Polymer/silica core–shell nanoparticles with temperature-dependent stability properties

This work aimed at the synthesis of hydrogel-based composite core/shell nanoparticles and their subsequent surface modification with thermoresponsive copolymers. Submicron hydrogel-based nanoparticles were obtained from the layer-by-layer coating of silica nanoparticles with two natural oppositely-charged polyelectrolytes, chitosan and sodium alginate. Further modifications with a PVAm-b-PNIPAM copolymer synthetized by RAFT polymerization was achieved by the "grafting to" approach. First, the optimum feed weight ratio (fwr) was determined by a combined approach of zeta potential and T2 relaxation time measurements. Then, diblock grafting at this optimum fwr was performed and characterized by XPS. XPS analysis confirmed the presence of copolymer at the particles' surface with the increase of C and N atomic percentage. The quantification study was carried out by spectrofluorimetry using the fluorescently labeled PVAm-b-P(NIPAM-stat-NVC) copolymer and revealed that the grafting efficiency could reach 60 %. Finally, a study of thermosensivity properties confirmed that our smart system allowed a temperature-induced destabilization of the particles suspension at 45 °C. This work has promising prospects in the field of controlled drug delivery.