scholarly journals 3D Printing of a Reactive Hydrogel Bio-Ink Using a Static Mixing Tool

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1986 ◽  
Author(s):  
María Puertas-Bartolomé ◽  
Małgorzata K. Włodarczyk-Biegun ◽  
Aránzazu del Campo ◽  
Blanca Vázquez-Lasa ◽  
Julio San Román
Keyword(s):  
3D Printing ◽  
Viscosity Solutions ◽  
Structural Integrity ◽  
Cell Types ◽  
High Viscosity ◽  
Soft Tissue Regeneration ◽  
Low Viscosity ◽  
Good Shape ◽  
Wide Range

Hydrogel-based bio-inks have recently attracted more attention for 3D printing applications in tissue engineering due to their remarkable intrinsic properties, such as a cell supporting environment. However, their usually weak mechanical properties lead to poor printability and low stability of the obtained structures. To obtain good shape fidelity, current approaches based on extrusion printing use high viscosity solutions, which can compromise cell viability. This paper presents a novel bio-printing methodology based on a dual-syringe system with a static mixing tool that allows in situ crosslinking of a two-component hydrogel-based ink in the presence of living cells. The reactive hydrogel system consists of carboxymethyl chitosan (CMCh) and partially oxidized hyaluronic acid (HAox) that undergo fast self-covalent crosslinking via Schiff base formation. This new approach allows us to use low viscosity solutions since in situ gelation provides the appropriate structural integrity to maintain the printed shape. The proposed bio-ink formulation was optimized to match crosslinking kinetics with the printing process and multi-layered 3D bio-printed scaffolds were successfully obtained. Printed scaffolds showed moderate swelling, good biocompatibility with embedded cells, and were mechanically stable after 14 days of the cell culture. We envision that this straightforward, powerful, and generalizable printing approach can be used for a wide range of materials, growth factors, or cell types, to be employed for soft tissue regeneration.

scholarly journals Distribution of horseradish peroxidase (HRP)-anti-HRP immune complexes in mouse spleen with special reference to follicular dendritic cells.

1978 ◽  
Vol 79 (1) ◽  
pp. 184-199 ◽  
Author(s):  
L L Chen ◽  
A M Frank ◽  
J C Adams ◽  
R M Steinman
Keyword(s):  
Dendritic Cells ◽  
Horseradish Peroxidase ◽  
Immune Complexes ◽  
Cell Types ◽  
Mouse Spleen ◽  
Follicular Dendritic Cells ◽  
Quantitative Studies ◽  
Wide Range ◽  
Follicular Dendritic

The distribution of immune complexes has been studied in mouse spleen stimulated to contain many germinal centers (GC's). Horseradish peroxidase (HRP)-anti-HRP complexes were used as an appropriately precise and sensitive model. We were primarily interested in the relative abilities of three cell types to interact with complexes: lymphocytes, macrophages, and follicular dendritic cells (FDC's). The latter are distinctive, nonendocytic, stellate cells located primarily at the transition of mantle and GC zones of 2 degrees lymphoid follicles (Chen, L. L., J. C. Adams, and R. M. Steinman, 1978, J. Cell Biol. 77:148). Binding of immune complexes to lymphocytes could not be visualized in situ. Macrophages avidly interiorized complexes into lysosomes, but did not retain them extracellularly. In contrast, FDC's could retain HRP-anti-HRP extracellularly under appropriate conditions, but did not endocytose them. Cytochemical reactivity accumulated progressively on FDC's 1--6 h after administration of complexes i.v., remained stable in amount and location for 1 day, and then was progressively lost over a 1- to 5-day period. Several variables in the association of complexes with macrophages and FDC's were pursued. Only 1 microgram of complexed HRP had to be administered to visualize binding to both cell types. Macrophages interiorized complexes formed in a wide range of HRP/anti-HRP ratios, while FDC's associated with complexes formed in HRP excess only. Quantitative studies with [125I]HRP-anti-HRP demonstrated that 20% of the splenic load of HRP associated with FDC's. Complexes formed with an F(ab')2 anti-HRP were distributed primarily in macrophages. When the levels of the third component of serum complement were depleted by prior treatment with cobra venom factor, uptake of complexes by macrophages was reduced some 50% whereas association with FDC's was abolished. The fact that antigen excess complexes are retained extracellularly strengthens the idea that they are immunogenic. Finally, the association of complexes with FDC's seems to retard the entry of antigen into the GC proper.

