Next Generation Biomaterials: Next Generation Biomaterials V
Program Organizers: R. Narayan, UNC/NCSU Joint Department of Biomedical Engineering; Kajal Mallick, University of Warwick; Vilupanur Ravi, California State Polytechnic University, Pomona; Kalpana Katti, North Dakota State University; Varshni Singh, Louisiana State University
Thursday 8:00 AM
October 11, 2012
Room: Room 319
Location: David L. Lawrence Convention Ctr
Session Chair: Marjorie Austero, Drexel University; Ilona Hoffmann, University of Kentucky
8:00 AM
Combined AFM and 3-D Optical Microscopy of Cells and Biomaterials: Yasemin Kutes1; Varun Vyas1; Vincent Palumbo2; Atif Rakin1; Yusuf Khan3; Bryan Huey2; 1University of Connecticut; 2UConn / Aarhus University iNANO; 3UConn Health Center
Cell development and function depends on the surrounding mechanical environment. However, the mechanical properties for this media can be challenging to measure, particularly in the case of porous, networked systems such as cell scaffolds, the extra-cellular-matrix, adjacent cells, etc. Furthermore, active mechanical forces acting on cells can be influential in their development, which is leveraged clinically for example via ultrasound to accelerate bone fracture healing. The global, and local, mechanical properties of these networked systems, along with the living response of cells to mechanical loading, is therefore an important area for investigation. This is achieved with a unique combined AFM and 3-d fluorescence microscopy system, providing nano to micro scale property mapping in 3-dimensions. Such results reveal heterogeneities in the direct response to mechanical loads, both in magnitude and direction, as well as variable relaxation profiles following loading.
8:20 AM
Non-Covalent Crosslinkers for Electrospun Chitosan Fibers: Marjorie Austero1; Caroline Schauer1; 1Drexel University
Chitosan (CS), the deacetylated form of chitin, is attractive for its potential biomedical, food and pharmaceutical applications due to its high biocompatibility, biodegradability and unique functionality. CS can be fabricated into nanofibers by electrospinning, a simple and inexpensive method of forming fibers with diameters reaching the nanoscale level. Here, CS mats are spun from an acidic solution that is placed in a needle-capped syringe. The needle is connected to a conductive target by electrodes attached to a high voltage power source. The produced mats are porous, with three-dimensional structure and increased surface area-to-volume ratio that are potential candidates for tissue scaffolds or filtration membranes. The CS mats however, are not chemically stable in a wide pH range. Previously, we reported successful fabrication of covalently-crosslinked CS fibers through electrospinning. Here, we demonstrate the use of glycerol phosphate, tripolyphosphate and tannic acid as a new set of ionic crosslinkers for electrospun chitosan.
8:40 AM
Parametric Studies on Femtosecond Laser Cutting of Ni-Ti Shape Memory Alloy: Hossein Lavvafi1; Dave Dudzinski2; Melissa Young2; Janet Gbur1; John Lewandowski1; John Lewandowski1; 1CWRU; 2Cleveland Clinic Foundation
Recent advances in minimally invasive surgical techniques and an increasing need to miniaturize medical devices has led to a surge in developing advanced manufacturing techniques. Laser machining is one tool harnessing an enormous potential for the manufacture of such finely detailed devices as well as providing a means for improving the local material effects as a result of processing. Surface damage resulting from traditional, thermal-based laser micromachining can affect the performance of components. Newer laser systems, utilizing athermal ablation, may aid in improving the performance of laser processed components by decreasing the amount of surface damage to the material. In this study, a femtosecond laser was used to machine nitinol tubes. The mechanical behavior was evaluated in uniaxial tension and in cyclic fatigue. The effects of laser input energy on the surface quality, heat affected zone (HAZ), and subsequent mechanical response will be reported along with plans for future work.
9:00 AM
Polydimethylsiloxane Substrates with Tunable Elastic Modulus: Independent Control of Stiffness Over a Three Order-of-Magnitude Range: Rachelle Palchesko1; Ling Zhang1; Yan Sun1; Adam Feinberg1; 1Carnegie Mellon University
Cells respond dynamically to their environment and recent work has shown that substrate mechanics can regulate cell shape, proliferation and stem cell differentiation. Mimicking the elastic modulus of soft tissue has been effective for studying mechanobiology, but new materials are needed in order to investigate a wider range of material properties. We hypothesized that blends of soft polydimethylsiloxane (PDMS) and stiff elastomeric PDMS would provide a tunable system where the elastic modulus could be adjusted to match any type of soft tissue . This PDMS system can be formulated with an elastic modulus from 8 kPa to 1.5 MPa, spanning a three order-of-magnitude range. The mechanical properties can be adjusted without modifying surface roughness, surface energy and ease of fabrication. This provides distinct advantages over tunable hydrogels, which have a limited elastic modulus range. For biological validation, PC12 and C2C12 cells were used to demonstrate mechano-sensitivity on our PDMS formulations.
