scholarly journals Two-Photon Polymerized Poly(2-Ethyl-2-Oxazoline) Hydrogel 3D Microstructures with Tunable Mechanical Properties for Tissue Engineering

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 5066
Author(s):  
Steffen Czich ◽  
Thomas Wloka ◽  
Holger Rothe ◽  
Jürgen Rost ◽  
Felix Penzold ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Computer Aided Design ◽  
Evaluation Method ◽  
Structural Integrity ◽  
Viscoelastic Behavior ◽  
Main Task ◽  
Two Photon ◽  
Wide Range ◽  
Tunable Mechanical Properties

The main task of tissue engineering (TE) is to reproduce, replicate, and mimic all kinds of tissues in the human body. Nowadays, it has been proven useful in TE to mimic the natural extracellular matrix (ECM) by an artificial ECM (scaffold) based on synthetic or natural biomaterials to regenerate the physiological tissue/organ architecture and function. Hydrogels have gained interest in the TE community because of their ability to absorb water similar to physiological tissues, thus mechanically simulating the ECM. In this work, we present a novel hydrogel platform based on poly(2-ethyl-2-oxazoline)s, which can be processed to 3D microstructures via two-photon polymerization (2PP) with tunable mechanical properties using monomers and crosslinker with different degrees of polymerization (DP) for future applications in TE. The ideal parameters (laser power and writing speed) for optimal polymerization via 2PP were obtained using a specially developed evaluation method in which the obtained structures were binarized and compared to the computer-aided design (CAD) model. This evaluation was performed for each composition. We found that it was possible to tune the mechanical properties not only by application of different laser parameters but also by mixing poly(2-ethyl-2-oxazoline)s with different chain lengths and variation of the crosslink density. In addition, the swelling behavior of different fabricated hydrogels were investigated. To gain more insight into the viscoelastic behavior of different fabricated materials, stress relaxation tests via nanoindentation experiments were performed. These new hydrogels can be processed to 3D microstructures with high structural integrity using optimal laser parameter settings, opening a wide range of application properties in TE for this material platform.

scholarly journals Biomimicry in Bio-Manufacturing: Developments in Melt Electrospinning Writing Technology Towards Hybrid Biomanufacturing

2019 ◽  
Vol 9 (17) ◽  
pp. 3540 ◽  
Author(s):  
Ferdows Afghah ◽  
Caner Dikyol ◽  
Mine Altunbek ◽  
Bahattin Koc
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Cell Attachment ◽  
Three Dimensional ◽  
Future Perspective ◽  
Melt Electrospinning ◽  
Wide Range ◽  
Challenges And Opportunities ◽  
Potential Applications ◽  
Homogeneous Cell

Melt electrospinning writing has been emerged as a promising technique in the field of tissue engineering, with the capability of fabricating controllable and highly ordered complex three-dimensional geometries from a wide range of polymers. This three-dimensional (3D) printing method can be used to fabricate scaffolds biomimicking extracellular matrix of replaced tissue with the required mechanical properties. However, controlled and homogeneous cell attachment on melt electrospun fibers is a challenge. The combination of melt electrospinning writing with other tissue engineering approaches, called hybrid biomanufacturing, has introduced new perspectives and increased its potential applications in tissue engineering. In this review, principles and key parameters, challenges, and opportunities of melt electrospinning writing, and particularly, recent approaches and materials in this field are introduced. Subsequently, hybrid biomanufacturing strategies are presented for improved biological and mechanical properties of the manufactured porous structures. An overview of the possible hybrid setups and applications, future perspective of hybrid processes, guidelines, and opportunities in different areas of tissue/organ engineering are also highlighted.

scholarly journals Tissue Engineering for the Insertions of Tendons and Ligaments: An Overview of Electrospun Biomaterials and Structures

2021 ◽  
Vol 9 ◽  
Author(s):  
Alberto Sensini ◽  
Gabriele Massafra ◽  
Carlo Gotti ◽  
Andrea Zucchelli ◽  
Luca Cristofolini
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Myotendinous Junction ◽  
Stress Concentrations ◽  
Comprehensive Overview ◽  
Electrospinning Technique ◽  
Junction Site ◽  
Wide Range ◽  
Myotendinous Junctions

