Preparation of polydopamine based redox-sensitive magnetic nanoparticles for doxorubicin delivery and MRI detection

To improve the water-dispersity of superparamagnetic iron oxide nanoparticles (SPIONs), a novel polydopamine based redox-sensitive copolymer modified SPIONs were prepared for the biomedical application to deliver doxorubicin (DOX) and magnetic resonance imaging (MRI) detection. The major components of this nanoparticle include SPIONs and the redox-sensitive polydopamine (rPDA) crosslinked copolymer, where N,N-Bis(acryloyl) cystamine served as cross-linker, dopamine methacrylamide and a long-chain polyethylene glyco methyl ether methacrylate acted as comonomers. Here the rPDA@SPIONs were formed by the ligand exchange reaction of dopamine moiety with the oleic acid layer capped on the surface of SPIONs, and the inner area of the nanoparticles formed a reservoir for DOX, while the hydrophilic PEG moiety helped the nanoparticles well-dispersible in aqueous solution. The DOX-loaded rPDA@SPIONs demonstrated a high drug loading efficiency of 857 μg DOX per mg iron, and a strong T2 relaxivity of 123 mM^-1·S^-1 for MRI. The drug release analysis of drug-loaded nanoparticles showed a sustained and high cumulative drug release in GSH up to 73% within 48 h, rather than the relatively low release rate of 37% in PBS (pH 7.4) without GSH. All the results showed that the designed magnetic nanoparticle may be a promising vehicle for anticancer drug delivery with stimuli-triggered drug release behavior, and also a foundation for building smart theranostic formulations for efficient detection through MRI.