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Studies towards DNA-polymer-silica-iron oxide hybrid nanoparticles as stimulus-responsive MR theranostics


Early detection and treatment of a disease is a desired goal for medical advancements. The concept of theranostics have been introduced to combine diagnosis and therapy. Developing nanoparticles for drug delivery has been considered because they increase therapeutic benefit while minimizing side effects. Synthesizing particles that can promote imaging of areas before, during, and after administration into the organism is beneficial for the treatment of diseases. In this work superparamagnetic iron oxide nanoparticles were synthesized as enhancers for MR imaging by using magnetic imaging resonance. Biocompatible, stimuli-responsive polymers were physisorbed to the particles in a layer-by-layer fashion to induce aggregation of iron oxide nanoparticles site specifically and deliver increased MR signals. The surfaces of the superparamagnetic particles were first modified with silica to increase biocompatability, reduce aggregation of the iron oxide particles and allow potential encapsulation of drugs. The surface of the iron oxide silica core shell particles were next treated with APTES, a coupling agent, to help adhere polymers to the particles. In this study poly(methacrylic acid) (PMA) and poly(N-vinylpyrrolidone) (PVP) were the polymers used for forming crosslinkable polymer shells on the particles through a layer-by-layer approach. The PMA chains were modified with thiol groups to crosslink the multiple layers deposited onto the particle surfaces. The polymer shells could easily be destabilized in the presence of reducing agents. Additionally, PMA was modified with DNA strands which would allow the silica coated iron oxide nanoparticles to aggregate and therefore increase the signal for MR imaging

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