23 research outputs found

    Application of high throughput microfabrication manufacturing processes for the fabrication of functional polymeric components of interest in the biomedical sector

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    184 p.El objetivo de la tesis se centra en el desarrollo de una metodología para el procesado de polímeros bio-absorbibles mediante tecnologías de alta productividad para la obtención de componentes micro-estructurados implantables. Para ello, se ha utilizado la tecnología de extrusión y se han seleccionado poliésteres bio-absorbibles, tanto de origen sintético como bacteriano, para obtener componentes que cumplan con los requisitos de la aplicación objetivo: implantes para la regeneración de nervio periférico. Se han estudiado las magnitudes de proceso características y su influencia en la capacidad de replicación de motivos micrométricos utilizando como plataforma de ensayo la microinyección, lo que permite el uso de diferentes estrategias de detección para analizar la correlación entre los parámetros y la replicación. Posteriormente se analizó la influencia de la adición de porosidad en componentes extruídos compuestos de poliéster bio-absorbible. Se analizó el cambio de propiedades mecánicas y dimensionales para adquirir conocimiento y establecer pautas para la selección de proporción y tamaño de las partículas de porogenerador. Finalmente, se procesó un novedoso blend de poliésteres de origen sintético y natural, obteniendo implantes tubulares de geometría, porosidad y propiedades mecánicas controladas que finalmente se ensayaron in-vivo, demostrando el éxito de los implantes fabricados mediante tecnologías de alta productividad

    Scientific Advances in STEM

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    Following a previous topic (Scientific advances in STEM: from professors to students; https://www.mdpi.com/topics/advances_stem), this new topic aims to highlight the importance of establishing collaborations among research groups from different disciplines, combining the scientific knowledge from basic to applied research as well as taking advantage of different research facilities. Fundamental science helps us to understand phenomenological basics, while applied science focuses on products and technology developments, highlighting the need to perform a transference of knowledge to society and the industrial sector

    Surface-Enhanced Spectroelectrochemistry using Synchrotron Infrared Radiation

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    Electrochemical reactions are inherently heterogeneous, occurring at the interface between a solid electrode and an electrolyte solution. Therefore, detailed mechanistic understanding requires the electrode/solution interface (ESI) to be interrogated. Doing so with spectroelectrochemical techniques generally encounters several analytical challenges. Sampling the ESI requires a surface-sensitive spectroscopy capable of addressing a buried interface, placing strong limitations on photon energy and spectroelectrochemical cell design. Furthermore, dynamic measurements are fundamentally limited by the finite rise time of the electrode. For many important processes with characteristic timescales in the milli- to microsecond regime, achieving a suitably low rise time requires the use of an electrode with critical dimensions in the hundreds of micrometers, i.e. a microelectrode. In this thesis, I develop the spectroscopic platform necessary to perform surface-sensitive, time-resolved infrared measurements in the milli- to microsecond regime. I will make the case that an infrared spectroelectrochemical technique, namely attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), is applicable because it is intrinsically surface-sensitive, yields detailed information on molecular structure, and is compatible with a range of electrocatalytic metals. I will show that the small size of the microelectrode requires an unconventional infrared source, namely highly focused synchrotron radiation. This thesis will present the characterization of a new internal reflection element which is fully compatible with ATR-SEIRAS and easily amenable to microfabrication. A custom horizontal microscope endstation will be developed at the mid-IR beamline at the Canadian Light Source. Its general utility beyond the primary goal of this thesis will be demonstrated with imaging experiments of a simple interfacial reaction in a microfluidic device. Finally, a 500 micrometer wide linear microelectrode compatible with ATR-SEIRAS will be fabricated and preliminary kinetic measurements of a model electrochemical process, namely the potential-induced desorption of 4-methoxypyridine, will be discussed

