Digital microfluidic assay for protein detection

Abstract

Global studies of the human proteome have revealed a plethora of putative protein biomarkers. However, their application for early disease detection remains at a standstill without suitable methods to realize their utility in the clinical setting. There thus continues to be tremendous interest in developing new technology for sensitive protein detection that is both low in cost and carries a small footprint to be able to be used at the point of care. The current gold standard method for protein biomarker detection is the ELISA, which measures protein abundance using bulky fluorescent scanners that lack portability. Here, we present a digital microfluidic platform for protein biomarker detection that is low in cost compared with standard optical detection methods, without any compromise in sensitivity. This platform furthermore makes use of simple electronics, enabling its translation into a portable handheld device, and has been developed in a manner that can easily be adapted to assay different types of proteomic biomarkers. We demonstrate its utility in quantifying not only protein abundance, but also activity. Interleukin-6 abundance could be assayed from concentrations as low as 50 pM (an order of magnitude lower than that detectable by a comparable laboratory designed ELISA) using less than 5 μL of sample, and Abelson tyrosine kinase activity was detectable in samples containing 100 pM of kinase.biosensor | decoupled architecture | bead-based assay R ecent decades of research have shown that the molecular mechanisms underlying human disease are much more complex than originally appreciated, with one or more rare genetic events often playing key roles in the transformation of a normal cell into a diseased cell. Not surprisingly, the diagnosis and treatment of many human diseases continue to struggle from the use of simplified models that are based on a handful of highly expressed biomarkers. Thanks to recent advances in microarray and next-generation sequencing technologies, a steadily increasing number of complete genomes have been sequenced, and considerable progress has been made using genomic biomarkers to better personalize healthcare. However, the ability to provide complete personalized healthcare demands the ability to monitor genetic biomarkers as well as protein biomarkers, and the development of proteomic technologies suitable for analyzing human samples has lagged considerably behind.To be well suited as a clinical diagnostic, a proteomic technology must be sensitive enough to detect endogenous levels of low abundance proteins, require low sample volumes, have a short assay time, and ideally be portable as to allow informed treatment decisions to be made at the point of care. Microfluidics, with its inherent advantages of low sample and reagent volumes, multiplex and automated capabilities, and precise control over the microenvironment, has emerged as a promising operation platform with which to develop sensitive proteomic technologies. Several groups have used microfluidic sandwich immunoassays ...

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