Microfluidic chips with reversed-phase monoliths for solid phase extraction and on-chip labeling

Nge, Pamela N.; Pagaduan, Jayson V.; Yu, Ming; Woolley, Adam T.

doi:10.1016/j.chroma.2012.08.095

Cited by 49 publications

(60 citation statements)

References 57 publications

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“…To avoid potential loss of hydrophobic analytes to polymer gasket materials (a process for which we find evidence especially from low-concentration analyte solutions), an all-glass microscopy flow cell was constructed from an optically flat float-glass top plate and coverslip, assembled by cold welding where the clean flat-glass surfaces are likely held together by strong hydrogen bonding interactions. A 0.5 mm wide by 0.2 mm deep flow channel was machined into a 25 mm diameter float-glass top 4 OH, which was then heated to 70°C for 10 min. The plate and coverslip were then rinsed with the deionized water, held in contact with an aluminum screw clamp, and heated to 180°C for at least 3 h. After a gradual lowering to room temperature (4−6 h), the coverslip and top plate were bonded, producing a sealed channel between the inlet and well.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Confocal Raman Microscopy for pH-Gradient Preconcentration and Quantitative Analyte Detection in Optically Trapped Phospholipid Vesicles

Hardcastle

Harris

2015

Anal. Chem.

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The ability of a vesicle membrane to preserve a pH gradient, while allowing for diffusion of neutral molecules across the phospholipid bilayer, can provide the isolation and preconcentration of ionizable compounds within the vesicle interior. In this work, confocal Raman microscopy is used to observe (in situ) the pH-gradient preconcentration of compounds into individual optically trapped vesicles that provide sub-femtoliter collectors for small-volume samples. The concentration of analyte accumulated in the vesicle interior is determined relative to a perchlorate-ion internal standard, preloaded into the vesicle along with a high-concentration buffer. As a guide to the experiments, a model for the transfer of analyte into the vesicle based on acid-base equilibria is developed to predict the concentration enrichment as a function of source-phase pH and analyte concentration. To test the concept, the accumulation of benzyldimethylamine (BDMA) was measured within individual 1 μm phospholipid vesicles having a stable initial pH that is 7 units lower than the source phase. For low analyte concentrations in the source phase (100 nM), a concentration enrichment into the vesicle interior of (5.2 ± 0.4) × 10(5) was observed, in agreement with the model predictions. Detection of BDMA from a 25 nM source-phase sample was demonstrated, a noteworthy result for an unenhanced Raman scattering measurement. The developed model accurately predicts the falloff of enrichment (and measurement sensitivity) at higher analyte concentrations, where the transfer of greater amounts of BDMA into the vesicle titrates the internal buffer and decreases the pH gradient. The predictable calibration response over 4 orders of magnitude in source-phase concentration makes it suitable for quantitative analysis of ionizable compounds from small-volume samples. The kinetics of analyte accumulation are relatively fast (∼15 min) and are consistent with the rate of transfer of a polar aromatic molecule across a gel-phase phospholipid membrane.

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Section: ■ Experimental Sectionmentioning

confidence: 99%

Confocal Raman Microscopy for pH-Gradient Preconcentration and Quantitative Analyte Detection in Optically Trapped Phospholipid Vesicles

Hardcastle

Harris

2015

Anal. Chem.

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“…38,[40][41][42][43][44][45][46][47][48] Recently, we presented the first application for PPMs on DMF 36 using PPM discs with C12 moieties as a reverse phase for SPE. With the goal of expanding this technique to include SCX extractions, Fig.…”

