The application of terahertz imaging in biomedical diagnostics is limited by the poor imaging contrast due to the strong absorption of terahertz waves by water molecules in the living body. To resolve this problem, gold nanorods (GNRs) have been considered as a possible contrast agent. However, the conventional preparation of GNRs requires using cetyltrimethylammonium bromide (CTAB) as a stabilizing surfactant, which is toxic to animals at high exposures. In this work, a modified seed-mediated growth method was proposed to synthesize silica-coated GNRs, which exhibited better stability and biocompatibility and the same cellular uptake efficiency as compared to those of uncoated GNRs. Moreover, silica-coated GNRs showed higher photothermal efficiency caused by the localized surface plasmon resonance that increased the terahertz reflection amplitude. In particular, the in vitro terahertz imaging of prostate cancer cells demonstrated noticeably higher contrast when silica-coated GNRs were used as a contrast agent. Hence, this study suggests a stable, biocompatible, and efficient contrast-enhancing agent for terahertz imaging, which can expand the scope of its clinical applications.

中文翻译：

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具有高光热效率和生物相容性的二氧化硅涂层金纳米棒，作为体外太赫兹成像的造影剂。

由于生物体内水分子对太赫兹波的强烈吸收，太赫兹成像在生物医学诊断中的应用受到成像对比度差的限制。为了解决这个问题，金纳米棒（GNR）被认为是可能的造影剂。但是，常规的GNR制备需要使用十六烷基三甲基溴化铵（CTAB）作为稳定的表面活性剂，该表面活性剂在高暴露量下对动物有毒。在这项工作中，提出了一种改良的种子介导的生长方法来合成二氧化硅包被的GNR，与未包被的GNR相比，它具有更好的稳定性和生物相容性以及相同的细胞吸收效率。此外，二氧化硅涂层的GNR表现出更高的光热效率，这是由于局部表面等离子体激元共振导致了太赫兹反射幅度的增加。当二氧化硅涂层的GNR用作造影剂时，前列腺癌细胞的体外太赫兹成像显示出明显更高的对比度。因此，这项研究提出了用于太赫兹成像的稳定，生物相容和有效的对比增强剂，可扩大其临床应用范围。