Ultrasound imaging and ultrasound-mediated gene and drug delivery are rapidly advancing diagnostic and therapeutic methods; however, their use is often limited by the need for microbubbles, which cannot transverse many biological barriers due to their large size. Here, the authors introduce 50-nm gas-filled protein nanostructures derived from genetically engineered gas vesicles(GVs) that are referred to as _{50 nm}GVs. These diamond-shaped nanostructures have hydrodynamic diameters smaller than commercially available 50-nm gold nanoparticles and are, to the authors’ knowledge, the smallest stable, free-floating bubbles made to date. _{50 nm}GVs can be produced in bacteria, purified through centrifugation, and remain stable for months. Interstitially injected _{50 nm}GVs can extravasate into lymphatic tissues and gain access to critical immune cell populations, and electron microscopy images of lymph node tissues reveal their subcellular location in antigen-presenting cells adjacent to lymphocytes. The authors anticipate that _{50 nm}GVs can substantially broaden the range of cells accessible to current ultrasound technologies and may generate applications beyond biomedicine as ultrasmall stable gas-filled nanomaterials.

中文翻译：

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50 纳米充气蛋白质纳米结构可通过超声波技术进入淋巴细胞

超声成像和超声介导的基因和药物输送正在迅速推进诊断和治疗方法；然而，它们的使用往往受到微泡需求的限制，由于微泡尺寸较大，无法跨越许多生物屏障。在这里，作者介绍了源自基因工程气体囊泡 (GV) 的 50 纳米充气蛋白质纳米结构，简称为_{50 纳米}GV。这些菱形纳米结构的流体动力学直径小于市售的 50 纳米金纳米粒子，据作者所知，它们是迄今为止制造的最小的稳定、自由漂浮的气泡。_{50 nm} GV 可以在细菌中产生，通过离心纯化，并保持稳定数月。间质注射的_{50 nm} GV 可以外渗到淋巴组织中并接近关键的免疫细胞群，淋巴结组织的电子显微镜图像揭示了它们在邻近淋巴细胞的抗原呈递细胞中的亚细胞位置。作者预计_{50 nm} GV 可以大大拓宽当前超声技术可利用的细胞范围，并可能产生生物医学以外的超小型稳定充气纳米材料的应用。