Proppant Placement Using Alternate-Slug Fracturing

SPE Journal ◽  
2014 ◽  
Vol 19 (05) ◽  
pp. 974-985 ◽  
Author(s):  
Sahil Malhotra ◽  
Eric R. Lehman ◽  
Mukul M. Sharma
Keyword(s):  
High Viscosity ◽  
Mixing Zone ◽  
Proppant Transport ◽  
Fracture Length ◽  
The Past ◽  
Low Viscosity ◽  
Viscous Fingers ◽  
Wide Range ◽  
Design Calculations ◽  
Viscosity Fluid

Summary New fracturing techniques, such as hybrid fracturing (Sharma et al. 2004), reverse-hybrid fracturing (Liu et al. 2007), and channel (HiWAY) fracturing (Gillard et al. 2010), have been deployed over the past few years to effectively place proppant in fractures. The goal of these methods is to increase the conductivity in the proppant pack, providing highly conductive paths for hydrocarbons to flow from the reservoir to the wellbore. This paper presents an experimental study on proppant placement by use of a new method of fracturing, referred to as alternate-slug fracturing. The method involves an alternate injection of low-viscosity and high-viscosity fluids, with proppant carried by the low-viscosity fluid. Alternate-slug fracturing ensures a deeper placement of proppant through two primary mechanisms: (i) proppant transport in viscous fingers, formed by the low-viscosity fluid, and (ii) an increase in drag force in the polymer slug, leading to better entrainment and displacement of any proppant banks that may have formed. Both these effects lead to longer propped-fracture length and better vertical placement of proppant in the fracture. In addition, the method offers lower polymer costs, lower pumping horsepower, smaller fracture widths, better control of fluid leakoff, less risk of tip screenouts, and less gel damage compared with conventional gel fracture treatments. Experiments are conducted in simulated fractures (slot cells) with fluids of different viscosity, with proppant being carried by the low-viscosity fluid. It is shown that viscous fingers of low-viscosity fluid and viscous sweeps by the high-viscosity fluid lead to a deeper placement of proppant. Experiments are also conducted to demonstrate slickwater fracturing, hybrid fracturing, and reverse-hybrid fracturing. Comparison shows that alternate-slug fracturing leads to the deepest and most-uniform placement of proppant inside the fracture. Experiments are also conducted to study the mixing of fluids over a wide range of viscosity ratios. Data are presented to show that the finger velocities and mixing-zone velocities increase with viscosity ratio up to viscosity ratios of approximately 350. However, at higher viscosity ratios, the velocities plateau, signifying no further effect of viscosity contrast on the growth of fingers and mixing zone. The data are an integral part of design calculations for alternate-slug-fracturing treatments.

scholarly journals Single-cell analysis in situ in a Bacillus subtilis swarming community identifies distinct spatially separated subpopulations differentially expressing hag (flagellin), including specialized swarmers

Microbiology ◽  
2011 ◽  
Vol 157 (9) ◽  
pp. 2456-2469 ◽  
Author(s):  
Kassem Hamze ◽  
Sabine Autret ◽  
Krzysztof Hinc ◽  
Soumaya Laalami ◽  
Daria Julkowska ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Single Cell ◽  
Single Cell Analysis ◽  
Laboratory Strain ◽  
Cell Types ◽  
Spatiotemporal Pattern ◽  
Cell Analysis ◽  
Wide Range ◽  
Low Humidity

The non-domesticated Bacillus subtilis strain 3610 displays, over a wide range of humidity, hyper-branched, dendritic, swarming-like migration on a minimal agar medium. At high (70 %) humidity, the laboratory strain 168 sfp + (producing surfactin) behaves very similarly, although this strain carries a frameshift mutation in swrA, which another group has shown under their conditions (which include low humidity) is essential for swarming. We reconcile these different results by demonstrating that, while swrA is essential for dendritic migration at low humidity (30–40 %), it is dispensable at high humidity. Dendritic migration (flagella- and surfactin-dependent) of strains 168 sfp + swrA and 3610 involves elongation of dendrites for several hours as a monolayer of cells in a thin fluid film. This enabled us to determine in situ the spatiotemporal pattern of expression of some key players in migration as dendrites develop, using gfp transcriptional fusions for hag (encoding flagellin), comA (regulation of surfactin synthesis) as well as eps (exopolysaccharide synthesis). Quantitative (single-cell) analysis of hag expression in situ revealed three spatially separated subpopulations or cell types: (i) networks of chains arising early in the mother colony (MC), expressing eps but not hag; (ii) largely immobile cells in dendrite stems expressing intermediate levels of hag; and (iii) a subpopulation of cells with several distinctive features, including very low comA expression but hyper-expression of hag (and flagella). These specialized cells emerge from the MC to spearhead the terminal 1 mm of dendrite tips as swirling and streaming packs, a major characteristic of swarming migration. We discuss a model for this swarming process, emphasizing the importance of population density and of the complementary roles of packs of swarmers driving dendrite extension, while non-mobile cells in the stems extend dendrites by multiplication.

scholarly journals New information about the mechanism of oil displacement from productive reservoirs using flow control technologies

