Pyridinium Amphiphiles in Gene Delivery – Present and Perspectives. In: Nagarajan R, editor. Amphiphiles: Molecular Assembly and Applications. Washington: American Chemical Society; 2011. pp. 23-38. [DOI: 10.1021/bk-2011-1070.ch002]

Novel Synthesis of Substituted 2-Trifluoromethyl and 2-Perfluoroalkyl N-Arylpyridinium Compounds-Mechanistic Insights

We report a new one-pot synthesis of 2-trifluoromethylated/2-perfluoroalkylated N-aryl-substituted pyridiniums, 5,6,7,8-tetrahydroquinoliniums and 6,7,8,9-tetrahydro-5H-cyclohepta[b]-pyridinium compounds starting from an activated β-dicarbonyl analogue (here a perfluoro-alkylated gem-iodoacetoxy derivative), an aromatic amine and a (cyclic or acyclic) ketone. The key step of this multicomponent reaction, involves the formation of a 3-perfluoroalkyl-N,N’-diaryl-1,5-diazapentadiene intermediate, various examples of which were isolated and characterized for the first time, together with investigation of their reactivity. We propose a mechanism involving a concurrent inverse electron demand Diels-Alder or Aza-Robinson cascade cyclisation, followed by a bis-de-anilino-elimination. Noteworthy, a meta-methoxy substituent on the aniline directs the reaction towards a 2-perfluoroalkyl-7-methoxyquinoline, resulting from the direct cyclization of the diazapentadiene intermediate, instead of pyridinium formation. This is the first evidence of synthesis of pyridinium derivatives from activated β-dicarbonyls, ketones, and an aromatic amine, the structures of which (both reactants and products) being analogous to species involved in biological systems, especially upon neurodegenerative diseases such as Parkinson’s. Beyond suggesting chemical/biochemical analogies, we thus hope to outline new research directions for understanding the mechanism of in vivo formation of pyridiniums, hence possible pharmaceutical strategies to better monitor, control or prevent it.

Interfacially Engineered Pyridinium Pseudogemini Surfactants as Versatile and Efficient Supramolecular Delivery Systems for DNA, siRNA, and mRNA

This article presents the synthesis, self-assembly, and biological activity as transfection agents for pDNA, siRNA, and mRNA of novel pyridinium pseudogemini surfactants, interfacially engineered from the most efficient gemini surfactants and lipids generated in our amphiphile research program. Formulation of novel amphiphiles in water revealed supramolecular properties very similar to those of gemini surfactants, despite their lipidlike charge/mass ratio. This dual character was found also to enhance endosomal escape and significantly increase the transfection efficiency. We were also successful in identifying the parameters governing the efficient delivery of pDNA, siRNA, and mRNA, drawing valuable structure-activity and structure-property relationships for each nucleic acid type, and establishing DNA/siRNA/mRNA comparisons. Several supramolecular complexes identified in this study proved to be extremely efficient nucleic acid delivery systems, displaying excellent serum stability and tissue penetration in three-dimensional organoids.

Tuning the self-assembling of pyridinium cationic lipids for efficient gene delivery into neuronal cells

We are reporting a new set of biocompatible, low-toxicity pyridinium cationic lipids based on a dopamine backbone on which hydrophobic alkyl tails are attached via an ether linkage. Due to their optimized hydrophilic/hydrophobic interface and packing parameter, the new lipids are able to strongly self-assemble either alone or when coformulated with colipids DOPE or cholesterol. The supra-molecular assemblies generated with the novel pyridinium amphiphiles were characterized in bulk and in solution via a combination of techniques including DSC, nanoDSC, SAXS, TOPM, TEM, DLS, zeta potential, and electrophoretic mobility measurements. These cationic bilayers can efficiently condense and deliver DNA to a large variety of cell lines, as proven by our self-assembling/physicochemical/biological correlation study. Using the luciferase reporter gene plasmid, we have also conducted a comprehensive structure-activity relationship study, which identified the best structural parameters and formulations for efficient and nontoxic gene delivery. Several formulations greatly surpassed established transfection systems with proved in vitro and in vivo efficiency, being able to transfect a large variety of malignant cells even in the presence of elevated levels of serum. The most efficient formulation was able to transfect selectively primary rat dopaminergic neurons harvested from nucleus accumbens, and neurons from the frontal cortex, a premise that recommends these synthetic vectors for future in vivo delivery studies for neuronal reprogramming.