Quantitative assays are of great importance for point-of-care (POC) diagnostics because they can offer accurate information on the analytes. However, current POC devices often require an accessory instrument to give quantitative readouts for protein biomarkers, especially for those at very low concentration levels. Here, we report a microfluidic platform, the digital volumetric bar-chart chip (DV-chip), for quantitative POC diagnostics with ultra-low detection limits that are readable with naked eyes. Requiring no calibration, the DV-chip presents a digital ink bar chart (representing multiple bits composed of 0 and 1) for the target biomarker based on direct competition between O2 generated by the experimental and control samples. The bar chart clearly and accurately defines target concentration, allowing identification of disease status. For the standard PtNP solutions, the detection limit of the platform is approximately 0.1 pM and the dynamic range covers four orders of magnitude from 0.1 to 1000 pM. CEA samples with concentrations of 1 ng/mL and 1.5 ng/mL could be differentiated on the device. We also performed ELISA assay for B-type natriuretic peptide (BNP) in 20 plasma samples from heart failure patients and the obtained on-chip data were in agreement with the clinical results. In addition, BNP was detectable at concentrations of less than 5 pM, which is three orders of magnitude lower than the detection limit of the previously reported readerless digital methods. By the integration of gas competition, volumetric bar chart, and digital readout, the DV-chip possesses merits of portability, visible readout, and ultra-low detection limit, which should offer a powerful platform for quantitative POC diagnostics in clinical settings and personalized detection.
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机译:定量测定对于即时诊断(POC)诊断非常重要,因为它们可以提供有关分析物的准确信息。但是,当前的POC设备通常需要使用辅助仪器来定量读取蛋白质生物标志物,特别是对于浓度非常低的蛋白质。在这里,我们报告了一种微流体平台,即数字体积条形图芯片(DV-chip),用于定量POC诊断,具有超低检测限,可通过肉眼读取。无需校准,DV芯片会根据实验样本和对照样本产生的O2之间的直接竞争,为目标生物标记物显示数字墨水条形图(代表由0和1组成的多个位)。条形图清楚,准确地定义了目标浓度,从而可以确定疾病状态。对于标准PtNP解决方案,平台的检测极限约为0.1 pM,动态范围涵盖从0.1到1000 pM的四个数量级。可以在设备上区分浓度为1 ng / mL和1.5 ng / mL的CEA样品。我们还对20例来自心力衰竭患者的血浆样本中的B型利钠尿肽(BNP)进行了ELISA测定,所获得的芯片数据与临床结果相符。此外,在小于5 pM的浓度下可检测到BNP,这比以前报道的无读取器数字方法的检测限低三个数量级。通过集成气体竞争,体积条形图和数字读数,DV芯片具有便携性,可见读数和超低检测限的优点,这将为临床设置和个性化检测中的定量POC诊断提供强大的平台。
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