As the emerging phototheranostic agents, near-infrared (NIR) organic small molecules have drawn more and more attention because of the unique advantages, such as well-defined chemical structure, high purity, good reproducibility, and facile modification. However, till now, most NIR organic agents suffer from poor photothermal and physiological stabilities, which tremendously limits their clinical applications. In this work, an NIR organic small molecule (namely PQs-TPA)-based pyrazino[2,3-g]quinoxaline (PQ) by employing a donor–acceptor design strategy was synthesized. Through enclosing it with an amphiphilic biocompatible copolymer (DSPE-mPEG2000), well-distributed PQs-TPA nanoparticles (NPs) were developed, which exhibited excellent photothermal stability, reactive oxygen/nitrogen species resistances, and a high photothermal conversion efficiency up to 59.5 ± 4%. Both in vitro and in vivo experiments manifested that PQs-TPA NPs could not only serve as a high-contrast probe for photoacoustic (PA) imaging but also effectively suppress tumor growth in living mice by PA imaging-guided photothermal therapy (PTT). This study would provide an insight to design novel NIR organic small molecules and stimulate more exciting research motivations on the investigation of effective NIR organic small molecule-based agents with high performance for phototheranostic applications in living systems.

中文翻译：

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基于吡嗪并[2,3-g]喹喔啉的纳米粒子作为近红外光热疗剂，可用于有效的光声成像引导光热疗法

作为新兴的光热敏治疗剂，近红外（NIR）有机小分子由于其独特的优势而受到越来越多的关注，如化学结构明确，纯度高，可重复性好，修饰简便等。但是，到目前为止，大多数NIR有机试剂都具有较差的光热和生理稳定性，这极大地限制了其临床应用。在这项工作中，通过采用供体-受体设计策略合成了一种基于近红外的有机小分子（即PQs-TPA）的吡嗪并[2,3-g]喹喔啉（PQ）。通过将其封入两亲生物相容性共聚物（DSPE-mPEG2000）中，开发了分布均匀的PQs-TPA纳米颗粒（NPs），该纳米颗粒具有出色的光热稳定性，抗活性氧/氮物种的能力，以及高达59.5±4％的高光热转换效率。两个都体外和体内实验表明，PQs-TPA NPs不仅可以用作光声（PA）成像的高对比度探针，而且可以通过PA成像引导的光热疗法（PTT）有效抑制活体小鼠的肿瘤生长。这项研究将为设计新颖的近红外有机小分子提供见识，并激发更多激动人心的研究动机，以研究有效的基于近红外有机小分子的高性能光热疗技术在生物体内的应用。