3D Bioplotter Research Papers

Displaying all papers by D. X. B. Chen (31 results)

Bioprinting and in vitro characterization of alginate dialdehyde–gelatin hydrogel bio-ink

Bio-Design and Manufacturing 2020 Volume 3, Pages 48–59

Cell-laden cardiac patches have recently been emerging to renew cellular sources for myocardial infarction (MI, commonly know as a heart attack) repair. However, the fabrication of cell-laden patches with porous structure remains challenging due to the limitations of currently available hydrogels and existing processing techniques. The present study utilized a bioprinting technique to fabricate hydrogel patches and characterize them in terms of printability, mechanical and biological properties. Cell-laden hydrogel (or bio-ink) was formulated from alginate dialdehyde (ADA) and gelatin (GEL) to improve the printability, degradability as well as bioactivity. Five groups of hydrogel compositions were designed to investigate the influence…

Printability of 3D Printed Hydrogel Scaffolds: Influence of Hydrogel Composition and Printing Parameters

Applied Sciences 2020 Volume 10, Issue 1, Article 292

Extrusion-based bioprinting of hydrogel scaffolds is challenging due to printing-related issues, such as the lack of capability to precisely print or deposit hydrogels onto three-dimensional (3D) scaffolds as designed. Printability is an index to measure the difference between the designed and fabricated scaffold in the printing process, which, however, is still under-explored. While studies have been reported on printing hydrogel scaffolds from one or more hydrogels, there is limited knowledge on the printability of hydrogels and their printing processes. This paper presented our study on the printability of 3D printed hydrogel scaffolds, with a focus on identifying the influence of…

Bioprinting Schwann cell-laden scaffolds from low-viscosity hydrogel compositions

Journal of Materials Chemistry B 2019 Volume 7, Issue 29, Pages 4538-4551

3D bioprinting techniques have been attracting attention for tissue scaffold fabrication in nerve tissue engineering applications. However, due to the inherent complexity of nerve tissues, bioprinting scaffolds that can appropriately promote the regeneration of damaged tissues is still challenging. This paper presents our study on bioprinting Schwann cell-laden scaffolds from low-viscosity hydrogel compositions including RGD modified alginate, hyaluronic acid and fibrin, with a focus on investigating the printability of hydrogel compositions and characterizing the functions of printed scaffolds for potential use in nerve tissue regeneration. We assessed the rheological properties of hydrogel precursors via temperature, time and shear rate sweeps,…

Printability and Cell Viability in Bioprinting Alginate Dialdehyde- Gelatin Scaffolds

ACS Biomaterials Science & Engineering 2019 Volume 5, Issue 6, Pages 2976-2987

Three-dimensional (3D) bioprinting is a promising technique used to fabricate scaffolds from hydrogels with living cells. However, the printability of hydrogels in bioprinting has not been adequately studied. The aim of this study was to quantitatively characterize the printability and cell viability of alginate dialdehyde (ADA)-gelatin (Gel) hydrogels for bioprinting. ADA-Gel hydrogels of various concentrations were synthesized and characterized using Fourier transform infrared spectroscopy, along with rheological tests for measuring storage and loss moduli. Scaffolds (with an area of 11 × 11 mm) of 1, 2, and 13 layers were fabricated from ADA-Gel hydrogels using a 3D-bioplotter under printing conditions…

Indirect 3D bioprinting and characterization of alginate scaffolds for potential nerve tissue engineering applications

Journal of the Mechanical Behavior of Biomedical Materials 2019 Volume 93, Pages 183-193

Low-concentration hydrogels have favorable properties for many cell functions in tissue engineering but are considerably limited from a scaffold fabrication point of view due to poor three-dimensional (3D) printability. Here, we developed an indirect-bioprinting process for alginate scaffolds and characterized the potential of these scaffolds for nerve tissue engineering applications. The indirect-bioprinting process involves (1) printing a sacrificial framework from gelatin, (2) impregnating the framework with low-concentration alginate, and (3) removing the gelatin framework by an incubation process, thus forming low-concentration alginate scaffolds. The scaffolds were characterized by compression testing, swelling, degradation, and morphological and biological assessment of incorporated or…

Bio-fabrication of peptide-modified alginate scaffolds: Printability, mechanical stability and neurite outgrowth assessments

