Técnicas instrumentales y computacionales para la caracterización de sistemas de macromoléculas y nanopartículas. Implementación y aplicaciones

Abstract

OBJECTIVES Metal nanoparticles have aroused great interest in the scientific community, due to their properties, making them very useful in industry and biomedicine. Therefore, much of this Thesis has focused on the study and characterization of these systems using different procedures to synthesize and characterize the properties of nanoparticle structures coated with polymer. Likewise, the behavior and structure of various macromolecules (proteins, polymers and biological and synthetic fluids) have been studied through the instrumental techniques present in our laboratory, which have been previously developed. Some of these experimental studies have been complemented with computational studies through the use of programs developed by our research group. Thus, through the experimental techniques of dynamic light scattering, analytical ultracentrifugation or rheometry and computational programs like HYDRO, we have been able to characterize macromolecules and to know their hydrodynamic properties. Therefore, the objectives that were set before starting this Doctoral Thesis were the following: 1. Synthesis of gold nanoparticles by usual methods of obtaining and coating these with biological and synthetic polymers. 2. Study and characterization of macromolecules by means of analytical ultracentrifugation, rheometry and viscosimetry techniques. 3. Theoretical study of the different synthetic and biological macromolecules studied experimentally, through the use of computer programs developed by our research group. METHODOLOGY The methodology that has been used during this Doctoral Thesis has two totally different aspects; on the one hand, experimental methods have been developed using the techniques available in our laboratory and the research support services of the University of Murcia: Dynamic light scattering, visible-ultraviolet spectroscopy and electron transmission microscopy for the characterization of synthesized nanoparticles; ultracentrifugation for the study of various proteins and polymers and rheometry for the study of the behavior of different biological and synthetic fluids. On the other hand, theoretical and computational methods have been used through complex calculation and simulation programs such as Hydropro, Visfit, Polycarlo and Simuflex for the study of hydrodynamic properties of macromolecules. We have also developed a program during this Doctoral Thesis, Rheofit, which has served us for the analysis of experimental results obtained in our research. CONCLUSIONS The results obtained in this Doctoral Thesis have been satisfactory due to the fulfillment of the objectives set. In addition, much of these results have been part of publications. The following are the most important conclusions of this Doctoral Thesis: 1. The techniques applied in the elaboration of this Doctoral Thesis have proved to be very useful for the analysis and characterization of the different macromolecular systems and nanoparticles that have been studied. Among them, the rheometry allowed us to know the value of the viscosity of biological fluids and artificial fluids with great interest for the reproduction, the viscosimetry allowed us to know the intercalating power of synthesized platinum organometallic complexes, due to the variation of the viscosity in the function of the binding mechanism of these complexes with DNA, with the technique of analytical ultracentrifugation, we were able to know the state of oligomerization of a prokaryotic enzyme and the dynamic light scattering allowed us to demonstrate that the current peaks obtained in an electrochemical process correspond to individual collisions of droplets of the emulsion with the interface. 2. In the study of gold nanoparticles, it was possible to verify that the stability of the nanoparticles decreases depending on the conditions of the medium in which they are found, giving rise to the aggregation of these. However, in the presence of chitosan, said nanoparticles are approximated by electrostatic attraction to the aggregates formed by it, thus avoiding the aggregation of nanoparticles. 3. We characterized PNIPAAM-b-PAMPTMA (+), a modified thermosensitive polymer, since its positive charge makes it of great interest for the coating of gold nanoparticles. First measurements of the polymer were made with gold nanoparticles, observing good results that leads us to continue this research. 4. In the study of the connection between gold nanoparticles and DNA, it was concluded that analytical ultracentrifugation is a suitable method for the characterization of complex mixtures of reaction products. This technique, together with the modeling programs created by our research group, allowed us to know more precisely the conformation of these compounds.