Physics and Astronomy Department, University of Padova, Via Marzolo 8, 35131 Padova, Italy.
Institute of Applied Physics, University of Münster, Corrensstrasse 2/4, 48149 Muenster, Germany.
Sensors (Basel). 2022 Feb 2;22(3):1144. doi: 10.3390/s22031144.
This paper deals with the quantification of proteins by implementing the Bradford protein assay method in a portable opto-microfluidic platform for protein concentrations lower than 1.4 mg/mL. Absorbance is measured by way of optical waveguides integrated to a cross-junction microfluidic circuit on a single lithium niobate substrate. A new protocol is proposed to perform the protein quantification based on the high correlation of the light absorbance at 595 nm, as commonly used in the Bradford method, with the one achieved at 633 nm with a cheap commercially available diode laser. This protocol demonstrates the possibility to quantify proteins by using nL volumes, 1000 times less than the standard technique such as paper-analytical devices. Moreover, it shows a limit of quantification of at least 0.12 mg/mL, which is four times lower than the last literature, as well as a better accuracy (98%). The protein quantification is obtained either by using one single microfluidic droplet as well by performing statistical analysis over ensembles of several thousands of droplets in less than 1 min. The proposed methodology presents the further advantage that the protein solutions can be reused for other investigations and the same pertains to the opto-microfluidic platform.
本文介绍了一种在便携式光微流控平台上实现 Bradford 蛋白分析方法，用于测量浓度低于 1.4mg/mL 的蛋白质。在单个铌酸锂衬底上的十字形微流控电路中集成光学波导来测量吸光度。提出了一种新的协议，基于在 595nm 处的光吸收与在 633nm 处使用廉价商用二极管激光获得的光吸收之间的高度相关性，来进行蛋白质定量。该协议表明可以使用纳升体积(nL)进行蛋白质定量，比纸分析器件等标准技术少 1000 倍。此外，它还显示了至少 0.12mg/mL 的定量下限，比最近的文献低四倍，并且具有更好的准确性（98%）。通过使用单个微流控液滴，或者通过在不到 1 分钟的时间内对数千个液滴的集合进行统计分析，可以实现蛋白质的定量。所提出的方法具有进一步的优势，即蛋白质溶液可以重复用于其他研究，而光微流控平台也是如此。
