Application of paper EWOD (electrowetting-on-dielectrics) chip: Protein tryptic digestion and its detection using MALDI-TOF mass spectrometry

Abstract

A paper-based open EWOD chip was used for protein tryptic digestion, and the resulting peptides were analyzed using MALDI-TOF mass spectrometry to identify the proteins. Although on-chip protein digestion was previously demonstrated on a glass-based EWOD platform, this is the first report to show that a paper-based EWOD can also be used for protein digestion and further analysis by mass spectrometry. A number of protein digestion processes, i.e., disulfide bond reduction, alkylation, buffering, and tryptic digestion, can be successfully conducted on the paper-based EWOD chip. Furthermore, a “Y”-shaped junction design was shown to be effective in successfully manipulating a droplet for protein digestion. A paper-based EWOD platform offers a cheap and versatile avenue for biological applications.