Jinhong Hou,Hongqian Liu,Qian Ma,Suying Xu,Leyu Wang
Accurate diagnosis of diseases located in deep tissues is always challenging. The “always-on” probe often leads to false-positive signals due to nonspecific interaction of nanoprobes. Thus, stimuli-responsive nanoprobes are highly desirable, which, however, require complicated surface modification so as to achieve trigger-induced signal changes. Here pH-triggered switchable magnetic resonance imaging (MRI) nanoprobes were constructed by coordination-driven self-assembly of monodispersed iron oxide nanoparticles (MIONPs) with simple amino acid derivatives, which displayed typical T2-weighted MRI features, yet, were turned into T1-weighted MRI under slightly acidic conditions at the tumor site. The dynamic assembly and disassembly properties of MIONPs afford T2/T1 switchable contrast imaging, enabling selective “turn-on” signals at the tumor site with high specificity.
Qiyue Wang,Tao Wang,Shengfei Yang,Hui Du,Bo Zhang,Sirui Cui,Daishun Ling,Fangyuan Li
Calcium ions (Ca 2+ ) play crucial roles as second messengers in living cells and are associated with the onset and development of chronic brain diseases, including epilepsy. Dynamic and real-time imaging of extracellular calcium levels ([Ca 2+ ] ex ) in the brain holds great potential for identifying disease foci. Magnetic resonance imaging (MRI) is a powerful non-invasive tool for Ca 2+ imaging with unlimited depth penetration. However, current available Ca 2+ MR sensors lack the sensitivity to monitor small [Ca 2+ ] ex alterations associated with chronic brain diseases in vivo. In this study, a highly sensitive Ca 2+ -dependent T2-T1 switchable magnetic nanosensor is reported, consisting of Ca 2+ -specific ligands engineered near-paramagnetic iron oxide nanoparticles. Surface ligand modifications can be adjusted to regulate the interaction energy between sensors and Ca 2+ , allowing for customizable response range and sensitivity to fulfill the in vivo imaging requirements. The optimized sensors enable non-invasive visualization of early-stage seizure focus in mice undergoing epilepsy.
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