Can Direct-Immersion Aqueous–Aqueous Microextraction Be Achieved When Using a Single-Drop System?

Abstract

For the analysis of biological analytes in complex matrices, it is difficult to achieve extraction of analytes and enrichment in an aqueous−aqueous single-drop microextraction system. In this study, we proposed a pH-dependent polydopamine (PDA)-coated vesicle/Fe 3 O 4 magnetic aqueous−aqueous in a single-drop microreactor (SDMR) for the direct fluorescence detection of glutathione S-transferase (GST), a metabolic enzyme involved with crucial biological processes, in biological samples. After extracting and enriching the GST target from an aqueous−aqueous single-drop interface, the extraction process was conducted rapidly in 6 s in the SDMR system. The GST was first extracted from the sample solution via the GST-Aptamer on the polydopamine-coated vesicle/ Fe 3 O 4 nanospheres (Fe 3 O 4 @PDA@GST-Aptamer). Then, as the pH changed from weakly acidic to weakly alkaline in the SDMR system, the GST and GST-Aptamer were released from Fe 3 O 4 @PDA@GST-Aptamer nanospheres and captured by polydiacetylene vesicles via the capture probe. These changes altered the effective conjugation length and angle of the vesicle trunk, generating a highly enhanced fluorescence signal. This not only achieved the purpose of target enrichment but also reduced interferences posed by matrix effects. The approach can be used for the direct detection of GST in genuine urine and blood without any sample pretreatment. The linear range was 0.005 to 0.5 μg/mL, and the limit of detection was 0.834 ng/mL. The recoveries of GST in genuine blood samples ranged from 90.8 to 108.0% and in urine from 91.6 to 102.8%. The method has the capability of handling complex samples directly by enabling microextraction in an aqueous−aqueous single-drop system.

Advancements in solvent microextraction: Recent developments and diverse applications in the modern era

“…Additionally, the extended microdroplet's symmetrical axis rotation promotes internal recirculation, which improves mass transfer inside the droplet. The larger droplet volume is then transferred via a cone‐shaped container and added to GC and HPLC equipment for analysis [65]. It is a microextraction technique used in analytical chemistry for the preconcentration and extraction of analytes from a liquid sample.…”

Spatial Confinement of Single-Drop System to Enhance Aggregation-Induced Emission for Detection of MicroRNAs

“…Microextraction technology is now a widely practiced sample pretreatment method, which is used in the fields of biological sample detection, environmental analysis, and forensic identification. , Single-drop microextraction (SDME) technology has attracted much attention, possessing of high enrichment factor (EF) and low solvent consumption. − For example, Tang et al developed a magnetic three-phase SDME technology to rapidly amplify the analysis signals of DNA and miRNA and achieved highly sensitive nucleic acid detection . Traditionally, the samples after SDME are directly sent to liquid chromatography (LC) or LC/mass spectrometry (MS) systems to generate signals, and some are also combined with optical signals or UV–vis color reactions. − However, there has been no report on the combination of SDME and AIE optical signals as yet.…”

“…Microextraction technology is now a widely practiced sample pretreatment method, which is used in the fields of biological sample detection, environmental analysis, and forensic identification. 40,41 Single-drop microextraction (SDME) technology has attracted much attention, possessing of high enrichment factor (EF) and low solvent consumption. 42−44 For example, Tang et al developed a magnetic threephase SDME technology to rapidly amplify the analysis signals of DNA and miRNA and achieved highly sensitive nucleic acid detection.…”