3D Bioplotter Research Papers

Displaying all papers from 2018 (58 results)

ZEB2, a master regulator of the epithelial-mesenchymal transition, mediates trophoblast differentiation

MHR: Basic science of reproductive medicine 2018 Volume 25, Issue 2, Pages 61–75

STUDY QUESTION Does the upregulation of the zinc finger E-box binding homeobox 2 (ZEB2) transcription factor in human trophoblast cells lead to alterations in gene expression consistent with an epithelial-mesenchymal transition (EMT) and a consequent increase in invasiveness? SUMMARY ANSWER Overexpression of ZEB2 results in an epithelial-mesenchymal shift in gene expression accompanied by a substantial increase in invasive capacity of human trophoblast cells.

Anisotropic Composite Material Phantom Tested Using Magnetic Resonance Elastography

Proceedings of the Sixteenth International Tissue Elasticity Conference 2018 Page 22

Background: The presence and progression of neuromuscular pathologies, including spasticity, dystrophy and hyperthyroidism, have been correlated with changes in the intrinsic mechanical properties of skeletal muscle tissue. Tools of noninvasively measuring and monitoring these properties, such as Magnetic Resonance Elastography (MRE), could benefit basic research into understanding neuromuscular pathologies, as well as translational research to develop therapies, by providing a means of assessing and tracking their efficacy. While various approaches have been proposed in the literature [1,2], there is not yet an accepted standard for the identification of the mechanical properties of anisotropic and viscoelastic tissues through MRE; advances in…

Gelatin Imaging

Reversible physical crosslinking strategy with optimal temperature for 3D bioprinting of human chondrocyte-laden gelatin methacryloyl bioink

Journal of Biomaterials Applications 2018 Volume 33, Issue 5, Pages 609-618

Gelatin methacryloyl is a promising material in tissue engineering and has been widely studied in three-dimensional bioprinting. Although gelatin methacryloyl possesses excellent biocompatibility and tunable mechanical properties, its poor printability/processability has hindered its further applications. In this study, we report a reversible physical crosslinking strategy for precise deposition of human chondrocyte-laden gelatin methacryloyl bioink at low concentration without any sacrificial material by using extrusive three-dimensional bioprinting. The precise printing temperature was determined by the rheological properties of gelatin methacryloyl with temperature. Ten percent (w/v) gelatin methacryloyl was chosen as the printing formula due to highest biocompatibility in three-dimensional cell cultures…

Defect-engineered reduced graphene oxide sheets with high electric conductivity and controlled thermal conductivity for soft and flexible wearable thermoelectric generators

Nano Energy 2018 Volume 54, Pages 163-174

The direct use of graphene for potential thermoelectric material requires the opening of its bandgap without loss of its high electric conductivity. We herein demonstrate a synchronous reduction and assembly strategy to fabricate large-area reduced graphene oxide films with high electric conductivity and optimized low thermal conductivity assembly. The reduced graphene oxide films have a high electric conductivity and low thermal conductivity, which results from high longitudinal carrier mobility of the lattice domains as well as the enhanced scattering of phonons in the defects and their boundary that substantially reduces the mean phonon free path and the thermal conductivity. Flexible…

Coating 3D Printed Polycaprolactone Scaffolds with Nanocellulose Promotes Growth and Differentiation of Mesenchymal Stem Cells

Biomacromolecules 2018 Voluem 19, Issue 11, Pages 4307-4319

3D printed polycaprolactone (PCL) has potential as a scaffold for bone tissue engineering, but the hydrophobic surface may hinder optimal cell responses. The surface properties can be improved by coating the scaffold with cellulose nanofibrils material (CNF), a multiscale hydrophilic biocompatible biomaterial derived from wood. In this study, human bone marrow-derived mesenchymal stem cells were cultured on tissue culture plates (TCP) and 3D printed PCL scaffolds coated with CNF. Cellular responses to the surfaces (viability, attachment, proliferation, and osteogenic differentiation) were documented. CNF significantly enhanced the hydrophilic properties of PCL scaffolds and promoted protein adsorption. Live/dead staining and lactate dehydrogenase…

Tough and Processable Hydrogels Based on Lignin and Hydrophilic Polyurethane

ACS Applied Bio Materials 2018 Volume 1, Issue 6, Pages 2073–2081

Lignin is a low-cost, natural polymer with abundant polar sites on its backbone that can be utilized for physical cross-linking of polymers. Here, we use lignin for additional cross-linking of hydrophilic polyether-based polyurethane (HPU) hydrogels, aiming to improve their mechanical properties and processability. Without reducing the swelling, simple addition of 2.5 wt % lignin increases the fracture energy and Young’s modulus of HPU hydrogels from, respectively, 1540 ± 40 to 2050 ± 50 J m–2 and 1.29 ± 0.06 to 2.62 ± 0.84 MPa. Lignin also increases the lap shear adhesiveness of hydrogels and induces an immediate load recovery of…

Trophoblast–endothelium signaling involves angiogenesis and apoptosis in a dynamic bioprinted placenta model

Biotechnology and Bioengineering 2018 Volume 116, Issue 1, Pages 181-192

Trophoblast invasion and remodeling of the maternal spiral arteries are required for pregnancy success. Aberrant endothelium–trophoblast crosstalk may lead to preeclampsia, a pregnancy complication that has serious effects on both the mother and the baby. However, our understanding of the mechanisms involved in this pathology remains elementary because the current in vitro models cannot describe trophoblast–endothelium interactions under dynamic culture. In this study, we developed a dynamic three‐dimensional (3D) placenta model by bioprinting trophoblasts and an endothelialized lumen in a perfusion bioreactor. We found the 3D printed perfusion bioreactor system significantly augmented responses of endothelial cells by encouraging network formations…

