Protein Separations in Microfluidic Chips

Abstract

Identifying protein structure, function, and expression level under varying environmental conditions in cells is an important activity in most life science research and pharmaceutical discovery. Determining the molecular weight and purity of protein samples is routinely done in laboratories using sodium dodecyl sulfate-polyacryamide gel electrophoresis (SDS-PAGE) in the last few decades (1, 2). This process is highly manual and takes many hours to prepare the gel, run the samples, stain and destain the protein fractions, capture the gel image, and analyze the image to determine the protein sizes against a ladder. With commercially available precast gel, the first step of the process is becoming simpler and less messy, but overall it is still a relatively slow and tedious procedure. In large-scale protein processing operations and proteomics research laboratories, protein analysis often is a bottleneck in the workflow. Over the last 10 years capillary gel electrophoresis-SDS (SDS-CGE) is being increasingly used for analysis of therapeutic proteins. Compared to SDS-PAGE, SDS-CGE offers advantages of on-column detection, improved quantitation and resolution, and automation. However, SDS-CGE is limited by low sensitivity, throughput, and reliability. In the past several years, microfluidic-based assay for sizing, quantitiation, and purity assessment of proteins are also finding rapid adoption. The benefits in integration, fast separation, automation, and ease of use offered by microfluidics address the limitations of SDS-PAGE and SDS-CGE, and have proven to be a faster and easier alternative to the traditional SDS-PAGE or SDS-CGE.