2020 ◽  
Vol 177 ◽  
pp. 01012
Author(s):  
Rustam Mukhametshin ◽  
Gulnara Kvon
Keyword(s):  
Oil Recovery ◽  
Experimental Studies ◽  
High Water ◽  
High Viscosity ◽  
Oil Displacement ◽  
Low Viscosity ◽  
Stage Of Development ◽  
Wide Range ◽  
Production Wells ◽  
Control Technologies

The article is devoted to improving the efficiency of methods application to increase oil recovery of deposits that are at the final stage of development. This stage is characterized by a high degree of waterlogging of reservoirs and extracted products. From a wide range of chemical methods for increasing oil recovery in Russian oil deposits, flow-regulating (flow-deflecting) technologies have become widespread. The article analyzes the results of purposeful use of thickened water for the completion of reserves of already flooded sandstone layers. Experimental studies were performed on two specially created five-point elements in the experimental sections of the Romashkinskoye deposit. To monitor the process of low-viscosity and high-viscosity oil displacement the following methods were used: a) intake, monitoring and production wells, in which the interval of productive horizons are lined with fiberglass pipes; b) method of high-frequency resistivity (technology of "VNIIneftepromgeophysics" Institute). The studies performed in the monitoring mode showed that, along with the increase in reservoir coverage by flooding at the macro level, there is also a displacement of part of the capillary-trapped oil in the already flooded layers’ intervals, that is, at the level of micro-uniformity of the porous medium. The paper concludes on the effectiveness of using flow-regulating technologies in conditions of high water availability of development objects.

A Novel Injectable Chitosan Sponge Containing Brain Derived Neurotrophic Factor (BDNF) to Enhance Human Oligodendrocyte Progenitor Cells' (OPC) Differentiation

2014 ◽  
Vol 1621 ◽  
pp. 127-132
Author(s):  
Mina Mekhail ◽  
Qiao-Ling Cui ◽  
Guillermina Almazan ◽  
Jack Antel ◽  
Maryam Tabrizian
Keyword(s):  
Progenitor Cells ◽  
Spinal Cord Injuries ◽  
Cell Types ◽  
Therapeutic Modality ◽  
Oligodendrocyte Progenitor Cells ◽  
High Porosity ◽  
Oligodendrocyte Progenitor ◽  
Wide Range ◽  
First Time

ABSTRACTWe developed a rapidly-gelling chitosan sponge crosslinked with Guanosine 5'-Diphosphate (GDP). GDP has not been previously explored as an anionic crosslinker, and it was used in this application since the nucleoside guanosine has been shown to improve remyelination in situ, and thus its presence in the sponge composition was hypothesized to induce Oligodendrocyte Progenitor Cells' (OPC) differentiation. In addition to the chemical composition tailored to target OPCs, the developed chitosan sponge possesses a wide range of desirable physicochemical properties such as: rapid gelation, high porosity with interconnected pores, moduli of elasticity resembling that of soft tissue and cytocompatibility with many cell types. Moreover, protein encapsulation into the sponges was possible with high encapsulation efficiencies (e.g. BMP-7 and NT-3). In this study, BDNF was encapsulated in the chitosan sponges with an encapsulation efficiency greater than 80% and a sustained release over a 16-day period was achieved. We demonstrate here for the first time, the attachment of human fetal OPCs to the sponges and their differentiation after 12 days of culture. Overall, this newly-introduced injectable sponge is a promising therapeutic modality that can be used to enhance remyelination post-spinal cord injuries.

scholarly journals  Effect of thickening agents on perceived viscosity  and acidity of model beverages

2012 ◽  
Vol 30 (No. 5) ◽  
pp. 442-445 ◽  
Author(s):  
Z. Panovská ◽  
A. Váchová ◽  
J. Pokorný
Keyword(s):  
Viscosity Solutions ◽  
Carboxymethyl Cellulose ◽  
Kinematic Viscosity ◽  
Xanthan Gum ◽  
Methyl Cellulose ◽  
High Viscosity ◽  
Sodium Carboxymethyl Cellulose ◽  
Hydroxyethyl Cellulose ◽  
Low Viscosity ◽  
Thickening Agents

The effect of thickening agents &ndash; methyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, and xanthan gum &ndash; solutions on the sensory viscosity was investigated in the concentration range of 0&ndash;0.8%. The perceived viscosity was proportional to the logarithm of kinematic viscosity in the presence of citric and malic acids. The viscosity was inversely proportional to the acidity at the viscosity levels higher than 10 mm<sup>2</sup>/s. A liquid of high viscosity thus possess lower acidity than aqueous or low-viscosity solutions. No significant differences were found between the effects of different thickening agents. &nbsp;

scholarly journals The Rheology of PEOT/PBT Block Copolymers in the Melt State and in the Thermally-Induced Sol/Gel Transition. Implications on the 3D-Printing Bio-Scaffold Process

