Non-invasive biological imaging requires materials capable of interacting with deeply penetrant forms of energy such as magnetic fields and sound waves. Here, we show that gas vesicles (GVs), a unique class of gas-filled protein nanostructures with differential magnetic susceptibility relative to water, can produce robust contrast in magnetic resonance imaging (MRI) at sub-nanomolar concentrations, and that this contrast can be inactivated with ultrasound in situ to enable background-free imaging. We demonstrate this capability in vitro, in cells expressing these nanostructures as genetically encoded reporters, and in three model in vivo scenarios. Genetic variants of GVs, differing in their magnetic or mechanical phenotypes, allow multiplexed imaging using parametric MRI and differential acoustic sensitivity. Additionally, clustering-induced changes in MRI contrast enable the design of dynamic molecular sensors. By coupling the complementary physics of MRI and ultrasound, this nanomaterial gives rise to a distinct modality for molecular imaging with unique advantages and capabilities.

非侵入性生物成像需要能够与深穿透形式的能量（例如磁场和声波）相互作用的材料。在这里，我们显示了气体囊泡（GV），这是一类独特的气体填充蛋白质纳米结构，相对于水具有不同的磁化率，可以在亚纳摩尔浓度下在磁共振成像（MRI）中产生强大的对比度，并且这种对比度可以原位超声灭活，以实现无背景成像。我们在体外，在将这些纳米结构表达为遗传编码的报告基因的细胞中以及在三种体内模型中展示了这种能力。GV的遗传变异具有不同的磁性或机械表型，可以使用参数MRI和差分声学灵敏度进行多重成像。此外，聚类诱发的MRI对比度变化使动态分子传感器的设计成为可能。通过结合MRI和超声的互补物理学，这种纳米材料为分子成像带来了独特的形式，具有独特的优势和功能。