Nanoparticles : Engineering, Assembly, and Biomedical Applications

Abstract: This thesis deals with novel aspects through Nanotechnologyof"bottom-up"and"top-down"strategies in combination with Biotechnology as aninterdisciplinary study. The feasibility of chemically tailoredsuperparamagnetic iron oxide nanoparticles (SPION) forin-vivobiomedical applications has beendemonstrated.The main objects of the present thesis are to design thesurface modified SPION with biocompatible agents, varying fromorganic to polymer and biocompatible materials such asproteins. The particles have been applied to intact organs ofliving animals (rat brain) to examine how they interactpreferentially in the brain tissue and to confirm thefeasibility of the SPION for biomedical applications using MRimaging as an exogenous contrast media.Several different types of materials including SPION (firstgeneration), immobilization of biocompatible materials on SPION(second generation), forin-vivobiomedical applications and nanowires andnanotubes have been approached from the aspect ofNanotechnology. Various processes and techniques for thepreparation of functional nanomaterials such as coprecipitaion,mE, template assisted electrodeposition aredeveloped.Core-shell structure nanocomposites are fabricated bytemplate-directed self-assembly (bottom-up), so-called layer-by-layer (LBL) assembly. Controlledelectroless deposition is used and the subsequently removal ofthe template core without destroying the formed Au shells. Thedevelopment of microcontact printing (µCP) techniques,where the ink used on the surface of the stamp is made ofaminopropyl trimethoxy silane (APTMS). The approaches aredemonstrated through the formation of 2D and 3D structures.Several different types of magnetic measurements of SPIONare investigated. Authentication of superparamagnetism has beencarried out by SQUID measurements, up to 7 Tesla, andevaluating the basic physical properties by the Langevientheory. Electron spin resonance (ESR) measurements have beenperformed as a function of temperature with different particlesizes. The line width of the ESR spectra can be correlated tothe distribution of the SPION exchange interactions. Microwaveenergy absorption rates of SPION have been calculated using anon-linear fitting to experimental data.Thein-vivoexperiments studied after injection of starchcoated SPION into the brain parenchyma in striatum, a strongphagocytic uptake of SPION is observed due to their strongaffinity to the body cell. Diffusion barriers between blood andneural tissue, in the endothelium of the parenchymal vessels(BBB) and in the epithelia of the chroid plexuses and arachnoidmembrane (blood-CSF barriers), severely restrict penetration inseveral diagnostic agents.The prediction of the SPION transport has been made for themodeling of the movement of a single SPION in biologicalcapillary system. The model was considered the four mostimportant factors, i.e. particle size, capillary diameter,distance between the magnet, and capillary length.Keywords: Nanoparticle, Superparamagnetism, Core-shellstructure, Ferrofluid, Anodic alumina, Electrodeposition,µE,In-vivo, Rat brain, MRI, Numerical modeling, Microwaveabsorption, ESA, Self-assembly, ESR, µCP

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