Advances in Biomaterials for 3D Printing: Advances in Biomaterials for 3D Printing
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Biomaterials Committee
Program Organizers: Changxue Xu, Texas Tech University; Jun Yin, Zhejiang University; Zhengyi Zhang, Huazhong University of Science and Engineering; Yifei Jin, University of Florida
Thursday 8:30 AM
February 27, 2020
Room: Oceanside
Location: Marriott Marquis Hotel
Session Chair: Changxue Xu, Texas Tech University; Yifei Jin, University of Nevada, Reno
8:30 AM
Guided Cell Migration on a Graded Micropillar Substrate: Srikumar Krishnamoorthy1; Zhengyi Zhang2; Changxue Xu1; 1Texas Tech University; 2Huazhong University of Science and Technology
Cell migration is facilitated by the interaction of cells with their local microenvironment including geometry, stiffness, and chemical gradients. Construction of an interface to achieve guided cell migration is of great significance for studying cell behaviors. In this presentation, a dynamic mask photolithography technique has been implemented to fabricate a graded micropillar substrate. Three different types of cells are seeded on the fabricated substrate after surface treatment. Successful guided cell migration has been demonstrated on the graded micropillar substrate. The effects of the micropillar gradient, diameter, and height on the migration speed and cellular morphology have been systematically investigated. Moreover, endothelial cells, fibroblasts, and breast cancer cells have been utilized to compare different migration behaviors on the graded micropillar substrate.
8:50 AM
Additively Manufactured Functionally Graded Biodegradable Porous Zinc: Yageng Li1; Prathyusha Pavanram2; Jie Zhou1; Karel Lietaert3; Marius Leeflang1; Holger Jahr2; Amir Zadpoor1; 1Delft University of Technology; 2University Hospital RWTH Aachen; 33D Systems - LayerWise NV
Additively manufactured (AM) functionally graded porous metallic biomaterials offer unique opportunities to satisfy the contradictory design requirements of an ideal bone substitute. However, no functionally graded porous structures have ever been 3D-printed from biodegradable metals, even though biodegradability is crucial both for full tissue regeneration and for the prevention of implant-associated infections in the long term. Here, we present the first report on 3D-printed functionally graded biodegradable porous zinc. Our results suggest that topological design in general, and functional gradients in particular can be used as an important tool for adjusting the biodegradation behavior of AM porous metallic biomaterials. The biodegradation rate and mass transport properties of AM porous zinc can be increased while maintaining the bone-mimicking mechanical properties of these biomaterials. The observations reported here underline the importance of proper topological design in the development of AM porous biodegradable metals.
9:10 AM
Design of Metallic Lattices for Bone Implants by Additive Manufacturing: Daniel Barba Cancho1; Roger Reed1; Enrique Alabort2; 1University of Oxford; 2OxMet Technologies
A broad range of synthetic trabecular-like metallic lattices are 3D printed in Ti-6Al-4V by SLM. The aim is to propose new conceptual types of implant structures for superior bio-mechanical matching and osseo-integration: synthetic bone. Systematic evaluation is then carried out: (i) their accuracy is characterised using HR X-ray tomography, to assess deviations from the original geometrical design intent and (ii) the mechanical properties -- stiffness and strength - are experimentally measured and compared. Finally, this new knowledge is synthesised in a conceptual framework in the form of implant design maps, to define the processing conditions of bone tailored substitutes. The design criteria emphasise (a) the bone stiffness-matching, (b) preferred range of pore structure for bone in-growth, (c) manufacturability and (d) choice of inherent materials properties for durable implants. The power of this framework is demonstrated in the design of a prototype spine fusion device.
