Nanostructures based on stimuli-responsive polymer and inorganic nanocrystals such as magnetic, fluorescent or metallic nanoparticles allow the development of multifunctional objects able to function as stimuli-responsive drug carriers and at the same time, acting as optical or magnetic probe thanks to the inclusion of inorganic nanocrystals within the same nanostructures. The presence of gold or magnetic nanocrystals would allow also the exploitation of such system as heat agents in thermal ablation therapy for the tumor treatment.
Our Department has recently developed a facile and robust one-step emulsion polymerization protocol to copolymerize allyl-polyethylene glycol capped inorganic nanoparticles of quantum dots (QDs), gold nanoparticles (AuNPs) or iron oxide nanoparticles (IONPs), both individually or in combination, with pH-responsive poly(2-vinylpyridine-co-divinylbenzene) nanogels (NGs). The late injection of nanoparticles during the polymerization was the critical step which allowed the preparation of a homogeneous nanoparticle-functionalized nanogel (NP-NG) sample. The pH-responsive nanogel functionalized with inorganic nanoparticles showed a typical swelling behavior at pH 4.3 causing a significant increase of the volume of the polymer.
This change in configuration might be exploited to release at acidic pH, typical of extracellular tumor environment, whatever payload molecule has been previously loaded into the NGs. We also found that the close proximity of the nanogel network to the surface of the inorganic nanoparticles affects their properties. For instance in the case of AuNPs, the quenching of the radical reaction occurred, thus affecting the final distribution of AuNP at the surface of the nanogel. Instead, in the case of QD-NGs a decay of the photoluminescence with respect to free QDs at different pH has been observed. This feature might be exploited for sensing applications. Finally, when IONPs were incorporated into the nanogel, a magnetic response to a magnet (of 0.3 T) 27 times higher than that of single IONPs was estimated. This response suggests a possible application of the nanogel as a magnetic carrier for the delivery of different payload molecules.
Relevant papers of the Nanochemistry Department on this highlight:
- A. Riedinger et al., “Nanohybrids” Based on pH-Responsive Hydrogels and Inorganic Nanoparticles for Drug Delivery and Sensor Applications”, Nano.Lett. 2011, 11, 3136-3141
- S. Deka et al., “Acidic pH-responsive nanogel as cargo system for the simultaneously loading and release of short oligonucleotide and magnetic nanoparticles”, Langmuir, 2010, 26 (12), 10315-10324