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Representative Research Publications

2017 > Representative Research Publications > Research Results Home

On-chip lipid extraction using super absorbent polymers for mass spectrometry

  • Analytical Chemistry / 2017 December
  • Kim, Jeong Ah(corresponding author)

Study Summary

Pre-treatment of samples is the one of 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 super absorbent 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 E. 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.

Expected Effects

Generally, conventional lipid extraction demands multiple steps, including drying, incubation, partitioning, and centrifugation, which results in tedious labor and low performance. However, the extraction of lipids using SAPs based on solid-phase extraction (SPE) is much simpler and faster because it eliminates the complex processes. With these advantages, we also fabricated a microfluidic chip-based and a multi-well plate-based lipid extraction platform by embedding SAPs for high-throughput extraction of lipids. It is anticipated that, in the future, microfluidic chip-based lipid extraction or multi-well plate lipid extraction can be conducted automatically in conjunction with a robotic system for the diagnosis of lipid-related diseases. Therefore, we believe that the SAP method is a very easy, fast, and reliable method that is especially important due to its use of small amounts of samples from complex biological specimens, such as plasma/serum, urine, saliva, and tissue, for the clinical use. In addition, SAPs can be attractive materials because they can enable minimal or flexible sample treatment in other applications.

Figure 1. (a) Schematic illustration showing the principle of lipid extraction based on super absorbent polymers (SAPs). (b) Pictures representing the ov­erall process of lipid extraction in a microcentrifuge tube. Figure 1. (a) Schematic illustration showing the principle of lipid extraction based on super absorbent polymers (SAPs). (b) Pictures representing the ov­erall process of lipid extraction in a microcentrifuge tube.

Figure 4. (a) Schematic illustrations and pictures of a microfluidic chip consisting of double-layered wells and micropillars for the lipid extraction of lipids. Micropillars underneath the top PDMS layer surround the inner well. (b) Experimental procedures of lipid extraction in a microfluidic chip. SAPs, samples, and solvent were loaded in sequence.Figure 4. (a) Schematic illustrations and pictures of a microfluidic chip consisting of double-layered wells and micropillars for the lipid extraction of lipids. Micropillars underneath the top PDMS layer surround the inner well. (b) Experimental procedures of lipid extraction in a microfluidic chip. SAPs, samples, and solvent were loaded in sequence.

Figure 6. Recovery of various lipid classes obtained by UPLC Q-TOF MS. (a) Lipid recovery depending on the sample volume varying from 10 to 100 μL. All values were compared to the averaged extraction value of the Folch process, *P < 0.05; **P <0.01, comparison of efficiency between volumes of 10 μL and 100 μL. (b) Comparison of lipid recovery by the SAP method and by the Folch method, *P < 0.05; **P < 0.01, comparison of efficiency between the SAP tube method and the Folch method. All values are presented as the mean ± S.D.; n = 3 for each group. PC, phosphatidylcholine; PE, phosphatidylethanolamine; PG, phosphatidylglycerol; PS, phosphatidylserine; PI, phosphatidylinositol; LPC, lyso-phosphatidylcholine; LPE, lyso-phosphatidylethanolamine; Chol Ester, cholesterol ester; DAG, diacylglycerol; TAG, triacylglycerol; SM, sphingomyelin.Figure 6. Recovery of various lipid classes obtained by UPLC Q-TOF MS. (a) Lipid recovery depending on the sample volume varying from 10 to 100 μL. All values were compared to the averaged extraction value of the Folch process, *P < 0.05; **P <0.01, comparison of efficiency between volumes of 10 μL and 100 μL. (b) Comparison of lipid recovery by the SAP method and by the Folch method, *P < 0.05; **P < 0.01, comparison of efficiency between the SAP tube method and the Folch method. All values are presented as the mean ± S.D.; n = 3 for each group. PC, phosphatidylcholine; PE, phosphatidylethanolamine; PG, phosphatidylglycerol; PS, phosphatidylserine; PI, phosphatidylinositol; LPC, lyso-phosphatidylcholine; LPE, lyso-phosphatidylethanolamine; Chol Ester, cholesterol ester; DAG, diacylglycerol; TAG, triacylglycerol; SM, sphingomyelin.