Ultrasonic De-cross-linking of the pH- and Magneto-ResponsivePHEMA/PMMA Microgel to Janus Nanoparticles: A New Synthesis Basedon Grafting from/Grafting to Polymerization

摘要

Stimuli-responsiveJanus nanoparticles (NPs) with a two-facialstructure have been used widely in biomedical applications. Amongseveral methods to prepare these NPs, surface-initiated atom transferradical polymerization (SI-ATRP) has received much attention due tothe precise deposition of polymers on the surface of the substrate.In this study, Janus nanoparticles with asymmetric surface chemistrywere prepared through a masking method in three steps involving thecovalent deposition of super paramagnetic iron oxide nanoparticles(SPIONs) on the cross-linked substrate based on methotrexate (MTX)-graftedpoly(2-hydroxyethyl methacrylate) (CPM), surface functionalizationof unreacted sites of immobilized SPIONs with 2-bromoisobutyryl bromide(BIBB) in order to prepare the macro-initiator (Br-Fe3O4-CPM), growing poly(methyl methacrylate) (PMMA) on the surfaceof the macro-initiator through the SI-ATRP method. Optical microscopywas utilized to monitor the successful modification of SPIONs. Poly(methylmethacrylate)-iron oxide-poly(2-hydroxyethyl methacrylate) (PMMA-Fe3O4-PHEMA) microgel was exposed to optimum ultrasound(US) waves to prepare the PMMA-Fe3O4-PHEMA nanoparticle.Transmission electron microscopy (TEM) was used to confirm the precisedeposition of polymers and the Janus structure. The MTX release ofUS-synthesized Janus NPs was studied in PBS at pH values of 7.4 and5.8. The release data were analyzed using the Excel add-in DDSolverprogram to evaluate the kinetics of the drug release process fromthe nanocarrier under different pH values.