3D Printing Bioactive PLGA Scaffolds Using DMSO as a Removable Solvent

Bioprinting 2018 Volume 10, June 2018, Article e00038

Present bioprinting techniques lack the methodology to print with bioactive materials that retain their biological functionalities. This constraint is due to the fact that extrusion-based printing of synthetic polymers is commonly performed at very high temperatures in order to achieve desired mechanical properties and printing resolutions. Consequently, current methodology prevents printing scaffolds embedded with bioactive molecules, such as growth factors. With the wide use of mesenchymal stem cells (MSCs) in regenerative medicine research, the integration of growth factors into 3D printed scaffolds is critical because it can allow for inducible MSC differentiation. We have successfully incorporated growth factors into extrusion…

A Bioprinted Cardiac Patch Composed of Cardiac-Specific Extracellular Matrix and Progenitor Cells for Heart Repair

Advanced Healthcare Materials 2018 Volume 7, Issue 23, Article 1800672

Congenital heart defects are present in 8 of 1000 newborns and palliative surgical therapy has increased survival. Despite improved outcomes, many children develop reduced cardiac function and heart failure requiring transplantation. Human cardiac progenitor cell (hCPC) therapy has potential to repair the pediatric myocardium through release of reparative factors, but therapy suffers from limited hCPC retention and functionality. Decellularized cardiac extracellular matrix hydrogel (cECM) improves heart function in animals, and human trials are ongoing. In the present study, a 3D‐bioprinted patch containing cECM for delivery of pediatric hCPCs is developed. Cardiac patches are printed with bioinks composed of cECM, hCPCs,…

Tyrosinase-doped bioink for 3D bioprinting of living skin constructs

Biomedical Materials 2018 Volume 13, Number 3, Article Number 035008

Three-dimensional bioprinting is an emerging technology for fabricating living 3D constructs, and it has shown great promise in tissue engineering. Bioinks are scaffold materials mixed with cells used by 3D bioprinting to form a required cell-laden structure. In this paper, a novel bioink made of gelatin methacrylamide (GelMA) and collagen (Col) doped with tyrosinase (Ty) is presented for the 3D bioprinting of living skin tissues. Ty has the dual function of being an essential bioactive compound in the skin regeneration process and also as an enzyme to facilitate the crosslink of Col and GelMA. Further, enzyme crosslinking together with photocrosslinking…

3D printed soft parallel actuator

Smart Materials and Structures 2018 Volume 27, Number 4

This paper presents a 3-dimensional (3D) printed soft parallel contactless actuator for the first time. The actuator involves an electro-responsive parallel mechanism made of two segments namely active chain and passive chain both 3D printed. The active chain is attached to the ground from one end and constitutes two actuator links made of responsive hydrogel. The passive chain, on the other hand, is attached to the active chain from one end and consists of two rigid links made of polymer. The actuator links are printed using an extrusion-based 3D-Bioplotter with polyelectrolyte hydrogel as printer ink. The rigid links are also…

Voltaglue Bioadhesives Energized with Interdigitated 3D‐Graphene Electrodes

Advanced Healthcare Materials 2018 Volume 7, Issue 21, Article 1800538

Soft tissue fixation of implant and bioelectrodes relies on mechanical means (e.g., sutures, staples, and screws), with associated complications of tissue perforation, scarring, and interfacial stress concentrations. Adhesive bioelectrodes address these shortcomings with voltage cured carbene‐based bioadhesives, locally energized through graphene interdigitated electrodes. Electrorheometry and adhesion structure activity relationships are explored with respect to voltage and electrolyte on bioelectrodes synthesized from graphene 3D‐printed onto resorbable polyester substrates. Adhesive leachates effects on in vitro metabolism and human‐derived platelet‐rich plasma response serves to qualitatively assess biological response. The voltage activated bioadhesives are found to have gelation times of 60 s or less…

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…

Alginate

Printed, Flexible pH Sensor Hydrogels for Wet Environments

Advanced Materials Technologies 2018 Volume 3, Issue 11, Article 1800137

Current sensors for monitoring environmental signals, such as pH, are often made from rigid materials that are incompatible with soft biological tissues. The high stiffness of such materials sets practical limitations on the in situ utilization of sensors under biological conditions. This article describes a soft yet robust hydrogel‐based pH sensor that can be 3D printed. The pH‐sensitive poly(3,4‐ethylenedioxythiophene) is combined with hydrophilic polyurethane to create novel printable inks with favorable biomechanical properties. These inks are employed to fabricate highly flexible pH sensors that linearly respond to pH in wet environments. The pH sensitive hydrogels can undergo extreme deformations including…

3D printed biofunctionalized scaffolds for microfracture repair of cartilage defects

Biomaterials 2018 Volume 185, Pages 219-231

While articular cartilage defects affect millions of people worldwide from adolescents to adults, the repair of articular cartilage defects still remains challenging due to the limited endogenous regeneration of the tissue and poor integration with implants. In this study, we developed a 3D-printed scaffold functionalized with aggrecan that supports the cellular fraction of bone marrow released from microfracture, a widely used clinical procedure, and demonstrated tremendous improvement of regenerated cartilage tissue quality and joint function in a lapine model. Optical coherence tomography (OCT) revealed doubled thickness of the regenerated cartilage tissue in the group treated with our aggrecan functionalized scaffold…

