Materials Science Forum Vols. 539-543

Abstract: Application of TiNi shape memory alloy in biomedical field is rapidly expanding. Some of the applications calls for non-conventional properties, which may require new methods of thermomechanical treatment and surface modification. In the present study, the effect of nanocrystallization/amorphization by various method of severe plastic deformation, such as, shot peening, cold rolling and high pressure torsion, was investigated on properties of TiNi shape memory alloys. Shot peening using iron based metallic glass media was found to be an effective method to obtain the amorphous surface. Surface amorphization improved the corrosion resistance. Nanocrystalline TiNi exhibited peculiar superelastic properties. Correlation between the microstructure and phase transformation in nanostructured TiNi was discussed.

Abstract: Nanotechnology is being used to mimic structural components of our tissues in synthetic materials intended for various implant applications. Recent studies have highlighted that when compared to flat or micron rough surfaces, surfaces with nanofeatures promote optimal initial protein interactions necessary to mediate cell adhesion and subsequent tissue regrowth. This has been demonstrated for a wide range of implant chemistries (from ceramics to metals to polymers) and for a wide range of tissues (including bone, vascular, cartilage, bladder, and the central and peripheral nervous system). Importantly, these results have been seen at the in vitro and in vivo level. This short review paper will cover some of the more significant advancements in creating better implants through nanotechnology efforts.

Abstract: The contact of a cell on the biomaterial’s surface is mediated by its adhesion components. The topography of titanium surfaces influences these adhesion components of osteoblasts, e.g. the integrins, the adapter proteins and the actin cytoskeleton. In our current experiments we were interested in why osteoblasts were strongly aligned to the grooves of a structured pure titanium surface (grade 2). The titanium was characterized by EIS to get insights in the electro-chemically active surface. We used MG-63 human bone cells, cultured in DMEM with 10% FCS at 37°C. For protein adsorption the titanium discs were incubated for 24h with complete medium containing soluble fibronectin at 37°C. Interestingly, only in the grooves cells adhered and were aligned and this is not dependent on the gravitation. The cell adhesion seems to depend on the protein adsorption of fibronectin which we could find to be adsorbed exclusively in the valleys. We speculate that there are local differences in electro-chemical characteristics of this structured titanium surface.

Abstract: There is a growing need for remote biological sensing in both laboratory and harsh field environments. Sensing and detection of biological entities such as anthrax, Ebola and other micro-organisms of interest involves sampling of the environment, amplification, analysis and identification of the target DNA. A key component of such a sensor is a low cost, portable, reusable, continuous flow polymerase chain reaction (PCR) thermal cycler. Fabrication with low temperature co-fired ceramics (LTCC) can provide a reusable low cost device capable of operating in a wide range of environments The design and manufacture of a prototype continuous flow micro-fluidic PCR device using low temperature co-fired ceramic is presented. Initial modeling of flow characteristics and heat transfer was carried out in SolidWorks™. The prototype device employs resistance heaters below the channels, buried and surface thermocouples for temperature monitoring, and air gaps for thermal isolation.

Abstract: Metallic Intravascular stents are medical devices used to scaffold a biological lumen, mostly diseased arteries, after balloon angioplasty. They are commonly made of 316L stainless steel or Nitinol, two alloys containing Nickel, an element classified as potentially toxic and carcinogenic. Although they are largely implanted, the long-term safety of such metallic elements is still controversial, since the corrosion processes may lead to the release of several metallic ions. In order to avoid the metallic ion release in the body and to improve the biocompatibility of metallic stents with their biological environments, polymer coatings have been deposited by two different technologies, i.e. plasma surface modifications and Electrospraying. The role of the polymer coating is then to encapsulate the stainless steel device, and to favour the chemical grafting of Phosphorylcholine, a molecule known for its hemocompatible properties.1 In this talk, the state of the art on low pressure and atmospheric pressure plasmas for deposition of organic coatings will be given and we will present the advantages and drawbacks of each process. Then, we will present an original technology that combine a Dielectric Barrier Discharge and an electrospraying system to deposit well-defined Polyacrylic acid and Polyallylamine films. The advantage of such system is the possibility to limit the extent of the monomer fragmentation and to give rise to rapid deposition of a highly functionalised plasma polymer layer, and also the possibility to cover three dimensional objects, such as stents. Thus, the theory of EHDA technology will be explained: special attention has been paid to define the Electrospray parameters (Voltage, flow of precursor, nozzle-substrate distance…) which control the size distribution of the charged droplets and as a consequence, the structure of the film coating. The film coatings have been analysed with XPS and by ATR. Moreover, special attention will be paid on the stability of the coating which is related to both spraying conditions as well as to the preliminary plasma treatment. The potentiality and the features of the EHDA process will be then presented.

