Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 103-116). Also available in electronic version. Access restricted to campus users.

Compared with traditional radioimmunoassay and fluoroimmunoassay for early diseases detection, the magnetic immunoassay utilizing magnetic nanoparticles as bio-labels and magnetic signal sensors as detectors has remarkable advantages because most biological samples exhibit no magnetic background and highly sensitive measurements can be performed. This thesis presents the development of biodetection platform taking advantage of the physical-and chemical-stability, low-toxicity, and environmentally-safety of magnetic iron oxide nanoparticles (IONPs) and the high-sensitivity, low-cost, and portable capabilities of magnetoresistive (MR) sensors. The first part explained why a magnetic biodetection platform is desirable, and what advantages it possesses. Then the magnetism of IONPs utilized in this detection system was introduced, followed by the introduction of main synthesis methods to obtain the desirable IONPs. The working principle of MR sensor was explained, and the recent advances about the biodetection platforms with various magnetoresistive sensors and magnetic IONPs labeling was reviewed. A brief summary of new contributions reported in this thesis was summarized. Then the establishment of home-made measurement setups for the characterization of MR sensor was described. The MR loops of MR sensors can be obtained with the instrument using two-point probe measurement, four-point probe measurement, or Wheatstone bridge measurement. The single MTJ sensor, MTJs array sensor, and the GMR spin valve sensor in Wheatstone bridge were characterized here. The magnetic IONPs were prepared through co-precipitation method and thermal decomposition method, and then surface-functionalized using citric acid and fatty acids to acquire carboxyl groups for the binding ability with biomolecules. The physical and chemical properties, sterilizing-treatment tolerability and biocompatibility of nanoparticles were studied. Furthermore, two new synthesis methods were developed to obtain novel magnetic gold/iron oxide nanocomposites for their potential use as magnetic bio-labels. A magnetic detection platform was built, and the detection of 10-nm superparamagnetic IONPs with MR sensor was first realized here. The output signal of the giant magnetoresistive (GMR) sensor in Wheatstone bridge exhibited log-linear function of the concentration of IONPs, making our sensing system suitable for use when ultra-small bio-labels are needed. The biodetection platform with MR sensor and IONPs was successfully developed and applied for the detection of antigen biomolecules. The feasibility of magnetic biodetection system, based on magnetic tunneling junction (MTJ) sensors and carboxyl-group functionalized IONPs, to detect AFP antigens (liver cancer biomarker) and p24 antigens (HIV biomarker) was demonstrated here for the first time. By taking advantages of its high sensitivity, low power consumption, low cost, and feasibility to be miniaturized, the development of magnetoresistive biodetection platform will bring revolutionary impact on the biodetection techniques for clinical early diseases diagnosis. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009. / Committee Chair: Z. John Zhang; Committee Member: Angus Wilkinson; Committee Member: C P Wong; Committee Member: E. Kent Barefield; Committee Member: Mostafa El-Sayed. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Nanoparticles produced with surfaces functionalised by highly specific molecular tags are able to target aberrant cells and detect or eliminate them without causing damage to surrounding healthy tissues. Single-stranded DNA (ssDNA) and RNA which fold to form secondary or tertiary structures, termed aptamers, represent a new class of such molecular tags. The nanoparticles, in turn, may carry therapeutic payload or luminescent entities which enable elimination or visualisation of targeted cells respectively. This project presents fabrication and isolation of a surface-functionalised nanoparticle construct, namely aptamer-tagged silica nanoparticles. DNA aptamers were chosen with the intention to make them useful for clinical or diagnostic applications of targeting neoplastic cells. Indeed, the ssDNA applied here is known to bind mucin-1 which in turn is a biomarker found on the surface of metastatic breast cancer cells. The separation of the construct was made possible by the inclusion of oligonucleotide-bound superparamagnetic particles in the construct; these enabled separation by magnetic capture. This project investigates two approaches to fabrication of the construct. In the first approach, aptamers, oligonucleotides and magnetic particles are mixed in solution. In the second, silica nanoparticles are functionalised with aptamers, oligonucleotides are bound to magnetic particles and the resulting two parts are hybridised together. The first approach gives higher yields. This may suggest that binding of silica nanoparticles to aptamers may hinder aptamer hybridisation to oligonucleotide fragments, thus resulting in lower construct synthesis yields. However, it is not known yet how the yield changes upon addition of silica nanoparticles into the solution. Therefore, the second experimental approach provides a starting point for fabrication and purification of an anti-cancer drug targeting platform in a simple bench-top setting. In addition, this thesis discusses the fabrication of silica nanoparticles which were intended to constitute an element of the construct. The work on nanoparticle fabrication aimed to develop a quick and repeatable synthesis method which would result in monodisperse entities. Despite trying various experimental approaches, suitable particles could not be reproducibly obtained. Agglomeration was identified as a major obstacle in the silica nanoparticle production process. Finally, this project assesses whether the chosen aptamers bind to the metastatic breast cancer cells, which would be necessary if they were to be used for diagnosis or therapy. FACS analysis indeed indicate that ssDNA aptamers attach to the MCF7 cell line, but the optimum conditions for that attachment remain to be determined.

No description available.