Determination of geometrical and viscoelastic properties of PLA/PHB samples made by additive manufacturing for urethral substitution

Journal of Biotechnology 2018 Volume 284, Pages 123-130

Additive manufacturing has a great potential for creating hard tissue substitutes, such as bone and cartilage, or soft tissues, such as vascular and skin grafts. This study is a pilot study for 3D printing of a new material mixture potentially used as a tubular substitute for urethra replacement. This new mixture is a blend of polylactic acid (PLA) and polyhydroxybutyrate (PHB). The basic aspect that affects the 3D printing process is correct material preparation and setting of 3D printer parameters. Selection of material and printing parameters depend on printing technology. The printing technology affects material behavior during printing process. The…

Collagen/hydroxyapatite bone grafts manufactured by homogeneous/ heterogeneous 3D printing

Materials Letters 2018 Volume 231, Pages 179-182

This paper presents a new way to obtain collagen/hydroxyapatite (COLL/HA) composite materials by 3D printing. Because of high tendency of segregation of COLL/HA composite materials, printing was done using COLL/Ca2+ gel (even COLL/Ca(OH)2) followed by precipitation of HA and crosslinking of COLL. The HA precipitation occurs simultaneously with crosslinking of COLL molecules, these processes being assured by the presence of glutaraldehyde supplemented PBS solution. By printing with COLL/Ca2+ at acidic pH homogeneity was increased. FTIR spectroscopy and microscopy reveal HA formation as the main inorganic phase these nanoparticles being homogeneously dispersed in the volume. In vitro biocompatibility assays were performed…

Heparin/Poly-L-lysine-coated 3D-printed PLGA scaffolds as drug carriers for local immune modulation in bone regeneration

Society for Biomaterials Annual Meeting and Exposition 2018 Presentation 584

Immune responses after injury play a critical role in bone regeneration. Initiation of inflammation at early stages of repair triggers tissue formation and remodeling; however, uncontrolled inflammation underlies a catabolic effect on tissues as commonly seen in arthritis where inflammation breaks down tissues and hinders regeneration. Our ultimate goal is to design a novel approach on bone scaffolds for which biodegradable scaffolds are loaded with inflammatory cytokines for local immunomodulation as well as bone regeneration. We employed nanoparticles (NPs) composed of heparin (Hep) and poly-L-lysine (PLL) as cytokine drug carriers adhered on 3D-printed poly(lactic-co-glycolic acid) (PLGA) scaffolds. The entire drug…

Polyelectrolyte Soft Actuators: 3D Printed Chitosan and Cast Gelatin

3D Printing and Additive Manufacturing 2018 Volume 5, Issue 2, Pages 138-150

With increasing utilization of robots in daily tasks, especially in biomedical and environmental monitoring applications, there would be demands for soft, biodegradable, or even edible actuators that provide more versatility than conventional rigid materials (e.g., metals and plastics). Polyelectrolyte hydrogels produce mechanical motion in response to electrical stimulus, making them good candidates for implementation of soft actuators. However, their conventional fabrication process has so far hindered their applicability in a broad range of controlled folding behaviors. A novel application of 3D printing in biodegradable and biocompatible soft robots is presented in this study. It is observed that the contactless electroactive…

3D Printing Nanoscale Bioactive Glass Scaffolds Enhance Osteoblast Migration and Extramembranous Osteogenesis through Stimulating Immunomodulation

Advanced Healthcare Materials 2018 Volume 7, Article 1800361

Bioactive glass (BG) can repair bone defects, however, it is not clear whether BG has the ability for bone augmentation without making any bone defect. Unlike the intramembranous osteogenesis in bone defect repair, the extramembranous osteogenesis occurs outside the cortical bone and the osteoprogenitor cells show the reversed migration. Herein, nanoscale bioactive glass scaffolds (BGSs) are fabricated, and their role and immunomodulation‐related mechanism in the extramembranous osteogenesis are investigated. The in vitro migration and differentiation of calvaria preosteoblasts are studied by culturing with peripheral macrophage‐conditioned medium after stimulating with BGSs. The results indicate that the proinflammatory environment significantly promotes preosteoblast…

3D Printing of Silk Particle-Reinforced Chitosan Hydrogel Structures and Their Properties

ACS Biomaterials Science & Engineering 2018 Volume 4, Issue 8, Pages 3036-3046

Hydrogel bioprinting is a major area of focus in the field of tissue engineering. However, 3D printed hydrogel scaffolds often suffer from low printing accuracy and poor mechanical properties because of their soft nature and tendency to shrink. This makes it challenging to process them into structural materials. In this study, natural chitosan hydrogel scaffolds were, for the first time, reinforced with milled silk particles and fabricated by 3D printing. Compared with pure chitosan scaffolds, the addition of silk particles resulted in up to a 5-fold increase in compressive modulus as well as significantly better printing accuracy and improved scaffold…

Flow-induced motions of flexible filaments hanging in cross-flow

Experimental Thermal and Fluid Science 2018 Volume 97, Pages 254-269

Experiments were carried out to study the dynamics of hanging cantilever flexible filaments in air cross-flow. Thirteen flexible filaments of 0.61 mm diameter and lengths from 20 mm to 60 mm were tested with wind speeds in the range of 1–15 m/s, corresponding to Reynolds numbers of 25 

