Mass Spectrometry Laboratory, MolSys Research Unit, University of Liège, Allée du 6 Août, 4000 Liège, Belgium.
Department of Pure and Applied Chemistry, Technology and Innovation Center, University of Strathclyde, 99 George Street, Glasgow G1 1RD, UK.
Analyst. 2022 Jul 12;147(14):3328-3339. doi: 10.1039/d2an00706a.
Folate receptor α (FRα) is a high affinity folate membrane receptor that is overexpressed in a wide variety of cancers. Detecting the overexpression of this receptor is important for cancer cells identification and to potentially guide the choice of treatment since several FRα-targeted drugs are currently in clinical trials. In this work, we built SERS nanotags based on core@shell Au@Ag nanoparticles labelled with resonant Raman-reporter and functionalised with a thiolated PEG linker bearing folic acid at the chain end. Using SERS mapping on single cells, we showed that the nanotags (FR-nanotags) could specifically target FRα on overexpressing HeLa cells and could measure the gradual blocking of FRα by free folic acid introduced in the media along the nanotags. With a control nanotag, we showed that the SERS response was 10-fold higher on HeLa cells when folic acid is present on the PEG linker compared to PEG chains without folic acid. Non-specific binding of the FR-nanotags was demonstrated to be low and mainly caused by the folic acid molecule at the PEG chain end. When comparing cancer cells with different expression levels of FRα, we obtained 4-fold higher SERS response on overexpressing HeLa cells compared to non-overexpressing A549 cells, allowing the discrimination of both cell lines with a high contrast. Owing to the biocompatibility of the developed nanotags, we demonstrated that measurements of FRα on live HeLa cells were also possible and gave similar results to measurements on fixed cells, indicating the versatility of the developed nanotags for detecting FRα under various experimental conditions.
叶酸受体α（FRα）是一种高亲和力的叶酸膜受体，在多种癌症中过表达。检测这种受体的过表达对于癌细胞的识别很重要，并且可能有助于指导治疗方案的选择，因为目前有几种 FRα 靶向药物正在临床试验中。在这项工作中，我们构建了基于核壳 Au@Ag 纳米粒子的 SERS 纳米标签，这些纳米粒子标记有共振拉曼报告分子，并通过带有巯基的 PEG 接头进行功能化，PEG 接头的链末端带有叶酸。通过对单细胞进行 SERS 图谱分析，我们表明纳米标签（FR-纳米标签）可以特异性地靶向过表达 FRα 的 HeLa 细胞，并可以通过向培养基中引入游离叶酸来逐步阻断 FRα，而游离叶酸可以与 FR-纳米标签结合。通过使用对照纳米标签，我们表明，与没有叶酸的 PEG 链相比，当叶酸存在于 PEG 接头时，FR-纳米标签在 HeLa 细胞上的 SERS 响应提高了 10 倍。FR-纳米标签的非特异性结合被证明很低，主要是由 PEG 链末端的叶酸分子引起的。当比较 FRα表达水平不同的癌细胞时，我们发现过表达的 HeLa 细胞的 SERS 响应比非过表达的 A549 细胞高 4 倍，这使得两种细胞系都可以通过高对比度来区分。由于所开发的纳米标签具有生物相容性，我们证明了对活 HeLa 细胞上 FRα 的测量也是可行的，并且与固定细胞的测量结果相似，这表明所开发的纳米标签在各种实验条件下检测 FRα 的多功能性。