The magnetic spinel ferrite nanoparticle is exceptionally intriguing nanocrystal system due to the industrial importance of various technical applications and the scientific significance of studying the quantum origin of magnetism. Studies of quantum influences upon magnetic properties have revealed that the spin-orbit coupling and the net magnetization greatly affect the net magnetic properties of each spinel ferrite system differently. In case of cobalt ferrite where spin-orbit coupling is relatively large, increasing Cr3+ doping concentration, which has smaller magnetic moment and zero angular moment, decreases blocking temperature, saturation magnetization, remnant magnetization and coercivity. However, in case of manganese ferrite where spin-orbit coupling is relatively small, increasing Cr3+ doping concentration, reduces all the magnetic parameters except coercivity. The coercivity increases due to smaller magnetocrystalline anisotropy energy constant which forces the coercivity to increase as saturation magnetization decreases in accordance with Stoner-Wohlfarth theory. In order to improve product quality and quantity, synthesis routes in hot oleylamine and aminolytic reaction were developed. Both methods were proven to be extremely effective, environmental friendly, inexpensive, and simple routes in the synthesis of a variety of spinel ferrite systems including CoFe2O4, MnFe2O4, NiFe2O4, and ZnFe2O4 from a single source metal precursor.

Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2017-06-12T20:01:54Z No. of bitstreams: 2 Dissertação - Débora Rodrigues Lima - 2016.pdf: 6221489 bytes, checksum: bf560c706557ba7d8de5ce229fb77634 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-06-13T13:50:30Z (GMT) No. of bitstreams: 2 Dissertação - Débora Rodrigues Lima - 2016.pdf: 6221489 bytes, checksum: bf560c706557ba7d8de5ce229fb77634 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-06-13T13:50:30Z (GMT). No. of bitstreams: 2 Dissertação - Débora Rodrigues Lima - 2016.pdf: 6221489 bytes, checksum: bf560c706557ba7d8de5ce229fb77634 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-05-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work for master degree magnetic nanoparticles (NPMs) of NiFe2O4 and CoFe2O4 were synthesized by the sol-gel-protein method from an aqueous solution containing gelatin (GelitaTM) and nickel (II) salts, cobalt (II) and iron (III). The resin obtained by the sol-gel after drying was submitted to a heat treatment in order to calcify the product formed and to impove the crystallinity of the nanoparticles at different temperatures, 250°C, 300°C, 400°C, 500°C, 600°C, 800°C and 1000°C. To remove residual organic matter, the nanoparticles were washed with hydrogen peroxide. The techniques used to characterize the electronic and geometric structures of NPs were: X-Ray Fluorescence (XRF); X-Ray Diffraction (XRD); Transmission Electron Microscopy (TEM); and X-Ray Photoelectron Spectroscopy (XPS). After the electronic and structural characterization, the hemocompatibility (erythrocytes and leukocytes) of the NPs of NiFe2O4 calcined at 250 °C and 800°C and CoFe2O4 calcined at 400 °C and 800 °C was checked. Cytotoxicity results were similar to those of the control test, therefore suggesting hemocompatibility of the tested materials.For in vivo test it was evaluated the acute toxicity with Wistar female rats, which were administered gavage 2000mg / kg of nickel ferrite and 500 mg / kg of cobalt ferrite. The animals were observed for 14 days for acute toxicity evaluation; then samples of animal blood, for hematological evaluation, and samples of the liver, kidney, spleen and lung were collecte for histopathological evaluation. The results of in vivo toxicity tests demonstrated that NPs of NiFe2O4 and CoFe2O4 presented biocompatibility, contributing to the evaluation of a future use of these materials in health. / Neste trabalho foram sintetizadas nanopartículas (NPs) de NiFe2O4 e CoFe2O4 pelo método Sol-Gel-Proteico, a partir de uma solução aquosa contendo gelatina comestível (GelitaTM) e sais de níquel (II), cobalto (II) e ferro (III). A resina obtida pelo método Sol-Gel-Proteico após secagem, recebeu tratamento térmico, com o objetivo de calcificar o produto formado e melhorar a cristalinidade das NPs: foram utilizadas diferentes temperaturas, 250ºC, 300ºC, 400ºC, 500ºC, 600ºC, 800ºC e 1000ºC. Para remover a matéria orgânica residual, as NPs foram lavadas com peróxido de hidrogênio. As técnicas utilizadas para a caracterização das estruturas eletrônica e geométrica das NPs foram: Fluorescência de Raios-X (FRX), Difração de Raios-X (DRX), Microscopia Eletrônica de Transmissão (MET) e Espectroscopia de Fotoelétrons Excitados por Raios-X (XPS). Após a caracterização estrutural e eletrônica, foi verificada a hemocompatibilidade (hemácias e leucócitos) das NPs de NiFe2O4 calcinadas a 250°C e 800ºC e de CoFe2O4 calcinadas a 400°C e 800ºC. Para o teste in vivo foi avaliado a toxicidade aguda, utilizando ratos Wistar fêmeas, em que foram administrados por gavagem 2000mg/kg da ferrita de níquel e 500 mg/kg da ferrita de cobalto. Os animais foram observados por 14 dias para avaliação da toxicidade aguda, depois foram coletadas amostras de sangue dos animais para avaliação hematológica e retirados fígado, rim, baço e pulmão para avaliação histopatológica. Foram obtidas NPs de NiFe2O4 e CoFe2O4 com alto grau de cristalinidade, com forma esférica e dimensões correspondentes ao utilizado para aplicações na área da saúde. Os resultados de citotoxicidade foram semelhantes ao ensaio controle, sugerindo, portanto, hemocompatibilidade dos materiais avaliados. Os resultados dos testes de toxicidade in vivo demonstraram que as NPs de NiFe2O4 e CoFe2O4 apresentaram biocompatibilidade, contribuindo para avaliação de uma futura utilização destes materiais na área da saúde.

No description available.

No description available.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / Please refer to full text to view abstract