Design and synthesis of biofunctional magnetic/fluorescent glyco-nanoparticles and quantum dots and their application as specific molecular imaging probes

Resumo

Nanotechnology presents very promising characteristics for its application in the biomedicine area. By now the most advanced application of nanoparticles in medicine is the use of iron oxide nanoparticles embedded in biocompatible polymers as magnetic resonance imaging (MRI) contrast agents. Nowadays MRI application relies either on inherent tissue contrast differences or on the unspecific accumulation of contrast agents in certain tissues. This status can be extended to other imaging techniques. These limitations do not enables the application of imaging techniques to many diagnostic problems such as the imaging of small or diffuse populations of tumour cells, or require the administration of large amounts of the contrast agents to achieve a clear diagnostic. Considering this, there is a clear need for the development of new probes able to target specifically cells, organs or tissues for high resolution imaging. In this thesis, we have first prepared nanomaterials with suitable properties to be used as imaging probes; on one hand magnetic nanoparticles based on water soluble goldcoated glyco-nanoferrites to be used as MRI T2 contrast agents, and on the other, CdTebased quantum dots with fluorescent emissions in the visible to the near infrared spectra to be used in optical molecular imaging. The biofunctionalization of these nanoprobes with different biomolecules has been explored. Magnetic glyconanoparticles and quantum dots (QDs) coupled to protein G and IgG antibodies have been prepared to get specific targeted imaging probes (immuno-nanoparticles) for MRI and optical imaging. Functionalised magnetic glyconanoparticles with single chain DNA molecules have also been produced as potential specific probes for genetic material sensing. Both kinds of immuno-nanoparticles have been applied in vitro for the specific labelling of a cell population within a simple mixture, or of sub-cellular structures (cytoskeleton). The application of immuno-magnetic glyconanoparticles (immuno-MGNPs) has been taken further with specific ex vivo labelling experiments in whole human blood. Finally, the immuno-MGNPs have been applied in in vivo studies to label and track endogenous neural stem cells to answer a fundamental question in neurobiology: Do neural stem cells migrate towards damaged brain areas? In conclusion, we have been able to design, prepare, and apply, specific biofunctional nanoprobes as targeted contrast agents for in vivo imaging techniques, especially for MRI.