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Electrospun Scaffolds for Tissue Engineering F. Spano, M. Liley, C. Hinderling, H. Sigrist • A novel nanofibrous material is being developed to be used in three dimensional scaffolds for the directed growth of cells, e. g. in nerve regeneration and guiding. The material will be produced in the form of an aligned mat of nanofibers by electrospinning. The potential of electrospun polymer nanofiber mats in tissue engineering has been established. There is strong medical interest in the development of scaffold materials for tissue regeneration and 2D and 3D cell culture. In the USA, the shortage of donor organs results in the deaths of over 6000 people each year. In 1990, there were more than 9000 patients waiting for organ transplants than there were donors, while today the difference is over 55000 [1] . Tissue engineering could potentially make a major contribution to reducing this shortage of donors. Tissue engineering includes all the techniques that combine cell biology, engineering and biochemistry to replace, repair or regrow injured or diseased organs: a way of producing natural or synthetic organs and tissues by mimicking nature. Electrospinning is a flexible and effective technique for the fabrication of polymer nanofibers. In this process, a solution of polymer(s) is fed at a continuous rate through a capillary. The capillary is charged to a high voltage (20 kV) with respect to a grounded counter electrode (Figure 1). This results in very high electrical fields at the capillary tip leading to the deformation of the polymer solution into a cone (the “Taylor cone”) in response to the electrostatic forces. If the electric field exceeds a certain threshold, the electrostatic forces overcome the surface tension: a thin jet of liquid is ejected from the tip of the Taylor cone and travels towards the counter electrode. Figure 1: Schematic of the electrospinning process In tissue engineering, electrospun nanofibrous materials have been used as three dimensional scaffolds for the directed growth of cells, e.g. in nerve regeneration and nerve guiding. The key property that differentiates electrospun materials from alternative tissue engineering materials is that they mimic the structure of the extracellular matrix (ECM) (Figure 2). The native ECM provides more than just a mechanical support for cells, it also serves as a substrate to display specific ligands and factors that control cell adhesion, migration and regulate cell proliferation and function [2] . The addition of ligands to electrospun materials potentially offers a simple way to control structural alignment and promote target cell binding. Different polymers can be used for electrospinning. This study focuses in particular on Dextran, a polymer known for its biodegradable and biocompatible properties. a) b) 20 µm Figure 2: Phase Contrast Light microscopy (a) and Laser Scanning Confocal Microscopy (b) images of Neural Stem Cells attached on aligned PLLA nanofibers [3] . Simple techniques [4] have been used to control and guide the nanofibers during electrospinning and create an anisotropic geometry, e.g. an uniaxially aligned array. Electrospinning onto shaped electrodes (parallel strips) has been particularly successful [5] . The diameter of the dextran fibers obtained is between 100 nm and approximately one micron. The morphology of the fibers can be tuned systematically by varying any one of a number of parameters such as concentration, voltage and distance to the counter electrode. Defect-free electrospun Dextran nanofibers (Figure 3a) have been generated in the form of aligned arrays (Figure 3b) and can thus mimic the structure of the native extracellular matrix (Figure 3) while exerting an orienting influence. a) b) Figure 3: a) SEM image of electrospun nanofibers. b) Optical image of aligned electrospun nanofibers. The following months work will focus on the introduction of biological guidance cues for the controlled growth of cells on or in aligned electrospun nanofibers. This work is done within the framework of the CCMX Project called FUNFIBER with the collaboration of Arrayon Biotechnology. • Arrayon Biotechnology, Neuchatel, Switzerland [1] American Society of Transplant Surgeons - www.asts.org [2] F. Yang, et al., Biomaterials, 26, (2005), 2603–2610 [3] F. Yang, et al., Biomaterials, 26 (2005) 2603–2610 [4] X. Mo, et al., Macromol. Symp. (2004), 217, 413-416 [5] Y. Xia, Adv. Mater., 16, No. 4 (2004), 361-366 50 µm 50 µm 57
Detection Methods for Nanotoxicology S. Angeloni, V. Matera • , E. Verrecchia • , M. Liley An understanding of the risks due to the short and long term toxicity of engineered nanoparticles requires the collection of a new body of data on nanoparticle toxicity. In vitro methods can contribute to the understanding of the mechanisms by which NPs enter the human body, but require a sensitive nanoparticle detection technique. Inductively coupled plasma mass spectroscopy is a promising candidate technique. An assessment of the hazards due to engineered nanoparticles (NPs) is highly complex, requiring extensive data collection on, among other things, the toxicology of NPs. One approach that can contribute to this assessment is based on the use of absorption models dealing with oral, inhalation and topical absorption of NPs (via the intestines, the lungs, and the skin, respectively) [1] . Figure 1: An in vitro model of biological barriers for nanotoxicological tests: a) transport of NPs to the biological barrier; b) microfabricated well for cell culture; c) cell culture chamber divided in two by a thin porous membrane (d) layer of epithelial cells acting as model biological barrier; e) detection of NPs by ICP-MS (see Figure 2). In vitro assays based on model biological barriers can contribute to the understanding of the mechanisms by which NPs gain access to the body (Figure 1). Studies on the transport (translocation) of NPs across these barriers require a detection method for NPs with excellent accuracy and sensitivity. Optical methods such as fluorescence detection or light scattering can be extremely sensitive. However, fluorescence labeling has been found to alter the transport properties of the