Encapsulation of fluidic tubing and microelectrodes in microfluidic devices: integrating off-chip process and coupling conventional capillary electrophoresis with electrochemical detection

Becirovic, Vedada; Doonan, Steven R.; Martin, R. Scott

doi:10.1039/c3ay40809d

Cited by 11 publications

(25 citation statements)

References 37 publications

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“…To further investigate the effect of the WJE on the electrode response, a smaller injection plug (40 nL) was obtained by pressure-based injection directly onto the capillary. 39 As can be seen in Figure 4C (injection of a 200 μM catechol solution), the WJE electrode resulted more intense peaks (52 ± 6 nA), as compared to the use of the TLE approach (16 ± 2 nA, a significant difference at the 95% confidence level).…”

Section: Resultsmentioning

confidence: 83%

Microchip-based electrochemical detection using a 3-D printed wall-jet electrode device

Munshi

Martin

2016

Analyst

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Three dimensional (3-D) printing technology has evolved dramatically in the last few years, offering the capability of printing objects with a variety of materials. Printing microfluidic devices using this technology offers various advantages such as ease and uniformity of fabrication, file sharing between laboratories, and increased device-to-device reproducibility. One unique aspects of this technology, when used with electrochemical detection, is the ability to produce a microfluidic device as one unit while also allowing the reuse of the device and electrode for multiple analyses. Here we present an alternate electrode configuration for microfluidic devices, a wall-jet electrode (WJE) approach, created by 3-D printing. Using microchip-based flow injection analysis, we compared the WJE design with the conventionally used thin-layer electrode (TLE) design. It was found that the optimized WJE system enhances analytical performance (as compared to the TLE design), with improvements in sensitivity and the limit of detection. Experiments were conducted using two working electrodes – 500 μm platinum and 1 mm glassy carbon. Using the 500 μm platinum electrode the calibration sensitivity was 16 times higher for the WJE device (as compared to the TLE design). In addition, use of the 1 mm glassy carbon electrode led to limit of detection of 500 nM for catechol, as compared to 6 μM for the TLE device. Finally, to demonstrate the versatility and applicability of the 3-D printed WJE approach, the device was used as an inexpensive electrochemical detector for HPLC. The number of theoretical plates was comparable to the use of commercially available UV and MS detectors, with the WJE device being inexpensive to utilize. These results show that 3D-printing can be a powerful tool to fabricate reusable and integrated microfluidic detectors in configurations that are not easily achieved with more traditional lithographic methods.

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Section: Resultsmentioning

confidence: 83%

Microchip-based electrochemical detection using a 3-D printed wall-jet electrode device

Munshi

Martin

2016

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“…19,21,22,31 The work described here utilizes PS for its ability to embed electrodes for analysis and fluidic tubing to provide a low dead-volume connection to direct flow from sample (or immobilized cells) to the analysis device. 16,18 Importantly, the ability to embed the tubing allows us to integrate the chip with off-chip, well-established culture methods such as conventional petri dishes in a manner that does not significantly degrade the temporal resolution (discussed in more detail below). The PS embedded Pd decoupler has a large surface area and is capable of absorbing the increased hydrogen production at the decoupler due to increased ionic strength and current.…”

Section: Resultsmentioning

confidence: 99%

“…For all studies, a 1 mm (in diameter) Pd decoupler was embedded 1 mm away from either a 25 µm Pt detection electrode or a 33 µm carbon fiber detection electrode. Fused-silica capillary was also embedded in the device 18 with the fabrication procedure being similar to that of making PS-embedded electrodes. A capillary is threaded through a hole in the aluminum weigh dish and plugged with PDMS to prevent PS particles from clogging the capillary during heating.…”

Section: Methodsmentioning

confidence: 99%

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Integrated hybrid polystyrene–polydimethylsiloxane device for monitoring cellular release with microchip electrophoresis and electrochemical detection

2015

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In this work, a polystyrene (PS)-polydimethylsiloxane (PDMS) hybrid device was developed to enable the integration of cell culture with analysis by microchip electrophoresis and electrochemical detection. It is shown that this approach combines the fundamental advantages of PDMS devices (the ability to integrate pumps and valves) and PS devices (the ability to permanently embed fluidic tubing and electrodes). The embedded fused-silica capillary enables high temporal resolution measurements from off-chip cell culture dishes and the embedded electrodes provide close to real-time analysis of small molecule neurotransmitters. A novel surface treatment for improved (reversible) adhesion between PS and PDMS is described using a chlorotrimethylsilane stamping method. It is demonstrated that a Pd decoupler is efficient at handling the high current (and cathodic hydrogen production) resulting from use of high ionic strength buffers needed for cellular analysis; thus allowing an electrophoretic separation and in-channel detection. The separation of norepinephrine (NE) and dopamine (DA) in highly conductive biological buffers was optimized using a mixed surfactant system. This PS-PDMS hybrid device integrates multiple processes including continuous sampling from a cell culture dish, on-chip pump and valving technologies, microchip electrophoresis, and electrochemical detection to monitor neurotransmitter release from PC 12 cells.

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“…To date, capillary emitters have only been used with glass devices with respect to MS. 16,17 Polymer microfluidic devices have been known to have integrated capillaries, but used electrochemical detection. 18 …”

Section: Introductionmentioning

confidence: 99%

Integrated electrodes and electrospray emitter for polymer microfluidic nanospray–MS interface

et al. 2016

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Interfacing of microfluidic devices to mass spectrometry has challenges including dilution from sheath liquid junctions, fragile electrodes, and excessive dead volumes which prevent optimum performance and common use. The goal of this work is to develop a stable nanospray chip-MS interface that contains easily integrated electrodes and an embedded capillary emitter to mitigate current chip-MS problems. This system uses a hybrid polystyrene-poly(dimethylsiloxane) (PS-PDMS) microfluidic platform with an embedded electrode and integrated capillary emitter used as the nanospray interface. Two chip designs were used to evaluate the performance, illustrate on-chip reaction capabilities. By direct infusion, this system showed good performance with LODs of GSH and caffeine of 9 nM and 1 nM, R2 of 0.996 and 0.992 and sensitivity of 12 counts/nM and 332 counts/nM over a linear dynamic range of 40 nM to 50 μM and 1 to 50 μM respectively. A reaction was performed on the chip with syringe pumps showing the oxidation of glutathione (GSH) to oxidized glutathione (GSSG) using H2O2. The on-chip reaction of GSH oxidation to GSSG, with online-MS detection, successfully demonstrate the stability and robustness of the nanospray interface.

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Encapsulation of fluidic tubing and microelectrodes in microfluidic devices: integrating off-chip process and coupling conventional capillary electrophoresis with electrochemical detection

Cited by 11 publications

References 37 publications

Microchip-based electrochemical detection using a 3-D printed wall-jet electrode device

Microchip-based electrochemical detection using a 3-D printed wall-jet electrode device

Integrated hybrid polystyrene–polydimethylsiloxane device for monitoring cellular release with microchip electrophoresis and electrochemical detection

Integrated electrodes and electrospray emitter for polymer microfluidic nanospray–MS interface

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