The musculoskeletal system is composed by hard and soft tissue. These tissues are characterized by a wide range of mechanical properties that cause a progressive transition from one to the other. These material gradients are mandatory to reduce stress concentrations at the junction site. Nature has answered to this topic developing optimized interfaces, which enable a physiological transmission of load in a wide area over the junction. The interfaces connecting tendons and ligaments to bones are called entheses, while the ones between tendons and muscles are named myotendinous junctions. Several injuries can affect muscles, bones, tendons, or ligaments, and they often occur at the junction sites. For this reason, the main aim of the innovative field of the interfacial tissue engineering is to produce scaffolds with biomaterial gradients and mechanical properties to guide the cell growth and differentiation. Among the several strategies explored to mimic these tissues, the electrospinning technique is one of the most promising, allowing to generate polymeric nanofibers similar to the musculoskeletal extracellular matrix. Thanks to its extreme versatility, electrospinning has allowed the production of sophisticated scaffolds suitable for the regeneration of both the entheses and the myotendinous junctions. The aim of this review is to analyze the most relevant studies that applied electrospinning to produce scaffolds for the regeneration of the enthesis and the myotendinous junction, giving a comprehensive overview on the progress made in the field, in particular focusing on the electrospinning strategies to produce these scaffolds and their mechanical, in vitro, and in vivo outcomes.

scholarly journals Viscoelastic Behavior of Embroidered Scaffolds for ACL Tissue Engineering Made of PLA and P(LA-CL) After In Vitro Degradation

2019 ◽  
Vol 20 (18) ◽  
pp. 4655 ◽  
Author(s):  
Judith Hahn ◽  
Gundula Schulze-Tanzil ◽  
Michaela Schröpfer ◽  
Michael Meyer ◽  
Clemens Gögele ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Cruciate Ligament ◽  
Viscoelastic Behavior ◽  
Ligament Injury ◽  
In Vitro Degradation ◽  
Knee Ligament ◽  
Cell Vitality ◽  
Reconstruction Methods

A rupture of the anterior cruciate ligament (ACL) is the most common knee ligament injury. Current applied reconstruction methods have limitations in terms of graft availability and mechanical properties. A new approach could be the use of a tissue engineering construct that temporarily reflects the mechanical properties of native ligament tissues and acts as a carrier structure for cell seeding. In this study, embroidered scaffolds composed of polylactic acid (PLA) and poly(lactic-co-ε-caprolactone) (P(LA-CL)) threads were tested mechanically for their viscoelastic behavior under in vitro degradation. The relaxation behavior of both scaffold types (moco: mono-component scaffold made of PLA threads, bico: bi-component scaffold made of PLA and P(LA-CL) threads) was comparable to native lapine ACL. Most of the lapine ACL cells survived 32 days of cell culture and grew along the fibers. Cell vitality was comparable for moco and bico scaffolds. Lapine ACL cells were able to adhere to the polymer surfaces and spread along the threads throughout the scaffold. The mechanical behavior of degrading matrices with and without cells showed no significant differences. These results demonstrate the potential of embroidered scaffolds as an ACL tissue engineering approach.

Application of a portable indentation rig with Rockwell indenter to determine mechanical properties and residual stresses on an aluminum plate

2020 ◽  
Vol 55 (7-8) ◽  
pp. 246-257
Author(s):  
Saba Salmani Ghanbari ◽  
Amir-Hossein Mahmoudi
Keyword(s):  
Mechanical Properties ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Indentation Load ◽  
Instrumented Indentation ◽  
Unknown Parameters ◽  
Plastic Properties ◽  
Wide Range ◽  
Portable Apparatus ◽  
Non Destructive

Measuring residual stresses is still a dilemma in many engineering applications. It is even more crucial when the industrial requirements demand for a non-destructive technique in order to avoid compromising the structural integrity of the engineering components. Furthermore, estimating the mechanical properties of the materials, especially when the components are aged, is of importance. Instrumented indentation has gained much interest in recent years. There are many studies in the literature which are focused on measuring residual stresses or mechanical properties using instrumented indentation. Since in many cases there is no possibility of transferring large samples or those under service, for possible measurements, having a portable rig can be very useful. Furthermore, indentation procedure is a low-cost non-destructive method with high accuracy which is able to measure the plastic properties of material as well as its residual stresses on which the designing and construction of the portable apparatus were based. The instrumented indentation testing details were followed according to the ASTM E2546-15 standard practice. In this research, a wide range of simulations were performed on a group of aluminum alloys in order to estimate the equi-biaxial residual stresses by analyzing the indentation load–displacement curves which were obtained from the experimental outcomes. Then neural networks were employed to estimate the unknown parameters. The performance accuracy of the designed portable apparatus and the acceptable precision of the introduced method were then verified with experimental tests performed on Al 2024-T351.

