Made available in DSpace on 2015-06-17T19:34:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-01-12. Added 1 bitstream(s) on 2015-06-18T12:48:27Z : No. of bitstreams: 1 000825246.pdf: 3464292 bytes, checksum: 907652ea25dcfa1a9a30ba9ee22fa099 (MD5) / O parafuso de interferência é o dispositivo de fixação mais usados em cirurgias de reconstrução ligamentar de joelho. O uso dos polímeros bioabsorvíveis está sendo cada vez mais utilizados nesta aplicação, devido suas vantagens relacionadas à excelente biocompatibilidade, bioabsorção, integração do enxerto/osso e também facilidade na revisão cirúrgica. O presente estudo tem por objetivo tem por objetivo o desenvolvimento de um parafuso de interferência bioabsorvível fabricado através do processo de injeção em dois polímeros bioabsorvíveis: PLDL (Poli L-D-ácido lático) e um compósito de PLDL+30% TCP (β Trifosfato de Cálcio). Para o desenvolvimento do projeto do produto foi usado um programa de análise estrutural por elementos finitos, de forma a obter a melhor geometria do encaixe de ferramenta. Através dos estudos de simulação por elementos finitos foi possível selecionar a geometria com maior resistência mecânica levando em conta o esforço de torção e além disso foi possível analisar a influência de furos transversais nas tensões mecânicas geradas pelos esforços de torção. Após a definição da melhor geometria, foram fabricadas amostras dos parafusos com os dois polímeros selecionados, os quais foram esterilizados por ETO (Óxido de etileno). Foram realizados testes mecânicos de torque inserção e torque de ruptura. A resistência mecânica do parafuso foi avaliada através da comparação entre os valores do torque de inserção comparando-se com o torque máximo de ruptura. Para contribuir o estudo foi executado teste de degradação in vitro, durante um período de 180 dias, onde foi avaliada a perda de massa dos implantes, resistência mecânica e queda do peso molecular dos implantes. Logo foi possível avaliar o compartamento mecânico dos implantes em degradação comparando-os com os requerimentos da aplicação. Pode-se observar que a degradação molecular do implante ao longo dos... / The interference screw is the fixation device most selected for Knee ligament reconstruction surgeries. The use of Bioabsorbable polymers in interference screws for this application is increasing due it has advantages like excellent biocompatibility, bioabsorption, good integration between graft / bone and also facility in the surgical revision. The aims of the present study were to develop a bioabsorbable interference screw manufactured by the injection moulding process with two distinct polymeric materials: PLDL, Poly(L,DL-Latic acid) and a composite PLDL + 30% TCP (β Tricalcium phosphate). A program for structural analysis by finite elements was used in the development of the screw design, in the intend to make the best geometry fit for the tool. Trough the study by finite elements simulation it was possible to chose the geometry with higher mechanical resistance taking in the account the torsion effort and analyse the influence of transversals holes in the mechanical tensions made by the torque efforts. After the definition of the best geometry, samples of the screw were manufactured with the two selected polymers, sterilized with ETO (ethylene oxide). Were performed mechanical tests, insertion test and torque to break. The mechanical strenght of the screw was evaluated through the comparison between the values of insertion torque and maximum rupture. In addition, a in vitro, degradation test was performed over a period of 180 year days. It was observed, the weight loss, mechanical strength of the implants was evaluated, and molecular weight drops of the implants. Therefore it was possible to evaluate the mechanical behavior in degradation and compare with the application requirements. It can be observed that the raise of the molecular degradation of the implant along the months had as result a loss of the mechanical resistance of the screw, ina slowly and gradual way for the PLDL material, yet the composite material (PLDL+TCP)...

