scholarly journals pH Modification of High-Concentrated Collagen Bioinks as a Factor Affecting Cell Viability, Mechanical Properties, and Printability

Gels ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 252
Author(s):  
Jana Stepanovska ◽  
Martin Otahal ◽  
Karel Hanzalek ◽  
Monika Supova ◽  
Roman Matejka
Keyword(s):  
Mechanical Properties ◽  
Cell Proliferation ◽  
Cell Viability ◽  
Limiting Factor ◽  
Mechanical Resistance ◽  
3D Bioprinting ◽  
Collagen Gels ◽  
High Concentration ◽  
Collagen Concentration ◽  
Static Conditions

The 3D bioprinting of cell-incorporated gels is a promising direction in tissue engineering applications. Collagen-based hydrogels, due to their similarity to extracellular matrix tissue, can be a good candidate for bioink and 3D bioprinting applications. However, low hydrogel concentrations of hydrogel (<10 mg/mL) provide insufficient structural support and, in highly concentrated gels, cell proliferation is reduced. In this study, we showed that it is possible to print highly concentrated collagen hydrogels with incorporated cells, where the viability of the cells in the gel remains very good. This can be achieved simply by optimizing the properties of the bioink, particularly the gel composition and pH modification, as well as by optimizing the printing parameters. The bioink composed of porcine collagen hydrogel with a collagen concentration of 20 mg/mL was tested, while the final bioink collagen concentration was 10 mg/mL. This bioink was modified with 0, 5, 9, 13, 17 and 20 μL/mL of 1M NaOH solution, which affected the resulting pH and gelling time. Cylindrical samples based on the given bioink, with the incorporation of porcine adipose-derived stromal cells, were printed with a custom 3D bioprinter. These constructs were cultivated in static conditions for 6 h, and 3 and 5 days. Cell viability and morphology were evaluated. Mechanical properties were evaluated by means of a compression test. Our results showed that optimal composition and the addition of 13 μL NaOH per mL of bioink adjusted the pH of the bioink enough to allow cells to grow and divide. This modification also contributed to a higher elastic modulus, making it possible to print structures up to several millimeters with sufficient mechanical resistance. We optimized the bioprinter parameters for printing low-viscosity bioinks. With this experiment, we showed that a high concentration of collagen gels may not be a limiting factor for cell proliferation.

Effect of Freezing on Cell Viability and Mechanical Strength of Bioartificial Tissues

2001 ◽  
Author(s):  
Ramachandra V. Devireddy ◽  
Michael R. Neidert ◽  
John C. Bischof ◽  
Robert T. Tranquillo
Keyword(s):  
Mechanical Properties ◽  
Mechanical Strength ◽  
Cell Viability ◽  
Ultimate Tensile Stress ◽  
Collagen Gels ◽  
Cooling Rates ◽  
Human Foreskin Fibroblasts ◽  
Lower Strain ◽  
Maximum Stiffness ◽  
Eden Prairie

Abstract The effect of freezing on the viability and mechanical strength of bioartificial tissues was determined under a variety of cooling conditions, with the ultimate aim of optimizing the cryopreservation process. Bioartificial tissues (i.e. tissue-equivalents or TEs) were prepared by incubating entrapped human foreskin fibroblasts in collagen gels for a period of 2 weeks. The bioartificial tissues were frozen using a controlled rate freezer at various cooling rates (0.5, 2, 5, 20, 40 and &gt; 1000°C/min or slam freezing). The viability (&lt; 60 min after thawing) of the fibroblasts in the bioartificial tissue was assessed using the Ethidium Homodimer (dead cells stain red) and Hoechst Give cells stain blue) assay. Uniaxial tension experiments were performed on an MTS Microbionix System (Eden Prairie, MN) to assess the post-thaw mechanical properties (Maximum Stiffness; Ultimate Tensile Stress; and Strain to Failure) of the frozen-thawed bioartificial tissue (≤ 3 hours after thawing). The results suggest that cooling rates of either 2 or 5°C/min are optimal for preserving both the cell viability and mechanical properties of the bioartificial tissues, post-freeze. Bioartificial tissues were also frozen using a directional solidification stage at 5°C/min. The post-thaw viability results are comparable in both the directionally cooled and the controlled rate freezer samples. However, the mechanical properties of the directionally cooled samples are significantly different (with a higher maximum stiffness and a lower strain to failure) than those obtained for samples frozen using a controlled rate freezer. This suggests that the directionality of ice propagation into the sample affects the measured mechanical properties.

