Resumen de Micro and nanotools for sensing and therapy
Ana Mafalda Nunes Rodrigues
The work presented develops three different branches of the supramolecular chemistry. Across the chapters that compose this thesis, results are discussed about different forms of self-assembled structures. The first chapter focus on obtaining nanostructured gels that are assembled due to the amphiphilic character of the gelator molecule. These gels are formed when compound 1•2Br is solubilised in a mixture of ethanol and water with adequate proportions. Due to the ability of the compound to complexate anions, we pursued the possibility of the formed gel to incorporate anions of therapeutic interest, namely anonic drugs. Ibuprofenate, indomethacin (anti-inflammatory drugs) and methotrexate (antitumor) could be incorporated within the gel fibbers (as confirmed by NMR) and could be released. Methotrexate showed differences comparing with the other two drugs: it render the gel more resistant and also presented a different release profile. The same molecule 1•2Br was also studied in the synthesis of gold nanoparticles. Following a biphasic method based on the Brust-Schiffrin method, 1•2Br could be used to obtain gold nanoparticles, filling the role of transfer agent and stabilizer. Due to the ability of 1•2Br to incorporate the drug, the same application was tested with the synthesized nanoparticles. Ibuprofenate was used as model, and could be successfully incorporated and released. Because the obtained nanoparticles were soluble in organic media, an alternative synthetic method was used in order to make them water soluble. These nanoparticles could also incorporate an anionic drug, piroxicam, which is poorly soluble in water. Besides the compound 1•2Br, an analogue with cyclic head was also used to obtain nanoparticles and could also incorporate ibuprofenate, but because this analogue has more affinity for anions, it retains more the ibuprofenate and releases less amounts. Nanoparticles were also obtained using 1•2Br in the form of gel, as template, and it was found that these had lower monodispersity and more uniform shapes than the ones obtained with 1•2Br in solution. It was also aimed the immobilization of peptides in gold nanoparticles, but because the nanoparticles with 1•2Br were not viable, they were synthesized through the citrate reduction method or synthesized in methanol. Different strategies were pursued for the immobilization using different thiols, the best results being obtained with the peptide bearing a chain with a thiol group on its end. In the same manner as the molecules assemble in the surface of the nanoparticles, they can also assemble in surfaces. Two different works regarding the self-assembly of monolayers on surfaces are discussed, one for obtaining layers with immobilized lanthanides that can be used as molecular thermometers, and other for the functionalization of surfaces and STM probe tips for the study of the interaction between biotin and streptavidin, serving as model to confirm that the studied tips can be used for the detection of intermolecular interactions. The affinity between antibodies anti-EGFR and their antigen were also assessed.
