MicroRNA (miRNA) sensing, especially the miRNA-200 family, is increasingly targeted for cancer diagnostics. As the sensing schemes often rely on nanoparticles functionalized with a specific oligonucleotide, we investigate the hydribization conditions using the common case of surface plasmon resonance (SPR) sensing of miRNA and a gold nanoparticle (Au NP) competitor. In this type of assays, the Au NPs compete with the microRNA to bind the capture probe immobilized on the gold surface. In our study, we simplify and improve the detection procedure by adopting 11-mercaptoundecanoic acid (11-MUA) as linker to the gold surface, not only omitting the blocking step of 6-mercapto-1-hexanol (MCH), but also increasing the probe density. We report that the response in our SPR sensing studies increased with the size of Au NPs according to the plasmon ruler equation, but the larger AuNPs of 32 nm lacked colloidal stability. In addition, decreasing the ratio of oligonucleotide to Au NPs and the addition of polyethylene glycol (PEG) to hybridization buffer also favored a better response in SPR sensing of miRNA. The optimization led to an improved detection sensitivity in our competition method and a detection limit as low as 500 pM for miRNA-200b without amplification of miRNA and use of other amplification schemes.

MicroRNA（miRNA）感测，尤其是miRNA-200家族，越来越成为癌症诊断的目标。由于传感方案通常依赖于用特定寡核苷酸功能化的纳米颗粒，因此我们使用miRNA和金纳米颗粒（Au NP）竞争者的表面等离振子共振（SPR）传感的常见情况研究了加水条件。在这种类型的测定中，Au NP与microRNA竞争以结合固定在金表面的捕获探针。在我们的研究中，我们通过采用11-巯基癸酸（11-MUA）作为金表面的连接剂来简化和改进检测程序，不仅省去了6-巯基-1-己醇（MCH）的阻滞步骤，而且还增加了探针密度。我们报告说，在我们的SPR传感研究中，响应随等离激元标尺方程而随着Au NP尺寸的增加而增加，但32 nm的较大AuNP缺乏胶体稳定性。此外，降低寡核苷酸与Au NPs的比例以及将聚乙二醇（PEG）添加到杂交缓冲液中也有利于在miRNA的SPR感测中获得更好的响应。通过优化，我们的竞争方法提高了检测灵敏度，并且在不扩增miRNA和使用其他扩增方案的情况下，miRNA-200b的检测限低至500 pM。