An impedance-based biosensor for the ultrasensitive, selective, and label-free detection of a blood miRNA associated to Alzheimer disease (AD), miRNA-206, was developed. The principle was grounded in the changes in the charge transfer resistance (R) as an effect of intramolecular forces between miRNAs and ferro/ferricyanide in a well-structured transducer platform. A compact well-ordered mixed monolayer made of co-immobilized miRNA capture to 6-mercapto-1-hexanol (MCH) in a 1:4 M ratio (at 37 °C), uplifted the performance of the sensor through effectively assisting the orientation of the oligonucleotides. In this work, the remarkable response of the sensor was generated through new insights into the use of different moieties of miRNA capture to MCH, aiming to control interfacial constants, surface densities, and hybridization efficiency.A very low limit of detection, 0.15 aM, is achieved and the sensor has a wide linear dynamic range (from 1 aM to 1 μM), high selectivity to mismatches, low non-specific binding of proteins (BSA) and good stability (<10 % change in response after 14 days storage). Importantly, the sensor successfully measured miRNA-206 concentrations in real plasma samples (>95 % recovery), correlating directly with qPCR results. Nanomolar concentrations of miRNA-206 were found in the plasma of confirmed AD patients, while healthy controls, had a concentration of pM or lower. The biosensor's ability to quantitatively detect miRNA-206 in plasma without target amplification, e.g., using PCR, is significant, opening the possibility of developing a point-of-care diagnostic device for AD screening, contributing to clinical trials and patient care.

中文翻译：

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人血浆中 miRNA-206 的超灵敏、无标记电化学检测：与阿尔茨海默病相关的潜在生物标志物

开发了一种基于阻抗的生物传感器，用于超灵敏、选择性和无标记地检测与阿尔茨海默病 (AD) 相关的血液 miRNA（miRNA-206）。该原理基于电荷转移电阻 (R) 的变化，这是结构良好的传感器平台中 miRNA 和铁/铁氰化物之间分子内力的影响。由以 1:4 M 比例（37 °C）共固定 miRNA 捕获到 6-mercapto-1-hexanool (MCH) 制成的紧凑有序混合单层，通过有效协助定向来提升传感器的性能寡核苷酸的。在这项工作中，传感器的显着响应是通过对使用 miRNA 捕获的不同部分到 MCH 的新见解产生的，旨在控制界面常数、表面密度和杂交效率。极低的检测限，0.15 aM，该传感器具有宽线性动态范围（从 1 aM 到 1 μM）、对错配的高选择性、低的蛋白质非特异性结合 (BSA) 和良好的稳定性（存储 14 天后响应变化 <10%） 。重要的是，该传感器成功测量了真实血浆样本中的 miRNA-206 浓度（>95% 回收率），与 qPCR 结果直接相关。在确诊的 AD 患者血浆中发现了纳摩尔浓度的 miRNA-206，而健康对照的浓度为 pM 或更低。该生物传感器能够定量检测血浆中的 miRNA-206，无需使用 PCR 等靶标扩增，这一能力非常重要，为开发用于 AD 筛查的护理点诊断设备提供了可能性，从而有助于临床试验和患者护理。