Enzyme assay using ultra-low volume surface micromachined sensors

Cooper, Jonathan M.; Bratten, Craig D. T.; Cobbold, P H

doi:10.1039/a708233i

Cited by 5 publications

(7 citation statements)

References 11 publications

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“…Finally, in order to remove the polymide residue, the Ti sacri®cial layer was removed using a reactive ion etching (RIE) in 30 sccm pure oxygen at 20 mTorr and 100 W RF power for 3 min followed by 10 sccm SF6 at 13 mTorr and 100 W for 9 min. These methods proved more satisfactory than, and differ from our previously published methods, where we have used a wet etch for NiCr [9].…”

Section: Fabrication Using Polyimidecontrasting

confidence: 59%

“…Schematic diagram of major fabrication steps: 1) Exposure of positive photoresist through a mask, in order to de®ne the template for microelectrode deposition; 2) development of exposed photoresist followed by; 3) evaporation of multilayers of metals to form the microsensor array; 4) lift off reveals the microsensor con®guration; (5) deposition of the negative photoresist (e.g., polyimide or SU-8) and exposure through a mask; 6) development of the exposed resist to reveal the microelectrodes within an analytical chamber. Postprocessing of the chambers may include a variety of wet or dry etches to remove residues, and or sacri®cial layers, and=or electrochemical or sputtered deposition of ad-layers, such as platinum (note bioelectrochemical experiments including the detection of hydrogen peroxide or the enzyme linked assay with glucose oxidase, involved the use of sputtered Pt on top of the Au surface, in order to reduce the required overpotential for detection [9]). 8 microchambers) multilayer structures.…”

Section: Electrodes Patternmentioning

confidence: 99%

“…Two methods were used to remove residual polyimide, both involving a sacri®cial layer. Previously, a wet etch was chosen to remove a NiCr layer [9], thereby freeing the Au surface from the residue. However, the acid etch solution removed the NiCr under the polyimide surface, undercutting the polymer.…”

Section: The Device Fabrication With Polyimide and Su-8mentioning

confidence: 99%

“…In an attempt to develop an integrated sensor technology, in which there is greater control over the geometry of the microelectrode con®guration, and=or the distance between a cell and the sensor, we have previously developed sub-nL sized electrochemical cells. These devices contain electrodes of ®xed surface area and geometry [8], which we have used to measure enzyme linked reactions [9], and more recently, the products resulting as a consequence of cell pathophysiology [10]. In this latter example, using the relatively large myocyte (with a volume of ca.…”

Section: Introductionmentioning

confidence: 99%

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Miniaturized Electroanalytical Sensor Systems in Micromachined Structures

2000

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Research into low volume electroanalytical sensors is becoming increasingly relevant, as scientists and engineers seek to explore the analytical benefits of miniaturization. This is particularly noticeable in the fields of biotechnology and drug discovery, where in the future, decrease in size holds a number of potential benefits, including for example, increased throughput. In this article, two methods for the fabrication of such microstructures are described, both involving the integration of metal microelectrodes on glass substrates, using different polymeric systems to fabricate (or “micromachine”) the surrounding titre chamber. In this context, photopolymerizable polyimide and SU‐8 were used to form chambers with volumes as small as 190 pL (with dimensions in the range 100–160 µm and depths between 20 and 25 µm). Such structures were characterized using model redox compounds including ferrocene monocarboxylic acid and hydrogen peroxide, and finally were applied to the quantitative detection of glucose, using glucose oxidase.

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Section: Fabrication Using Polyimidecontrasting

confidence: 59%

Section: Electrodes Patternmentioning

confidence: 99%

Section: The Device Fabrication With Polyimide and Su-8mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Miniaturized Electroanalytical Sensor Systems in Micromachined Structures

2000

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“…In a typical procedure, the first shadow mask was used to successively deposit a 20-nm thick titanium (Ti) layer, a 20-nm thick palladium (Pd) layer, and a 500-nm thick gold (Au) layer onto a glass substrate by electron beam deposition (Denton Vaccum, Moorestown, NJ, USA). The thicknesses of the Ti and Pd layers were chosen according to optimized parameters reported in the literature 52 . In this study 20-nm thickness of the Ti layer was selected to achieve the strong adhesion of the Au layer.…”

Section: Methodsmentioning

confidence: 99%

Automated microfluidic platform of bead-based electrochemical immunosensor integrated with bioreactor for continual monitoring of cell secreted biomarkers

Riahi

Shaegh

Ghaderi

et al. 2016

Sci Rep

143

138

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There is an increasing interest in developing microfluidic bioreactors and organs-on-a-chip platforms combined with sensing capabilities for continual monitoring of cell-secreted biomarkers. Conventional approaches such as ELISA and mass spectroscopy cannot satisfy the needs of continual monitoring as they are labor-intensive and not easily integrable with low-volume bioreactors. This paper reports on the development of an automated microfluidic bead-based electrochemical immunosensor for in-line measurement of cell-secreted biomarkers. For the operation of the multi-use immunosensor, disposable magnetic microbeads were used to immobilize biomarker-recognition molecules. Microvalves were further integrated in the microfluidic immunosensor chip to achieve programmable operations of the immunoassay including bead loading and unloading, binding, washing, and electrochemical sensing. The platform allowed convenient integration of the immunosensor with liver-on-chips to carry out continual quantification of biomarkers secreted from hepatocytes. Transferrin and albumin productions were monitored during a 5-day hepatotoxicity assessment in which human primary hepatocytes cultured in the bioreactor were treated with acetaminophen. Taken together, our unique microfluidic immunosensor provides a new platform for in-line detection of biomarkers in low volumes and long-term in vitro assessments of cellular functions in microfluidic bioreactors and organs-on-chips.

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Microfabrication of screen-printed nanoliter vials with embedded surface-modified electrodes

et al. 2006

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A self-contained ion-selective sensing system within a nanoliter-volume vial has been developed by integrating screen printing, laser ablation, and molecular imprinting techniques. Screen printing and laser ablation are used in tandem to fabricate nanoliter-volume vials with carbon and Ag/AgCl ring electrodes embedded in the sidewalls. Using multisweep cyclic voltammetry, the surface of the carbon electrode can be modified with a polypyrrole film. By polymerizing pyrrole in the presence of nitrate, pores complementary to the nitrate anion in size, shape, and charge distribution are formed in the resulting film. Electrochemical cells modified with this nitrate-imprinted polypyrrole film show a near-Nernstian response to nitrate, and excellent reproducibility. The integration of molecular recognition and electrochemical response in the nanoliter vials is demonstrated by the detection of as little as 0.36 ng nitrate in nanoliter-volume samples. The integration of tailored molecular recognition within nanoliter vials via established fabrication and imprinting protocols should result in a number of nanosensor devices with applications in BioMEMS and micro total analysis systems.

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Enzyme assay using ultra-low volume surface micromachined sensors

Cited by 5 publications

References 11 publications

Miniaturized Electroanalytical Sensor Systems in Micromachined Structures

Miniaturized Electroanalytical Sensor Systems in Micromachined Structures

Automated microfluidic platform of bead-based electrochemical immunosensor integrated with bioreactor for continual monitoring of cell secreted biomarkers

Microfabrication of screen-printed nanoliter vials with embedded surface-modified electrodes

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