    Micromachining

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    To present their work in the field of micromachining, researchers from distant parts of the world have joined their efforts and contributed their ideas according to their interest and engagement. Their articles will give you the opportunity to understand the concepts of micromachining of advanced materials. Surface texturing using pico- and femto-second laser micromachining is presented, as well as the silicon-based micromachining process for flexible electronics. You can learn about the CMOS compatible wet bulk micromachining process for MEMS applications and the physical process and plasma parameters in a radio frequency hybrid plasma system for thin-film production with ion assistance. Last but not least, study on the specific coefficient in the micromachining process and multiscale simulation of influence of surface defects on nanoindentation using quasi-continuum method provides us with an insight in modelling and the simulation of micromachining processes. The editors hope that this book will allow both professionals and readers not involved in the immediate field to understand and enjoy the topic

    Design and development of an implantable biohybrid device for muscle stimulation following lower motor neuron injury

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    In the absence of innervation caused by complete lower motor neuron injuries, skeletal muscle undergoes an inexorable course of degeneration and atrophy. The most apparent and debilitating clinical outcome of denervation is the immediate loss of voluntary use of muscle. However, these injuries are associated with secondary complications of bones, skin and cardiovascular system that, if untreated, may be fatal. Electrical stimulation has been implemented as a clinical rehabilitation technique in patients with denervated degenerated muscles offering remarkable improvements in muscle function. Nevertheless, this approach has limitations and side effects triggered by the delivery of high intensity electrical pulses. Combining innovative approaches in the fields of cell therapy and implanted electronics offers the opportunity to develop a biohybrid device to stimulate muscles in patients with lower motor neuron injuries. Incorporation of stem cell-derived motor neurons into implantable electrodes, could allow muscles to be stimulated in a physiological manner and circumvent problems associated with direct stimulation of muscle. The hypothesis underpinning this project is that artificially-grown motor neurons can serve as an intermediate between stimulator and muscle, converting the electrical stimulus into a biological action potential and re-innervating muscle via neuromuscular interaction. Here, a suitable stem cell candidate with therapeutic potential was identified and a differentiation protocol developed to generate motor neuron-like cells. Thick-film technology and laser micromachining were implemented to manufacture electrode arrays with features and dimensions suitable for implantation. Manufactured electrodes were electrochemically characterised, and motor neuron-like cells incorporated to create biohybrid devices. In vitro results indicate manufactured electrodes support motor neuron-like cell growth and neurite extension. Moreover, electrochemical characterisation suggests electrodes are suitable for stimulation. Preliminary in vivo testing explored implantation in a rat muscle denervation model. Overall, this thesis demonstrates initial development of a novel approach for fabricating biohybrid devices that may improve stimulation of denervated muscles