Section: Ppm Formation and Characterisationmentioning

confidence: 99%

Strong and small: strong cation-exchange solid-phase extractions using porous polymer monoliths on a digital microfluidic platform

et al. 2014

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We present the first method for digital microfluidics-based strong cation-exchange solid-phase extractions. Digital microfluidics is a microscale fluid handling technique in which liquid droplets are actuated over an array of electrodes by electrodynamic forces. Strong cation exchange has gained considerable importance in the field of proteomics as a separation mode for protein and peptide extractions. The marriage of these two techniques is achieved by incorporating sulphonatefunctionalised porous polymer monolith discs onto digital microfluidic chips. By manipulating sample and solvent droplets onto and off of these porous polymer monoliths, proteins and peptides are extracted by controlling solution pH and ionic strength. This novel microscale extraction method has efficiency comparable to commercially available strong cationexchange ZipTips and is highly effective for sample cleanup. We anticipate that this digital microfluidic strong cationexchange extraction technique will prove useful for microscale proteomic analyses and other applications requiring separation of cationic compounds.Résumé : Nous présentons ici la toute première méthode d'extraction sur phase solide à échange cationique fort basée sur la microfluidique digitale. La microfluidique digitale est une technique de la manipulation des volumes de fluides micro-échelles, dans laquelle des gouttelettes liquides sont déplacées sur une matrice d'électrodes par des forces électrodynamiques. Le phénomène d'échange cationique fort, utilisé comme mode de séparation dans l'extraction des protéines et des peptides, a pris une importance considérable dans le domaine de la protéomique. La combinaison de ces deux techniques (extraction sur phase solide et microfluidique digitale) est atteinte par l'intégration des disques de monolithes polymériques poreux possédant des groupements fonctionnels sulfonate sur les puces microfluidiques. En manipulant des gouttelettes d'échantillon et de solvant sur et hors de ces monolithes polymériques poreux, des protéines et des peptides sont extraits en contrôlant le pH et la force ionique de la solution. Cette méthode novatrice de microextraction, aussi efficace que la technique commercialisée à échange cationique fort ZipTips, est très efficace pour nettoyer les échantillons. Nous prévoyons que cette technique d'extraction basée sur l'échange cationique fort et utilisant la microfluidique digitale s'avèrera utile pour les analyses protéomiques micro-échelles et pour d'autres applications nécessitant la séparation de composés cationiques.Mots-clés : microfluidique, microfluidique digitale, extraction sur phase solide, échange cationique fort, échange d'ions, monolithes polymériques poreux.

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“…Importantly, there is a need for integrated microfluidic systems with monoliths for sample preparation. Recently, Nge et al [39] reported a monolith prepared from butyl methacrylate for SPE and on-chip labeling. However, pretreatment of the monolith by rinsing with 30% acetonitrile was necessary to obtain the best retention.…”

Section: Introductionmentioning

confidence: 99%

On chip preconcentration and fluorescence labeling of model proteins by use of monolithic columns: device fabrication, optimization, and automation

Yang

Pagaduan

et al. 2014

Anal Bioanal Chem

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Microfluidic systems are developed with monolithic columns for preconcentration and on-chip labeling of model proteins. Monoliths are prepared in microchannels via photopolymerization, and the properties of monoliths are optimized by varying the composition and concentration of monomers to improve flow and extraction. On-chip labeling of proteins is achieved by driving solutions through the monolith using voltage and incubating fluorescent dye with protein retained in the monolith. Subsequently, the labeled proteins are eluted by applying voltages to reservoirs on the microdevice and then detected by laser-induced fluorescence. Monoliths prepared from octyl methacrylate show the best combination of protein retention while still allowing unattached fluorescent label to be eluted in a separate fraction with 50% acetonitrile. Finally, automated on-chip extraction and fluorescence labeling of a model protein is successfully demonstrated. This work provides facile sample pretreatment, and therefore offers promising potential for future integrated bioanalysis microchips.

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Microfluidic chips with reversed-phase monoliths for solid phase extraction and on-chip labeling

Cited by 49 publications

References 57 publications

Confocal Raman Microscopy for pH-Gradient Preconcentration and Quantitative Analyte Detection in Optically Trapped Phospholipid Vesicles

Confocal Raman Microscopy for pH-Gradient Preconcentration and Quantitative Analyte Detection in Optically Trapped Phospholipid Vesicles

Strong and small: strong cation-exchange solid-phase extractions using porous polymer monoliths on a digital microfluidic platform

On chip preconcentration and fluorescence labeling of model proteins by use of monolithic columns: device fabrication, optimization, and automation

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