ICMCTF2008 Session TS3-2: TS3: Bioactive Coatings and Surface Biofunctionalization

Monday, April 28, 2008 1:30 PM in Room Sunrise

Monday Afternoon

Start	Invited?	Item
1:30 PM	Invited	TS3-2-1 Bioactive Glass Coatings on Metallic Implants E. Saiz, A.P. Tomsia (Lawrence Berkeley National Laboratory) Metals have been used successfully for decades in fracture fixation, joint replacement, and dental applications. More recently, high strength technical ceramics are also being considered for the fabrication of orthopedic implants. In many cases surface treatments are used to improve the materials bonding ability to living tissues, particularly bone. This talk will review recent advances in the fabrication of novel graded glass and glass-ceramic coatings on Ti-based and Co-Cr alloys using a simple enameling technique. These coatings exhibit excellent adhesion to the alloy and bioactive surfaces. The effect of the coating composition and the processing conditions on the adhesion to the metal, the mechanical properties of the coating and the in vitro behavior will be discussed.
2:10 PM	Invited	TS3-2-6 Non-Fouling Surfaces in Marine and Biomedical Environments M. Grunze (Universität Heidelberg, Germany) In this talk I will compare common features and distinct differences of non-fouling surfaces used in biomedical applications and in marine environments. We find that chemistry is highly specific to different organisms, whereas surface charge and topography can be indiscriminate. The effect of different sugars and RGD peptide sequences on settlement and their specific effects on different organisms will be demonstrated. Solvation forces and negative surface charge determine the adsorption characteristics of "inert" organic surfaces. The subtle and distance dependent balance between these forces determines under which (external) conditions surfaces adsorb or repel proteins, cells or marine organisms. Last I discuss how topographic features in the nano-and micrometer length scale influence settlement and how these different design concepts can be combined.
2:50 PM		TS3-2-9 Cell Growth and Proliferation on Polyethylene Plasma-Implanted With Copper and Gas Ions Z. Wei, P.K. Chu (City University of Hong Kong) It has been discovered that Cu plasma immersion ion implantation (PIII) can endow Polyethylene (PE) with excellent antibacterial properties, and gas plasma co-implantation can prolong the antibacterial effects. However, when the materials are implanted into the human body, the surface biological properties and cell behavior on the materials are also important issues. In this work, we investigate the growth and proliferation of cells on the surface of PE samples that have been plasma-implanted with copper as well as gas species such as O₂, N₂, or NH₃. The human fetal osteoblastic cell line (hFOB) assays indicate that Cu PIII can give rise to excellent biocompatibility as well as good antibacterial characteristics. The effects mainly result from the formation of functional groups such as C-O and C=C after Cu PIII and that the amount of implanted Cu is low enough not to affect cell bone growth on the surface. O₂, N₂, or NH₃ PIII further modifies the surface chemical functional groups affecting the adhesion and proliferation of the bone cells. Under the same culturing conditions, the Cu and O₂ co-PIII sample exhibits the best bone cell growth, but nitrogen-containing functional groups such as C-N and C=N created by N2 PIII negatively impact proliferation of the hFOBs on the surface. On the other hand, our results reveal that gas PIII in concert with Cu PIII have very little effects on the adhesion and proliferation of Chinese Hamster Ovary cells (CHO) as compared to the control samples. Even though different cell lines respond to the plasma treatment differently, our results indicate that by using the proper treatment, the PE surface can have both excellent antibacterial properties and biocompatibility.
3:10 PM		TS3-2-10 Tribological Behavior of UHMWPE Sliding Against Nitrided Ti-6Al-4V Alloys by Plasma Immersion Ion Implantation W.F. Tsai (Institute of Nuclear Energy Research, Taiwan); W.M. Weng (National Yang Ming University, Taiwan); C.F. Ali (Institute of Nuclear Energy Research, Taiwan); R. Tsay (Nation Yang Ming University, Taiwan) Plasma Immersion Ion Implantation (PIII) is an advanced technique that applies a pulsed high negative bias voltage on a target immersed in a plasma which can accelerate the ions towards the targeted specimen from all directions and causes 3D ion implantation. By properly controlling the implantation condition, one can modify the targeted surface in beneficial ways to make it harder, reduce its friction coefficient and enhance its wear resistance. Literature reports indicated that ion implantation has a great potential in increasing the life time of a biomedical device, such as an artificial joint since the plasma ion implanted