9:20 AM Break
9:40 AM
Human Liver Cell Culturing in Porous Hydroxyapatite/Hydrogel Composites: Anthony Finoli1; Eva Schmelzer2; Jörg Gerlach2; Ian Nettleship1; 1University of Pittsburgh; 2McGowan Institute of Regenerative Medicine
Chronic liver disease is one of the leading causes of death in the United States. Transplantation is generally the only cure but available organs are far outnumbered by the patients need. One potential solution is to create appropriate amounts of transplantable tissue in-vitro using bioreactors. The core of such reactors will require resorbable, three dimensional scaffold materials that support tissue restructuring. This project aims to culture human liver cells from both adult and fetal sources, in a bioactive composite consisting of a hydroxyapatite foam in a type-I collagen or hyaluronic acid hydrogel matrix. The processing of this bioactive composite will be presented with the results of long term cell culturing experiments, including gene expression, protein analysis and fluorescent imaging.
10:00 AM
Cytocompatibility and Stimulated Osteoblasts Functions Induced by Graphene Oxide in Polymeric Biomaterials
: Pushkraj Chaudhari1; Devesh Misra1; 1University of Louisiana at Lafayette
We describe here the in vitro biological response of a new hybrid nylon polymer system containing a promising nano-sized biomaterial, graphene oxide. Graphene oxide favorably modulated cellular and molecular reactions in promoting osteoinductive signaling of surface adherent cells, in the present case, osteoblasts for joint reconstruction. The cell-substrate interactions on stand alone Nylon 6,6 and Nylon 6,6-graphene oxide hybrid system were investigated in terms of cell attachment, viability, proliferation, and assessment of proteins, actin, vinculin and fibronectin. The enhanced biological functions in the nanostructured hybrid system are attributed to relatively superior hydrophilicity of the surface and to the presence of graphene oxide. Furthermore, it is proposed that the negatively-charged graphene oxide interacts with the polar nature of cells and the culture medium, such that the interaction is promoted through polar forces.
10:20 AM
Prediction of the Stress Distribution and the Coating Delamination in Cardiovascular Drug-Eluting Stent (DES) Medical Devices: Chang-Soo Kim1; Solki Lee1; Marjan Nezafati1; 1University of Wisconsin-Milwaukee
Drug-eluting stent (DES) is one of the most widely used medical devices to treat cardiovascular diseases avoiding the high risk of surgical procedures. Typical DES is composed of metallic stent platform and drug-polymer composite coatings. Because the coating fracture and delamination during the deployment of stent is one of the major issues to create clinical adverse effects, it is essential to understand the stress distributions and delamination/fracture mechanisms of drug-polymer coatings in DES applications. In this study, we have employed a finite-element analysis (FEA) computational technique to predict these stress distributions in the stent platform and coating. In developing the model, we have incorporated the necessary elastic and plastic physical properties of constituent materials such as metallic platform, drug, polymer, atherosclerotic plaque, and arterial wall. The presentation will include the FEA model development and the resultant stress distributions in the DES-plaque-arterial wall system along with the predicted coating delamination/fracture mechanisms.
10:40 AM
Effect of Cold Work and Aging on a Cobalt-Nickel Based Multiphase Alloy: Song Cai1; Larry Kay1; 1Fort Wayne Metals Research Products Corp.
Cobalt-nickel based MP35N alloy has been used in aerospace and oil industries for years and recently in medical applications like implants and pace maker leads due to its high strength, ductility, corrosion resistance and biocompatibility. In this study, experiments were carried out to investigate the influence of cold work and aging on its mechanical properties. Material was cold drawn to 30-90% reduction and aged at temperatures from 400 to 700˚C for 10 minutes to 16 hours. Results show a rapid and strong work hardening effect. Aging provides a secondary strengthening depending on the cold work level. A significant strength increment can be obtained after aging at temperatures from 500 to 600˚C for ~2 hours, where extremely high strength (e.g. yield strength >2000MPa and a tensile strength >2200MPa) and good ductility (e.g. RA ~40%) was achieved. TEM analysis was used to understand the strengthening mechanism during cold work and aging treatment.