Bioprinting 2019 Volume 14, Article e00045

Peripheral nerve tissue requires appropriate biochemical and physical cues to guide the regeneration process after injury. Bioprinted peptide-conjugated sodium alginate (PCSA) scaffolds have the potential to provide physical and biochemical cues simultaneously. Such scaffolds need characterisation in terms of printability, mechanical stability, and biological performance to refine and improve application in nerve tissue regeneration. In this study, it was hypothesized that 3D scaffold printed with low concentrated multiple PCSA precursor would be supportive for axon outgrowth. Therefore, a 2% (w/v) alginate precursor was conjugated with either arginine-glycine-aspartate (RGD) or tyrosine-isoleucine-glycine-serine-arginine (YIGSR) peptides, or a mixture of RGD and YIGSR (1:2)…

Homogeneous hydroxyapatite/alginate composite hydrogel promotes calcified cartilage matrix deposition with potential for three-dimensional bioprinting

Biofabrication 2019 Volume 11, Issue 1, Article 015015

Calcified cartilage regeneration plays an important role in successful osteochondral repair, since it provides a biological and mechanical transition from the unmineralized cartilage at the articulating surface to the underlying mineralized bone. To biomimic native calcified cartilage in engineered constructs, here we test the hypothesis that hydroxyapatite (HAP) stimulates chondrocytes to secrete the characteristic matrix of calcified cartilage. Sodium citrate (SC) was added as a dispersant of HAP within alginate (ALG), and homogeneous dispersal of HAP within ALG hydrogel was confirmed using sedimentation tests, electron microscopy, and energy dispersive spectroscopy. To examine the biological performance of ALG/HAP composites, chondrocyte survival…

Characterization of Cell Damage and Proliferative Ability during and after Bioprinting

ACS Biomaterials Science & Engineering 2018 Volume 4, Issue 11, Pages 3906–3918

When a biomaterial solution containing living cells is subject to bioprinting, the cells experience process-induced stresses, including shear and extensional stresses. These process-induced stresses breach cell membranes and can lead to cell damage, thus reducing cell viability and functioning within the printed constructs. Studies have been conducted to determine the influence of shear stress on cell damage; however, the effect of extensional stress has been typically ignored in the literature until the recently collected evidence of its importance. This paper presents a novel method to characterize and quantify the cell damage caused by both shear and extensional stresses in bioprinting….

Modeling of the Mechanical Behavior of 3D Bioplotted Scaffolds Considering the Penetration in Interlocked Strands

Applied Sciences 2018 Volume 8, Issue 9, Pages 1422-1436

Three-dimensional (3D) bioplotting has been widely used to print hydrogel scaffolds for tissue engineering applications. One issue involved in 3D bioplotting is to achieve the scaffold structure with the desired mechanical properties. To overcome this issue, various numerical methods have been developed to predict the mechanical properties of scaffolds, but limited by the imperfect representation of one key feature of scaffolds fabricated by 3D bioplotting, i.e., the penetration or fusion of strands in one layer into the previous layer. This paper presents our study on the development of a novel numerical model to predict the elastic modulus (one important index…


3D bioprinting of scaffolds with living Schwann cells for potential nerve tissue engineering applications

Biofabrication 2018 Volume 10, Number 3, Article 035014

Three-dimensional bioprinting of biomaterials shows great potential for producing cell-encapsulated scaffolds to repair nerves after injury or disease. For this, preparation of biomaterials and bioprinting itself are critical to create scaffolds with both biological and mechanical properties appropriate for nerve regeneration, yet remain unachievable. This paper presents our study on bioprinting Schwann cell-encapsulated scaffolds using composite hydrogels of alginate, fibrin, hyaluronic acid, and/or RGD peptide, for nerve tissue engineering applications. For the preparation of composite hydrogels, suitable hydrogel combinations were identified and prepared by adjusting the concentration of fibrin based on the morphological spreading of Schwann cells. In bioprinting, the…

Influence of crosslinking on the mechanical behavior of 3D printed alginate scaffolds: Experimental and numerical approaches

Journal of the Mechanical Behavior of Biomedical Materials 2018 Volume 80, Pages 111-118

