Abstract
Magnetic resonance imaging (MRI) is often used to diagnose diseases due to its high spatial, temporal and soft tissue resolution. Frequently, probes or contrast agents are used to enhance the contrast in MRI to improve diagnostic accuracy. With the development of molecular imaging techniques, molecular MRI can be used to obtain 3D anatomical structure, physiology, pathology, and other relevant information regarding the lesion, which can provide an important reference for the accurate diagnosis and treatment of the disease in the early stages. Among existing contrast agents, smart or activatable nanoprobes can respond to selective stimuli, such as proving the presence of acidic pH, active enzymes, or reducing environments. The recently developed environment-responsive or smart MRI nanoprobes can specifically target cells based on differences in the cellular environment and improve the contrast between diseased tissues and normal tissues. Here, we review the design and application of these environment-responsive MRI nanoprobes.
Highlights
Biomedical imaging is an important diagnostic tool in medical treatment
Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) involve radioactive materials and only provide physiological information; Ultrasound imaging (US) technology is widely used in clinical research in obstetrics, cardiology, and surgical guidance, but the effect of detailed observation of deep tissues is not ideal; X-ray is an important tool for clinics since they are cost-effective, fast, and high resolution and have no depth limits, but there are radiation problems; Computed Tomography (CT) has no depth limit and can provide anatomical and physiological information and it is often used for bone disease diagnosis, tumor location, image-guided surgery, and radiotherapy diagnosis [1,2]
Magnetic resonance imaging (MRI) is undergoing a fast transformation from traditional non-specific physical imaging to specific molecular and gene-level imaging
Summary
Biomedical imaging is an important diagnostic tool in medical treatment. The most commonly used clinical imaging modalities are: Magnetic Resonance Imaging (MRI), X-ray, Computed Tomography (CT), Ultrasound imaging (US), Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT). MR molecular imaging uses tissue-specific expression products as the imaging targets, provides image contrast using non-aqueous molecules, and uses MR molecular probes to understand the physiological and pathological processes at the cellular and molecular level to qualitatively or quantitatively investigate the gene expression, biological metabolism, etc. This enables a comprehensive biological and imaging diagnostic analysis for disease diagnosis, treatment, and relevant basic research [6]. This significantly increases the cumulative release rate of nanomolecular imaging probes, improves the in vivo imaging efficiency and drug availability, and improves the tracer SNR between the diseased sites and normal tissues [8]
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