POLY(DISULFIDE) NANOPARTICLES FOR siRNA DELIVERY: A STRUCTURE-PROPERTIES RELATIONSHIP STUDY ON THE COATING STRUCTURE

The therapeutic landscape is increasingly being reshaped by the potential of nucleic acids, particularly small interfering RNA (siRNA), offering novel avenues for treating diseases currently lacking effective therapies. The underlying mechanism of RNA interference, which allows for precise post-transcriptional gene silencing, holds significant promise. However, the successful clinical translation of these powerful molecules is inherently challenged by their susceptibility to enzymatic degradation by RNases, rapid systemic clearance via renal excretion, and an inherent inability to efficiently traverse cellular membranes to reach their intracellular targets. Addressing these limitations necessitates the development of sophisticated and robust drug delivery systems. This thesis focuses on the innovative design and synthesis of novel organic nanoparticles (NPs) tailored for nucleic acid delivery. Our initial work involved the formulation of NPs with a cross-linked poly-lipoic acid core, a structural modification introduced to significantly enhance the inherent stability of conventional solid lipid nanoparticles (SLNs), which primarily rely on weak hydrophobic interactions. Building upon this foundation, our research progressed with two distinct primary objectives. The first goal was to investigate the strategic replacement of polyethylene glycol (PEG) with polyoxazolines (such as polymethyloxazoline and polyethyloxazoline) as the polymeric coating. While PEG is widely utilized for its "stealth" properties, a growing body of evidence indicates the potential for anti-PEG antibody formation in patients, which can compromise the efficacy and safety of nanoparticles formulations. Polyoxazolines represent a promising alternative, potentially offering a different immunological profile that could be advantageous, particularly in vaccine applications where the induction of complement protein recruitment might be beneficial. The second objective aimed to evaluate the impact of substituting saturated lipid chains with unsaturated ones within the nanoparticle formulation. Our hypothesis posits that the introduction of saturated chains may lead to increased structural rigidity within the NP architecture. This enhanced rigidity, in turn, diminishes the encapsulation efficiency of siRNA, a critical parameter determining the therapeutic payload and efficacy of the delivery system. On the opposite, the unsaturated lipid chains could potentially mantain a sufficient fluidity of the membrane, guarantying a high siRNA entrapment. Through this comprehensive work, we aim to provide fundamental insights into the intricate relationship between the chemical composition of NPs – specifically the nature of their polymeric coating and the saturation of their lipid chains – and their capacity to encapsulate and effectively deliver nucleic acids. Our findings contribute to the advancement of more stable, efficient, and immunologically optimized drug delivery systems for nucleic acid-based therapeutics.