AbstractWater-soluble and functional copper nanoclusters (CuNCs) were prepared by using folic acid (FA) that serves both as a reducing reagent and a stabilizer. FA also acts as a functional ligand on the surface of the CuNCs, and this can be exploited to target the folate receptor which is over-expressed on the surface of HeLa cells. The FA-modified CuNCs nanoclusters have an average size of ca. 0.9 nm and are stable in aqueous medium for 30 days. Under photoexcitation at λex 270 and 350 nm, the FA-CuNCs display strong blue fluorescence with an emission peak at 440 nm. The FA-CuNCs exhibit low cytotoxicity and favorable biocompatibility as demonstrated by an MTT assay. A cell viability of >80% is found when incubating HeLa cells for 20 h with FA-CuNCs at levels of up to 200 μg mL−1. The targeting capability of the FA-CuNCs is demonstrated by live cell imaging. It is shown that HeLa cells with over-expressed folate receptor are much brighter than A549 cells where the receptor is not over-expressed. This is further corroborated by the fact that the copper content in HeLa cells (1.5 pg/cell) is 6.5-fold higher than that of A549 cells (0.23 pg/cell), both measured after the same incubation time of 3 h. If free FA is introduced into the cell culture medium, the folate receptors will be preoccupied with FA, and this results in a significant decrease in the cellular uptake of the FA-CuNCs by HeLa cells. Graphical AbstractBiocompatible copper nanoclusters (CuNCs) coated with folic acid (FA) were prepared and are shown to be viable probes for the differentiation between FR-positive HeLa cells and FR-negative A549 cells.

中文翻译：

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叶酸修饰的铜纳米团簇用于过表达叶酸受体的癌细胞的荧光成像

摘要 利用叶酸 (FA) 作为还原剂和稳定剂制备了水溶性和功能性铜纳米团簇 (CuNCs)。FA 还充当 CuNCs 表面的功能配体，这可用于靶向在 HeLa 细胞表面过度表达的叶酸受体。FA 修饰的 CuNCs 纳米团簇的平均尺寸约为 0.9 nm，在水性介质中稳定 30 天。在 λex 270 和 350 nm 的光激发下，FA-CuNCs 显示出强烈的蓝色荧光，发射峰位于 440 nm。FA-CuNCs 表现出低细胞毒性和良好的生物相容性，如 MTT 测定所示。将 HeLa 细胞与 FA-CuNCs 以高达 200 μg mL-1 的水平孵育 20 小时时，发现细胞活力 >80%。活细胞成像证明了 FA-CuNCs 的靶向能力。结果表明，叶酸受体过度表达的 HeLa 细胞比受体未过度表达的 A549 细胞亮得多。HeLa 细胞中的铜含量 (1.5 pg/细胞) 比 A549 细胞 (0.23 pg/细胞) 的铜含量高 6.5 倍这一事实进一步证实了这一点，两者都是在 3 小时相同的孵育时间后测量的。如果将游离 FA 引入细胞培养基中，叶酸受体将被 FA 占据，这会导致 HeLa 细胞对 FA-CuNCs 的细胞摄取显着减少。图形摘要制备了包覆有叶酸 (FA) 的生物相容性铜纳米团簇 (CuNCs)，并证明其是区分 FR 阳性 HeLa 细胞和 FR 阴性 A549 细胞的可行探针。结果表明，叶酸受体过度表达的 HeLa 细胞比受体未过度表达的 A549 细胞亮得多。HeLa 细胞中的铜含量 (1.5 pg/细胞) 比 A549 细胞 (0.23 pg/细胞) 的铜含量高 6.5 倍这一事实进一步证实了这一点，两者都是在 3 小时相同的孵育时间后测量的。如果将游离 FA 引入细胞培养基中，叶酸受体将被 FA 占据，这会导致 HeLa 细胞对 FA-CuNCs 的细胞摄取显着减少。图形摘要制备了包覆有叶酸 (FA) 的生物相容性铜纳米团簇 (CuNCs)，并证明其是区分 FR 阳性 HeLa 细胞和 FR 阴性 A549 细胞的可行探针。结果表明，叶酸受体过度表达的 HeLa 细胞比受体未过度表达的 A549 细胞亮得多。HeLa 细胞中的铜含量 (1.5 pg/细胞) 比 A549 细胞 (0.23 pg/细胞) 的铜含量高 6.5 倍这一事实进一步证实了这一点，两者都是在 3 小时相同的孵育时间后测量的。如果将游离 FA 引入细胞培养基中，叶酸受体将被 FA 占据，这会导致 HeLa 细胞对 FA-CuNCs 的细胞摄取显着减少。图形摘要制备了包覆有叶酸 (FA) 的生物相容性铜纳米团簇 (CuNCs)，并证明其是区分 FR 阳性 HeLa 细胞和 FR 阴性 A549 细胞的可行探针。