    Hybrid bio-robotics: from the nanoscale to the macroscale

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    [eng] Hybrid bio-robotics is a discipline that aims at integrating biological entities with synthetic materials to incorporate features from biological systems that have been optimized through millions of years of evolution and are difficult to replicate in current robotic systems. We can find examples of this integration at the nanoscale, in the field of catalytic nano- and micromotors, which are particles able to self-propel due to catalytic reactions happening in their surface. By using enzymes, these nanomotors can achieve motion in a biocompatible manner, finding their main applications in active drug delivery. At the microscale, we can find single-cell bio-swimmers that use the motion capabilities of organisms like bacteria or spermatozoa to transport microparticles or microtubes for targeted therapeutics or bio-film removal. At the macroscale, cardiac or skeletal muscle tissue are used to power small robotic devices that can perform simple actions like crawling, swimming, or gripping, due to the contractions of the muscle cells. This dissertation covers several aspects of these kinds of devices from the nanoscale to the macro-scale, focusing on enzymatically propelled nano- and micromotors and skeletal muscle tissue bio-actuators and bio-robots. On the field of enzymatic nanomotors, there is a need for a better description of their dynamics that, consequently, might help understand their motion mechanisms. Here, we focus on several examples of nano- and micromotors that show complex dynamics and we propose different strategies to analyze their motion. We develop a theoretical framework for the particular case of enzymatic motors with exponentially decreasing speed, which break the assumptions of constant speed of current methods of analysis and need different strategies to characterize their motion. Finally, we consider the case of enzymatic nanomotors moving in complex biological matrices, such as hyaluronic acid, and we study their interactions and the effects of the catalytic reaction using dynamic light scattering, showing that nanomotors with negative surface charge and urease-powered motion present enhanced parameters of diffusion in hyaluronic acid. Moving towards muscle-based robotics, we investigate the application of 3D bioprinting for the bioengineering of skeletal muscle tissue. We demonstrate that this technique can yield well-aligned and functional muscle fibers that can be stimulated with electric pulses. Moreover, we develop and apply a novel co-axial approach to obtain thin and individual muscle fibers that resemble the bundle-like organization of native skeletal muscle tissue. We further exploit the versatility of this technique to print several types of materials in the same process and we fabricate bio-actuators based on skeletal muscle tissue with two soft posts. Due to the deflection of these cantilevers when the tissue contracts upon stimulation, we can measure the generated forces, therefore obtaining a force measurement platform that could be useful for muscle development studies or drug testing. With these applications in mind, we study the adaptability of muscle tissue after applying various exercise protocols based on different stimulation frequencies and different post stiffness, finding an increase of the force generation, especially at medium frequencies, that resembles the response of native tissue. Moreover, we adapt the force measurement platform to be used with human-derived myoblasts and we bioengineer two models of young and aged muscle tissue that could be used for drug testing purposes. As a proof of concept, we analyze the effects of a cosmetic peptide ingredient under development, focusing on the kinematics of high stimulation contractions. Finally, we present the fabrication of a muscle-based bio-robot able to swim by inertial strokes in a liquid interface and a nanocomposite-laden bio-robot that can crawl on a surface. The first bio-robot is thoroughly characterized through mechanical simulations, allowing us to optimize the skeleton, based on a serpentine