Zein regulating apatite mineralization, degradability, in vitro cells responses and in vivo osteogenesis of 3D-printed scaffold of n-MS/ZN/PCL ternary composite

RSC Advances 2018 Volume 8, Pages 18745-18756

Bioactive and degradable scaffolds of nano magnesium silicate (n-MS)/zein (ZN)/poly(caprolactone) (PCL) ternary composites were prepared by 3D-printing method. The results showed that the 3D-printed scaffolds possessed controllable pore structure, and pore morphology, pore size, porosity and pore interconnectivity of the scaffolds can be efficiently adjusted. In addition, the apatite-mineralization ability of the scaffolds in simulated body fluids was obviously improved with the increase of ZN content, in which the scaffold with 20 w% ZN (C20) possessed excellent apatite-mineralization ability. Moreover, the degradability of the scaffolds was significantly enhanced with the increase of ZN content in the scaffolds. The degradation of…

Mechanically robust cryogels with injectability and bioprinting supportability for adipose tissue engineering

Acta Biomaterialia 2018 Volume 74, Pages 131-142

Bioengineered adipose tissues have gained increased interest as a promising alternative to autologous tissue flaps and synthetic adipose fillers for soft tissue augmentation and defect reconstruction in clinic. Although many scaffolding materials and biofabrication methods have been investigated for adipose tissue engineering in the last decades, there are still challenges to recapitulate the appropriate adipose tissue microenvironment, maintain volume stability, and induce vascularization to achieve long-term function and integration. In the present research, we fabricated cryogels consisting of methacrylated gelatin, methacrylated hyaluronic acid, and 4arm poly(ethylene glycol) acrylate (PEG-4A) by using cryopolymerization. The cryogels were repeatedly injectable and stretchable, and…

Response of hPDLSCs on 3D printed PCL/PLGA composite scaffolds in vitro

Molecular Medicine Reports 2018 Volume 18 Issue 2, Pages 1335-1344

Three‑dimensional printed (3DP) scaffolds have become an excellent resource in alveolar bone regeneration. However, selecting suitable printable materials remains a challenge. In the present study, 3DP scaffolds were fabricated using three different ratios of poly (ε‑caprolactone) (PCL) and poly‑lactic‑co‑glycolic acid (PLGA), which were 0.1PCL/0.9PLGA, 0.5PCL/0.5PLGA and 0.9PCL/0.1PLGA. The surface characteristics and degradative properties of the scaffolds, and the response of human periodontal ligament stem cells (hPDLSCs) on the scaffolds, were assessed to examine the preferable ratio of PCL and PLGA for alveolar bone regeneration. The results demonstrated that the increased proportion of PLGA markedly accelerated the degradation, smoothed the surface…

3D printed mesoporous bioactive glass/metal-organic framework scaffolds with antitubercular drug delivery

Microporous and Mesoporous Materials 2018 Volume 272, Pages 24-30

Three-dimensional (3D) porous scaffolds with sustained drug delivery are pursued for osteoarticular tuberculosis therapy after surgery. In this study, mesoporous bioactive glass/metal-organic framework (MBG/MOF) scaffolds with sustained antitubercular drug release have been fabricated by 3D printing. The results showed that the MBG/MOF scaffolds possess macropores of ca. 400 μm and enhanced compressive strength of 3–7 MPa, also exhibited good biocompatibility and apatite forming ability in vitro. Furthermore, the drug release rate and pH microenvironment of the MBG/MOF scaffolds could be controlled due to the MOF degradation. These results indicated that the 3D printed MBG/MOF scaffolds are promising for treating osteoarticular tuberculosis.

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…

Surface nanogrooving of carbon microtubes

Scientific Reports 2018 Volume 8, Article 9924

Extrusion processing of carbon tubes can be problematic due to their poor interfacial interactions with polymeric matrices. Surface chemical modification of carbon tubes can be utilized to create bonding sites to form networks with polymer chains. However, chemical reactions resulting in intermolecular primary bonding limit processability of extrudate, since they cause unstable rheological behaviour, and thus decrease the stock holding time, which is determinative in extrusion. This study presents a method for the synthesis of carbon microtubes with physically modified surface area to improve the filler and matrix interfacial interactions. The key concept is the formation of a nanogrooved topography,…

Label free process monitoring of 3D bioprinted engineered constructs via dielectric impedance spectroscopy

Biofabrication 2018 Volume 10, Article 035012

Biofabrication processes can affect biological quality attributes of encapsulated cells within constructs. Currently, assessment of the fabricated constructs is performed offline by subjecting the constructs to destructive assays that require staining and sectioning. This drawback limits the translation of biofabrication processes to industrial practice. In this work, we investigate the dielectric response of viable cells encapsulated in bioprinted 3D hydrogel constructs to an applied alternating electric field as a label-free non-destructive monitoring approach. The relationship between β-dispersion parameters (permittivity change—Δε, Cole–Cole slope factor—α, critical polarization frequency—f c ) over the frequency spectrum and critical cellular quality attributes are investigated. Results…

3D fiber deposited polymeric scaffolds for external auditory canal wall

Journal of Materials Science: Materials in Medicine 2018 Volume 29, Issue 5, Article 63