9:30 AM Cancelled
Biomimetic 3D printed Chitosan-hydroxyapatite Scaffold for Bone Tissue Engineering: Wei Huang1; Julian Cutler1; David Kisailus1; 1University of California Riverside
Bones are among the toughest structural biological materials designed by nature. Scaffolds applied in tissue engineering for bone regeneration need to meet the mechanical requirements, such as strength, stiffness and toughness. Microscale structures that have been identified as key design elements help to improve the toughness of materials in natural organisms, such as helicoidal, tubular and lamellar structures, are realized in 3D printed chitosan scaffolds. Similar to the biomineralization process, these organic scaffolds are mineralized through double diffusion experiments. The growth of hydroxyapatite crystals on chitosan scaffolds are characterized with SEM, TEM, Raman spectroscopy and synchrotron wide-angle X-ray diffraction (WAXD). The mechanical strength and toughness of the mineralized chitosan-hydroxyapatite scaffolds thus can be tuned by not only changing the 3D printing parameters, but also the crystal growth process.
9:50 AM
Effects of Photoinitiators on Cell Viability in 3D Bioprinting: Jazzmin Casillas1; Heqi Xu1; Changxue Xu1; 1Texas Tech University
Photocrosslinkable polymers such as gelatin methacrylate (GelMA) have been widely utilized in various 3D bioprinting application. These polymers crosslink when exposed to UV radiation in the presence of a photoinitiator. However, the photoinitiator may have negative effects on cell viability when the cell-laden bioink is used for printing. This study investigates the effects of photoinitiators on the cell viability in 3D bioprinting. The bioink contains 5% (w/v) gelatin methacrylate and 0.3-0.9% (w/v) photoinitiators. Two different photoinitiators, Irgacure 2959 and lithium phenyl-,2,4,6-trimethylbenzoylphosphinate (LAP), are used to compare different effects on cell viability during and after 3D bioprinting. During 3D bioprinting, cell viability is measured every 15 minutes within one hour. After crosslinking, the cell viability is measured after 0, 6, 12, and 24-hour incubation. The results show the significantly different effects of these two photoinitiators on cell viability in 3D bioprinting.
10:10 AM Break
10:30 AM
Investigation of Cell Sedimentation in Inkjet-based Bioprinting of Cell-Laden Bioink: Heqi Xu1; Jazzmin Casillas1; Srikumar Krishnamoorthy1; Changxue Xu1; 1Texas Tech University
Inkjet-based bioprinting has been widely used for various applications in tissue engineering and regenerative medicine. The bioink used is considered as a suspension incorporating living cells. Because the typical bioprinting process may take several hours, the suspended cells in the bioink sediment with time, which significantly affects the bioink stability as well as the following printing accuracy and reliability. This study investigates the effects of polymer concentration and standing time on the cell sedimentation velocity and cell concentration, and the effect of cell sedimentation on the cell distribution within droplets. The results show that the cell sedimentation velocity is almost constant at different standing times, and with the increase of the polymer concentration the cell sedimentation velocity decreases. It is also seen that the cell gravitational force may change, because water flows into cells through the mechanism of osmosis due to concentration gradient of solute across the cell membrane.
10:50 AM
From Microstructural Design to Surface Engineering: A Tailored Approach for Improving Fatigue Life of Additively Manufactured Lattice Titanium: Vera Popovich1; S.M. Ahmadi2; 1Delft University of Technology; 2Amber Implants
Recently, lattice titanium manufactured by additive manufacturing techniques has been utilized in various applications, including aerospace and biomedical. The effects of topological design and processing on the fatigue behaviour of such metamaterials have been studied and show that the fatigue life of such lattice structures is limited. This study aims to provide an in-depth investigation into the effects of heat treatments, hot isostatic pressing (HIP), sand blasting, and chemical etching on the microstructure, surface morphology and fatigue resistance of titanium metamaterials. It was found that the combination of microstructural design and surface engineering, induced by HIP and sand blasting respectively, allows to increase the endurance limit of these lattice metamaterials by a factor of two. HIP treatment substantially decreased the internal porosity and transformed the microstructure to a more ductile mixture of α+β phases. Sand blasting allowed to eliminate surface imperfections and induce the compressive stress on the struts surface.