Collagen Network Topology is Influenced by Collagen Concentration, But Not by Co-Gelation With Fibrin

2011 ◽  
Author(s):  
Victor K. Lai ◽  
Edward A. Sander ◽  
Spencer P. Lake ◽  
Robert T. Tranquillo ◽  
Victor H. Barocas
Keyword(s):  
Mechanical Properties ◽  
Healing Process ◽  
Biological Tissues ◽  
Wound Healing Process ◽  
Type I ◽  
Collagen Gels ◽  
Collagen Network ◽  
Modeling Framework ◽  
Collagen Concentration ◽  
Cardiovascular Tissue

Extracellular matrix (ECM) proteins (e.g. collagen, elastin) play an important role in biological tissues. In addition to conferring mechanical strength to a tissue, the ECM provides a biochemical environment essential for modulation of cellular responses such as growth and migration. Collagens are the dominant protein of the ECM, with collagen type I being most abundant. Our group and others have shown that the mechanical properties of a collagen I matrix change with collagen concentration, and when formed in the presence of a secondary fibril network such as fibrin [1]. We are interested in collagen-fibrin systems because our group uses fibrin as the starting scaffold material for cardiovascular tissue engineering, which produces interpenetrating collagen-fibrin matrices during the remodeling process as the fibrin network is degraded and replaced with cell-deposited collagen [2]. Fibrin and collagen networks are also present together around the thrombus during the wound healing process. Research has shown that ECM mechanical properties are correlated with their overall network structure characteristics such as fibril diameter [3]. Currently we have a modeling framework that generates an ECM microstructural network which can be used to predict the overall properties of a bioengineered tissue [4]. This framework allows exploration of the structure-function relation, but how the structure depends on composition remains poorly understood, especially in multi-component gels. Thus, the objective of this work was to quantify the collagen network architecture in pure collagen gels of different concentrations and in collagen-fibrin co-gels.

scholarly journals Design and construction of a novel measurement device for mechanical characterization of hydrogels: A case study

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0247727
Author(s):  
Shayan Shahab ◽  
Mehran Kasra ◽  
Alireza Dolatshahi-Pirouz
Keyword(s):  
Mechanical Properties ◽  
Shear Modulus ◽  
Magnetic Beads ◽  
Mechanical Characterization ◽  
Collagen Gel ◽  
Biological Tissues ◽  
Elastic Behavior ◽  
Collagen Gels ◽  
Collagen Concentration

Natural biopolymer-based hydrogels especially agarose and collagen gels, considering their biocompatibility with cells and their capacity to mimic biological tissues, have widely been used for in-vitro experiments and tissue engineering applications in recent years; nevertheless their mechanical properties are not always optimal for these purposes. Regarding the importance of the mechanical properties of hydrogels, many mechanical characterization studies have been carried out for such biopolymers. In this work, we have focused on understanding the mechanical role of agarose and collagen concentration on the hydrogel strength and elastic behavior. In this direction, Amirkabir Magnetic Bead Rheometry (AMBR) characterization device equipped with an optimized electromagnet, was designed and constructed for the measurement of hydrogel mechanical properties. The operation of AMBR set-up is based on applying a magnetic field to actuate magnetic beads in contact with the gel surface in order to actuate the gel itself. In simple terms the magnetic beads leads give rise to mechanical shear stress on the gel surface when under magnetic influence and together with the associated bead-gel displacement it is possible to calculate the hydrogel shear modulus. Agarose and Collagen gels with respectively 0.2–0.6 wt % and 0.2–0.5 wt % percent concentrations were prepared for mechanical characterization in terms of their shear modulus. The shear modulus values for the different percent concentrations of the agarose gel were obtained in the range 250–650 Pa, indicating the shear modulus increases by increasing in the agar gel concentration. In addition to this, the values of shear modulus for the collagen gel increase as function of concentration in the range 240–520 Pa in accordance with an approximately linear relationship between collagen concentration and gel strength.

