A potential dual-modality optical imaging probe based on the pH-responsive micelle

A series of pH-responsive and dual-modality imaging polyurethane micelles as potential dual-modality optical imaging probes were developed by introducing superparamagnetic iron oxide nanoparticles (Fe3O4) for MRI imaging and fluorescent dye fluorescein isothiocyanate (FITC) for optical imaging. 1,4-bis (hydroxyethyl) piperazine, which has amino groups with isolated electron pairs, was employed as a pH-responsive segment to offer pH-responsive capacity. The pH-responsive polymeric micelle can self-assemble into a core-shell structure at physiological pH, consequently, the Fe3O4 nanoparticles can be well encapsulated into hydrophobic core via the hydrophobic interaction. The morphology of Fe3O4 coated by polyurethane nanoparticles were observed by the Transmission Electron Microscopy (TEM) and the thermal stability was also performed by thermo gravimetric analysis (TGA). Subsequently, the optical property was measured by fluorescence spectrometry and ultraviolet visible spectroscopy. Moreover, the cytotoxicity evaluation was measured using an MTT assay and the result showed the low cytotoxicity of polyurethane micelle, making it a promising candidate as an intelligent vehicle as well as a dual-modality optical imaging probe.