This thesis focuses on the design of an ultrasonography compatible implantable sensor platform, as a novel approach that implements a miniaturized, battery-less, real-time trackable parallel biosensing system. In addition to the frontend circuit, a sub-nW fully integrated pH sensor is designed in a way that can be easily integrated with the proposed sonography-compatible sensor platform. Combining the two integrated circuits together, the whole system will be able to map in vivo physiological information acquired from a distributed set of sensors on top of the ultrasound movie, leading to the idea envisioned as “augmented ultrasonography”. Implemented in a 0.18 μm technology, an ultrasound power and data frontend circuit is designed to enable medical sensing implants to operate in an ultrasonography compatible way. When placed within the field of view of an imaging transducer, the frontend circuit harvests the power through a piece of piezo crystal from a minimally modified brightness-mode (B-mode) ultrasound imaging process that is commonly adopted in modern medical practices. The implant can also establish bi-directional data communication channels with the imaging transducer, allowing data to be transmitted in a way synchronized to the frame rate of the B-mode film. The design of the circuit is made possible by a combination of ultra-low-power circuit techniques and novel frontend circuit topologies, as imaging ultrasound waves in the form of short pulses with extremely low duty cycle poses challenges that has not previously seen in other implantable sensor systems. The proposed prototype achieves a total area of 0.6mm² for the integrated circuit (IC), as well as 71mm theoretical maximum implantable depth (up to 40 mm is verified experimentally). These two together give opportunities for this design to become the next generation solution for deep-tissue bio-sensing implants. Realized using the same 0.18 μm technology, the fully integrated pH sensor is designed to deliver accurate pH readouts, at a reasonable speed of 1 sample per second, while consuming only 0.72 nW of power. Using an ion-sensitive field effect transistor (ISFET) and reference field effect transistor pair (REFET), the IC requires minimum additional post fabrication to deliver 10-bit resolution pH readouts at an end-to-end sensitivity of 65.8 LSB/pH. When working as a standalone device, this work advances the state-of-the-art of ISFET based pH sensor design. With an addition of 0.46 mm² of area, it is possible to integrate it with the ultrasound sonography compatible implant platform. This potential integration will further advance the vision of the augmented ultrasonography: real-time display of physiological information in a B-mode film, with the help from a distributed bio-sensor system for deep-tissue physiology monitoring.

Diabetes mellitus is a metabolic disease with abnormally high concentration of glucose in blood in patients. Continuous glucose monitoring, which involves measuring glucose concentration in the patient throughout the day and night, can significantly reduce the risk of diabetes-related complications. Commercially available CGM sensors are not yet suited for long-term applications due to reliability and accuracy issues associated with the irreversible, consumptive nature of the underlying electrochemical reactions. Affinity sensing methods, which are based on reversible affinity binding between glucose and a recognition molecule, hold the potential to address these challenges in CGM applications. These methods do not involve the consumption of glucose and can offer improved stability and accuracy for CGM. When combined with impedance-based transduction methods, affinity sensors can also offer a high level of miniaturization, allow low-cost instrumentation, and are amenable to physical and functional integration. The affinity sensors investigated in this thesis include hydrogel-based affinity microsensors and graphene-based affinity nanosensors. We first present a dielectric affinity microsensor that consists of a pair of coplanar electrodes functionalized in situ with a glucose-responsive hydrogel for dielectrically based affinity measurement of glucose in subcutaneous tissue. We present a study of the effects of the choice of hydrogel compositional parameters on the characteristics of the hydrogel-based microsensor, allowing the identification of the optimal hydrogel composition for the microsensor to sensitively and rapidly respond to changes in glucose concentration. A differential design is then demonstrated, both in vitro and in vivo, to effectively minimize the influence of fluctuations in the environmental conditions, thereby allowing the hydrogel-based microsensor to function appropriately as a subcutaneously implanted device. In addition, we present a preliminary study on affinity nanosensors for non-invasive monitoring of glucose concentrations in physiological media such as tears. The affinity nanosensor is based on a chemically modified graphene field-effect transistor for the electrical measurement of glucose concentrations. The study explores the sensing mechanism of the nanosensors and demonstrates a device with high sensitivity and low limit of detection, which satisfies the requirement for monitoring glucose concentrations in tears. Experimental results demonstrate that these affinity micros and nanosensors are capable of measuring glucose concentrations with a suitable sensitivity and dynamic range for the intended physiological media, with potential applications to minimally invasive or non-invasive continuous glucose monitoring in diabetes care.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Metallurgy and Material Science, 1974. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. Bibliography: leaves 56-59. / by Thomas Maurice Devine, Jr. / Ph.D.

published_or_final_version / Orthopaedics and Traumatology / Master / Master of Philosophy

No description available.

