Confined Gel-Electromembrane Extraction of Oligonucleotides.

Gel-electromembrane extraction (G-EME) is an increasingly popular green variant of electromembrane extraction (EME). However, the electroendosmosis (EEO) flow associated with G-EME greatly limits the development of this technology. To address this challenge, the current study proposed the concept of confined G-EME (CG-EME), and a three-dimensional-printed modular device was elaborately designed to realize this concept. The device blocked the EEO flow by limiting the volume of the sample compartment. Moreover, the mesh structure at the bottom of the extraction module helps to prepare thin and stable gel films, which enhance the electromigration driving force and shorten the migration path. In addition, polar oligonucleotides, a nucleic acid analyte, were extracted for the first time to prove the concept of CG-EME. After optimization, 62% of the oligonucleotides were extracted at 50 V voltage for 15 min using a 3 mm thick agarose (3%) gel film. Finally, the application capability of CG-EME was further demonstrated by recovering DNA primers and isolating disease biomarkers (miRNA-181b) from real samples. In combination with CG-EME and quantitative polymerase chain reaction (qPCR) analysis, the upregulation of miRNA-181b expression in the peripheral blood of patients with schizophrenia was observed. In conclusion, this study proposes CG-EME to diminish EEO and push EME into the clinical field to isolate nucleic acid biomarkers, which will greatly expand the application scenarios of this emerging technology.