Next Generation Biomaterials: Next Generation Biomaterials
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 2:00 PM
October 19, 2011
Room: C215
Location: Greater Columbus Convention Center
Session Chair: Sarit Bhaduri, The University of Toledo ; Eldon Case, Michigan State Univ
2:00 PM Invited
Porosity Dependent Strength and Elastic Modulus of Hydroxyapatite and Other Oxide and Non-Oxide Materials: Eldon Case1; Xiaofeng Fan1; Fei Ren2; Melissa Baumann1; Y Shu1; 1Michigan State Univ; 2Oak Ridge National Laboratory
Both dense and porous hydroxyapatite (HA) have a wide range of biomedical uses, ranging from dense coatings on implantable devices to porous bulk HA applications such as filters to block the flow of microorganisms in fluids and engineered bone materials. In each of these applications the mean fracture strength, <σf>, and the Young’s modulus, E, are important parameters. The dependence of <σf> and E on the volume fraction porosity, P, will be discussed for HA specimens over the porosity range from 0.08 to 0.62. We show that a single functional form can describe well the <σf> versus P and the E versus P behaviors for HA as well as for several oxides other than HA and non-oxide ceramics. Some possible connections to percolation theory will also be presented.
2:20 PM
Synthesis and Properties of Nano-Calcium Phosphates for Biomedical Applications: Darcy Wagner1; Huan Zhou1; Joseph Lawrence1; Sarit Bhaduri1; 1University of toledo
Calcium phosphate (CaP) materials are widely used in medical applications, but their biological interactions are primarily determined by their nanoscale properties. The majority of the conventional synthesis methods for CaP yield large grain sizes which are associated with poor mechanical properties. Therefore, these materials have had limited applicability. Advancements in synthesis methods for nano-CaP have broadened their potential applications. While a variety of heat treatment methods exist, microwave sintering of nano-CaP produces materials with smaller grain sizes and produces a material with enhanced mechanical properties. The thermal profile generated via bulk microwave heating increases porosity and total surface area. Increased porosity is associated with increased cellular adhesion and proliferation, both of which are critical for tissue engineering applications. Increases in surface area are known to be beneficial for drug and gene therapies. Calcium phosphates are especially promising in orthopedics owing to their similarity with mammalian bone.
2:40 PM Student
Processing Effects on the Crystallinity, Microstructure, and Mechanical Properties of Hydroxyapatite Reinforced Polyetheretherketone Scaffolds: Timothy Conrad1; David Jaekel2; Steven Kurtz2; Ryan Roeder1; 1University of Notre Dame; 2Drexel University
Hydroxyapatite (HA) whisker reinforced polyetheretherketone (PEEK) scaffolds were designed to exhibit mechanical properties similar to human vertebral trabecular bone and promote bone ingrowth by bioactive HA crystals. The objective of this study was to investigate processing effects on the crystallinity, microstructure, and mechanical properties of HA whisker reinforced PEEK scaffolds. The effects of the mold temperature, cooling rate, porogen morphology, and flow during compression molding were investigated in scaffolds comprising of 20 vol% HA whiskers and 75% porosity. Increased mold temperature resulted in improved sintering, but decreased crystallinity. The compressive yield strength, yield strain, and modulus increased with increased temperature to a maxima at 380-385°C. Decreased cooling rate did not significantly affect mechanical properties. Scaffolds prepared with a spherical porogen resulted in increased interconnectivity with no change in mechanical properties. Static compression molding resulted in segregation of HA between PEEK particles, but shear flow led to improved dispersion of HA.
3:00 PM
Preparing PLA Powders for Powder-Based Processing Using a Solvent-Non-Solvent Mediated Technique: Huan Zhou1; Sarit Bhaduri1; 1University of toledo
PLA (poly lactic acid) is one of the most frequently investigated biopolymers for various biomedical applications including sutures, implants and in regenerative medicine. Of late, an important fabrication technique for producing complex shapes has emerged: powder-based rapid prototyping. Since PLA is commercially available in the form of pellets instead of loose powders, there is a need for a simple and scalable technique to produce loose PLA powders. This paper reports a new solvent-non-solvent mediated technique for preparing uniform micron-sized PLA powders from pellets. The mechanism of powder formation can be explained by the relative solubility of PLA in the solvent and the non-solvent. The production percentage can be approximately 100% and this process can be easily scaled up to produce large quantities of PLA powders.
