This article reports a simple one-step method for anisotropic gold nanoparticle synthesis for plasmonic photothermal therapy medical purposes, using 1,4-bis[(2-ethylhexyl) oxy]-1,4-dioxo-2-butanesulfonic acid-sodium (AOT) reverse micelles as nanoreactor, where under specific condition, AOT acts as both a reducing and stabilizing agent. Obtained AuNPs were functionalized by attaching compounds derived from 2-aminopteridin-4(3H)-ona (pterin family) such as (2S)-2-[(4-{[(2-amino-4-hydroxypteridin-6-yl) methyl] amino} phenyl) formamido] pentanedioic acid (folic acid/FA) and 2-amino-4-hydroxypteridine-6-carboxylic acid (PCA) in order to evaluate its effect as targets for folate receptor-mediated cellular uptake in HeLa and normal human endocervical cells. The nanoconjugates were characterized through transmission electron microscopy (TEM), ultraviolet-visible, fluorescence, and Fourier transform infrared spectroscopies. Results showed an effective photothermal response of AuNPs in solution under NIR exposure with concentration dependence and none effect of the conjugation. In vitro studies in HeLa cells showed a concentration-dependent cytotoxicity of AuNPs; thus, conjugation to biomolecules such as FA or PCA has provided a biocompatible coating onto AuNPs and made them highly cytocompatible. Results demonstrated despite AF and PCA are analogue molecules, the folate receptors in HeLa cells are specific, and the different chemical groups available on the AuNPs surface have drastically different cell membrane penetration properties. The specific cell uptake through folate receptor (FR) was observed for short treatment time, while for a long treatment time, other mechanisms as penetration or adhesion were shown involved. In the particular case, of AF@AuNPs, the cell uptake through FR-mediated endocytosis was evidenced to have been decreasing cell viability in 24% after 2 h of treatment and 5 min under NIR exposure. This was confirmed by morphological changes in cells, as well the selective uptake of the FA@AuNPs by HeLa cells compared to normal cells, due folate receptor overexpression in HeLa cells. The findings from this study will have implications in the chemical design of nanostructures for plasmonic photothermal therapy. The obtained results provide evidences at in vitro level to support the fact that AF@AuNP nanoconjugate will accumulate in the affected tissue preferentially through the EPR (enhanced permeability and retention) effect by folate-targeting mechanism which will significantly enhance the efficacy of NIR-induced local photothermal effects.

中文翻译：

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通过蝶呤衍生物共轭各向异性金纳米粒子用于选择性等离子体光热疗法：HeLa 和正常人宫颈管细胞的体外研究

本文报道了一种用于等离子体光热治疗医学目的的各向异性金纳米颗粒合成的简单一步法，使用 1,4-双[(2-乙基己基)氧基]-1,4-二氧-2-丁磺酸钠 (AOT) ) 反胶束作为纳米反应器，在特定条件下，AOT 既充当还原剂又充当稳定剂。通过连接衍生自 2-aminopteridin-4(3H)-ona（蝶呤家族）的化合物，如 (2S)-2-[(4-{[(2-amino-4-hydroxypteridin-6-yl)甲基]氨基}苯基)甲酰氨基]戊二酸（叶酸/FA）和2-氨基-4-羟基蝶啶-6-羧酸（PCA），以评估其作为叶酸受体介导的细胞摄取靶点在HeLa和正常人子宫颈内膜细胞。通过透射电子显微镜（TEM）表征纳米共轭物，紫外-可见光、荧光和傅立叶变换红外光谱。结果表明，在 NIR 暴露下溶液中 AuNP 的有效光热响应具有浓度依赖性，并且没有共轭效应。HeLa 细胞的体外研究表明 AuNPs 具有浓度依赖性的细胞毒性；因此，与生物分子（如 FA 或 PCA）的结合为 AuNP 提供了生物相容性涂层，并使它们具有高度的细胞相容性。结果表明，尽管 AF 和 PCA 是类似分子，但 HeLa 细胞中的叶酸受体是特异性的，并且 AuNPs 表面上可用的不同化学基团具有截然不同的细胞膜渗透特性。通过叶酸受体 (FR) 的特定细胞摄取在较短的治疗时间内被观察到，而对于较长的治疗时间，显示涉及渗透或粘附等其他机制。在 AF@AuNPs 的特殊情况下，经 FR 介导的内吞作用的细胞摄取被证明在处理 2 小时后和在 NIR 暴露下 5 分钟后降低了 24% 的细胞活力。这通过细胞的形态学变化以及与正常细胞相比 HeLa 细胞对 FA@AuNP 的选择性摄取得到证实，这是由于 HeLa 细胞中叶酸受体的过度表达。这项研究的结果将对用于等离子体光热疗法的纳米结构的化学设计产生影响。