On the mechanism of radiation synthesis of nanogels

Abstract

Radiation-engineered poly(N-vinyl pyrrolidone) nanogels are very interesting biocompatible nanocarriers for i.v. administration of therapeutics and contrast agents for bioimaging among other applications. Nanogels are usually produced upon irradiation of dilute aqueous polymer solutions. Under these conditions, the polymer radicals formed primarily react via intramolecular radical-radical combination forming intramolecular crosslinks. The manufacturing process is fast and effective and grants excellent control of particle size and simultaneous sterilization of the formed nanogels. Interestingly, primary amino groups and carboxyl groups, useful for (bio)conjugation, are also formed in a dose-dependent fashion when manufacturing PVP-nanogels. In this presentation, the origin of nanogel size control and functionalization are discussed in relation to dose, dose rate, polymer concentration and chemical conditions. The latter can be directly altered by purging the solutions with N2O or N2 or indirectly through the formation of H2O2 in systems with low polymer concentration. The discussion is based on recent experimental work and kinetics simulations. this understanding offers a new dimension for the design and production of radiation-sculptured multifunctional nanocarriers from aqueous solutions of polymers. In addition, the inherent boundaries of these systems in terms of processing parameters are explored.