Sensitive and specific detection of tumor exosomes is of great significance for early cancer diagnosis. In this paper, we report an aptamer strategy for exosome detection based on aptamer recognition-induced multi-DNA release and cyclic enzymatic amplification. First, we use aptamer–magnetic bead bioconjugates to capture tumor exosomes derived from LNCaP cells, leading to the release of three kinds of messenger DNAs (mDNAs). After magnetic separation, the released mDNAs hybridized with the probe DNAs immobilized on a gold electrode. Electroactive Ru(NH₃)₆³⁺ was used as the signal reporter because of its electrostatic attraction to DNA. Subsequent Exo III cyclic digestion caused the electrochemical signal to “turn off”. Because the electrochemical signal reflects the concentration of Ru(NH₃)₆³⁺ and the concentration of Ru(NH₃)₆³⁺ is correlated with the mDNA concentration, which is correlated with the exosome concentration, the tumor exosomes can be detected by examining the decrease in the peak current of Ru(NH₃)₆³⁺. In this paper, the signal was amplified by the numerous mDNAs released from the magnetic bead and the Exo III-assisted mDNA recycling. Under the optimal conditions, a detection limit down to 70 particles/μL was achieved, which is lower than the LODs of most currently available methods. Furthermore, this assay can be used to detect tumor exosomes in complex biological samples, demonstrating potential application in real sample diagnosis.

中文翻译：

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基于适体识别诱导的多DNA释放和循环酶扩增的肿瘤外泌体的高灵敏电化学检测。

敏感，特异地检测肿瘤外来体对于早期癌症诊断具有重要意义。在本文中，我们报告了基于适体识别诱导的多DNA释放和循环酶促扩增的外泌体检测的适体策略。首先，我们使用适体-磁珠生物共轭物来捕获源自LNCaP细胞的肿瘤外泌体，从而导致三种信使DNA（mDNA）的释放。磁分离后，释放的mDNA与固定在金电极上的探针DNA杂交。电活性Ru（NH ₃）₆ ³⁺由于其对DNA的静电吸引，被用作信号报告基因。随后的Exo III循环消化导致电化学信号“关闭”。因为电化学信号反映了Ru（NH ₃）₆ ³⁺的浓度，并且Ru（NH ₃）₆ ³⁺的浓度与mDNA浓度相关，而mDNA浓度与外泌体浓度相关，所以可以通过以下方法检测肿瘤外泌体研究Ru（NH ₃）₆ ³⁺的峰值电流的减小。在本文中，通过磁珠释放的大量mDNA和Exo III辅助的mDNA回收扩增了信号。在最佳条件下，达到了最低70颗粒/μL的检测限，这比大多数当前可用方法的LOD低。此外，该测定法可用于检测复杂生物样品中的肿瘤外泌体，证明其在实际样品诊断中的潜在应用。