Fe₃O₄ Nanoparticles Embedded in Pectin–Doxorubicin Composites as pH-Responsive Nanoplatforms for Tumor Diagnosis and Therapy by T₁-Weighted Magnetic Imaging

Multifunctional nanomaterials with diagnostic and therapeutic capabilities offer promising customized nanomedicines for cancers. However, achieving good execution of these functions in vivo employing a single nanoframework remains challenging, and only a few of these magnetic nanocarriers have been validated for clinical use. In this study, based on biocompatibility and remarkable multifunctionalities, we describe a novel approach to synthesize small Fe3O4 nanoparticles conjugated with natural polysaccharide pectin and assembled into a pH-responsive T1-weighted magnetic resonance imaging contrast agent, Fe3O4@PD, for better chemotherapeutic efficacy. In vitro studies revealed that the conjugated doxorubicin (DOX) was quickly released in the tumor microenvironment by cleavage of the acid-sensitive acylhydrazone bond at a release rate of 89.72% and exerted a considerable inhibitory effect on breast cancer cells. In vivoT1-weighted images of mice showed that Fe3O4@PD displayed darkening to brightening contrast enhancement at tumor sites, and the relative signal-to-noise ratio of the tumor site reached its maximum (increased to about 2.27-fold) for distinguishing the normal and tumor tissues. Thus, this Fe3O4@PD-based system has the potential to be a multifunctional nanodrug delivery system, and as a smart theragnostic platform, it has broad application prospects in clinical and biological works, such as cell-based diagnostics and in vivo medication monitoring.