Self-Adhesive Hydrogels for Tissue Engineering

2021 ◽  
Author(s):  
Yating Yi ◽  
Chaoming Xie ◽  
Jin Liu ◽  
Yonghao Zheng ◽  
Jun Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Three Dimensional ◽  
Biocompatible Polymers ◽  
Tunable Mechanical Properties ◽  
Hydrophilic Network

Hydrogels consisting of a three-dimensional hydrophilic network of biocompatible polymers have been widely used in tissue engineering. Owing to their tunable mechanical properties, hydrogels have been applied in both hard...

A Robust True Direct-Print Technology for Tissue Engineering

2007 ◽  
Author(s):  
B. Li ◽  
T. Dutta Roy ◽  
C. M. Smith ◽  
P. A. Clark ◽  
K. H. Church
Keyword(s):  
Tissue Engineering ◽  
Computer Aided Design ◽  
Fused Deposition Modeling ◽  
Three Dimensional ◽  
Layer By Layer ◽  
Fused Deposition ◽  
Wide Range ◽  
Computer Aided ◽  
Liquid Material ◽  
Print Process

Numerous solid freeform fabrication (SFF) or rapid prototyping (RP) techniques have been employed in the field of tissue engineering to fabricate specially organized three-dimensional (3-D) structures such as scaffolds. Some such technologies include, but are not limited to, laminated object manufacturing (LOM), three-dimensional printing (3-DP) or ink-jet printing, selective laser sintering (SLS), and fused deposition modeling (FDM). These techniques are capable of rapidly producing highly complex 3-D scaffolds or other biomedical structures with the aid of a computer-aided design (CAD) system. However, they suffer from lack of consistency and repeatability, since most of these processes are not fully controlled and cannot reproduce the previous work with accuracy. Also, these techniques (excluding FDM) are not truly direct-print processes. Certain material removing steps are involved, which in turn increases the complexity and the cost of fabrication. The FDM process has good repeatability; however, the materials that can be used are limited due to the high temperature needed to melt the feedstock. Some researchers also reported that the scaffolds fabricated by FDM lack consistency in the z-direction. In this paper, we will present a true direct-print technology for repeatedly producing scaffolds and other biomedical structures for tissue engineering with the aid of our Computer Aided Biological (CAB) tool. Unlike other SFF techniques mentioned above, our direct-print process fabricates scaffolds or other complex 3-D structures by extruding (dispensing) a liquid material onto the substrate with a prescribed pattern generated by a CAD program. This can be a layer-by-layer 2.5 dimension build or a true 3-D build. The dispensed liquid material then polymerizes or solidifies, to form a solid structure. The flexibility in the types of materials that can be extruded ranges from polymers to living cells, encapsulated in the proper material. True 3-D structures are now possible on a wide range of substrates, including even in vivo. Some of the advantages of the process are a) researchers have full control over the patterns to be created; b) it is a true direct-print process with no material removing steps involved; c) it is highly consistent and repeatable; and d) it is highly efficient and cost-effective. This paper will first give a detailed description of the CAB tool. Then, it will present a detailed process for printing polycaprolactone (PCL) into a defined 3-D architecture, where the primary focus for these constructs is for use in tissue engineering applications. Finally, mechanical characterization results of the printed scaffolds will be included in the paper.

