Photoacoustic tomography (PAT) with genetically encoded near-infrared probes enables visualization of specific cell populations in vivo at high resolution deeply in biological tissues. However, because of a lack of proper probes, PAT of cellular dynamics remains unexplored. Here, the authors report a near-infrared Forster resonance energy transfer (FRET) biosensor based on a miRFP670-iRFP720 pair of the near-infrared fluorescent proteins, which enables dynamic functional imaging of active biological processes in deep tissues. By photoacoustically detecting the changes in the optical absorption of the miRFP670 FRET-donor, they monitored cell apoptosis in deep tissue at high spatiotemporal resolution using PAT. Specifically, they detected apoptosis in single cells at a resolution of ≈3 µm in a mouse ear tumor, and in deep brain tumors (>3 mm beneath the scalp) of living mice at a spatial resolution of ≈150 µm with a 20 Hz frame rate. These results open the way for high-resolution photoacoustic imaging of dynamic biological processes in deep tissues using NIR biosensors and PAT.

中文翻译：

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基因编码近红外 FRET 生物传感器的多尺度光声断层扫描

具有基因编码近红外探针的光声断层扫描 (PAT) 能够以高分辨率对生物组织深处的体内特定细胞群进行可视化。然而，由于缺乏适当的探针，细胞动力学的 PAT 仍未得到探索。在此，作者报告了一种基于 miRFP670-iRFP720 近红外荧光蛋白对的近红外福斯特共振能量转移 (FRET) 生物传感器，该传感器能够对深层组织中的活跃生物过程进行动态功能成像。通过光声检测 miRFP670 FRET 供体的光吸收变化，他们使用 PAT 以高时空分辨率监测深层组织中的细胞凋亡。具体来说，他们在小鼠耳部肿瘤中以约 3 µm 的分辨率检测到单细胞的凋亡，并以约 150 µm 的空间分辨率和 20 Hz 帧在活体小鼠的深部脑肿瘤（头皮下 > 3 mm）中检测到细胞凋亡速度。这些结果为使用近红外生物传感器和 PAT 对深层组织动态生物过程进行高分辨率光声成像开辟了道路。