Tissue scaffolds fabricated by three-dimensional (3D) bioprinting are attracting considerable attention for tissue engineering applications. Because the mechanical properties of hydrogel scaffolds should match the damaged tissue, changing various parameters during 3D bioprinting has been studied to manipulate the mechanical behavior of the resulting scaffolds. Crosslinking scaffolds using a cation solution (such as CaCl2) is also important for regulating the mechanical properties, but has not been well documented in the literature. Here, the effect of varied crosslinking agent volume and crosslinking time on the mechanical behavior of 3D bioplotted alginate scaffolds was evaluated using both experimental and numerical methods. Compression…


Evaluation of PBS Treatment and PEI Coating Effects on Surface Morphology and Cellular Response of 3D-Printed Alginate Scaffolds

Journal of Functional Biomaterials 2017 Volume 8, Issue 4, Article 48

Three-dimensional (3D) printing is an emerging technology for the fabrication of scaffolds to repair/replace damaged tissue/organs in tissue engineering. This paper presents our study on 3D printed alginate scaffolds treated with phosphate buffered saline (PBS) and polyethyleneimine (PEI) coating and their impacts on the surface morphology and cellular response of the printed scaffolds. In our study, sterile alginate was prepared by means of the freeze-drying method and then, used to prepare the hydrogel for 3D printing into calcium chloride, forming 3D scaffolds. Scaffolds were treated with PBS for a time period of two days and seven days, respectively, and PEI…

UV-assisted 3D bioprinting of nano-reinforced hybrid cardiac patch for myocardial tissue engineering

Tissue Engineering Part C: Methods 2017 Volume: 24 Issue 2, Pages 74-88

Biofabrication of cell supportive cardiac patches that can be directly implanted on myocardial infarct is a potential solution for myocardial infarction repair. Ideally, cardiac patches should be able to mimic myocardium extracellular matrix for rapid integration with the host tissue, raising the need to develop cardiac constructs with complex features. In particular, cardiac patches should be electrically conductive, mechanically robust and elastic, biologically active and pre-vascularized.. In this study, we aim to biofabricate a nano-reinforced hybrid cardiac patch laden with human coronary artery endothelial cells (HCAECs) with improved electrical, mechanical and biological behavior. A safe UV exposure time with insignificant…

Bioprinting pattern-dependent electrical/mechanical behavior of cardiac alginate implants: characterization and ex-vivo phase-contrast microtomography assessment

Tissue Engineering Part C: Methods 2017 Volume 23, Issue 9, Pages 548-564

Three-dimensional (3D)-bioprinting techniques may be used to modulate electrical/mechanical properties and porosity of hydrogel constructs for fabrication of suitable cardiac implants. Notably, characterization of these properties after implantation remains a challenge, raising the need for the development of novel quantitative imaging techniques for monitoring hydrogel implant behavior in-situ. This study aims to (i) assess the influence of hydrogel bioprinting patterns on electrical/mechanical behavior of cardiac implants based on a 3D-printing technique and (ii) investigate the potential of synchrotron X-ray phase contrast computed tomography (PCI-CT) for estimating elastic modulus/impedance/porosity and microstructural features of 3D-printed cardiac implants in-situ via an ex-vivo study….

Potential of propagation-based synchrotron X-ray phase-contrast computed tomography for cardiac tissue engineering

Journal of Synchrotron Radiation 2017 Volume 24, Pages 842-853

Hydro­gel-based cardiac tissue engineering offers great promise for myocardial infarction repair. The ability to visualize engineered systems in vivo in animal models is desired to monitor the performance of cardiac constructs. However, due to the low density and weak X-ray attenuation of hydro­gels, conventional radiography and micro-computed tomography are unable to visualize the hydro­gel cardiac constructs upon their implantation, thus limiting their use in animal systems. This paper presents a study on the optimization of synchrotron X-ray propagation-based phase-contrast imaging computed tomography (PCI-CT) for three-dimensional (3D) visualization and assessment of the hydro­gel cardiac patches. First, alginate hydro­gel was 3D-printed into…

Modeling flow behavior and flow rate of medium viscous alginate for scaffold fabrication with 3D bioplotter

Journal of Manufacturing Science and Engineering 2017 Volume 139, Issue 8, Article 081002

