Next Generation Biomaterials: Frontiers in Biological and Biomedical Materials
Sponsored by: MS&T Organization
Program Organizers: R. Narayan, UNC/NCSU Joint Department of Biomedical Engineering; Kalpana Katti, North Dakota State University; Kajal Mallick, University of Warwick; Vilupanur Ravi, California State Polytechnic University, Pomona; Varshni Singh, Louisiana State University
Wednesday 8:00 AM
October 19, 2011
Room: B200/201
Location: Greater Columbus Convention Center
Session Chair: Leon Shaw , University of Connecticut; Christian Bonhomme, Laboratoire de Chimie de la Matière Condensée
8:00 AM
Angiogenic Bioactive Borate Glasses: Steven Jung1; Delbert Day2; Roger Brown2; 1Mo-Sci Corporation; 2Missouri University of Science and Technology
Porous bioactive glass scaffolds composed of randomly oriented bioactive borate glass fibers doped with CuO were implanted in the soft tissue of laboratory rats for up to six weeks to study the biological and angiogenic response. No inflammation or infection was detected at any of the implant sites with a CuO concentration at or below 0.4wt%. Scaffolds made from fibers containing (0.1 to 2wt%) CuO had a marked increase in blood vessels surrounding the scaffolds after two and four weeks in-vivo. After six weeks, a blinded histological blood vessel analysis (PAS) of the tissue present in the scaffolds showed that 0.4wt% CuO produced a statistically significant (p<0.05) increase in blood vessel area compared to the un-doped scaffold. It was also found that seeding the scaffolds with mesenchymal stem cells also increased the number of blood vessels present in the subcutaneous implants.
8:20 AM Invited
Biomaterials: From Models to Spectroscopic Characterization: Christian Bonhomme1; 1UPMC Paris 6
In this lecture, the latest developments in first principles calculations of biocompatible materials will be presented. New resonance techniques including solid state NMR, EPR and DNP will be described in close connection with ab initio calculations of spectroscopic parameters. The role of amorphous hybrid interfaces will be emphasized as such interfaces play a crucial role in the physico-chemical properties of the corresponding materials.
8:40 AM
In-Vivo Evaluation of 13-93 Bioactive Glass Scaffolds Made by Selective Laser Sintering (SLS): Mariano Velez1; Krishna Kolan2; Ming Leu3; Steve Jung1; Delbert Day3; Tien-Min Chu4; 1Mo-Sci Corporation; 2Missouri University of Science and Technology ; 3Missouri University of Science and Technology; 4Indiana University
Bioactive glass is a synthetic material that reacts in-vivo and forms an inorganic hydroxyapatite-like (HA) phase that mimics the HA found in human bone and can stimulate osteoconduction. Selective Laser Sintering (SLS) was used to fabricate “green” bone scaffolds using 13-93 bioactive glass particles (<75 µm) mixed with stearic acid. After heat treatment, the scaffolds had a hollow cylindrical structure and were designed to mimic the structure and mechanical properties of human trabecular bone. In-vitro, the compressive strength of the SLS scaffolds was measured as a function of time for up to three months when immersed in Dubelcos Modified Eagles Medium (DMEM) at 38ºC. In-vivo, the cylindrical scaffolds with and without bone morphogenic protein-2 (BMP-2), were implanted in rat femurs for up to three months. The data from the in-vivo study is compared to similar biodegradable polymer scaffolds treated with BMP-2 in critical sized defects of rats.
9:00 AM Invited
Low Temperature Sintering of Ti-6Al-4V for Orthopedic Implant Applications
: Kyle Crosby1; Leon Shaw1; 1University of Connecticut
Titanium alloys are widely used in orthopedic implants due to their high strength to weight ratio and proven biological stability. However, coatings are often required to improve the bioactivity of Ti-based implants. Another approach to enhancing the bioactivity is to fabricate functionally graded Ti-6Al-4V (Ti)/hydroxyapatite (HA) implants, thus avoiding a sharp interface between the Ti core and HA coating. To fabricate such graded implants, the sintering temperature of Ti must be 1000°C or lower to prevent embrittlement of the Ti alloy. Here we investigate the creation of nanostructured Ti powders via high-energy ball milling, while preventing their oxidation in the subsequent powder pressing and sintering processes. It is found that methods for green body formation can affect the sintered density while the use of nanostructured Ti powder can reduce sintering temperature substantially. These results reveal that nanostructured Ti powders have great potential for achieving functionally graded Ti/HA orthopedic implants.
9:20 AM Cancelled
Mechanical Properties of Implant Rods Made of Ti-29Nb-13Ta-4.6Zr for Spinal Fixture: Mitsuo Niinomi1; Masaaki Nakai1; Junko Hieda1; 1Tohoku University
While using low modulus titanium alloys, which is advantageous to suppress stress shielding, some surgeons specializing in spinal diseases pointed out that the amount of spring-back in the implant rods should be small so that the implant offers better handling ability during surgeries; the high Young’s modulus suppress spring-back. Titanium alloys, which satisfy the requirements of both surgeons (high Young’s modulus leading to suppress spring-back) and patients (low Young’s modulus leading to suppress stress shielding) with regard to the Young’s modulus of the implant rod, are currently being developed. The authors have proposed Ti-12Cr as a candidate alloy for solving this problem. Ti-12Cr subjected to solution treatment (Ti-12Cr-ST) exhibits a low Young’s modulus of <70 GPa. On the other hand, the Young’s modulus of Ti-12Cr subjected to cold rolling (Ti-12Cr-CR), is >80 GPa. This increase in the Young’s modulus is due to the deformation-induced omega phase.