The external auditory canal (EAC) is an osseocartilaginous structure extending from the auricle to the eardrum, which can be affected by congenital, inflammatory, and neoplastic diseases, thus reconstructive materials are needed. Current biomaterial-based approaches for the surgical reconstruction of EAC posterior wall still suffer from resorption (biological) and extrusion (synthetic). In this study, 3D fiber deposited scaffolds based on poly(ethylene oxide terephthalate)/poly(butylene terephthalate) were designed and fabricated to replace the EAC wall. Fiber diameter and scaffold porosity were optimized, leading to 200 ± 33 µm and 55% ± 5%, respectively. The mechanical properties were evaluated, resulting in a Young’s modulus of 25.1 ± 7.0 MPa. Finally, the EAC…

Comparison of the degradation behavior of PLGA scaffolds in micro-channel, shaking, and static conditions

Biomicrofluidics 2018 Volume 12, Article 034106

Degradation of scaffolds is an important problem in tissue regeneration management. This paper reports a comparative study on degradation of the printed 3D poly (lactic-co-glycolic acid) scaffold under three conditions, namely, micro-channel, incubator static, and incubator shaking in the phosphate buffer saline (PBS) solution. In the case of the micro-channel condition, the solution was circulated. The following attributes of the scaffold and the solution were measured, including the mass or weight loss, water uptake, morphological and structural changes, and porosity change of the scaffold and the pH value of the PBS solution. In addition, shear stress in the scaffold under…

PLGA Drug Release

Vascularization of Natural and Synthetic Bone Scaffolds

Cell transplantation 2018 Volume 27, Issue 8, Pages 1269–1280

Vascularization of engineered bone tissue is critical for ensuring its survival after implantation. In vitro pre-vascularization of bone grafts with endothelial cells is a promising strategy to improve implant survival. In this study, we pre-cultured human smooth muscle cells (hSMCs) on bone scaffolds for 3 weeks followed by seeding of human umbilical vein endothelial cells (HUVECs), which produced a desirable environment for microvasculature formation. The sequential cell-seeding protocol was successfully applied to both natural (decellularized native bone, or DB) and synthetic (3D-printed Hyperelastic “Bone” scaffolds, or HB) scaffolds, demonstrating a comprehensive platform for developing natural and synthetic-based in vitro vascularized…

Dynamics of Cellulose Nanocrystal Alignment during 3D Printing

ACS Nano 2018 Volume 12, Issue 7, Pages 6926–6937

The alignment of anisotropic particles during ink deposition directly affects the microstructure and properties of materials manufactured by extrusion-based 3D printing. Although particle alignment in diluted suspensions is well described by analytical and numerical models, the dynamics of particle orientation in the highly concentrated inks typically used for printing via direct ink writing (DIW) remains poorly understood. Using cellulose nanocrystals (CNCs) as model building blocks of increasing technological relevance, we study the dynamics of particle alignment under the shear stresses applied to concentrated inks during DIW. With the help of in situ polarization rheology, we find that the time period…

Engineering Human Neural Tissue by 3D Bioprinting

Biomaterials for Tissue Engineering 2018 Pages 129-138

Bioprinting provides an opportunity to produce three-dimensional (3D) tissues for biomedical research and translational drug discovery, toxicology, and tissue replacement. Here we describe a method for fabricating human neural tissue by 3D printing human neural stem cells with a bioink, and subsequent gelation of the bioink for cell encapsulation, support, and differentiation to functional neurons and supporting neuroglia. The bioink uniquely comprises the polysaccharides alginate, water-soluble carboxymethyl-chitosan, and agarose. Importantly, the method could be adapted to fabricate neural and nonneural tissues from other cell types, with the potential to be applied for both research and clinical product development.

Three-dimensional printing of β-tricalcium phosphate/calcium silicate composite scaffolds for bone tissue engineering

Bio-Design and Manufacturing 2018 Volume 1, Issue 2, Pages 146-156

Bioactive scaffolds with interconnected porous structures are essential for guiding cell growth and new bone formation. In this work, we successfully fabricated three-dimensional (3D) porous β-tricalcium phosphate (β-TCP)/calcium silicate (CS) composite scaffolds with different ratios by 3D printing technique and further investigated the physiochemical properties, in vitro apatite mineralization properties and degradability of porous β-TCP/CS scaffolds. Moreover, a series of in vitro cell experiments including the attachment, proliferation and osteogenic differentiation of mouse bone marrow stromal cells were conducted to testify their biological performances. The results showed that 3D printed β-TCP/CS scaffolds possessed of controllable internal porous structures and external…

3D Printing of Thermoresponsive Polyisocyanide (PIC) Hydrogels as Bioink and Fugitive Material for Tissue Engineering

Polymers 2018 Volume 10, Issue 5, Article 555

Despite the rapid and great developments in the field of 3D hydrogel printing, a major ongoing challenge is represented by the development of new processable materials that can be effectively used for bioink formulation. In this work, we present an approach to 3D deposit, a new class of fully-synthetic, biocompatible PolyIsoCyanide (PIC) hydrogels that exhibit a reverse gelation temperature close to physiological conditions (37 °C). Being fully-synthetic, PIC hydrogels are particularly attractive for tissue engineering, as their properties—such as hydrogel stiffness, polymer solubility, and gelation kinetics—can be precisely tailored according to process requirements. Here, for the first time, we demonstrate…

