Nanoscale distance-dependent phenomena, such as Förster resonance energy transfer, are important interactions for use in sensing and imaging, but their versatility for bioimaging can be limited by undesirable photon interactions with the surrounding biological matrix, especially in in vivo systems^1,2,3,4. Here, we report a new type of magnetism-based nanoscale distance-dependent phenomenon that can quantitatively and reversibly sense and image intra-/intermolecular interactions of biologically important targets. We introduce distance-dependent magnetic resonance tuning (MRET), which occurs between a paramagnetic ‘enhancer’ and a superparamagnetic ‘quencher’, where the T₁ magnetic resonance imaging (MRI) signal is tuned ON or OFF depending on the separation distance between the quencher and the enhancer. With MRET, we demonstrate the principle of an MRI-based ruler for nanometre-scale distance measurement and the successful detection of both molecular interactions (for example, cleavage, binding, folding and unfolding) and biological targets in in vitro and in vivo systems. MRET can serve as a novel sensing principle to augment the exploration of a wide range of biological systems.

纳米级距离相关现象，例如Förster共振能量转移，是传感和成像中的重要相互作用，但是其与生物成像的通用性可能受到与周围生物基质的不良光子相互作用的限制，尤其是在体内系统中^{1,2， 3,4}。在这里，我们报告了一种新型的基于磁性的纳米级距离相关现象，该现象可以定量且可逆地感知和成像生物学上重要目标的分子内/分子间相互作用。我们介绍了距离相关的磁共振调谐（MRET），它发生在顺磁“增强器”和超顺磁“淬灭器”之间，其中T ₁取决于淬灭剂和增强剂之间的距离，将磁共振成像（MRI）信号调整为ON或OFF。借助MRET，我们演示了基于MRI的标尺用于纳米级距离测量的原理，并成功检测了体外和体内系统中的分子相互作用（例如，裂解，结合，折叠和展开）以及生物学靶标。MRET可以作为一种新颖的传感原理来增强对广泛生物系统的探索。