Effect of Different Heat Treatments on Mechanical Properties of Laser Sintered Additive Manufactured Parts

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Sagar Sarkar ◽  
Cheruvu Siva Kumar ◽  
Ashish Kumar Nath
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Yield Strength ◽  
Computer Aided Design ◽  
Tensile Strain ◽  
Wear Loss ◽  
Layer By Layer ◽  
Solution Annealing ◽  
Sem Images ◽  
Wide Range

One of the most popular additive manufacturing processes is laser-based direct metal laser sintering (DMLS) process, which enables us to make complex three-dimensional (3D) parts directly from computer-aided design models. Due to layer-by-layer formation, parts built in this process tend to be anisotropic in nature. Suitable heat treatment can reduce this anisotropic behavior by changing the microstructure. Depending upon the applications, a wide range of mechanical properties can be achieved between 482 °C and 621 °C temperature for precipitation-hardened stainless steels. In the present study, effect of different heat treatment processes, namely solution annealing, aging, and overaging, on tensile strength, hardness, and wear properties has been studied in detail. Suitable metallurgical and mechanical characterization techniques have been applied wherever required, to support the experimental observations. Results show H900 condition gives highest yield strength and lowest tensile strain at break, whereas solution annealing gives lowest yield strength and as-built condition gives highest tensile strain at break. Scanning electron microscope (SEM) images show that H900 and H1150 condition produces brittle and ductile morphology, respectively, which in turn gives highest and lowest hardness value, respectively. X-ray diffraction (XRD) analysis shows presence of austenite phases, which can increase ductility at the cost of hardness. Average wear loss for H900 condition is highest, whereas it is lowest for solution annealed condition. Further optical and SEM images have been taken to understand the basic wear mechanism involved.

A Brief Review of the Modelling of the Time Dependent Mechanical Properties of Tissue Engineering Scaffolds

2010 ◽  
Vol 6 ◽  
pp. 19-33 ◽  
Author(s):  
N.K. Bawolin ◽  
W.J. Zhang ◽  
Xiong Biao Chen
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Treatment Process ◽  
Effective Properties ◽  
Critical Role ◽  
Time Dependent ◽  
Tissue Engineering Scaffolds ◽  
Wide Range ◽  
Scaffold Degradation

The functionality of tissue scaffolds in vivo plays a critical role in the treatment process. Due to the time dependent nature of the mechanical properties of the constituent phases of the scaffold, a wide range of mechanical property histories may be observed during the treatment process, possibly influencing outcomes. The critical nature of the mechanical properties in load bearing applications indicates a need for the simultaneous modelling of both scaffold degradation and tissue regeneration with time, and the resulting effective properties of the tissue engineering construct. To this end, a review of the literature is conducted to identify the various existing approaches to modelling scaffold degradation, tissue behavior, and the dependency of the two processes on one another.

scholarly journals Soft-Tissue-Mimicking Using Hydrogels for the Development of Phantoms

Gels ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 40
Author(s):  
Aitor Tejo-Otero ◽  
Felip Fenollosa-Artés ◽  
Isabel Achaerandio ◽  
Sergi Rey-Vinolas ◽  
Irene Buj-Corral ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Soft Tissues ◽  
Mechanical Response ◽  
Viscoelastic Behavior ◽  
Linear Elastic ◽  
Lack Of Information ◽  
Wide Range ◽  
Significant Difference ◽  
Promising Solution ◽  
Living Tissues

With the currently available materials and technologies it is difficult to mimic the mechanical properties of soft living tissues. Additionally, another significant problem is the lack of information about the mechanical properties of these tissues. Alternatively, the use of phantoms offers a promising solution to simulate biological bodies. For this reason, to advance in the state-of-the-art a wide range of organs (e.g., liver, heart, kidney as well as brain) and hydrogels (e.g., agarose, polyvinyl alcohol –PVA–, Phytagel –PHY– and methacrylate gelatine –GelMA–) were tested regarding their mechanical properties. For that, viscoelastic behavior, hardness, as well as a non-linear elastic mechanical response were measured. It was seen that there was a significant difference among the results for the different mentioned soft tissues. Some of them appear to be more elastic than viscous as well as being softer or harder. With all this information in mind, a correlation between the mechanical properties of the organs and the different materials was performed. The next conclusions were drawn: (1) to mimic the liver, the best material is 1% wt agarose; (2) to mimic the heart, the best material is 2% wt agarose; (3) to mimic the kidney, the best material is 4% wt GelMA; and (4) to mimic the brain, the best materials are 4% wt GelMA and 1% wt agarose. Neither PVA nor PHY was selected to mimic any of the studied tissues.

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