Photoacoustic imaging is gaining great attention in the medical world due to its significant potential for clinical translation. Light excitation in the second near-infrared (NIR-II) window (1000-1350 nm) has resolution and penetration depth suitable for several clinical applications. However, the significant challenge exists for clinical translation because of the absence of notable intrinsic chromophores in this clinically significant optical range to generate diagnostic images.

Methods: We present newly developed a biocompatible nickel dithiolene-based polymeric nanoparticle (NiPNP), which have a strong and sharp absorption peak at 1064 nm, as a photoacoustic contrast agent to boost specific absorbance in the NIR-II window for in vivo deep tissue imaging.

Results: We confirm the enhanced PA signal by NiPNP's strong light absorption in the NIR-II window (287% higher than that of NIR-I) and deep tissue imaging capability (~5.1 cm) through in vitro experiment. We have successfully acquired diagnostic-quality in vivo photoacoustic images in deep tissue (~3.4 cm) of sentinel lymph nodes, gastrointestinal tracts, and bladders of live rats by using clinically viable imaging system.

Conclusions: Our results prove that with strong absorption in the NIR-II window and with deeper imaging depth, the clinical translation of photoacoustic imaging with NiPNP is feasible for preclinical studies and thus would facilitate further clinical investigations.

光声成像由于其临床转化的巨大潜力而​​受到医学界的广泛关注。第二近红外 (NIR-II) 窗口（1000-1350 nm）中的光激发具有适合多种临床应用的分辨率和穿透深度。然而，由于在这个具有临床意义的光学范围内缺乏显着的内在生色团来生成诊断图像，因此临床转化存在重大挑战。

方法：我们提出了一种新开发的生物相容性二硫醇镍基聚合物纳米颗粒（NiPNP），它在 1064 nm 处具有强而尖锐的吸收峰，作为光声造影剂，可提高体内深层组织在 NIR-II 窗口中的比吸光度成像。

结果：我们通过体外实验证实了 NiPNP 在 NIR-II 窗口中的强光吸收（比 NIR-I 高 287%）和深层组织成像能力（~5.1 cm）增强 PA 信号。我们通过使用临床上可行的成像系统，成功地在活体大鼠的前哨淋巴结、胃肠道和膀胱的深部组织（~3.4 cm）中获得了诊断质量的体内光声图像。

结论：我们的结果证明，由于 NiPNP 光声成像在 NIR-II 窗口的强吸收和更深的成像深度，其临床转化对于临床前研究是可行的，从而有助于进一步的临床研究。