On-Chip Lipid Extraction Using Superabsorbent Polymers for Mass Spectrometry.

Pretreatment of samples is one of the most important steps in analytical methods for efficient and accurate results. Typically, an extraction method used for lipid analysis with mass spectrometry is accompanied by complex liquid-liquid extraction. We have devised a simple, rapid, and efficient lipid extraction method using superabsorbent polymers (SAPs) and developed a high-throughput lipid extraction platform based on a microfluidic system. Since SAPs can rapidly absorb an aqueous solution from a raw sample and convert it into the gel, the lipid extraction process can be remarkably simplified. The hydrophobic lipid components were captured into the fibrous SAP gel and then solubilized and eluted directly into the organic solvent without significant interference by this polymer. The small-scale lipid extraction process minimizes the liquid handling and unnecessary centrifugation steps, thereby enabling the implementation of a SAP-integrated microfluidic lipid extraction platform. The SAP method successfully induced reproducible extraction and high recovery rates (95-100%) compared to the conventional Folch method in several lipid classes. We also demonstrated the feasibility of the SAP method for the analysis of lipids in complex biological samples, such as the brain and liver, as well as Escherichia coli. This small-scale SAP method and its microfluidic platform will open up new possibilities in high-throughput lipidomic research for diagnosing diseases because this new technique saves time, labor, and cost.