pH对生物合成超声分子影像探针气囊充放气的调控

气囊（gas vesicles，GVs）是一种存在于蓝藻及古菌等微生物中调节浮力的类细胞器纳米结构，由蛋白质外壳包裹气体组成。近年来的研究表明，气囊具有作为超声分子影像探针的潜力。然而，气囊的充放气机制并不明确，限制了生物合成超声分子影像探针的保存和气体更换。本研究发现环境pH值是调节气囊充放气的一个重要因素。其不仅可以调节藻细胞内的气囊充放气进而使微囊藻呈现不同的漂浮状态，还可对提纯的气囊充放气进行体外调节，且该调节过程可逆。该机制的阐明为生物合成超声分子影像探针的大规模生产和保存，特别对气囊中的气体进行更换以满足不同的诊疗需求提供了技术支持，助力生物合成超声造影剂在疾病诊疗中的应用。

Regulation of pH on inflation and deflation of biosynthetic gas vesicles used as ultrasound molecular imaging probes

Gas vesicles (GVs) are gas-filled protein nanostructures that can regulate the buoyancy of microorganisms such as cyanobacteria and archaea. Recent studies have shown that GVs have the potential to be used as ultrasound molecular imaging probes in disease diagnosis and treatment. However, the mechanism of the inflation and deflation of GVs remains unclear, which hampers the preservation of GVs and gas replacement. In the present study, the environmental pH value was found to be an important factor in regulating the inflation and deflation of GVs. It can not only regulate the inflation and deflation of GVs in vivo to make Microcystis sp. cells present distinct levitation state, but also regulate the inflation and deflation of purified GVs in vitro, and the regulation process is reversible. Our results may provide a technical support for the large-scale production and preservation of biosynthetic ultrasound molecular imaging probes, especially for gas replacement to meet different diagnostic and therapeutic needs, and would facilitate the application of biosynthetic ultrasound molecular imaging probes.