Department of Biological Engineering, Massachusetts Institute of Technology, 150 Albany Street, NW14-2213, Cambridge, Massachusetts 02139, USA.
Inorg Chem. 2010 Mar 15;49(6):2589-91. doi: 10.1021/ic100150e.
We introduce a mechanism for ion sensing by MRI in which analytes compete with paramagnetic ions for binding to polydentate chelating agents. Displacement of the paramagnetic ions results in alteration of solvent interaction parameters and consequent changes in relaxivity and MRI contrast. The MRI changes can be tuned by the choice of chelator. As an example, we show that calcium-dependent displacement of Mn(2+) ions bound to EGTA and BAPTA results in a T(1)-weighted MRI signal increase, whereas displacement from calmodulin results in a signal decrease. The changes are ion selective and can be explained using relaxivity theory. The ratio of T(2) to T(1) relaxivity is also calcium-dependent, indicating the feasibility of "ratiometric" analyte detection, independent of the probe concentration. Measurement of paramagnetic ion displacement effects could be used to determine analyte ion concentrations with spatial resolution in opaque specimens.
我们介绍了一种通过 MRI 进行离子感应的机制，其中分析物与顺磁离子竞争结合多齿螯合剂。顺磁离子的置换会导致溶剂相互作用参数的改变，从而导致弛豫率和 MRI 对比的变化。通过选择螯合剂可以调整 MRI 的变化。例如，我们表明，与 EGTA 和 BAPTA 结合的 Mn(2+)离子的钙依赖性置换会导致 T(1)加权 MRI 信号增加，而从钙调蛋白置换则会导致信号减少。这些变化是离子选择性的，可以用弛豫率理论来解释。T(2)与 T(1)弛豫率的比值也与钙有关，这表明了“比率式”分析物检测的可行性，与探针浓度无关。顺磁离子置换效应的测量可用于在不透明样本中以空间分辨率确定分析物离子浓度。