Tissue regeneration with scaffold is one of the most promising approaches now a day, where application of dispensing-based rapid prototyping technique is drawing attention due to its capability to offer operational flexibility and print complex structure with utmost uniformity. In a pneumatic dispensing system, it is a critical issue to control the flow rate of biomaterial from dispensing tip, as some variables (material viscosity, temperature, needle geometry, and dispensing pressure) regulates the flow rate . In this context, model equations can play a vital role to control and predict the flow rate of dispensing material, and thus can eliminate the…

Remote Determination of Time-Dependent Stiffness of Surface-Degrading-Polymer Scaffolds Via Synchrotron-Based Imaging

Journal of Biomechanical Engineering 2017 Volume 139, Issue 4, Article 041004

Surface-degrading polymers have been widely used to fabricate scaffolds with the mechanical properties appropriate for tissue regeneration/repair. During their surface degradation, the material properties of polymers remain approximately unchanged, but the scaffold geometry and thus mechanical properties vary with time. This paper presents a novel method to determine the time-dependent mechanical properties, particularly stiffness, of scaffolds from the geometric changes captured by synchrotron-based imaging, with the help of finite element analysis (FEA). Three-dimensional (3D) tissue scaffolds were fabricated from surface-degrading polymers, and during their degradation, the tissue scaffolds were imaged via the synchrotron-based imaging to characterize their changing geometry. On…

PCL Imaging

Traditional invasive and synchrotron-based non-invasive assessments of 3D-printed hybrid cartilage constructs

Tissue Engineering Part C: Methods 2017 Volume 23, Issue 3, Pages 156-168

Three-dimensional (3D)-printed constructs made of polycaprolactone (PCL) and chondrocyte-impregnated alginate hydrogel (hybrid cartilage constructs) mimic the biphasic nature of articular cartilage, offering promise for cartilage tissue engineering (CTE) applications. However, the regulatory pathway for medical device development requires validation of such constructs through in vitro bench tests and in vivo preclinical examinations premarket approval. Furthermore, non-invasive imaging techniques are required for effective evaluation of the progress of these cartilage constructs, especially when implanted in animal models or human subjects. However, characterization of the individual components of the hybrid cartilage constructs and their associated time-dependent structural changes by currently available non-invasive…

Low-dose phase-based X-ray imaging techniques for in situ soft tissue engineering assessments

Biomaterials 2016 Volume 82, Pages 151–167

In tissue engineering, non-invasive imaging of biomaterial scaffolds and tissues in living systems is essential to longitudinal animal studies for assessments without interrupting the repair process. Conventional X-ray imaging is inadequate for use in soft tissue engineering due to the limited absorption difference between the soft tissue and biomaterial scaffolds. X-ray phase-based imaging techniques that derive contrast from refraction or phase effects rather than absorption can provide the necessary contrast to see low-density biomaterial scaffolds and tissues in large living systems. This paper explores and compares three synchrotron phase-based X-ray imaging techniques—computed tomography (CT)-diffraction enhanced imaging (DEI), -analyzer based imaging…

Bioprinted fibrin-factor XIII-hyaluronate hydrogel scaffolds with encapsulated Schwann cells and their in vitro characterization for use in nerve regeneration

Bioprinting 2016 Volume 5, March 2017, Pages 1-9

The blood clotting protein fibrin contains cell-binding domains, providing potential advantage for the fabrication of tissue repair scaffolds and for live cell encapsulation. However, fabrication of fibrin scaffolds with encapsulated cells using three dimensional (3D) printing has proven challenging due to the mechanical difficulties of fabricating protein hydrogel scaffolds with defined microstructure. For example, extrusion based 3D printing of fibrin is generally unfeasible because of the low viscosity of precursor fibrinogen solution. Here we describe a novel technique for bioprinting of fibrin scaffolds by extruding fibrinogen solution into thrombin solution, utilizing hyaluronic acid (HA) and polyvinyl alcohol (PVA) to increase…

Synchrotron-Based in Situ Characterization of the Scaffold Mass Loss from Erosion Degradation

Journal of Functional Biomaterials 2016 Volume 7, Issue 3, 17

The mass loss behavior of degradable tissue scaffolds is critical to their lifespan and other degradation-related properties including mechanical strength and mass transport characteristics. This paper presents a novel method based on synchrotron imaging to characterize the scaffold mass loss from erosion degradation in situ, or without the need of extracting scaffolds once implanted. Specifically, the surface-eroding degradation of scaffolds in a degrading medium was monitored in situ by synchrotron-based imaging; and the time-dependent geometry of scaffolds captured by images was then employed to estimate their mass loss with time, based on the mathematical model that was adopted from the…