Materials ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 226 ◽  
Author(s):  
Veronica Vanzanella ◽  
Marco Scatto ◽  
Erwin Zant ◽  
Michele Sisani ◽  
Maria Bastianini ◽  
...  
Keyword(s):  
Phase Transition ◽  
Block Copolymers ◽  
3D Printing ◽  
Sol Gel ◽  
Rheological Characterization ◽  
Thermally Induced ◽  
Low Viscosity ◽  
Oscillatory Shear Flow ◽  
Wide Range ◽  
Sol Gel Transition

Poly(ethyleneoxideterephthalate)/poly(butyleneterephthalate) (PEOT/PBT) segmented block copolymers are widely used for the manufacturing of 3D-printed bio-scaffolds, due to a combination of several properties, such as cell viability, bio-compatibility, and bio-degradability. Furthermore, they are characterized by a relatively low viscosity at high temperatures, which is desired during the injection stages of the printing process. At the same time, the microphase separated morphology generated by the demixing of hard and soft segments at intermediate temperatures allows for a quick transition from a liquid-like to a solid-like behavior, thus favoring the shaping and the dimensional stability of the scaffold. In this work, for the first time, the rheology of a commercial PEOT/PBT material is studied over a wide range of temperatures encompassing both the melt state and the phase transition regime. Non-isothermal viscoelastic measurements under oscillatory shear flow allow for a quantitative determination of the material processability in the melt state. Additionally, isothermal experiments below the order–disorder temperature are used to determine the temperature dependence of the phase transition kinetics. The importance of the rheological characterization when designing the 3D-printing scaffold process is also discussed.

Microrheometry for Studying the Rheology and Dynamics of Polymers Near Interfaces

1999 ◽  
Vol 9 (1) ◽  
pp. 27-33 ◽  
Author(s):  
Gavin J.C. Braithwaite ◽  
Gareth H. McKinley
Keyword(s):  
Surface Force ◽  
High Viscosity ◽  
Polymer Processing ◽  
Interfacial Instabilities ◽  
Polymeric Fluids ◽  
Length Scales ◽  
Molecular Weights ◽  
Industrial Coating ◽  
Wide Range

Abstract The design of an instrument capable of opto-mechanical studies of the rheology of viscoelastic polymeric fluids near solid interfaces is described. The instrument probes the ‘meso’-scale (length scales of 0 (μm)) and bridges the gap between molecular-scale devices such as the Surface Force Apparatus (SFA) and conventional rheometers. The high viscosity materials and intermediate length scales probed with the current device are of direct relevance to industrial coating and thin film polymer processing operations, in addition to fundamental investigations of slip and interfacial instabilities. The device utilises small fluid samples (of the order of 1 μL), allows a wide range of viscosities (and thus molecular weights) to be investigated and can also be used with different substrate materials and surface coatings. Direct optical access to the sample also permits in-situ rheo-optical studies of material response under different loading conditions and flow histories.

Evaluating fabrication feasibility and biomedical application potential of in situ 3D printing technology

2016 ◽  
Vol 22 (6) ◽  
pp. 947-955 ◽  
Author(s):  
Yigong Liu ◽  
Qudus Hamid ◽  
Jessica Snyder ◽  
Chengyang Wang ◽  
Wei Sun
Keyword(s):  
3D Printing ◽  
Structural Stability ◽  
Structural Integrity ◽  
Biomedical Application ◽  
Three Dimensional ◽  
Travel Speed ◽  
Cross Linking ◽  
Content Type ◽  
Fabrication Parameters

Purpose This paper aims to present a solid freeform fabrication-based in situ three-dimensional (3D) printing method. This method enables simultaneous cross-linking alginate at ambient environmental conditions (temperature and pressure) for 3D-laden construct fabrication. The fabrication feasibility and potentials in biomedical applications were evaluated. Design/methodology/approach Fabrication feasibility was evaluated as the investigation of fabrication parameters on strut formability (the capability to fabricate a cylindrical strut in the same diameter as dispensing tip) and structural stability (the capability to hold the fabricated 3D-laden construct against mechanical disturbance). Potentials in biomedical application was evaluated as the investigation on structural integrity (the capability to preserve the fabricated 3D-laden construct in cell culture condition). Findings Strut formability can be achieved when the flow rate of alginate suspension and nozzle travel speed are set according to the dispensing tip size, and extruded alginate was cross-linked sufficiently. A range of cross-linking-related fabrication parameters was determined for sufficient cross-link. The structural stability and structural integrity were found to be controlled by alginate composition. An optimized setting of the alginate composition and the fabrication parameters was determined for the fabrication of a desired stable scaffold with structural integrity for 14 days. Originality/value This paper reports that in situ 3D printing is an efficient method for 3D-laden construct fabrication and its potentials in biomedical application.

Sign in / Sign up

Export Citation Format

Share Document