NPs, while scattering methods have been found to lack specificity. Figure 2: Diagram of an inductively coupled plasma mass spectrometer (ICP-MS, Perkin Elmer): the liquid sample is introduced (a) into a radiofrequency plasma (b). Ions generated are extracted from the plasma - (c) and (d) - and separated according to their mass-to-charge ratio by a mass spectrometer (e); detector (f). As an alternative to optical detection, inductively coupled plasma mass spectroscopy (ICP-MS) has been tested for the detection and quantification of nanoparticles (Figure 2). ICP- MS is a classical technique based on the chemical identification of the NPs and profiting from recent improvements to achieve a better sensitivity (multi-element ultra trace analysis) [2] . Different water-soluble NPs were analyzed by this technique, namely, a commercially available titanium oxide NP suspension (TiO2), cadmium telluride quantum dots (CdTe), gold colloids (Au, mean size 20 nm), 58 and gold NPs (Au, mean size less than 2 nm [3] ). The NPs were analysed as pure suspensions, as blends of different NPs and also in cell culture medium (Figure 3). No interference was detected between the different NPs or from the culture medium. A linear response was observed for all selected NPs allowing not only detection but also facile quantification. In addition, the sensitivities obtained achieved the desired detection limits. Fi gure 3: ICP-MS response (vertical axis) against known concentration for gold (top graph) and CdTe NPs (lower graph). A linear response is obtained despite size differences or the presence of multiple NPs or cellular culture medium. In conclusion, the detection and quantification of NPs has been shown to be possible for inorganic metal NPs down to concentrations of 0.1 ppb (microgram/liter). Next steps will involve greatly reducing the sample volume (currently 1 ml) in order to make ICP-MS based detection compatible with a miniaturized screening test. This work was partially financed by the European Commission in the framework of NANOSAFE2 (NMP2-CT-2005-615843). CSEM thanks them for their support. • Institut de Géologie et Hydrogéologie, University of Neuchatel, Switzerland [1] Cell Culture Models of Biological Barriers. Lehr, C.-M. ed.; Taylor and Francis: London, (2002), 430 [2] D. Beauchemin, Anal.Chem., 78, 12, (2006) 4111-4136 [3] C. Gautier, et al., J.Am.Chem.Soc.,128, 34, (2006) 11079-11087
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centre suisse d’électronique et
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CONTENTS PREFACE 5 RESEARCH ACTIVIT
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PREFACE Dear Reader, In this report
Page 9 and 10: TissueOptics - Portable SpO2 Monito
Page 11 and 12: Counterfeit - Machine Readable Cove
Page 13 and 14: ArrayFM - An Atomic Force Microscop
Page 15 and 16: Encoder - Nanometric Optical Absolu
Page 17 and 18: PackTime - Zero-Level Packaging of
Page 19 and 20: TissueOptics - Portable SpO2 Monito
Page 21 and 22: spectrometer applications so CSEM h
Page 23 and 24: As a first step, CSEM is building s
Page 25 and 26: Data Fusion for Wireless Distribute
Page 27 and 28: A High-Performance 2.4 GHz RF Front
Page 29 and 30: Quasi-Harmonic Quadrature CMOS Rela
Page 31 and 32: icycam, a System-On Chip (SoC) for
Page 34 and 35: PHOTONICS Nicolas Blanc The Photoni
Page 36 and 37: Optoelectronic Test Equipment for I
Page 38 and 39: Compact Illumination Modules Based
Page 40 and 41: Efficient Screening and Formulation
Page 42: Optical Fill Factor Enhancement for
Page 45 and 46: Dissolved Oxygen Sensor with Self-C
Page 47 and 48: Metal Micro-Parts Fabrication F. Ca
Page 49 and 50: Towards an Optical Switch with J-ag
Page 51 and 52: Towards Plasmon Enhanced Detectors
Page 53 and 54: Sol-Gel based Nanoporous Layers as
Page 55 and 56: Nanoporous Membranes for Medical Di
Page 57: Parallel Nanoscale Dispensing of Li
Page 61 and 62: Composite Materials for Bone Implan
Page 63 and 64: Smart Wound Dressing with Integrate
Page 65 and 66: Food Safety with the Help of a Mini
Page 68 and 69: NANOMEDICINE Peter Seitz Mandated b
Page 70: X-Ray Microscopy and Micrometer-Res
Page 73 and 74: Micro-Vibration Analysis Setup for
Page 75 and 76: the signals with a reference to sta
Page 77 and 78: Prediction of Neurocardiovascular E
Page 79 and 80: Continuous Arterial Blood Pressure
Page 81 and 82: UWB Antenna with Improved Bandwidth
Page 83 and 84: A Wireless Sensor Network for Fire
Page 85 and 86: A MAC Protocol for UWB-IR Wireless
Page 87 and 88: Wireless Sensor Networks for Monito
Page 89 and 90: Wearable Systems to Protect Rescuer
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Page 93 and 94: NanoHand - A System for Automated N
Page 95 and 96: Isolation and Reversible Immobiliza
Page 97 and 98: Sensor and Connector Integration in
Page 99 and 100: Pressure Sensing Strip - Packaging
Page 101 and 102: Optical / Fluidic Integration of Si
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Page 105 and 106: PRN-cw Backscatter Lidar Prototype
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Quality Control A. Dommann, A. Ibza
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[18] A.-C. Pliska, C. Bosshard "Adh
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[21] E. Onillon, P. Theurillat, A.
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A. Bonfiglio, N. Carbonaro, C. Chuz
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H. Heinzelmann "CSEM and CSEM Brazi
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C. Piguet "High Level Energy and Po
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J. Solà I Caros "Annual meeting of
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8241.2 DCPP-NM SOLID Solid on Liqui
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LISA-PAAM Development, demonstratio
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University Institute Professor Fiel
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128 Title of lecture Context Locati
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Name Professor / University Theme /
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C. Piguet Member of the Board of th
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