This study strategically fabricates a nucleic acid functionalized gold nanoparticle and graphene oxide composite probe (AuNP/GO probe) to achieve both the recognition and in situ monitoring of cytoplasmic target precursor microRNAs (pre-miRNAs) and mature microRNAs (miRNAs) in living cells. The pre-miRNA-21 detection with AuNP probes has a good linear range of 0-300 nM and a limit of detection (LOD) of 4.5 nM, whereas the GO probe has a linear relationship with mature miRNA-21 from 0.1 to 10 nM with a LOD of 1.74 nM. This assay was utilized to directly visualize the relative expression levels of pre- and mature forms of miRNA-21 and let-7a. The results suggested that the expression levels of precursor miRNAs remain constant in cancer cells and normal cells. However, the expression levels of mature miRNAs vary widely, demonstrating the "up-regulation" of miRNA-21 and "down-regulation" of let-7a in cancer cells in contrast to that in normal cells. The practicality of this strategy was verified by in situ monitoring changes in cytoplasmic pre-miRNA-21 and mature miRNA-21 in response to small-molecule inhibitors of miRNA-21.

中文翻译：

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使用金纳米颗粒和氧化石墨烯复合探针原位监测细胞质前体和成熟的 microRNA

本研究战略性地制造了核酸功能化的金纳米颗粒和氧化石墨烯复合探针（AuNP/GO 探针），以实现活细胞中细胞质靶标前体 microRNA（pre-miRNA）和成熟 microRNA（miRNA）的识别和原位监测。使用 AuNP 探针检测 pre-miRNA-21 具有 0-300 nM 的良好线性范围和 4.5 nM 的检测限 (LOD)，而 GO 探针与成熟 miRNA-21 具有 0.1 至 10 nM 的线性关系LOD 为 1.74 nM。该测定用于直接可视化 miRNA-21 和 let-7a 的前体和成熟形式的相对表达水平。结果表明前体miRNA的表达水平在癌细胞和正常细胞中保持恒定。然而，成熟miRNA的表达水平差异很大，表明“