Microstructure and Processing of 3D Printed Tungsten Microlattices and Infiltrated W–Cu Composites

Advanced Engineering Materials 2018 Volume 20, Article 1800354

ungsten is of industrial relevance due its outstanding intrinsic properties (e.g., highest melting‐point of all elements) and therefore difficult to 3D‐print by conventional methods. Here, tungsten micro‐lattices are produced by room‐temperature extrusion‐based 3D‐printing of an ink comprising WO3–0.5%NiO submicron powders, followed by H2‐reduction and Ni‐activated sintering. The green bodies underwent isotropic linear shrinkage of ≈50% during the thermal treatment resulting in micro‐lattices, with overall 35–60% open‐porosity, consisting of 95–100% dense W–0.5%Ni struts having ≈80–300 μm diameter. Ball‐milling the powders and inks reduced the sintering temperature needed to achieve full densification from 1400 to 1200 °C and enabled the ink to be extruded…

Tuning the viscoelastic features required for 3D printing of PVC-acrylate copolymers obtained by single electron transfer-degenerative chain transfer living radical polymerization (SET-DTLRP)

eXPRESS Polymer Letters 2018 Volume 12, Issue 9, Pages 824-835

Random poly (vinyl chloride-co-butyl acrylate) and poly (vinyl chloride-co-2-ethylhexyl acrylate copolymers obtained by single electron transfer-degenerative chain transfer living radical polymerization (SET- DTLRP) are investigated as potential candidates for 3D Printing. The analysis of the rheological implications of 3D Printing process allows establishing the basic viscoelastic conditions that the samples should fulfil to be printable, avoiding the ‘trial and error’ procedure. The effect of temperature and acrylates concentration on the rheological properties and 3D printing feasibility is contemplated. Eventually, thermal degradation is also considered. It is demonstrated that the copolymers which contain butyl acrylate comonomer, instead of 2-ethylhexyl acrylate, give…

3D Printed, PVA–PAA Hydrogel Loaded-Polycaprolactone Scaffold for the Delivery of Hydrophilic In-Situ Formed Sodium Indomethacin

Materials 2018 Voule 11, Issue 6, Article 1006

3D printed polycaprolactone (PCL)-blended scaffolds have been designed, prepared, and evaluated in vitro in this study prior to the incorporation of a polyvinyl alcohol–polyacrylic acid (PVA–PAA) hydrogel for the delivery of in situ-formed sodium indomethacin. The prepared PCL–PVA–PAA scaffold is proposed as a potential structural support system for load-bearing tissue damage where inflammation is prevalent. Uniaxial strain testing of the PCL-blended scaffolds were undertaken to determine the scaffold’s resistance to strain in addition to its thermal, structural, and porosimetric properties. The viscoelastic properties of the incorporated PVA–PAA hydrogel has also been determined, as well as the drug release profile of…

Stable gelatin-based phantom materials with tunable x-ray attenuation properties and 3D printability for x-ray imaging

Physics in Medicine & Biology 2018 Volume 63, Number 9, Article 09NT01

We report a novel method for developing gelatin-based phantom materials for transmission x-ray imaging with high stability at room temperature and tunable x-ray attenuation properties. This is achieved by efficiently cross-linking gelatin in a glycerin solution with only 10% water by volume and systematically decreasing their x-ray attenuation coefficients by doping with microbubbles that are originally designed to be used as lightweight additives for paints and crack fillers. For demonstration, we mimic breast glandular and adipose tissues by using such gelatin materials and also study the feasibility of 3D printing them based on the extrusion-based technique. Results from x-ray spectroscopy…

Iterative feedback bio-printingderived cell-laden hydrogel scaffolds with optimal geometrical fidelity and cellular controllability

Scientific Reports 2018 Volume 8, Article number: 2802

For three-dimensional bio-printed cell-laden hydrogel tissue constructs, the well-designed internal porous geometry is tailored to obtain the desired structural and cellular properties. However, significant differences often exist between the designed and as-printed scaffolds because of the inherent characteristics of hydrogels and cells. In this study, an iterative feedback bio-printing (IFBP) approach based on optical coherence tomography (OCT) for the fabrication of cell-laden hydrogel scaffolds with optimal geometrical fidelity and cellular controllability was proposed. A custom-made swept-source OCT (SS-OCT) system was applied to characterize the printed scaffolds quantitatively. Based on the obtained empirical linear formula from the first experimental feedback loop,…

3D-printed thick structured gelatin membrane for engineering of heterogeneous tissues

Materials Letters 2018 Volume 217, Pages 39-43

Although biological membranes may look like a 2D assembly, they often have complex structures in their 3rd dimension. Using layer-by-layer assembly, 3D-printing can offer an advanced and unique approach for the fabrication of such models. However, printing of some widely used hydrogels, such as gelatin, encounters experimental difficulties due to their rheological properties. In this paper, we (a) discuss the complexities involved in printing gelatin, (b) offer a reproducible approach to overcome such difficulties, and (c) present the detailed design criteria and the production process of such 3D-printed gelatin membranes by exemplifying scaffolds suitable for growth of full-thickness oral mucosa…

A 3D bioprinted in situ conjugated‐co‐fabricated scaffold for potential bone tissue engineering applications

Journal of Biomedical Materials Research A 2018 Volume 106, Issue 5, Pages 1311-1321

