Radiation-induced synthesis of nanogels: advances in research and applications

From their first appearance in 1969, when Schnagel and Borwardt reported the radiochemical synthesis of poly(ethylene oxide) microgels by gamma-irradiation, the possibility of generating crosslinked micro- and nanoparticles from ”pure” aqueous solutions of macromolecules, have triggered the imagination of material scientists on the search for ”clean” processes and products for biomedical applications. Thanks to the seminal studies of Rosiak and co-workers, who have clarified, both experimentally and mechanistically, the key role of intra-molecular crosslinking in controlling the particle size, the scientific community has now a powerful tool to design and manufacture radiation-synthetized nanogel particles with a terrific potential in targeted drug delivery therapies. We have recently demonstrated that nanogels can be produced by e-beam irradiation with industrial accelerators and with the typical set-ups and doses applied for sterilization; therefore, the synthesis may not even represent an additional cost in the production process. Particle size, molecular weight and functionalization can be controlled, hence tuned, by selecting the dose rate, the polymer concentration and the total dose imparted, without necessarily adding other chemicals but the crosslinking polymer. The generated functionalized nanocolloids are amenable of decoration with (bio)molecules and cell receptors-specific ligands of therapeutic and/or diagnostic relevance. In particular, the prospects of using insulin-conjugated radiation-synthetized poly(N-vinyl pyrrolidone) nanogels for achieving brain targeted insulin delivery for the treatment of Alzheimer's disease will be presented.