Department of Chemistry, Capital Normal University, Xisanhuan North Road. 105, Beijing, 100048, China.
Department of Chemistry, Capital Normal University, Xisanhuan North Road. 105, Beijing, 100048, China.
Anal Chim Acta. 2024 May 8;1302:342509. doi: 10.1016/j.aca.2024.342509. Epub 2024 Mar 20.
Functional nucleic acids (FNAs) have attracted a lot of attention for the rapid detection of metal ions. Cr is one of the major heavy metal ions in natural waters. Due to the slow ligand exchange rate of Cr, the FNA-based Cr sensors require long assay times, limiting the on-site applications. In this study, we report that the good's buffers containing amino and polyhydroxy groups greatly increase the ligand exchange rate of Cr. Using EDTA as a model coordinate ligand, the Tris buffer (100 mM, pH 7.0) showed the best acceleration effect among the eight buffers. It improved the rate constant ∼20-fold, shorten the half-time 19-fold, and lowered the activation energy ∼70% at 40 °C. The Tris buffer was then applied for sensor based on the Cr-binding induced fluorescence quenching of fluorescein (FAM)-labeled and single-stranded DNA (ssDNA), which shortened the assay time from 1 h to 1 min. The Tris buffer also ∼100% enhanced the fluorescence intensity of FAM, achieving the 11.4-fold lower limit of detection (LOD = 6.97 nM, S/N = 3). By the combination use of the Tris buffer and ascorbic acid, the strong interference from Cu, Pb, and Fe suffered in many previous reported Cr sensors was avoided. The practical application of the sensor for the detection of Cr spiked in the real water samples were demonstrated with high recovery percentages. The Tris buffer could be applied for other metal ions with slow ligand exchange rate (such as V, Co and Fe) to solve diverse issues such as long assay time and low synthesis yield of metal complexes, without the need of heating treatment.
功能性核酸 (FNAs) 因其能够快速检测金属离子而受到广泛关注。Cr 是天然水中主要的重金属离子之一。由于 Cr 的配体交换速率较慢，基于 FNA 的 Cr 传感器需要较长的检测时间，限制了其现场应用。在这项研究中，我们报告了含有氨基和多羟基的良好缓冲液大大提高了 Cr 的配体交换速率。以 EDTA 作为模型配位配体，在八种缓冲液中，Tris 缓冲液（100 mM，pH 7.0）显示出最佳的加速效果。它将速率常数提高了约 20 倍，将半衰期缩短了 19 倍，在 40°C 下将活化能降低了约 70%。然后，Tris 缓冲液被应用于基于荧光素（FAM）标记的单链 DNA（ssDNA）与 Cr 结合诱导荧光猝灭的传感器，将检测时间从 1 小时缩短至 1 分钟。Tris 缓冲液还将 FAM 的荧光强度提高了约 100%，实现了 11.4 倍的更低检测限（LOD=6.97 nM，S/N=3）。通过 Tris 缓冲液和抗坏血酸的联合使用，可以避免许多先前报道的 Cr 传感器中 Cu、Pb 和 Fe 产生的强烈干扰。该传感器在实际水样中检测 Cr 的加标实验中表现出了较高的回收率。Tris 缓冲液可用于其他配体交换速率较慢的金属离子（如 V、Co 和 Fe），以解决如检测时间长和金属配合物合成产率低等问题，而无需进行加热处理。
