Herein, we present a novel gold nanoparticle (AuNP) enumeration-based colorimetric aptamer biosensor for ultrasensitive detection of nucleic acid. This AuNP enumeration-based colorimetric method takes advantages of the distinctive and strong localized surface plasmon resonance light scattering with the dark-field microscope. In our model system, first, cost-effective DNA1 instead of expensive 2-thioethyl ether acetic acid was capped on the surface of AuNPs to form a dense DNA1 layer. Then, two DNA strands (DNA2 and DNA3) in two different solutions were separately asymmetrically functionalized on the AuNPs capped dense DNA1 layer. The subsequent binding of the target DNA could trigger the formation of perfect complementary DNA with a Y shape and adjust the distance between nanoparticles to form AuNP dimers, accompanied by a color change from green to yellow as observed, and thereby modulated the performance of the sensor, which resulted in the ultrahigh sensitivity. With this design, a 43 aM limit of detection was obtained, which exhibited an increase of at least 5–9 orders of magnitude in sensitivity over other colorimetric sensors fabricated using conventional strategies.

中文翻译：

---

Y型DNA双链体结构触发的金纳米粒子二聚体，用于暗场显微镜的核酸超灵敏比色检测。

在这里，我们提出了一种新颖的基于金纳米粒子（AuNP）枚举的比色适体生物传感器，用于核酸的超灵敏检测。这种基于AuNP枚举的比色方法利用了暗场显微镜独特而强大的局部表面等离振子共振光散射的优势。在我们的模型系统中，首先，将具有成本效益的DNA1而不是昂贵的2-硫代乙醚乙酸盖在AuNP的表面上，以形成致密的DNA1层。然后，两个不同的解决方案中的两个DNA链（DNA2和DNA3）分别在AuNPs覆盖的致密DNA1层上不对称地功能化。随后与靶标DNA的结合可能会触发形成Y形的完美互补DNA，并调节纳米颗粒之间的距离以形成AuNP二聚体，伴随着观察到的颜色从绿色到黄色的变化，从而调节了传感器的性能，从而实现了超高灵敏度。通过这种设计，获得了43 aM的检测限，与使用常规策略制造的其他比色传感器相比，其灵敏度提高了至少5–9个数量级。