Oblique-incidence reflectivity difference (OIRD) is a dielectric constant-sensitive technique and exhibits intriguing applications in label-free and high-throughput detection of protein microarrays. With the outstanding advantage of being compatible with arbitrary substrates, however, the effect of the substrate, particularly its dielectric constant on the OIRD sensitivity has not been fully disclosed. In this paper, for the first time we investigated the dependence of OIRD sensitivity on the dielectric constant of the substrate under top-incident OIRD configuration by combining theoretical modeling and experimental evaluation. Optical modeling suggested that the higher dielectric constant substrate exhibits a higher intrinsic sensitivity. Experimentally, three substrates including glass, fluorine-doped tin oxide (FTO) and silicon (Si) with different dielectric constants were selected as microarray substrates and their detection performances were evaluated. In good agreement with the modeling, high dielectric constant Si-based microarray exhibited the highest sensitivity among three chips, reaching a detection limit of as low as 5 ng mL with streptavidin as the model target. Quantification of captured targets on three chips with on-chip enzyme-linked immunosorbent assay (ELISA) further confirmed that the enhanced performance originates from the high dielectric constant enhanced intrinsic OIRD sensitivity. This work thus provides a new way to OIRD-based label-free microarrays with improved sensitivity.

中文翻译：

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高介电常数基底上蛋白质微阵列的无标记 OIRD 检测，具有增强的内在灵敏度

斜入射反射率差 (OIRD) 是一种介电常数敏感技术，在蛋白质微阵列的无标记和高通量检测中展现出有趣的应用。然而，尽管具有与任意基材兼容的突出优势，基材，特别是其介电常数对OIRD灵敏度的影响尚未完全公开。在本文中，我们首次通过理论建模和实验评估相结合的方式研究了顶部入射 OIRD 配置下 OIRD 灵敏度对基底介电常数的依赖性。光学模型表明介电常数较高的基板表现出较高的固有灵敏度。实验上选择了不同介电常数的玻璃、掺氟氧化锡（FTO）和硅（Si）三种基板作为微阵列基板，并评估了它们的检测性能。与模型非常吻合，高介电常数硅基微阵列在三种芯片中表现出最高的灵敏度，以链霉亲和素作为模型目标，检测限低至 5 ng/mL。使用片上酶联免疫吸附测定 (ELISA) 对三个芯片上捕获的目标进行定量进一步证实，性能的增强源于高介电常数增强的固有 OIRD 灵敏度。因此，这项工作为基于 OIRD 的无标记微阵列提供了一种新方法，具有更高的灵敏度。