Benito Hernández, Juan ManuelGarcía Fernández, José ManuelLópez Fernández, José2025-11-172025-11-172025-07-18https://hdl.handle.net/11441/179004The approval and global commercialization of the first two mRNA-based vaccines for COVID-19 in 2021 marked a pivotal moment in the pharmaceutical industry. Their rapid development, achieved in less than a year, was made possible by ground-breaking advances in mRNA research, alongside the use of lipid nanoparticle (LNP) delivery systems, which had already been clinically validated with the approval of ONPATTRO. This success demonstrated the immense therapeutic potential of nucleic acids, yet also highlighted a major challenge: the need for efficient and safe delivery systems. Nucleic acids possess an unparalleled mode of action among most drug candidates in terms of high specificity, rational design and predictability, making them promising therapeutic agents. However, their clinical application is hindered by significant limitations, as they lack the fundamental properties required for conventional drug candidates, such as metabolic stability and abilities to overcome physiological barriers. Thus, effective delivery remains one of the greatest challenges, as nucleic acids must overcome numerous physiological barriers to exert their expected therapeutic action. Many promising projects focused at the development of the required delivery systems stall due to issues such as toxicity, unappropriated cellular uptake, or an insufficient understanding of structure-activity relationship interplay. One of the main obstacles is the reliance on materials with poorly defined molecular structures, which severely hampers precisely-controlling and manipulating delivery capabilities though molecular tailoring. This doctoral thesis explores whether precision synthetic approaches can offer an alternative by introducing functional capabilities at a molecular level. It is hypothesized that the use of well-defined, molecularly discrete candidates combined with diversity-oriented synthetic strategies would enable the development of libraries that reveal key structure-function relationships. By integrating iterative feedback and rational design, this approach aims to optimize the effectiveness of nucleic acid delivery systems. In particular, this doctoral thesis is divided into two main sections. The first (chapters 3 to 5) focuses on the structural modification of cyclooligosaccharide scaffolds, aiming to enhance pDNA cell transfection through stimuli-responsive mechanisms, such as pH and redox potential. Additionally, the chemical structure of the vectors influences the morphology of the nanoparticle assemblies, as well as their transfection efficiency, toxicity, and in vivo tropism. The second section (chapters 6 to 8) focuses on the high-throughput analysis of structure-function relationships in amphiphilic disaccharide scaffolds based on trehalose and sucrose for RNA delivery. This study explores how variations in molecular structure influence key physicochemical properties, such as self-assembly behaviour and stability. Additionally, it examines their impact on transfection efficiency, cytotoxicity, and immunomodulatory effects, providing valuable insights into their potential as next-generation RNA delivery vectors.application/pdf451 p.engAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/info:eu-repo/semantics/doctoralThesisinfo:eu-repo/semantics/embargoedAccess