Search

Advances in contrast agents have greatly enhanced the sensitivity of magnetic resonance imaging (MRI) technique for early diagnosis of cancer. However, the commercial superparamagnetic iron oxide nanoparticles (SPION)-based contrast agents synthesized by co-precipitation method are not monodisperse with irregular morphologies and ununiform sizes. Other reported SPION-based contrast agents synthesized by solvothermal method or thermal decomposition method are limited by the bad water-dispersibility and low specificity to cancer cells. Herein, we propose a new strategy for exploring SPION-based MRI contrast agents with excellent water-dispersibility and high specificity to cancer cells. The SPION was synthesized by a polyol method and then entrapped into albumin nanospheres (AN). After that, a ligand folic acid (FA) was conjugated onto the surface of the AN to construct a SPION-AN-FA composite. The transmission electron microscope (TEM) and dynamic light scattering (DLS) results indicate that the SPION-AN-FA has a spherical shape, a uniform size and an excellent water-dispersibility (polydispersity index (PDI) <0.05). The results of laser scanning confocal microscope (LSCM) and flow cytometry demonstrate that the SPION-AN-FA nanoparticles are highly specific to MCF-7 and SPC-A-1 cells due to the recognition of ligand FA and folate receptor α (FRα). The r 2 / r 1 value of SPION-AN-FA is around 40, which is much higher than that of Resovist ® indicating that our SPION-AN-FA has a stronger T 2 shortening effect. The T 2 -weighted images of MCF-7 cells incubated with SPION-AN-FA are significantly darker than those of MCF-7 cells incubated with AN, indicating that our SPION-AN-FA has a strong MR imaging efficacy. In view of the excellent water-dispersibility, the high specificity to cancer cells and the strong MR imaging efficacy, our SPION-AN-FA can be used as a negative MR contrast agent. [ABSTRACT FROM AUTHOR]

Highlights: [•] An improved double emulsion technology with in situ reaction of lysine (Lys) and glutaraldehyde (GA) to fabricate autofluorescent PLGA microcapsules. [•] A novel ultrasonic/fluorescent dual-modality contrast agents without conjugation to any fluorescent agent. [•] This reaction product Lys-GA is found to exhibit bright and stable autofluorescence. [•] The integration of the autofluorescence into ultrasonic contrast agent of PLGA microcapsules. [Copyright &y& Elsevier]