3:20 PM Break
4:00 PM Invited
Biological Aspects of Chemically Bonded Ca-Aluminate Based Biomaterials: Leif Hermansson1; 1Doxa AB
The presentation will give background aspects to the observed nanostructures (nanocrystals and nanoporosity) of the chemically bonded Ca-aluminate biomaterials (CBCA) with special reference to the following observed biological features; biocompatibility in general, bioactivity, chemical and antibacterial aspects,and sealing and integration of contact zones between the biomaterial and surrounding tissue. Both a nanomechanical and chemical integration, as well as and a biologically induced integration seem to contribute to sealing of biomaterial-tissue interfaces. One important aspect in this is the early properties developed in the biomaterial. The presentation will focus on the chemistry behind, including the precipitation mechanisms. These types of biomaterials are now establishing their use as injectable biomaterials within dentistry and orthopedics, and as carriers for drug delivery.
4:20 PM
Enhancement of Apatite Formation by Oxynitridation of Ti Substrate: Masami Hashimoto1; Kazumi Kashiwagi1; Satoshi Kitaoka1; 1Japan Fine Ceramics Center
Biomedical titanium metals subjected to gas under precisely regulated oxygen partial pressures (PO2) from 10-18 to 105 Pa at 973 K for 1 hour were soaked in a simulated body fluid at 37 oC for up to 7 days. The most apatite was formed on the titanium metal heated under a PO2 of 10-14 Pa, followed by the sample heated under a PO2 of 104 Pa. The titanium metal heated under a PO2 of 105 Pa experienced far less apatite formation than either of the former two titanium samples. Similarly, very little weight change was observed for the titanium metal heated under a PO2 of 10-18 Pa. Nitrogen (N)-doped TiO2 (Interstitial N) was formed on Ti under a PO2 of 10-14 Pa. The effect of nitrogen on apatite formation was assessed using X-ray photoelectron spectroscopy, secondary ion mass spectrometry or surface charge of heat-treated titanium samples.
4:40 PM
Corrosion Behaviour of Ti-Base Alloys in Biocompatible Solutions: Sailendra Paul1; Smita Sahu2; Manish Roy3; 1VNIT; 2IIT; 3DMRL
The biocompatibility performance of a metallic alloys is closely associated with its corrosion resistance and the biocompatibility of its corrosion products. Corrosion data shows excellent resistance for titanium and its alloys though some precaution should be taken in order to optimize their composition. β-titanium alloys generally show attractive corrosion behavior. Their corrosion resistance again depends on alloy composition and environment. In present investigation corrosion behavior of C.P.Ti, Ti-6Al-4Fe, Ti-13Nb-13Zr, Ti-13Ta-29Nb-4.6Zr, Ti-18Nb-4Sn were studied. The electrochemical and corrosion behavior of C.P.Ti, Ti-6Al-4Fe, Ti-18Nb-4Sn, Ti-13Ta-29Nb-4.6Zr, Ti-13Nb-13Zr alloys have been evaluated in hank’s solution, Ringer solution, Hank’s with bovine serum albumin solution and Ringer with bovine serum albumin solution at ambient temperature. These materials didn’t passivate immediately in solution. The corrosion rates were estimated by Tafel extrapolation method. It has been observed that Ti-6Al-4Fe is showing high corrosion resistance in Hank’s and Hank’s with bovine serum albumin. In contrast Ti-13Ta-29Nb-4.6Zr showing good corrosion resistance in Ringer and Ringer with bovine serum albumin.
5:00 PM
Electrochemical Characterization of the Eastern Oyster Crassostrea Virginica Shell as a Bioceramic Material: Yuhchae Yoon1; Douglas Hansen1; Karolyn Hansen2; Andrew Mount3; 1University of Dayton Research Institute; 2University of Dayton; 3Clemson University
The shell of the Eastern oyster (Crassostrea virginica) was investigated the effects of shell thickness, orientation and layer composition on its electrochemical behavior using EIS, potentiodynamic polarization and SEM-EDS. The resistance and electrolyte conductivity measurements through the shell using a four electrode cell configuration were made. SEM-EDS analysis of the oyster shell revealed that the multilayered biocomposite material is composed of calcium carbonate (CaCO3) with numerous incongruent “chalky” and “non-chalky” layers. The electrolyte conductivity within the pores of the shell was shown to be dependent on the ionic concentration of the electrolyte. The impedance of the whole oyster shell in the low frequency region exhibited high impedance values which exhibited a decreasing trend with increasing immersion time. The limiting currents through the shell were observed to increase when the outer layers of the shell were sequentially removed by grinding, thus decreasing the shell thickness. More details will be present.