There is a demand for progressive approaches in bone tissue engineering to repair and regenerate bone defects resulting from trauma or disease. This investigation sought to engineer a single‐step in situ conjugated polymeric scaffold employing 3D printing technology as an innovative fabricating tool. A polymeric scaffold was engineered in situ employing sodium alginate as a bio‐ink which interacted with a poly(ethyleneimine) solution on bioprinting to form a polyelectrolyte complex through ionic bond formation. Silica gel was included in the bio‐ink as temporal inorganic support component and for ultimate enhancement of osteoinduction. Characterization of the biorelevant properties of the scaffold was…

3D-printed IFN-γ-loading calcium silicate-β-tricalcium phosphate scaffold sequentially activates M1 and M2 polarization of macrophages to promote vascularization of tissue engineering bone

Acta Biomaterialia 2018 Volume 71, Pages 96-107

To promote vascularization of tissue-engineered bone, IFN-γ polarizing macrophages to M1 was loaded on 5% calcium silicate/β-tricalcium phosphate (CaSiO3-β-TCP) scaffolds. IFN-γ and Si released from the scaffold were designed to polarize M1 and M2 macrophages, respectively. β-TCP, CaSiO3-β-TCP, and IFN-γ@CaSiO3-β-TCP were fabricated and biocompatibilities were evaluated. Polarizations of macrophages were detected by flow cytometry. Human umbilical vein endothelial cells with GFP were cultured and induced on Matrigel with conditioned culture medium extracted from culture of macrophages loaded on scaffolds for evaluating angiogenesis. Four weeks after the scaffolds were subcutaneously implanted into C57B1/6, vascularization was evaluated by visual observation, hematoxylin and…

3D-printed gelatin scaffolds of differing pore geometry modulate hepatocyte function and gene expression

Acta Biomaterialia 2018 Volume 69, Pages 63-70

Three dimensional (3D) printing is highly amenable to the fabrication of tissue-engineered organs of a repetitive microstructure such as the liver. The creation of uniform and geometrically repetitive tissue scaffolds can also allow for the control over cellular aggregation and nutrient diffusion. However, the effect of differing geometries, while controlling for pore size, has yet to be investigated in the context of hepatocyte function. In this study, we show the ability to precisely control pore geometry of 3D-printed gelatin scaffolds. An undifferentiated hepatocyte cell line (HUH7) demonstrated high viability and proliferation when seeded on 3D-printed scaffolds of two different geometries….

Effects of tunable, 3D-bioprinted hydrogels on human brown adipocyte behavior and metabolic function

Acta Biomaterialia 2018 Volume 71, Pages 486-495

Obesity and its related health complications cause billions of dollars in healthcare costs annually in the United States, and there are yet to be safe and long-lasting anti-obesity approaches. Using brown adipose tissue (BAT) is a promising approach, as it uses fats for energy expenditure. However, the effect of the microenvironment on human thermogenic brown adipogenesis and how to generate clinically relevant sized and functioning BAT are still unknown. In our current study, we evaluated the effects of endothelial growth medium exposure on brown adipogenesis of human brown adipose progenitors (BAP). We found that pre-exposing BAP to angiogenic factors promoted…

A novel surgical technique for a rat subcutaneous implantation of a tissue engineered scaffold

Acta Histochemica 2018 Volume 120, Issue 3, Pages 282-291

Objectives Subcutaneous implantations in small animal models are currently required for preclinical studies of acellular tissue to evaluate biocompatibility, including host recellularization and immunogenic reactivity. Methods Three rat subcutaneous implantation methods were evaluated in six Sprague Dawley rats. An acellular xenograft made from porcine pericardium was used as the tissue-scaffold. Three implantation methods were performed; 1) Suture method is where a tissue-scaffold was implanted by suturing its border to the external oblique muscle, 2) Control method is where a tissue-scaffold was implanted without any suturing or support, 3) Frame method is where a tissue-scaffold was attached to a circular frame…

3D-printing porosity: A new approach to creating elevated porosity materials and structures

Acta Biomaterialia 2018 Volume 72, Pages 94-109

We introduce a new process that enables the ability to 3D-print high porosity materials and structures by combining the newly introduced 3D-Painting process with traditional salt-leaching. The synthesis and resulting properties of three 3D-printable inks comprised of varying volume ratios (25:75, 50:50, 70:30) of CuSO4 salt and polylactide-co-glycolide (PLGA), as well as their as-printed and salt-leached counterparts, are discussed. The resulting materials are comprised entirely of PLGA (F-PLGA), but exhibit porosities proportional to the original CuSO4 content. The three distinct F-PLGA materials exhibit average porosities of 66.6–94.4%, elastic moduli of 112.6-2.7 MPa, and absorbency of 195.7–742.2%. Studies with adult human mesenchymal…

Mechanical characterization and numerical simulation of a subcutaneous implantable 3D printed cell encapsulation system

Journal of the Mechanical Behavior of Biomedical Materials 2018 Volume 82, Pages 133-144

Cell transplantation in bioengineered scaffolds and encapsulation systems has shown great promise in regenerative medicine. Depending on the site of implantation, type of cells and their expected function, these systems are designed to provide cells with a physiological-like environment while providing mechanical support and promoting long-term viability and function of the graft. A minimally invasive 3D printed system termed neovascularized implantable cell homing and encapsulation (NICHE) was developed in polylactic acid for subcutaneous transplantation of endocrine cells, including pancreatic islets. The suitability of the NICHE for long term in vivo deployment is investigated by assessing mechanical behavior of both fresh…

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…

Alginate

Use of 3D Printing to Prototype a Custom Shape Memory Alloy Penile Prosthesis

The Journal of Urology 2018 Volume 197, Number, 4, Pages e313ff

Three-dimensional (3D) printing or additive printing is a new technology that allows for construction of complex shapes and designs outside the constraints of traditional manufacturing techniques. Traditional 3D printing was limited to thermosensitive plastics that have limited medical applications. Herein, we describe the application of a cutting edge process that allows for 3D printing of shape memory alloys (SMA) using inks of shape memory alloy powder. Using our previously described concept of a SMA penile prosthesis for the treatment of erectile dysfunction, we sought to construct an intracavernosal cylinder using 3D printing technology.

