Tumor-specific theranostics with stimulus-responsive MRI nanoprobes: Current advances and future perspectives

Abstract

Currently, magnetic resonance imaging (MRI) enhancement scanning is a commonly used technique for cancer diagnosis in clinical practice. However, the conventional of MRI contrast agents (CAs) frequently presents challenges in achieving precise tumor diagnosis and early detection of small lesions. Tumor microenvironment (TME) is critically involved in tumor progression and metastasis. The development of stimulus-responsive MRI nanoprobes, specifically designed to interact with the TME, allows for the modulation of signal activation and deactivation. These stimulus-responsive MRI nanoprobes facilitate precise tumor-specific diagnosis while minimizing background interference from normal tissues. In this review, we concentrate on the utilization of stimulus-responsive proton relaxation-based MRI nanoprobes in tumor-specific theranostics. Firstly, we delineate the foundational principles underlying the structural design and imaging mechanisms, specifically Magnetic Resonance Tuning (MRET). The regulation of MRI nanoprobes is predominantly influenced by endogenous factors, such as pH, glutathione (GSH), and enzymes, among others. In addition, we also summarize the applications of exogenous stimuli and multi-stimuli-responsive MRI nanoprobes in tumor-specific theranostics applications. Furthermore, we explore the potential and challenges associated with the development of these stimulus-responsive MRI nanoprobes, aiming to inform the strategic design of MRI nanoprobes and advance the early and accurate diagnosis and treatment of tumors.