Pan American Materials Congress: Advanced Biomaterials: Implants, Bone Graft and Drug Delivery
Sponsored by: Third Pan American Materials Congress Organizing Committee
Program Organizers: Carlos Elias, Instituto Militar de Engenharia; Wen Yang, University of California, San Diego

Thursday 2:00 PM
March 2, 2017
Room: Mission Hills
Location: Marriott Marquis Hotel

Session Chair: Mayara Alvarez-Lemus, Juarez Autonomous University of Tabasco; Ke Yang, Institute of Metal Research, Chinese Academy of Sciences

2:00 PM  
In Vivo Study on New Coronary Stents Made of Nickel-free High-nitrogen Stainless Steel: Qingchuan Wang1; Shanshan Chen1; Hui Yang1; Bingchun Zhang1; Ke Yang1; 1Institute of Metal Research, Chinese Academy of Sciences
    This study was focused on the preclinical in vivo study of a novel kind of coronary stents made of high-nitrogen nickel-free stainless steel (HNNFSS). Both bio-safety and effectiveness of HNNFSS stents with and without drug-eluting coating were compared with commercial available stents after 14, 28 and 90 days implantations in porcine coronary arteries, respectively. It was found that all the stents showed well expansion and sufficient radial force without significant elastic recoil. After 28 days implantation, the bare stents control group showed the most serious degree of intimal hyperplasia, and the experimental groups displayed mild inflammatory response and more intact internal elastic lamina. It is worth noting that the experimental bare stents had significant advantage over the control group after 90 days implantation (P<0.05). In conclusion, HNNFSS stents showed better biocompatibility, lower in-stent restenosis and obvious advantage on degree of intimal hyperplasia after long-term implantation.

2:20 PM  
Effect of Rapid Solidification on the Microstructure of a Biomaterial Co-Cr-Mo-C Alloy: Hugo Lopez1; Hamid-Reza Erfanian-Naziftoosi1; 1University of Wisconsin-Milwaukee
    A Co-Cr-Mo-C biomedical grade alloy was cast using a rapid solidification wedge V-shaped copper and sand molds under an argon gas atmosphere. Scanning electron microscopy and optical microscopy were employed to investigate the effect of rapid solidification rates on the exhibited microstructure of of the cast alloys. In addition, the amount of athermal -hcp developed via rapid solidification was determined by X-ray diffraction.. A uniform distribution of fine carbides were found to precipitate along primary and secondary dendrites arms. In particular, it is found that the dendrite structure becomes highly refined including the carbide size and carbide distribution when rapid solidification is dominant. Moreover, the exhibited amount of athermal -hcp martensite increases from 4% to over 60% by increasing the alloy solidification rates (up to 278 K/s approx).

2:40 PM  
Influence of Time and Temperature of Acid Treatment in the Morphology and Roughness of Osseointegrable Implants: Ariel do Lago1; Beatriz Torres1; Carlos Elias1; 1Instituto Militar de Engenharia
    Surface of implants influences greatly its stability, which makes that a fundamental variable in the world of orthodontics. One of the used methods to reach the desired surface morphology and roughness is acid treatment. In the present paper, a mathematical analysis of variance of commercially pure Titanium surface preparation’s parameter was done. Samples were treated for 3 different times (55, 60 and 65 minutes) as 3 temperatures (55, 65 and 70 oC) were applied. Relevant roughness parameters and surface morphology were evaluated utilizing a 3D perfilometer and a SEM, respectively. Applying a multiple regression, roughness parameters were determined as functions of time and temperature of the treatment. The equations obtained fitted well to the data acquired (p<0,05). Through these, it is possible to predict the best values of temperature and time of treatment to acquire TI cp implants with a surface optimal for osseointegration based on its roughness parameters.

3:00 PM  
Optical Properties of CeO2@ZnO Core@shell Nanostructures Synthesized by Solvothermal Method: Saeed Farhang1; Felipe Sanhueza1; Pandiyarajan Thangaraj1; Mangalaraja Ramalinga Viswanathan1; 1Concepcion University
    Cerium oxide (CeO2) and zinc oxide (ZnO) are the important rare earth and semiconductor oxides used in sun protection cream due to their strong absorption of ultraviolet radiation. The present work aimed to synthesis CeO2, ZnO nanoparticles and their CeO2@ZnO core@shell nanostructure by solvothermal method. To explore the structural and optical properties, the synthesized nanomaterials were characterized using X-Ray diffraction (XRD), UV-visible and photoluminescence (PL) spectroscopies. The structural results confirmed that the synthesized nanomaterials calcined at 500C were completely crystalline nature with cubic and hexagonal wurtzite structures for CeO2 and ZnO, respectively. The observed peaks of both CeO2 and ZnO confirmed the formation of core@shell nanostructure. The optical absorption spectra showed bands at 291 and 356 nm that ascribed to the absorption of CeO2 and excitonic absorption of ZnO bands, respectively. The photoluminescence measurement was carried out at an excitation wavelength of 330 nm.

