Photoacoustic (PA) imaging has received extensive attention in the recent decade due to its ultra-high resolution in deep tissue penetration, whereas functional PA probes with tunable molecular structure at a low cost level remain a significant challenge. Herein, we have rationally designed three triple-pyridyl iron complexes with different water solubilities. These complexes show a higher photothermal conversion efficiency due to their rapid excited-state deactivation, making them suitable as PA probes. Notably, the photothermal conversion efficiency of one complex named S-Fe could reach as high as 29.6%. In addition, S-Fe has excellent solubility and biocompatibility, which enable PA imaging in vivo. Significantly, further pharmacokinetics evaluation demonstrated that this complex showed minimal invasiveness for live animals and displayed a relatively fast metabolism rate. This study using inexpensive iron complexes as PA agents upgraded the toolbox for PA imaging and correlated multi-modal imaging applications.

中文翻译：

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用于体内光声成像的功能性吡啶基铁配合物

光声（PA）成像由于其在深层组织穿透中的超高分辨率而在最近十年中受到了广泛的关注，而具有低成本可调分子结构的功能性PA探针仍然是一项重大挑战。本文中，我们合理设计了三种水溶性不同的三吡啶铁配合物。这些配合物由于其快速的激发态失活而显示出更高的光热转换效率，使其适合用作PA探针。值得注意的是，一种名为S-Fe的配合物的光热转化效率可高达29.6％。此外，S-Fe具有出色的溶解性和生物相容性，可在体内进行PA成像。重要的是，进一步的药代动力学评估表明，该复合物对活体动物的侵袭性最小，并且代谢速度相对较快。这项使用廉价铁络合物作为PA试剂的研究升级了PA成像和相关多峰成像应用的工具箱。