POLYPATH · The Journey Matters: Pathway Complexity in Polyplex Formation

A vast number of pathologies have a genetic origin. Yet, using gene therapy to directly intervene at the genetic root remains a rarity within today’s pharmaceutical arsenal. The main hurdles in promoting gene therapy from the lab to the clinic are the complex delivery pathways and biological instability of the therapeutic nucleic acids. Polyplexes, nanoscale coacervates of nucleic acids and (synthetic) polymers, hold the prospect of being highly tunable, scalable and robust transport vehicles and as such a key enabler for gene therapy.Despite years of active research, however, polyplexes have yet to fulfil their claimed potential. Our understanding of polyplex formation and the followed assembly pathways are presently insufficient for the rational design of efficient and selective gene delivery vehicles. Prototypical polyplex formation routes are ill-defined, yielding a broad spectrum of unequilibrated structures. The effect of this structural polydispersity on gene delivery and transfection efficiency is unknown, critically hampering the potency of polyplexes.The aim of POLYPATH is to develop polyplex fabrication routes via controllable and predictable assembly pathways. These routes rely on the in situ growth of the encapsulating polymers in the presence of the nucleic acids and yield temporal, on-demand control of the attractive interactions that drive polyplex formation. With this synthetic control, we will create a systematic, predictable library of structurally well-defined polyplexes. The assembly processes will be elucidated with state-of-the-art time-resolved X-ray scattering and spectrally-resolved NMR relaxometry and diffusometry. To bridge the knowledge gap between polyplex structure and function, we will use fluorescence correlation spectroscopy to directly measure polyplex stability and fate in cellular environments. Ultimately, POLYPATH will provide mechanistic insights that can finally bring functional polyplexes towards the clinic.