layer does not have the delamination problem often encountered for a coated film. Numerous studies have shown that wear arising from the counter-friction of UHMWPE element against metal is one of the major causes for the failure of joint arthroplasty. The aim of this work is to reduce wear debris of UHMWPE by strengthening its counter Ti-6Al-4V alloy surface using PIII technique. Treatments were carried out in a nitrogen plasma at bias voltages of 15, 25, and 35 kV for 1 to 3 hours. The PIII nitrided layers were characterized by a secondary ion spectrometer (SIMS), a grazing incidence X-ray diffraction (GIXRD) and a nanoindentor. Also, a six-station wear testing system built based on ASTM F732 were applied to simulate the wear condition of an artificial joint. The results show that as the implantation voltage increases, the penetration depth of nitrogen ions increases and therefore enhances the surface hardness. By comparing with untreated samples, the hardness of a 35 kV PIII treated sample increases with a factor of three. The results also show that friction coefficient decreases substantially with the PIII treatment. By increasing the bias voltage from 15 to 35 kV or by increasing implantation time from 1 to 3 hours, the friction coefficient of an UHMWPE pin to the PIII treated Ti-6Al-4V alloy surface decreases.
3:30 PM		TS3-2-7 Nanocrystalline Passivation Layer On Magnetron Sputtered TiNi Shape Memory Thin Films For Biomedical Applications D. Kaur, A. Kumar (Indian Institute of Technology Roorkee, India) Proper passivation to prevent surface layer degradation and nickel releasing into the environment has been considered crucial for the medical applications of TiNi based shape memory alloys. To apply TiNi surgical devices in the human body, the surface properties and corrosion resistance are important material characteristics. Therefore, a stable, biocompatible and corrosion resistant passive layer is required.The present study explored the deposition and effect of nanocrystalline TiN protective layer on TiNi thin films prepared by dc magnetron sputtering to improve the surface properties and biocompatibility of SMA thin films. Deposition temperature was found to have a great impact on the structural properties of both pure TiNi and TiN/TiNi thin films. The structural, electrical, mechanical and optical studies were performed on both uncoated and TiN coated TiNi films and the results were compared. The size and preferred orientation of grains in the TiN passivation layer was observed to have a significant influence on the properties of TiN/TiNi heterostructure. Two way SMA behaviour had been observed in both pure TiNi and TiN coated TiNi thin films. Nanoindentation studies were performed at temperatures of 298° K, 323° K, and 380° K to determine the hardness and reduced modulus. Topographical in-situ images taken on the surface of pure TiNi and TiN coated TiNi showed an improvement in surface roughness after passivation coating. It was found that the presence of nanocrystalline TiN layer on TiNi based shape memory thin films improves the surface and mechanical properties, while retaining the shape memory effect.
3:50 PM		TS3-2-8 Nanocrystalline Fe₃O₄ Thin Films for Biosensor R.N. Goyal, A.K. Pandey, P. Singh, I. Deepak, A. Kumar, D. Kaur (Indian Institute of Technology Roorkee, Roorkee, India) Magnetite (Fe₃O₄) is the famous magnetic material used in biotechnology and medicinal field due to its biocompatibility, catalytic activity and low toxicity. It has a band gap of 0.1 eV, so a good conducting material. It can be used as a sensor for the detection of some biologically important compounds especially in the field of dope test. We hereby report the synthesis of highly oriented nanocrystalline iron oxide thin films on quartz, MgO (100), and Si (100) substrates by pulsed laser deposition technique using excimer KrF laser (248 nm). Target used was bulk a-Fe₂O₃ pellet sintered at 1000°C for 2 hours. Substrate temperature was found to have great impact on the structural properties of the films. The crystallinity of the films was found to change with deposition temperature in case of quartz substrate. The preferred orientation of the film was changing from [311] to [400] with increase in deposition temperature from room temperature to 500°C. The crystallite size, lattice parameters etc. were studied using XRD. The surface morphology of the deposited films was studied using FE-SEM, and AFM. The morphology shows spherical ball like regular features of nanometer size. The magnetic properties were studied by Superconducting Quantum Interference Device (SQUID) magnetometer in the magnetic field (±7 tesla). The electrochemical response was studied on Bioanalytical system (BAS) CV-50 W, using three electrode systems which were composed of an Ag/AgCl reference electrode, a platinum wire counter electrode and the iron oxide thin film as working electrode.