Department of Physics, University of Nebraska Omaha, 6001 Dodge Street, Omaha, NE 68182, USA.
Molecules. 2020 Jul 2;25(13):3026. doi: 10.3390/molecules25133026.
Micro RNA (miR) are regulatory non-coding RNA molecules, which contain a small number of nucleotides ~18-28 nt. There are many various miR sequences found in plants and animals that perform important functions in developmental, metabolic, and disease processes. miRs can bind to complementary sequences within mRNA molecules thus silencing mRNA. Other functions include cardiovascular and neural development, stem cell differentiation, apoptosis, and tumors. In tumors, some miRs can function as oncogenes, others as tumor suppressors. Levels of certain miR molecules reflect cellular events, both normal and pathological. Therefore, miR molecules can be used as biomarkers for disease diagnosis and prognosis. One of these promising molecules is miR-21, which can serve as a biomarker with high potential for early diagnosis of various types of cancer. Here, we present a novel design of miR detection and demonstrate its efficacy on miR-21. The design employs emissive properties of DNA-silver nanoclusters (DNA/AgNC). The detection probe is designed as a hairpin DNA structure with one side of the stem complimentary to miR molecule. The binding of target miR-21 opens the hairpin structure, dramatically modulating emissive properties of AgNC hosted by the C loop of the hairpin. "Red" fluorescence of the DNA/AgNC probe is diminished in the presence of the target miR. At the same time, "green" fluorescence is activated and its intensity increases several-fold. The increase in intensity of "green" fluorescence is strong enough to detect the presence of miR-21. The intensity change follows the concentration dependence of the target miR present in a sample, which provides the basis of developing a new, simple probe for miR detection. The detection strategy is specific, as demonstrated using the response of the DNA/AgNC probe towards the scrambled miR-21 sequence and miR-25 molecule. Additionally, the design reported here is very sensitive with an estimated detection limit at ~1 picomole of miR-21.
微 RNA (miR) 是调节性非编码 RNA 分子，其包含少数核苷酸~18-28 个核苷酸。在动植物中发现了许多不同的 miR 序列，它们在发育、代谢和疾病过程中发挥着重要作用。miRs 可以与 mRNA 分子中的互补序列结合，从而使 mRNA 沉默。其他功能包括心血管和神经发育、干细胞分化、细胞凋亡和肿瘤。在肿瘤中，一些 miR 可以作为癌基因，另一些作为肿瘤抑制因子。某些 miR 分子的水平反映了正常和病理细胞事件。因此，miR 分子可以用作疾病诊断和预后的生物标志物。其中一种很有前途的分子是 miR-21，它可以作为一种具有高潜力的生物标志物，用于早期诊断各种类型的癌症。在这里，我们提出了一种新的 miR 检测设计，并展示了其对 miR-21 的功效。该设计利用了 DNA-银纳米簇 (DNA/AgNC) 的发射特性。检测探针设计为具有发夹 DNA 结构，其茎的一侧与 miR 分子互补。靶 miR-21 的结合打开发夹结构，极大地调节发夹 C 环中 AgNC 的发射特性。在存在靶 miR-21 的情况下，“红色”荧光的 DNA/AgNC 探针减弱。同时，“绿色”荧光被激活，其强度增加数倍。“绿色”荧光强度的增加足以检测到 miR-21 的存在。强度变化遵循存在于样品中的靶 miR 的浓度依赖性，这为开发新的简单 miR 检测探针提供了基础。该检测策略是特异性的，如通过 DNA/AgNC 探针对乱序 miR-21 序列和 miR-25 分子的响应来证明。此外，报告的设计非常灵敏，估计 miR-21 的检测限约为 1 皮摩尔。