9:40 AM Break
10:00 AM Invited
Next Generation Orthopaedic Implants by Additive Manufacturing Using Electron Beam Melting: L. Murr1; Sara Gaytan1; Edwin Martinez1; Frank Medina2; Ryan Wicker2; 1University of Texas at El Paso; 2W.M. Keck Center for 3D Innovation, University of Texas at El Paso
This paper presents some examples of knee and hip implant components containing porous structures and fabricated in monolithic forms utilizing electron beam melting (EBM). In addition, utilizing stiffness or relative stiffness versus relative density design plots for open-cellular structures (mesh and foam components) of Ti-6Al-4V and Co-29Cr-6Mo alloy fabricated by EBM, it is demonstrated that stiffness compatible implants can be fabricated for optimal stress shielding for bone regimes as well as bone cell ingrowth. Implications for the fabrication of patient specific, monolithic, multi-functional orthopaedic implants using EBM are described along with microstructures and mechanical properties characteristic of both Ti-6Al-4V and Co-29Cr-6Mo alloy prototypes; including both solid and open-cellular prototypes manufactured by additive manufacturing (AM) using EBM.
10:20 AM Invited
Origins of the Fracture Resistance of Bone and Its Biological Degradation: Robert Ritchie1; 1University of California Berkeley
The origins of the toughness of human cortical bone are examined in terms of the contributing micro-mechanisms and their characteristic length-scales in relation to its hierarchical structure. It is shown that at length-scales below a micron, toughening mechanisms in bone are primarily intrinsic, and include mechanisms such as collagen fibrillar sliding; these are essentially “plasticity” mechanisms. At length-scales above a micron, toughening mechanisms are primarily extrinsic, and associated with crack deflection and bridging. Here we evaluate the effects of aging, irradiation, vitamin-D deficiency and certain bone diseases, using in situ fracture-mechanics testing in an environmental scanning electron microscope combined with structure characterization using Raman spectroscopy, SAXS/WAXS and synchrotron x-ray computed microtomography, to determine the microstructural features that underlie the toughness of bone and how this can degrade with biological factors.
10:40 AM Invited
Scaffolds to Guide Stem Cells for Bone and Dentin Regeneration: Peter Ma1; 1University of Michigan
ScBone and dentin tissue loss remains a major clinical challenge. Regenerative medicine aims for biological restoration of lost or diseased tissues. Our lab develops biomimetic polymer scaffolds that recapitulate certain advantageous features of the natural extracellular-matrices (ECM) and impart engineering design to facilitate tissue regeneration. Novel phase separation techniques have been developed in our laboratory to create biodegradable ECM-mimicking nanofibrous scaffolds. Porous network design and computer assisted body-part shape creation allows for patient specific scaffold fabrication. We also develop novel polymer/calcium phosphate composite scaffolds to facilitate mineralized tissue regeneration. In addition, we design novel polymers and self-assembled nanospheres for controlled biomolecule delivery in the scaffolds to recapitulate certain developmental programs. Enhanced bone and dentin regeneration outcomes by various stem cells demonstrate the excitement of the biomimetic materials in regenerative medicine.
11:00 AM Invited
Titanium with Designed Elongated Pores for Biomedical Implants: David Dunand1; 1Northwestern University
This talk reviews methods based on selective densification of powders by laser or e-beam melting, as well as sintering of printed 2D or 3D structures, to create periodic lattice/reticulated titanium structures for permanent skeletal implants. Other methods based on space-holders to create elongated pores in Ti will be discussed: (i) freeze casting of Ti powders followed by ice sublimation and powder sintering and (ii) embedding of fine steel wires in titanium followed by electro-dissolution, to create a network of micro-channels. Finally, the applicability of these methods to shape-memory NiTi will be addressed.
11:20 AM Cancelled
Bioprinting of Living Cells for 3D Tissues: Wei Sun1; 1Drexel University
In the new paradigm of tissue science and engineering, living cells and biomolecules are used as basic building blocks for biofabrication of cell-integrated medical therapeutic products and/or non-medical biological systems with applications found as tissue substitutes, 3D cell and organ biological models, microfluidic biochips and biosensors, and tissue models for study of disease pathogenesis, drug discovery and toxicity testing. This presentation will introduce our recent research in the emerging field of cell printing and report our work on using additive technology for direct cell writing for construction of 3D cell assemble and tissue structures. Presentation topic will include: 1) introduction of direct cell writing process; 2) effect of the process parameters on cell survivability; 3) characterization of biological responses of various cells to the printing process; and 4) applications to the field of tissue science and engineering.
11:40 AM Invited
Predicting Microstructure Evolution in Drug Eluting Coatings: David Saylor1; 1FDA-CDRH-OSEL
Drug eluting coatings, composed of drug in a polymer matrix, represent combination medical products that incorporate controlled release technologies with traditional devices to improve functionality and performance. The coating microstructure, which depends on the constituents and manufacturing conditions, can have a profound affect on drug release and, therefore, the ability of coated devices to function successfully. We have developed a diffuse interface model to predict microstructure development during coating fabrication and the impact of microstructure on subsequent release kinetics. We find our calculations are consistent with experimental observations and the basic model can be extended to account for crystallization, chemical bonding between constituents, and biodegradation. Thus, the model provides a tool to determine the relationships between materials and manufacturing variables, microstructure, and performance. Establishing these relationships can reduce empiricism in product and process design, providing an efficient means to tailor the microstructure to achieve a desired drug release behavior.