Integrated electrokinetically driven microfluidic devices with pH‐mediated solid‐phase extraction coupled to microchip electrophoresis for preterm birth biomarkers

Abstract

Integration in microfluidics is important for achieving automation. Sample preconcentration integrated with separation in a microfluidic setup can have a substantial impact on rapid analysis of low-abundance disease biomarkers. Here, we have developed a microfluidic device that uses pH-mediated solid phase extraction (SPE) for the enrichment and elution of preterm birth (PTB) biomarkers. Furthermore, this SPE module was integrated with microchip electrophoresis for combined enrichment and separation of multiple analytes, including a PTB peptide biomarker (P1). A reversed-phase octyl methacrylate monolith was polymerized as the SPE medium in polyethylene glycol diacrylate modified cyclic olefin copolymer microfluidic channels. Eluent for pH-mediated SPE of PTB biomarkers on the monolith was optimized using different pH values and ionic concentrations. Nearly 50-fold enrichment was observed in single channel SPE devices for a low nanomolar solution of P1, with great elution time reproducibility (<7% RSD). The monolith binding capacity was determined to be 400 pg (0.2 pmol). A mixture of a model peptide (FA) and a PTB biomarker (P1) was extracted, eluted, injected, and then separated by microchip electrophoresis in our integrated device with ~15-fold enrichment. This device shows important progress towards an integrated electrokinetically operated platform for preconcentration and separation of biomarkers.

Microchip electrophoresis separation of a panel of preterm birth biomarkers

“…This flow was contrary to the expected direction of migration and was also observed by Sonker et al. , who photografted the COC surface with PEGDA to yield more reproducible EOF. We used a similar photografting method to that of Sonker et al.…”

“…Importantly, by using on‐chip sample preparation steps prior to separation of the biomarkers, we should be able to detect these PTB biomarkers below their risk levels. Using immunoaffinity extraction from blood serum and SPE as described previously, we should be able to achieve sixfold and 50‐fold preconcentrations, respectively, for a combined 300‐fold enrichment of the biomarkers. These enrichment factors should lower the biomarker LODs to near or below the risk level concentrations.…”

“…Prior to μCE experiments, COC device channels were coated using a photografting method adapted from one used previously in our lab . PEGDA was filtered through inhibitor remover beads to remove the methyl ether hydroquinone polymerization inhibitor.…”

“…In an effort to create an integrated microfluidic PTB biomarker analysis system capable of multiplexing, our lab has previously demonstrated SPE enrichment of select PTB biomarkers and integration of this system with microchip electrophoresis (μCE) for subsequent separation . Additionally, we have shown the ability to capture and purify PTB biomarkers from blood serum using immunoaffinity extraction coupled with μCE for subsequent separation .…”

Recent advances in microfluidic sample preparation and separation techniques for molecular biomarker analysis: A critical review

“…Although a real sample matrix was not tested, this work lays a foundation for the development of pneumatically operated integrated microfluidic systems for biomarker analysis, potentially integrating additional sample preparation steps like analyte labeling. Very recently, Sonker et al [47] reported an integrated SPE device for electrokinetic preconcentration of preterm birth biomarkers. A reversed-phase monolith inside a COC microchannel was used to perform pH-based SPE of clinically relevant low nanomolar concentrations of preterm birth biomarkers with 50-fold sample preconcentration.…”