Quantum dot (QD)-based digital immunoassays play an important role in ultrasensitive biomarker detection. However, the requirement of an objective with a high numerical aperture (NA) limits the application of this immunoassay. Here, high-quality imaging of massive single-QDs was achieved by the combination of an air objective (20×/0.4 NA) and liquid-immersed microspheres (150 μm, n = 2.2). The signal-to-noise ratio was comparable to that of a 100×/1.4 NA oil objective. Digital analysis of prostate-specific antigen (PSA) was performed within the dynamic range of 0–50 ng/mL and a limit of detection of 0.17 ng/mL. The measured serum data from the PSA were close to the values provided by a hospital. Using a low-magnification and low-NA objective may reduce the barrier of microscopy miniaturization and is beneficial to popularize biomolecular digital analysis.

中文翻译：

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用于基于量子点的数字免疫分析的液浸介电微球增强的低数值孔径显微镜物镜

基于量子点 (QD) 的数字免疫分析在超灵敏生物标志物检测中发挥着重要作用。然而，对具有高数值孔径 (NA) 的物镜的要求限制了这种免疫测定的应用。在这里，通过空气物镜（20×/0.4 NA）和浸液微球（150 μm，n= 2.2)。信噪比与 100×/1.4 NA 油品物镜相当。前列腺特异性抗原 (PSA) 的数字分析在 0–50 ng/mL 的动态范围内和 0.17 ng/mL 的检测限内进行。PSA 测得的血清数据接近医院提供的值。使用低倍率和低数值孔径的物镜可以降低显微镜小型化的障碍，有利于普及生物分子数字分析。