Patients who have undergone treatment that has included the surgical implantation of a prosthetic device can become dissatisfied for many reasons. One cause for dissatisfaction is any adverse event where there is a demonstrable causal nexus with the failure of a device that is defective or at risk of being so. The magnitude of therapeutic product failure is considerable and therapeutic goods such as Vioxx, Thalidomide, silicon-gel-filled breast implants, contaminated blood products, cardiac pacemakers and valves, and orthopaedic devices are testimony to this. Many of these events have exposed a greyish area of Australian law that balances medical negligence with consumer protection and contract law. Australian product liability legislation that regulates the use of therapeutic goods is a complex amalgam of law that has at its foundations the Trade Practices Act 1974 (Cth) and the Therapeutic Goods Act 1989 (Cth). When a surgical device fails there can be exposure to liability. This thesis explores those important issues that can impact on individuals or on organisations and it is evident that where issues of product liability concern implanted surgical devices the current regulations for consumer protection may not always be the most appropriate. It is evident that there is a culture of under-reporting of adverse events to a Therapeutic Good Administration that does not have the resources to investigate the cause for failure of a surgical device. Furthermore, there is a potential for bias and conflict of interest in an environment where the regulator depends on the regulated for the funding of its existence. Other issues include the complex and often undesirable consequences of those partnerships that can evolve with the development of an implantable device and with the undertaking of clinical trials, the role of the learned intermediary, that interface between manufacturer and consumer, and the role of the expert witness, that interface between justice and injustice. These and other matters that can significantly influence any debate of implantable surgical device product liability are explored and recommendations are made that might form the basis of a Therapeutic Goods (Safe Medical Devices) Amendment Act.

Biomaterial surface energy, chemical composition, charge, wettability and roughness all play an important role in determining the degree of the direct bone-to-implant interface, termed osseointegration. Surface chemistry, which is influenced by surface energy, wettability, and composition, is another factor that determines osteoblast phenotype and regulates osteoblast maturation. Increased surface energy is desirable for bone implants due to enhanced interaction between the implant surface and the biological environment. The extent of bone formation in vivo is also increased with increasing water wettability of implants. The physiological role of implant surface chemistry is important in determining the success of implant osseointegration because of molecular rearrangements, surface reactions, contamination, and release of toxic or biologically active ions that are determined by the starting chemistry. However, the role of surface chemistry on osteoblast response is not fully studied. Therefore, the overall goal of this dissertation is to understand how the surface chemistry, including wettability, chemical composition, and charge density, of titanium biomaterials impacts osteoblast maturation (in vitro). This study focuses on the general hypothesis that modifications of surface chemistry of titanium surfaces with sterilization or polyelectrolyte coating on titanium surfaces regulate osteoblast response.

Thesis (M.S.)--Mississippi State University. Department of Agricultural and Biological Engineering. / Title from title screen. Includes bibliographical references.

All artificial organ systems and medical devices that operate in direct contact with blood elicit activation of coagulation and platelets, and their long-term use often necessitates antithrombotic therapies that carry significant cost and bleeding risk. Thrombomodulin (TM) is a major endogenous inhibitor of blood coagulation localized on the endothelial cell surface. The overall objective of this research is to develop clinically durable synthetic materials by incorporating TM as a solid-supported film to actively and sustainably attenuate thrombus formation at the blood-contacting interface. During the course of this research, we developed site-specific approaches to covalently attach TM on the luminal surface of commercial vascular grafts using bioorthogonal chemistry that was compatible with ethylene oxide sterilization. Notably, we demonstrated the superior efficacy of TM to reduce platelet deposition compared with commercial heparin modified grafts using a non-human primate model of acute graft thrombosis. Finally, we optimized a novel reversible chemistry to rapidly and repeatedly regenerate immobilized TM, with the potential to significantly extend the lifetime of biologically active films.