Ultrasonic Setup for Testing Hydrogels: Preliminary Experiments on Collagen Gels

2011 ◽  
Vol 409 ◽  
pp. 146-151 ◽  
Author(s):  
Ramiro M. Irastorza ◽  
Matteo Achilli ◽  
Marta Amadei ◽  
Eugenia Blangino ◽  
Bernard Drouin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Speed Of Sound ◽  
Mass Density ◽  
Acoustic Properties ◽  
Collagen Gels ◽  
Experimental Conditions ◽  
Collagen Concentration ◽  
Bulk Compressibility ◽  
Acoustic Transducer ◽  
Pulse Echo

The assessment of mechanical properties of highly hydrated natural materials remains a challenge because, in general, their mechanical evaluation implies invasive and finally destructive methods. Acoustic-based tests may represent the appropriate tools to investigate the mechanical properties of such materials, particularly collagen gels, whose acoustic properties are poorly understood. The objective of this work is to develop two experimental setups for the assessment of acoustic properties of such a hydrogels. In the first one, a typical pulse echo reflectometer was implemented. The acoustic parameters were measured at controlled temperature in an especially designed chamber. In the second one, the previous configuration was combined with a setup for compressive tests, allowing to interrogate simultaneously both the acoustic and mechanical properties of the sample under test. The frequency of the acoustic transducer was 10MHz. The acoustic and mechanical properties of collagen gels prepared according to different experimental conditions (pH and collagen concentration) were evaluated. The first set of experiment was useful to accomplish estimation of the speed of sound, attenuation and acoustic impedance. The second one allowed us to monitor the speed of sound during the evolution of the compression test. This approach could be a potential tool to study the changes in hydrogels mass density and bulk compressibility.

scholarly journals Evaluation of mechanical properties of CAD/CAM ceramic systems: literature review

2020 ◽  
Vol 68 ◽  
Author(s):  
Ana Emanuela Cisne de LIMA ◽  
Hilmo Barreto Leite FALCÃO FILHO ◽  
Helena de Freitas Oliveira PARANHOS
Keyword(s):  
Mechanical Properties ◽  
Literature Review ◽  
Computer Aided Design ◽  
Limiting Factor ◽  
Mechanical Resistance ◽  
Aesthetic Result ◽  
Computer Aided ◽  
Cad Cam ◽  
Aided Design ◽  
Cam Systems

ABSTRACT Computer aided design / computer aided manufacturing (CAD/CAM) systems are among the most technological advanced techniques in oral rehab today. Compared with conventional techniques, they can optimize the resistance and the adaptation of dental ceramics. Thus, their indications of use have been widened, making the technique more and more well-known and widespread. Therefore, the aim of this study is to present a literature review on comparative studies of the mechanical properties of ceramic systems produced by CAD / CAM. A search for scientific articles published between 2009 and 2019, in English, Spanish or Portuguese, was performed through the databases SCIELO, BIREME and PUBMED, using the descriptors “Ceramics”, “Computer Aided Design” and “ Partial Fixed Prosthesis “. Currently, all ceramic systems appear to have adequate strength for simple rehabilitations, but ceramic restorations produced by CAD/CAM systems present greater reliability than other manufacturing methods, presenting a wider array of indications due to their higher mechanical resistance. These systems, besides their versatility, also present an excellent aesthetic result, guaranteeing appropriate optical properties such as translucency and fluorescence, similar to natural teeth. Although the cost is a limiting factor, CAD/CAM technology is in full development and with high success rates that qualifies it as the state of art in oral rehabilitation.

scholarly journals Hair fiber characteristics and methods to evaluate hair physical and mechanical properties

2009 ◽  
Vol 45 (1) ◽  
pp. 153-162 ◽  
Author(s):  
Maria Valéria Robles Velasco ◽  
Tania Cristina de Sá Dias ◽  
Anderson Zanardi de Freitas ◽  
Nilson Dias Vieira Júnior ◽  
Claudinéia Aparecida Sales de Oliveira Pinto ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Optical Coherence Tomography ◽  
Natural Fiber ◽  
Physical And Mechanical Properties ◽  
Movement Control ◽  
Mechanical Resistance ◽  
Static Electricity ◽  
High Concentration ◽  
Hair Fiber

The hair thread is a natural fiber formed by keratin, a protein containing high concentration of sulfur coming from the amino acid cystine. The main physical proprieties of the hair depend mostly on its geometry; the physical and mechanical properties of hair involve characteristics to improve: elasticity, smoothness, volume, shine, and softness due to both the significant adherence of the cuticle scales and the movement control (malleability), as well as the easiness of combing, since they reduce the fibers static electricity. The evaluation of these effects on hair may be carried out by several methods, as: optical and electron microscopy, mechanical resistance measuring, shine evaluation and optical coherence tomography (OCT).

scholarly journals Image-based Characterization of 3D Collagen Networks and the Effect of Embedded Cells

2019 ◽  
Vol 25 (4) ◽  
pp. 971-981 ◽  
Author(s):  
Vanesa Olivares ◽  
Mar Cóndor ◽  
Cristina Del Amo ◽  
Jesús Asín ◽  
Carlos Borau ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cell Activity ◽  
Three Dimensional ◽  
Collagen Fibers ◽  
Collagen Gels ◽  
Culture Dish ◽  
Collagen Concentration ◽  
A Cell ◽  
3D Collagen