3:20 PM Break

3:40 PM  
Investigation of Properties in Glass-ceramics Based on Li2O-SiO2 System during Li2SiO3-Li2Si2O5 Transformation: Bruno Simba1; Marcos Ribeiro1; Claudinei Santos2; Paulo Suzuki3; Luís Hein1; Manuel Alves2; 1Unesp-FEG - Universidade Paulista-Faculdade de Engenharia de Guaratinguetá; 2UERJ-FAT - Universidade do Estado do Rio de Janeiro-Faculdade de Tecnologia; 3USP-EEL - Universidade de São Paulo-Escola de Engenharia de Lorena
    Lithium metasilicate glass-ceramic, Li2SiO3, for CAD/CAM (Computer-aided design/Computer-aided manufacturing) machining has unparalleled aesthetic properties for the manufacture of dental restorations. This material is milled to obtain partial or total replacement components to natural teeth. After milling, the prostheses are submitted to heat treatment to the transformation of Li2SiO3 in lithium disilicate, Li2Si2O5. In this work, Li2SiO3 samples were heat treated at 820°C at different holding times from one to nine minutes under vacuum. Samples were characterized by X-ray diffraction, SEM (Scanning Electron Microscopy), hardness, fracture toughness, biaxial flexure test. The results indicate a progressive increase in Li2SiO3-Li2Si2O5 transformation, hardness around 580 HV, a slight increase in fracture toughness (1.8 to 2.0 MPam1/2) and increased bending resistance associated with Li2Si2O5 rise, which is composed of grains with high aspect ratio.

4:00 PM  
Structure and Toughening Mechanism of Carp Fish Scales: Haocheng Quan1; Wen Yang2; Robert Ritchie3; Marc Meyers1; 1UCSD; 2ETH-Zurich; 3 Lawrence Berkeley National Laboratory
    Carp fish (Cyprinus carpio) is a common modern ray-finned fish which is adapted to the freshwater all around the world. The scale of carp is a typical elasmoid scale with cycloid shape, the outer layer of which is a thin but highly mineralized layer and the inner layer is a soft collagenous layer with laminated structure. Each lamella of the inner layer is composed of parallel arranged collagen fibers and the orientations of different lamella form a typical Bouligand structure, with a rotation angle around 65°. Due to such structure, the scale has an in-plan anisotropic tensile behavior. However, no matter along the longitudinal direction or transverse direction, the tensile stress-strain curves all have a bell-shape, which indicates the excellent toughness. By using in situ synchrotron small-angle X-ray scattering during mechanical tensile tests, the toughening mechanism of carp scales have been quantitatively investigated.

4:20 PM  
Synthesis and Characterization of Ni0.5Zn0.5Fe2O4@mSiO2 Core Shell Nanocarrier for Drug Delivery Applications: Mohd Qasim1; Khushnuma Asghar1; Dibakar Das1; 1University of Hyderabad
    Ni0.5Zn0.5Fe2O4@mesoporousSiO2 (NZF@mSiO2) core shell nanocarrier was synthesized by sol-gel method using TEOS and CTAB and characterized for different physicochemical and biocompatible properties using XRD, HRTEM, FESEM, BET, VSM techniques and MTT assay. XRD pattern and TEM micrographs confirmed the coexistence of Ni0.5Zn0.5Fe2O4 and SiO2 phases in the nanocomposites. Average crystallite size of Ni0.5Zn0.5Fe2O4 NPs was found to be around ~21 nm. Particles sizes of NZF@mSiO2 measured by TEM and FESEM were found to be ~200-400 nm. HRTEM results confirmed successful formation of NZF@mSiO2 core shell nanocomposites having well symmetric structure and ellipsoidal shape. Both BET and HRTEM analysis confirmed the presence of pores (5-10 nm) on the surface of SiO2 nanosphere. NZF and NZF@mSiO2 have been found super-paramagnetic in nature. The Ms values for Ni0.5Zn0.5Fe2O4 and NZF@mSiO2 were found to be 55 and 10 emu/gm respectively. MTT assay confirmed the biocompatible nature of NZF and NZF@mSiO2 nanoparticles.

4:40 PM  
The design and development of low modulus Ti-Nb-Zr based alloy system for biomedical application: Afrin Mehjabeen1; Ma Qian1; Dong Qiu1; Wei Xu2; 1RMIT; 2Macquarie University
    Titanium (Ti) and Zirconium (Zr) are the prime candidates among all the metallic materials being used in biomedical implant fabrication because of their excellent biocompatibility, favorable mechanical properties, and high corrosion resistance. In the design of new biomedical alloys, stress shielding plays a vital role and should be considered carefully. Stress shielding occurs due to the mismatch of Young’s modulus between bone and implant which may result in refracture of the bone. The d-electron theory is developed based on the DV-Xα molecular orbital calculation of electronic structures of atoms. It explains some potential relationships between phase stability and elastic modulus through two electronic parameters: bond order, and d orbital energy level. In particular, a Bo -Md map is introduced to design new Ti-based alloys by d-electron theory where Bo and Md are the compositional average of Bo and Md respectively. Another useful parameter in alloy design is the electron to atom ratio, e/a, although there is controversy about the effect of e/a on elastic properties. In this research, these two tools are used together to design promising Ti-Nb-Zr alloys in conjunction with the use of the basic principles of physical metallurgy.