCs) has been shown to improve cardiac function following myocardial infarction. Main drawback in cardiac cell therapy is the major loss of injected cells within few hours. Increase the retention of these injected cells could increase their efficacy, where cardiac patches with various cell types showed better outcome. Among, collagen patch plays lead role as a cell-laden matrix in cardiac tissue engineering. Creating a detailed understanding of how collagen matrix changes the cellular phenotype could provide seminal insights to regeneration therapy. Hypothesis: Growing CMCs in three dimensional (3D) collagen matrix could alter the expression of extracellular matrix (ECM) and adhesion molecules, which may enhance their efficacy. Methods: The bovine type I collagen was chemically modified and solubilized in culture medium with photo-initiator. The mouse CMCs were isolated and resuspended in collagen solution, printed using 3D bioprinter and UV-crosslinked to form 3D-CMC construct. The 3D-CMC construct was submerged in growth medium and cultured for 48h and analyzed for the expression of ECM and adhesion molecules (n=5/group). CMCs cultured in regular plastic tissue culture dish was used as control. Results: RT profiler array showed changes in the ECM and adhesion molecules expression, specifically certain integrins and matrix metalloproteinases (MMPs) in CMCs cultured 3D collagen construct compared to 2D monolayer. Subsequent qRT-PCR analysis revealed significant (p<0.01) upregulation of integrins such as Itga2 (2.96±0.13), Itgb1 (3.18±0.2) and Itgb3 (2.4±0.27) and MMPs such as MMP13 (37.2±3.36), MMP9 (5.23±1.06) and MMP3 (7.14±2.07). Western blot analysis further confirmed significant elevation of these integrins and matrix metalloproteinases at protein level. Collagen encapsulation did not alter the expression of N-cadherin in CMCs, which is a potential mesenchymal cadherin adhesion molecule. Conclusion: Integrin αβ heterodimers transduce signals that facilitate cell homing, migration, survival and differentiation. Similarly, MMPs plays vital role in cell migration and proliferation. Our results demonstrate that the 3D-collagen Niche enhances the expression of certain integrins and MMPs in CMCs. This suggest that the efficacy of CMCs could be magnified by providing 3D architecture with collagen matrix and further in vivo experiments would reveal functional benefits from CMCs for clinical use.

scholarly journals Analysis of microscopic bone properties in an osteoporotic sheep model: a combined biomechanics, FE and ToF-SIMS study

2019 ◽  
Vol 16 (151) ◽  
pp. 20180793 ◽  
Author(s):  
R. Müller ◽  
A. Henss ◽  
M. Kampschulte ◽  
M. Rohnke ◽  
A. C. Langheinrich ◽  
...  
Keyword(s):  
Biomechanical Testing ◽  
Tissue Level ◽  
Osteoporotic Bone ◽  
Compression Tests ◽  
Micro Computed Tomography ◽  
Deficient Diet ◽  
Element Analysis ◽  
Sheep Model ◽  
Tissue Properties ◽  
Bone Properties

The present study deals with the characterization of bone quality in a sheep model of postmenopausal osteoporosis. Sheep were sham operated ( n = 7), ovariectomized ( n = 6), ovariectomized and treated with deficient diet ( n = 8) or ovariectomized, treated with deficient diet and glucocorticoid injections ( n = 7). The focus of the study is on the microscopic properties at tissue level. Microscopic mechanical properties of osteoporotic bone were evaluated by a combination of biomechanical testing and mathematical modelling. Sample stiffness and strength were determined by compression tests and finite-element analysis of stress states was conducted. From this, an averaged microscopic Young’s modulus at tissue level was determined. Trabecular structure as well as mineral and collagen distribution in samples of sheep vertebrae were analysed by micro-computed tomography and time-of-flight secondary ion mass spectrometry. In the osteoporotic sheep model, a disturbed fibril structure in the triple treated group was observed, but bone loss only occurred in form of reduced trabecular number and thickness and cortical decline, while quality of the residual bone was preserved. The preserved bone tissue properties in the osteoporotic sheep model allowed for an estimation of bone strength which behaves similar to the human case.

Magnetoelectric 3D scaffolds for enhanced bone cell proliferation

2019 ◽  
Vol 16 ◽  
pp. 290-300 ◽  
Author(s):  
Fajer Mushtaq ◽  
Harun Torlakcik ◽  
Queralt Vallmajo-Martin ◽  
Erdem Can Siringil ◽  
Jianhua Zhang ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Bone Cell ◽  
3D Scaffolds ◽  
Bone Cell Proliferation
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