PCL Imaging

3D Printing of Porous Cell-Laden Hydrogel Constructs for Potential Applications in Cartilage Tissue Engineering

ACS Biomaterials Science and Engineering 2016 Volume 2, Issue 7, Pages 1200–1210

Hydrogels are particularly attractive as scaffolding materials for cartilage tissue engineering because their high water content closely mimics the native extracellular matrix (ECM). Hydrogels can also provide a three-dimensional (3D) microenvironment for homogeneously suspended cells that retains their rounded morphology and thus facilitates chondrogenesis in cartilage tissue engineering. However, fabricating hydrogel scaffolds or cell-laden hydrogel constructs with a predesigned external shape and internal structure that does not collapse remains challenging because of the low viscosity and high water content of hydrogel precursors. Here, we present a study on the fabrication of (cell-laden) alginate hydrogel constructs using a 3D bioplotting system…

Using synchrotron radiation inline phase-contrast imaging computed tomography to visualize three-dimensional printed hybrid constructs for cartilage tissue engineering

Journal of Synchrotron Radiation 2016 Volume 23, Issue 3, Pages 802-812

Synchrotron radiation inline phase-contrast imaging combined with computed tomography (SR-inline-PCI-CT) offers great potential for non-invasive characterization and three-dimensional visualization of fine features in weakly absorbing materials and tissues. For cartilage tissue engineering, the biomaterials and any associated cartilage extracellular matrix (ECM) that is secreted over time are difficult to image using conventional absorption-based imaging techniques. For example, three-dimensional printed polycaprolactone (PCL)/alginate/cell hybrid constructs have low, but different, refractive indices and thicknesses. This paper presents a study on the optimization and utilization of inline-PCI-CT for visualizing the components of three-dimensional printed PCL/alginate/cell hybrid constructs for cartilage tissue engineering. First, histological analysis…

3D Printing of Porous Alginate/gelatin Hydrogel Scaffolds and Their Mechanical Property Characterization

International Journal of Polymeric Materials and Polymeric Biomaterials 2016 Volume 66, Issue 6, Pages 299-306

Hydrogel scaffolds with well-defined internal structure and interconnected porosity are important for tissue engineering. 3D Bioplotting technique supplemented with thermal/submerged ionic crosslinking process was used to fabricate hydrogel scaffolds. Six scaffold geometries were fabricated and their influence on mechanical performance was investigated. 0/90-0.8 group with the lowest porosity showed the highest Young’s modulus while the Shift group showed the lowest Young’s modulus. Same trend has also been observed for the dynamic modulus of each group. Results demonstrated that the mechanical performance of hydrogel scaffolds can be tuned by changing the internal structure parameters including strands orientation and spacing between strands.

Alginate Gelatin

Analyzing biological performance of 3D-printed, cell-impregnated hybrid constructs for cartilage tissue engineering

Tissue Engineering Part C: Methods 2016 Volume 22, Issue 3, Pages 173-188

Three-dimensional (3D) bioprinting of hybrid constructs is a promising biofabrication method for cartilage tissue engineering because a synthetic polymer framework and cell-impregnated hydrogel provide structural and biological features of cartilage, respectively. During bioprinting, impregnated cells may be subjected to high temperatures (caused by the adjacent melted polymer) and process-induced mechanical forces, potentially compromising cell function. This study addresses these biofabrication issues, evaluating the heat distribution of printed polycaprolactone (PCL) strands and the rheological property and structural stability of alginate hydrogels at various temperatures and concentrations. The biocompatibility of parameters from these studies was tested by culturing 3D hybrid constructs bioprinted…

Use of the polycation polyethyleneimine to improve the physical properties of alginate-hyaluronic acid hydrogel during fabrication of tissue repair scaffolds

Journal of Biomaterials Science, Polymer Edition 2015 Volume 26, Issue 7, Pages 433-445

Recently alginate-based tissue repair scaffolds fabricated using 3D printing techniques have been extensively examined for use in tissue engineering applications. However, their physical and mechanical properties are unfavorable for many tissue engineering applications because these properties are poorly controlled during the fabrication process. Some improvement of alginate gel properties can be realized by addition of hyaluronic acid (HA), and this may also improve the ability of cells to interact with the gel. Here, we report improvement of the physical properties of alginate–HA gel scaffolds by the addition of the polycation polyethyleneimine (PEI) during the fabrication process in order to stabilize…

