CONTROLLING THE DIMENSIONS OF POLYMER NANOPARTICLES FOR IN VIVO APPLICATIONS

Research of nanoparticle based medical diagnosis and treatment has continued to advance rapidly, the small sizes permitting the existing biomolecule distribution systems to be exploited. The inverse relationship between particle diameter and both cellular uptake and toxicity however demonstrated the importance of control over nanoparticle dimensions. Previous analysis of particle properties and synthetic conditions have largely been reliant on empirical results supplemented with intuitive assumptions, with few exceptions models of synthesis explaining the diversity in observed diameter of nanoparticles and the requirements for successful synthesis are missing. This work is a first-time attempt to directly apply a Flory-Huggins theory based thermodynamic model to analyze the phase boundaries associated with development of polymer nanoparticles. Distinguishing between spinodal-character and binodal-character separation under various conditions then gives predictive models of polymer nanoparticle dimensions and the potential for successful synthesis, dependent on D(nm) = -74Δχ_spinodal + 367 nm, where Δχ_spinodal must be positive for successful separation. Variation with total polymer fraction over a limited range can also be observed to follow a trend of approximately D(nm) = 173ln[(xN)²10^-36/Δχ_spinodal] – 193 nm, thus giving a more general description of polymerization. These findings also support the presumptions of a regular structure at the core of nucleated polymers formed by a binodal-character separation, in additional to providing useful guides for predictive design of polymeric nanomaterials.