Printing Biological Liquid On Hydrophobic 3D Electrodes

Solid-State, Actuators, and Microsystems Workshop 2018 Papes 144-147

This paper presents for the first time a programmable and scalable 3D electro-bioprinting (3D-EBP) process for patterning bionanoreceptors, cysteine-modified Tobacco mosaic virus (TMV1cys), on high-density micropillar array electrodes. The structural hydrophobicity in high aspect ratio geometries of micro/nano devices poses a critical challenge for assembling 3D biomaterial-device interfaces. Here, we have successfully integrated electrowetting principles with a modified state-of-the-art bioprinter for automated, high-throughput, and large-scale patterning of TMV1cys particles on hydrophobic 3D electrodes. The 3D-EBP processed bionanoreceptors maintained both structural and chemical functions as characterized via SEM and fluorescence microscopy. Overall, the innovative 3D biomanufacturing process creates excellent opportunities for…

Optimisation of mixture properties for 3D printing of geopolymer concrete

35th International Symposium on Automation and Robotics in Construction 2018

Freedom of design, customisation, automation, waste minimisation, reduced labour and building complex structures with cheaper materials are the main initiatives for developing 3D printed structures. The fresh properties of concrete are the most important aspects of a successful 3D printing. Concrete requires high workability for extrusion, optimum open time and high early strength in order to support the subsequent layers for 3D printing. Therefore, a mixture design that can satisfy these requirements is needed. Geopolymer concrete is a sustainable solution to traditional Portland cement-based concrete that uses waste materials. In addition, the controlled alkali-activation of geopolymer precursors in order to…

3D Bioprinting of Breast Cancer Models for Drug Resistance Study

ACS Biomaterials Science & Engineering 2018 Volume 4, Issue 12, Pages 4401-4411

Adipose-derived mesenchymal stem/stromal cells (ADMSC) are one of the major stromal cells in the breast cancer microenvironment that promote cancer progression. Previous studies on the effects of ADMSC on breast cancer metastasis and drug resistance, using two-dimensional (2D) cultures, remained inconclusive. In the present study, we compared cocultured ADMSC and human epidermal receptor 2 positive breast primary breast cancer cells (21PT) in 2D and three-dimensional (3D) cultures and then examined their response to doxorubicin (DOX). We examined 3D bioprinted constructs with breast cancer cells in the middle and ADMSC in the edge region, which were made by using dual hydrogel-based…

Rheological, In Situ Printability and Cell Viability Analysis of Hydrogels for Muscle Tissue Regeneration

Proceedings of the 29th Annual International Solid Freeform Fabrication Symposium – An Additive Manufacturing Conference 2018 Pages 835-846

Advancements in additive manufacturing have made it possible to fabricate biologically relevant architectures from a wide variety of materials. Hydrogels have garnered increased attention for the fabrication of muscle tissue engineering constructs due to their resemblance to living tissue and ability to function as cell carriers. However, there is a lack of systematic approaches to screen bioinks based on their inherent properties, such as rheology, printability and cell viability. Furthermore, this study takes the critical first-step for connecting in-process sensor data with construct quality by studying the influence of printing parameters. Alginate-chitosan hydrogels were synthesized and subjected to a systematic…

Sintering of micro-trusses created by extrusion-3D-printing of lunar regolith inks

Acta Astronautica 2018 Volume 143, Pages 1-8

The development of in situ fabrication methods for the infrastructure required to support human life on the Moon is necessary due to the prohibitive cost of transporting large quantities of materials from the Earth. Cellular structures, consisting of a regular network (truss) of micro-struts with ∼500 μm diameters, suitable for bricks, blocks, panels, and other load-bearing structural elements for habitats and other infrastructure are created by direct-extrusion 3D-printing of liquid inks containing JSC-1A lunar regolith simulant powders, followed by sintering. The effects of sintering time, temperature, and atmosphere (air or hydrogen) on the microstructures, mechanical properties, and magnetic properties of…

Determination of the normal fluid load on inclined cylinders from optical measurements of the reconfiguration of flexible filaments in flow

Journal of Fluids and Structures 2018 Volume 76, Pages 488-505

Reconfigured flexible filaments exposed to steady fluid load were investigated using a novel non-contact optical technique to measure the normal fluid force due to the fluid loading on inclined cylinders for Reynolds numbers from 25 to 460: a range not covered in previous studies that is of relevance in drag reduction and energy harvesting applications. The ranges of the buoyancy number and the Cauchy number covered in the tests were 3.6 × 10^4 ≤ B ≤ 2.1 × 10^6 and 7.6 × 10^4 ≤ Ca ≤ 1.4 × 10^7. These newly generated data were then used to assess and extend…