利用銅銀奈米團簇偵測銅離子

Abstract

本論文利用以DNA為模板所合成之銅銀奈米團簇 (DNA-Cu/Ag nanoclusters, DNA-Cu/Ag NCs) 配合巰基丙酸 (3-mercaptopropionic acid, MPA) 發展出一種簡單、免標定(label-free) 之銅離子螢光探針。其偵測機制是由於MPA與DNA-Cu/Ag NCs上之金屬離子作用導致團簇的構形瓦解，使螢光消光；此時在有額外銅離子存在下，MPA先和銅離子生成錯合物並進一步被氧化成雙硫形式 (disulfide)，隨著銅離子濃度增加，使未作用的MPA濃度下降，導致DNA-Cu/Ag NCs螢光被消光的程度會下降，因此螢光強度會隨著銅離子濃度增加而增強。在最佳化的反應條件，其偵測極限 (limit of detection，LOD) 為3.5 nM，線性範圍5-200 nM (R2 = 0.988)。此方法對於銅離子具有極高的選擇性，為其他金屬離子的2300倍。將此方法應用於偵測土壤樣品中銅離子濃度，所測得濃度為2.60 (± 0.23) μM，與利用感應耦合電漿質譜分析儀 (Inductively coupled plasma mass spectrometry; ICP-MS) 分析結果一致，顯示此方法適合用於環境樣品的分析。

This thesis focuses on devoloping a simple and homogeneous fluorescence assay—comprising 3-mercaptopropionic acid (MPA) with DNA-Cu/Ag nanoclusters (NCs) in aqueous solution—for the detection of Cu2+ ions. The sensing mechanism is based on the suppression of MPA induced fluorescence quenching of the DNA-Cu/Ag NCs by Cu2+. MPA-induced fluorescence quenching is due to changes in the DNA conformation as a result of the interactions between MPA and Cu/Ag clusters. The MPA-induced fluorescence quenching followed a typical characteristic of a Stern-Volmer plot and followed a static quenching mechanism. The presence of Cu2+ resulted in the oxidation of MPA to form disulfide, leading to suppression of the MPA-induced fluorescence quenching. The fluorescence of the DNA-Cu/Ag NCs in the presence of MPA increased upon increasing the concentration of Cu2+ over the range 5-200 nM. The DNA-Cu/Ag NC probe provided the limit of detection at a signal-to-noise of 3 of 2.7 nM for Cu2+ ions, with high selectivity (at least 2300-folds over tested metal ions). The practicality of this approach has been validated by the analyses of Montana soil and water samples (3 replicate measurements), showing the potential of the probe for detection of Cu2+ ions in environmental samples.