The sensitive detection of molecular biomarkers has critical significance for early disease diagnoses and treatments. And, monitoring sarcosine levels in urine has increasing become new potential method for prostate cancer diagnosis. However, current techniques for sarcosine detection suffer simplicity, sensitivity, and specificity limitations. In this study, we introduce a novel enzyme-free, cascaded and autocatalytic nucleic acid circuit exponential amplification means for fluorescent aptamer-based sarcosine assay. Such amplification methodology is based on the synergistic cross-activation between Mg²⁺-dependent DNAzyme cleavage and autocatalytic hybridization chain reaction (acHCR). The sensing approach allows target binding to and altering the conformation of aptamer within the DNA duplex, thereby releasing active DNAzyme that cyclically cleaves signal hairpin substrate to initiate subsequent activation of DNAzyme/acHCR amplification circuit. This results in HCR-mediated autonomous assembly formation of many concatenated DNAzymes, which again catalyze signal substrate cleavages and in turn activates HCR amplifier. Consequently, such cascaded cross-feedback circuit leads to cleavage of plenty of signal hairpins and amplifies the target recognition event into significantly enhanced fluorescence signals, allowing for sensitive detection of as low as 6.9 nM sarcosine within 10 nM and 2 μM. Furthermore, our method demonstrates notable selectivity for detecting low levels of sarcosine in diluted artificial urine samples, making such assay hold considerable potential as a versatile tool for the sensitive monitoring of various biomarkers by simple replacement of appropriate aptamers.

中文翻译：

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级联和自催化核酸回路，用于肌氨酸癌症生物标志物的指数扩增和基于适配体的超灵敏荧光生物传感


分子生物标志物的灵敏检测对早期疾病诊断和治疗具有重要意义。而且，监测尿液中的肌氨酸水平已成为前列腺癌诊断的新潜在方法。然而，目前的肌氨酸检测技术存在简单性、敏感性和特异性方面的限制。在这项研究中，我们介绍了一种新的无酶、级联和自催化核酸回路指数扩增手段，用于基于荧光适配体的肌氨酸测定。这种扩增方法基于 Mg²⁺ 依赖性 DNAzyme 切割和自催化杂交链反应 （acHCR） 之间的协同交叉激活。传感方法允许靶标结合并改变 DNA 双链体内适配体的构象，从而释放活性 DNAzyme，循环切割信号发夹底物，以启动 DNAzyme/acHCR 扩增回路的后续激活。这导致 HCR 介导的许多串联 DNA 酶的自主组装形成，这再次催化信号底物切割，进而激活 HCR 放大器。因此，这种级联交叉反馈电路导致大量信号发夹的切割，并将靶标识别事件放大为显着增强的荧光信号，从而可以在 10 nM 和 2 μM 内灵敏地检测低至 6.9 nM 的肌氨酸。此外，我们的方法在检测稀释的人工尿液样品中低水平肌氨酸方面表现出显着的选择性，这使得这种测定具有相当大的潜力，作为一种通过简单地更换适当的适配体来灵敏监测各种生物标志物的多功能工具。