Magnetic resonance imaging (MRI) contrast agent (CA) is a powerful tool for disease diagnosis. However, the "always on" state of clinically used CAs affects the specificity of tumor MR imaging in vivo. Herein, we constructed a tumor microenvironment "switch on" type nanoprobe (TSN) with distance-dominated property for specific tumor MR imaging, which employed superparamagnetic hollow mesoporous iron oxide nanoparticle (HMIN) as the carrier to encapsulate T1-field CA (Gd) and then blocking the mesoporous with biocompatible hyaluronic acid (HA). In the normal tissues with low-level hyaluronidase (HAase), Gd was restricted inside of HMIN, the distance between the two substances is quite close, and the magnetic field of Gd is interfered by superparamagnetic HMIN, T1-field signal is “turned off”; while in tumor tissues with high-level HAase, Gd is rapidly released from HMIN by specifically responding to overexpressed HAase, the distance between the two substances is significantly enlarged, and the magnetic field of Gd has not been interfered, T1-field signal is “turned on”, thus to achieve tumor-specific "switch on" MR imaging via distance-controlling manner. T1-field signal ratio of tumor/normal tissue with TSN treatment increased 1.9-times compared to the free Gd-DTPA, attributing to high Gd loading content, tumor-targeting ability of HA as well as tumor-specific responsibility. Such a distance-controlled switchable nanoprobe provides an alternative strategy for high-resolution tumor imaging with high specificity.

Specific "Switch-on" type magnetic resonance nanoprobe with distance-dominate property for high resolution imaging of tumors

ACS Spring Meeting 2021

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