or spring-like structure. Moreover, we compare the motion of symmetric and asymmetric designs, demonstrating that, although symmetric bio-robots can achieve some motion due to spontaneous symmetry breaking during its self-assembly, asymmetric bio-robots are faster and more consistent in their directionality. The nanocomposite-laden crawling bio-robot consisted of embedded piezoelectric boron nitride nanotubes that improved the differentiation of the muscle tissue due to a feedback loop of piezoelectric effect activated by the same spontaneous contractions of the tissue. We find that bio-robots with those nanocomposites achieve faster motion and stronger force outputs, demonstrating the beneficial effects in their differentiation. This research presented in this thesis contributes to the development of the field of bio-hybrid robotic devices. On enzymatically propelled nano- and micromotors, the novel theoretical framework and the results regarding the interaction of nanomotors with complex media might offer useful fundamental knowledge for future biomedical applications of these systems. The bioengineering approaches developed to fabricate murine- or human-based bio-actuators might find applications in drug screening or to model heterogeneous muscle diseases in biomedicine using the patient’s own cells. Finally, the fabrication of bio-hybrid swimmers and nanocomposite crawlers will help understand and improve the swimming motion of these devices, as well as pave the way towards the use of nanocomposite to enhance the performance of future actuators.[spa] La bio-robótica híbrida es una disciplina cuyo objetivo es la integración de entidades biológicas con materiales sintéticos para superar los desafíos existentes en el campo de la robótica blanda, incorporando características de los sistemas biológicos que han sido optimizadas durante millones de años de evolución natural y no son fáciles de reproducir artificialmente. Esta tesis cubre varios aspectos de este tipo de dispositivos desde la nanoescala a la macroescala, enfocándose en nano- y micromotores propulsados enzimáticamente y bio-actuadores y bio-robots basados en tejido muscular esquelético. En el campo de nanomotores enzimáticos, existe la necesidad de encontrar mejores modelos que puedan describir la dinámica de su movimiento para llegar a entender sus mecanismos de propulsión subyacentes. Aquí, nos enfocamos en diversos ejemplos de nano- y micromotores que muestran dinámicas de movimiento complejas y proponemos diferentes estrategias que se pueden utilizar para analizar y caracterizar este movimiento. Moviéndonos hacia robots basados en células musculares, investigamos la aplicación de la técnica de bioimpresión en 3D para la biofabricación de músculo esquelético. Demostramos que esta técnica puede producir fibras musculares funcionales y bien alineadas que puede ser estimuladas y contraerse con pulsos eléctricos. Investigamos la versatilidad de esta técnica para imprimir varios tipos de materiales en el mismo proceso y fabricamos bio-actuadores basados en músculo esquelético. Debido a los movimientos de unos postes gracias a las contracciones musculares, podemos obtener medidas de la fuerza ejercida, obteniendo una plataforma de medición de fuerzas que podría ser de utilidad para estudios sobre el desarrollo del músculo o para testeo de fármacos. Finalmente, presentamos la fabricación de un bio-robot basado en músculo esquelético capaz de nadar en la superficie de un líquido y un bio-robot con nanocompuestos incrustados que puede arrastrarse por una superficie sólida. El primer de ellos es minuciosamente caracterizado a través de simulaciones mecánicas, permitiéndonos optimizar su esqueleto, basado en una estructura tipo serpentina o muelle. El segundo bio-robot contiene nanotubos piezoeléctricos incrustados en su tejido, los cuales ayudan en la diferenciación del músculo debido a una retroalimentación basada en su efecto piezoeléctrico y activada por las contracciones espontáneas del tejido. Mostramos que estos bio-robots pueden generar un movimiento más rápido y una mayor generación de fuerza, demostrando los efectos beneficiales en la diferenciación del tejido

