Design of new nanostructures systems with applications in the field of recognition and diagnosis

Resumen

The present doctoral thesis entitled "Design of new nanostructured systems with applications in the field of recognition and diagnosis" is focused on the design and synthesis of new hybrid materials with molecular gate function. The first chapter presents the design of a new nanodevice for the detection of Bisphenol A, lethal toxin. Mesoporous silica nanoparticles loaded with rhodamine B and functionalized with isocyanate groups have been used. The design is based on the use of an aptamer, which recognizes Bisphenol A, as a molecular gate. This aptamer is attached to the surface of the nanoparticles blocking the pores. Only in the presence of Bisphenol A, the release of the dye is activated, which can be measured by fluorescence spectroscopy. Until now, any material using the molecular gate concept for the fluorogenic detection of Bisphenol A has been described. In the next chapter, new nanodevices have been designed for the detection of Ochratoxin A, a carcinogenic molecule. It is composed of mesoporous silica nanoparticles where the pores are capped with a specific aptamer for this analyte. These nanoparticles are loaded with rhodamine B and its surface is functionalized with isocyanate or amino groups, which allow the aptamer to be attched covalently or electrostatically, respectively. In the presence of the molecule, the aptamer recognizes it by displacemen from the surface and allowing the release of the dye that can be measured by fluorescence spectroscopy. The system has high efficiency in real media, in addition to providing a simple and low cost method to perform the measurements. In another chapter, a nanodevice has been developed for the detection of cocaine based on nanoporous anodic alumina supports, loaded with the rhodamine B dye and where the pores are closed using a specific aptamer for cocaine. In the presence of the narcotic drug, the aptamer is displaced from the nanoporous surface, allowing rhodamine B to escape from the interior of the pores to the solution. The system responds in real media. In addition, the reuse of alumina support was studied. In the next chapter a new nanodevice capable of detecting DNA from Candida albicans is developed. Nanoporous anodic alumina has been used as support, loaded with rhodamine B and functionalized with isocyanate groups. A specific sequence for C. albicans blocks the pores. Thus, in the presence of C. albicans DNA, the oligonucleotide has more affinity for the DNA than for functionalized alumina surface binding, it is separated from the surface producing the release of the dye in the external medium. An extensive study of this system has been carried out in the presence of DNA from other pathogens, demonstrating the great selectivity. Finally, the system has been validated in real samples of patients infected by C. albicans, obtaining excellent results that improve in time to those that are routinely used for their detection. The developed system has been protected through a patent. The seventh chapter of the thesis describes the synthesis, characterization and sensory capacities of silica nanoparticles for the detection of miRNA-145. The design in mesoporous silica nanoparticles loaded with rhodamine B, functionalized with isocyanate or amino groups and using several specific and selective sequences to this miRNA to block the pores of the nanoparticles. In the presence of miRNA-145, the formation of structures between the sequences and the miRNA-145 triggers the release of the dye that can be followed by fluorescence spectroscopy. In addition, the functioning of the system in human serum is shown. It is a simple, transportable method that can be easily modified for different types of miRNA.