Characterization of Mechanical Properties of Tissue Scaffolds by Phase Contrast Imaging and Finite Element Modeling

Journal of Biomechanical Engineering 2015 Volume 137, Issue 8, Article 081004

In tissue engineering, the cell and scaffold approach has shown promise as a treatment to regenerate diseased and/or damaged tissue. In this treatment, an artificial construct (scaffold) is seeded with cells, which organize and proliferate into new tissue. The scaffold itself biodegrades with time, leaving behind only newly formed tissue. The degradation qualities of the scaffold are critical during the treatment period, since the change in the mechanical properties of the scaffold with time can influence cell behavior. To observe in time the scaffold’s mechanical properties, a straightforward method is to deform the scaffold and then characterize scaffold deflection accordingly….

PDMS Imaging

Computed Tomography Diffraction-Enhanced Imaging for In Situ Visualization of Tissue Scaffolds Implanted in Cartilage

Tissue Engineering Part C: Methods 2014 Volume 20, Issue 2, Pages 140-148

Long-term in vivo studies on animal models and advances from animal to human studies should rely on noninvasive monitoring methods. Synchrotron radiation (SR)-diffraction enhanced imaging (DEI) has shown great promise as a noninvasive method for visualizing native and/or engineered tissues and bio-microstructures with appreciable details in situ. The objective of this study was to investigate SR-DEI for in situ visualization and characterization of tissue-engineered scaffolds implanted in cartilage. A piglet stifle joint implanted with an engineered scaffold made from poly-ɛ-caprolactone was imaged using SR computed tomography (CT)-DEI at an X-ray energy of 40 keV. For comparison, in situ visualization was also…

Bioplotting Alginate/Hyaluronic Acid Hydrogel Scaffolds with Structural Integrity and Preserved Schwann Cell Viability

3D Printing and Additive Manufacturing 2014 Volume 1, Issue 4, Pages 194-203

Bioplotting is an emerging freeform scaffold fabrication technique useful for creating artificial tissue scaffolds containing living cells. Simultaneous maintenance of scaffold structural integrity and cell viability is a challenging task. In this article, we present strategies developed to bioplot alginate-based three-dimensional tissue scaffolds containing hyaluronic acid and living Schwann cells for potential use in peripheral nerve tissue engineering. The fabrication platform, upon which the scaffold is created, was coated with the polycation polyethylenimine to immobilize the first layer of the scaffold on the platform. Each layer was then dispensed into a bath containing calcium chloride to cross-link the alginate, polyvinyl…

Novel crosslinked alginate/hyaluronic acid hydrogels for nerve tissue engineering

Frontiers of Materials Science 2013 Volume 7, Issue 3, Pages 269-284

Artificial tissue engineering scaffolds can potentially provide support and guidance for the regrowth of severed axons following nerve injury. In this study, a hybrid biomaterial composed of alginate and hyaluronic acid (HA) was synthesized and characterized in terms of its suitability for covalent modification, biocompatibility for living Schwann cells and feasibility to construct three dimensional (3D) scaffolds. Carbodiimide mediated amide formation for the purpose of covalent crosslinking of the HA was carried out in the presence of calciumions that ionically crosslink alginate. Amide formation was found to be dependent on the concentrations of carbodiimide and calcium chloride. The double-crosslinked composite…

Development of Schwann Cell-Encapsulated Alginate Scaffolds for the Repair of Peripheral Nerve Injury

CMBES Proceedings 35 2012

Nerve conduits for peripheral nerve repair have progressed from simple silicon tubes to complex engineered scaffolds. Recent advances in scaffold fabrication have enabled the incorporation of neurotrophins, extracellular matrix components and various cells into scaffolds for enhanced biologic properties. Bioplotting is one of the emerging methods, where the scaffold material, in form of a solution, is dispensed from a needle, layer by layer forming a three-dimensional structure. It enables the use of a wide range of materials, ranging from synthetic polymers (like polycaprolactone, polyglycolic acid, etc.) to naturally occurring polymers like alginate, chitosan, etc. Notably, the use of hydrogels gives…