Abstract: The primary purpose of this study was to characterize the main features of a BCP-loaded chitosan-GP composite. The two-syringe design improves the storage conditions, facilitates the sterilization procedure and provides an easy-to-use injectable biomaterial, ensuring reproducible properties with minimal manipulation. Rheological measurements confirm that the chitosan- GP/BCP composite retains the thermosensitive properties already described for chitosan-GP hydrogels. At 37°C, the system gels within 10 minutes and reaches sufficient consistency after 30 minutes to prevent the mineral granules from migration into the surrounding tissues in vivo. The compressive force needed for the injection of chitosan-GP/BCP before gelation is approximately 6.6 N, only about 6 times that required for water and much lower than the average force that the majority of adults can exert. Morphology was investigated by environmental scanning electron microscopy (ESEM), which revealed 3-D dispersion of BCP granules embedded in chitosan-GP hydrogel. This open, porous structure affords complete access for body fluids and cells to each mineral granule immediately following implantation. The design using disposable syringes equipped with 16G hypodermic needles described here allows easy in vivo delivery of a fully injectable biomaterial containing porous scaffold that naturally enhances the osteogenic activity recognized for both chitosan and BCP.

Abstract: Superficial bladder cancer is often treated by removing the cancerous portion of the bladder wall combined with immuno-chemotherapy; in more extreme cases, it is often necessary to remove the entire bladder wall. This diagnosis brings an obvious need for bladder tissue replacement designs with a high degree of efficacy. Since bladder cells are accustomed to interacting with extracellular matrix proteins having dimensions on the nanometer scale, this study aimed to design the next generation of tissue-engineered bladder replacement constructs with nanometer (less than 100 nm) surface features. For this purpose, porous and biodegradable PLGA and PU scaffolds were treated with various concentrations of NaOH or HNO3, respectively, for various periods of time to create nanometer surface roughness. Resulting surface properties were characterized using SEM (to visualize scaffold properties) and BET. Cell experiments conducted on these polymeric scaffolds provided evidence of enhanced bladder smooth muscle cell attachment, growth, and elastin/collagen production (critical extracellular matrix proteins in the bladder tissue regeneration process) as surface feature dimensions were reduced into the nanometer regime. In vivo augmentation surgeries with nano-structured PLGA and PU patches will provide further information regarding total bladder capacity, anastomotic integrity, burst pressure, epithelialization, muscular ingrowth, and neovascularization. In vitro and in vivo proof of material usefulness and technique would provide urologists with a readily accessible graft for bladder tissue replacement applications.

Abstract: Most biomaterials widely used in nerve regeneration are either inert or modified with ECM proteins or their epitopes. Neurotransmitters play a key role in neuronal development and function. Thus we decided to investigate the feasibility of using neurotransmitters to create biofunctional materials that actively engage nerve cells to achieve functional restoration after injury of the nervous system. Our data indicated that a properly designed biodegradable polymer with dopamine functional groups was more capable of promoting neurite growth. Such biofunctional materials can potentially provide a new strategy for nerve regeneration.

Abstract: Calcium phosphate films were coated on commercially pure titanium substrates by radiofrequency magnetron sputtering using β-tricalcium phosphate targets. The films consisted of amorphous calcium phosphate and oxyapatite phases. Immersion tests of the films were carried out in Hanks’ solution and PBS(-), and apatite formation and calcium ion elution from the films were investigated. The titanium cylinders coated with calcium phosphate films were implanted into the mandibles of beagle dogs. These results suggest that coating with calcium phosphate improves the biocompatibility of titanium implants with bone tissue.