    Bioprinting and characterization of medium viscosity alginate scaffold for nerve tissue regeneration

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    Injured peripheral nerves with a gap >2mm often demonstrate poor regeneration ability, where scaffolds made from biomaterials are possibly used to bridge the gap for functional recovery. To fabricate such scaffolds, extrusion-based three dimensional (3D) printing technique shows promising due to its ability to precisely extrude biomaterial solution and build 3D structures by a layer-by-layer fashion. However, the 3D printing technique faces several challenges in fabricating scaffolds for nerve tissue regeneration. Among them, the printability, structural integrity, and biological performance of scaffolds printed from sodium alginate (SA) (a biomaterial widely used in nerve tissue regeneration) are the key issues. To address the issues, this thesis aims to develop SA scaffolds for potential application in peripheral nerve regeneration. Three specific objectives are set so as to investigate (1) the effect of fluid (i.e., SA solution) flow behavior, printing parameters, and concentration of ionic crosslinkers on the printability of SA scaffolds, (2) the influence of SA precursor and ionic crosslinker concentrations on the mechanical and biological properties of scaffolds, and (3) the influence of peptide conjugation with SA molecules on the biological performance of the scaffolds for nerve tissue regeneration. The flow rate in the printing process is critical to the scaffold structure and printability. The first part of dissertation is to examine the flow rate of SA solution or precursor extruded through a tapered needle in the scaffold fabrication process by developing a novel model for its representation. Specifically, the flow rate of the medium viscosity SA precursor was modeled by taking into account of both slip and shear flow from a tapered needle. Since the flow rate of SA precursor depends on its flow behavior, model predicting the flow behavior of the hydrogel precursor was also developed from regression of experimental data. For different extrusion pressures (e.g. 20, 25, 30, and 40 kPa) and concentrations (e.g. 2, 3, and 4%) of SA precursor, the flow rate model predicted with reasonable accuracy (coefficient of determination, R2 = 0.98). Further, at various needle diameters (0.2, 0.25, 0.41, and 0.61 mm) and temperatures (25, 35, 45, and 55°C) the flow rate model predicted more accurately for low dispensing pressure (20 kPa, R2=0.99) compared to high pressure (30 kPa, R2=0.98). The mechanical and biological properties of SA scaffold largely depend on the ionic crosslinker used in bioprinting of scaffolds from SA. The second part of dissertation is to conduct a comparative study of three ionic crosslinkers including calcium chloride (CaCl2), barium chloride (BaCl2), and zinc chloride (ZnCl2) on the mechanical and biological properties of 3D printed SA scaffolds. Multiple regression equations were developed to predict the mechanical properties of SA scaffolds; and the printability of SA precursor was evaluated at varying concentrations of both ionic crosslinkers and SA precursor. Experimental results revealed that the elastic modulus of the hydrogels decreasing in the order BaCl2>CaCl2>ZnCl2 over 42 days while Schwann cell (SC) viability decreased in the order CaCl2>BaCl2>ZnCl2 over 7 days. The predictions of multiple regression equations show reasonable agreement with experimental data, while the 3% (w/v) SA precursor demonstrates acceptable printability in CaCl2 and BaCl2 solution. The experimental and predicted results obtained in this part of work would be useful in selecting the appropriate ionic crosslinkers and concentration of SA precursor for bioprinting of tissue scaffolds. Notably, SA precursor lacks of cell binding motifs in the molecular structure, which significantly limits its applications in nerve tissue regeneration. For improvement, the third part of dissertation is to conjugate peptide molecules into SA, resulting in peptide conjugated SA (PCSA) and to further examine the effect of single and composite PCSA scaffolds on axon regeneration in vitro. In particular, a 2% (w/v) SA precursor was conjugated with either arginine-glycine-aspartate (RGD) or tyrosine-isoleucine-glycine-serine-arginine (YIGSR) peptides, or mixture of RGD and YIGSR (1:2), and was bioprinted into cuboid structures. The printability of the composite PCSA precursor was evaluated in terms of the strand width, pore geometry, and angle-formation accuracy at varying concentration of CaCl2 (i.e. 50 - 150 mM); and the mechanical stability of scaffolds was examined over 3 weeks in terms of swelling, degradation, and compression modulus; and surface morphology of the degraded scaffolds. Axon regeneration ability of PCSA scaffolds were assessed by quantifying the viability, morphology, amount of secreted brain derived neurotrophic factor (BDNF) of incorporated SCs, and directional neurite outgrowth in a 2D culture. Experimental results reveal that composite PCSA precursor extruded in 50 mM CaCl2 has good printability and that PCSA scaffolds remains porous over 3 weeks with the elastic modulus decreased by ~70%. Also, the results illustrates that composite PCSA scaffolds facilitate better the viability and morphology of SCs, as well as support greater directional neurite outgrowth as compared to those of single PCSA scaffolds. Taken together, the thesis develops methods to fabricate SA and PCSA scaffolds with results illustrating their potential applications in the regeneration of damaged peripheral nerves

    Nanotechnology in peripheral nerve repair and reconstruction

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    The recent progress in biomaterials science and development of tubular conduits (TCs) still fails in solving the current challenges in the treatment of peripheral nerve injuries (PNIs), in particular when disease-related and long-gap defects need to be addressed. Nanotechnology-based therapies that seemed unreachable in the past are now being considered for the repair and reconstruction of PNIs, having the power to deliver bioactive molecules in a controlled manner, to tune cellular behavior, and ultimately guide tissue regeneration in an effective manner. It also offers opportunities in the imaging field, with a degree of precision never achieved before, which is useful for diagnosis, surgery and in the patientâ s follow-up. Nanotechnology approaches applied in PNI regeneration and theranostics, emphasizing the ones that are moving from the lab bench to the clinics, are herein overviewed.The authors acknowledge the Portuguese Foundation for Science and Technology (FCT) for the financial support provided to Joaquim M. Oliveira (IF/01285/2015) and Joana Silva-Correia (IF/00115/2015) under the program “Investigador FCT”.info:eu-repo/semantics/publishedVersio
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