AbstractCollagen microstructure is closely related to the mechanical properties of tissues and affects cell migration through the extracellular matrix. To study these structures, three-dimensional (3D) in vitro collagen-based gels are often used, attempting to mimic the natural environment of cells. Some key parameters of the microstructure of these gels are fiber orientation, fiber length, or pore size, which define the mechanical properties of the network and therefore condition cell behavior. In the present study, an automated tool to reconstruct 3D collagen networks is used to extract the aforementioned parameters of gels of different collagen concentration and determine how their microstructure is affected by the presence of cells. Two different experiments are presented to test the functionality of the method: first, collagen gels are embedded within a microfluidic device and collagen fibers are imaged by using confocal fluorescence microscopy; second, collagen gels are directly polymerized in a cell culture dish and collagen fibers are imaged by confocal reflection microscopy. Finally, we investigate and compare the collagen microstructure far from and in the vicinities of MDA-MB 23 cells, finding that cell activity during migration was able to strongly modify the orientation of the collagen fibers and the porosity-related values.

Effect of nitric oxide on Sertoli cell microtubule of piglets

2009 ◽  
Vol 6 (3) ◽  
pp. 257-263 ◽  
Author(s):  
Yang Li ◽  
Wang Xian-zhong ◽  
Yang Meng-bo ◽  
Zhang Jia-hua
Keyword(s):  
Nitric Oxide ◽  
Enzyme Activity ◽  
Protein Kinase ◽  
Cell Viability ◽  
Sodium Nitroprusside ◽  
Sertoli Cell ◽  
Sertoli Cells ◽  
High Concentration ◽  
Treatment Results ◽  
Anti Oxidant

AbstractTo illustrate the effect of nitric oxide (NO) on the microtubules of Sertoli cells (SC), SCs of piglets were treated with sodium nitroprusside (SNP). Changes in cell viability, anti-oxidant activity, enzyme activity and p38 mutagen-activated protein kinase (p38MAPK) activation were detected. The results were as follows. A low concentration of NO can keep SC microtubule and cell viability normal, and a high concentration of NO could increase p38MAPK activation, decrease anti-oxidant activity and transferrin secretion, and destroy the structure and distribution of the microtubules. The results suggest that SNP treatment results in an increase in NO in SCs and decreased cell anti-oxidant activity. The high concentration of NO destroys cell microtubules by activating p38MAPK.

scholarly journals Optimization of Spheroid Colony Culture and Cryopreservation of Nucleus Pulposus Cells for the Development of Intervertebral Disc Regenerative Therapeutics

2021 ◽  
Vol 11 (8) ◽  
pp. 3309
Author(s):  
Kosuke Sako ◽  
Daisuke Sakai ◽  
Yoshihiko Nakamura ◽  
Erika Matsushita ◽  
Jordy Schol ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Cell Viability ◽  
Nucleus Pulposus ◽  
Mass Culture ◽  
Formation Rate ◽  
Proliferation Rate ◽  
Cell Phenotype ◽  
Mrna Levels ◽  
Spheroid Formation ◽  
Positive Nucleus

After the discovery of functionally superior Tie2-positive nucleus pulposus (NP) progenitor cells, new methods were needed to enable mass culture and cryopreservation to maintain these cells in an undifferentiated state with high cell yield. We used six types of EZSPHERE® dishes, which support spheroid-forming colony culture, and examined NP cell spheroid-formation ability, number, proliferation, and mRNA expression of ACAN, COL1A2, COL2A1, and ANGPT1. Six different types of cryopreservation solutions were examined for potential use in clinical cryopreservation by comparing the effects of exposure time during cryopreservation on cell viability, Tie2-positivity, and cell proliferation rates. The spheroid formation rate was 45.1% and the cell proliferation rate was 7.75 times using EZSPHERE® dishes. The mRNA levels for COL2A1 and ANGPT1 were also high. In cryopreservation, CryoStor10 (CS10) produced ≥90% cell viability and a high proliferation rate after thawing. CS10 had a high Tie2-positive rate of 12.6% after culturing for 5 days after thawing. These results suggest that EZSPHERE enabled colony formation in cell culture without the use of hydrogel products and that CS10 is the best cryopreservation medium for retaining the NP progenitor cell phenotype and viability. Together, these data provide useful information of NP cell-based therapeutics to the clinic.

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