Interfacing Digital Microfluidics with Ambient Mass Spectrometry Using SU-8 as Dielectric Layer
Drug Research Program, Faculty of Pharmacy, Division of Pharmaceutical Chemistry and Technology, University of Helsinki, Viikinkaari 5E, 00790 Helsinki, Finland
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Micromachines 2018, 9(12), 649; https://doi.org/10.3390/mi9120649
Received: 20 November 2018
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Revised: 27 November 2018
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Accepted: 6 December 2018
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Published: 8 December 2018
(This article belongs to the Special Issue SU-8 for Microfluidics and Lab-on-a-chip)
This work describes the interfacing of electrowetting-on-dielectric based digital microfluidic (DMF) sample preparation devices with ambient mass spectrometry (MS) via desorption atmospheric pressure photoionization (DAPPI). The DMF droplet manipulation technique was adopted to facilitate drug distribution and metabolism assays in droplet scale, while ambient mass spectrometry (MS) was exploited for the analysis of dried samples directly on the surface of the DMF device. Although ambient MS is well-established for bio- and forensic analyses directly on surfaces, its interfacing with DMF is scarce and requires careful optimization of the surface-sensitive processes, such as sample precipitation and the subsequent desorption/ionization. These technical challenges were addressed and resolved in this study by making use of the high mechanical, thermal, and chemical stability of SU-8. In our assay design, SU-8 served as the dielectric layer for DMF as well as the substrate material for DAPPI-MS. The feasibility of SU-8 based DMF devices for DAPPI-MS was demonstrated in the analysis of selected pharmaceuticals following on-chip liquid-liquid extraction or an enzymatic dealkylation reaction. The lower limits of detection were in the range of 1–10 pmol per droplet (0.25–1.0 µg/mL) for all pharmaceuticals tested.
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Keywords:
digital microfluidics; SU-8; desorption/ionization; ambient mass spectrometry; liquid-liquid extraction; drug distribution; drug metabolism; cytochrome P450; microreactor; desorption atmospheric pressure photoionization
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MDPI and ACS Style
Sathyanarayanan, G.; Haapala, M.; Sikanen, T. Interfacing Digital Microfluidics with Ambient Mass Spectrometry Using SU-8 as Dielectric Layer. Micromachines 2018, 9, 649. https://doi.org/10.3390/mi9120649
AMA Style
Sathyanarayanan G, Haapala M, Sikanen T. Interfacing Digital Microfluidics with Ambient Mass Spectrometry Using SU-8 as Dielectric Layer. Micromachines. 2018; 9(12):649. https://doi.org/10.3390/mi9120649
Chicago/Turabian StyleSathyanarayanan, Gowtham, Markus Haapala, and Tiina Sikanen. 2018. "Interfacing Digital Microfluidics with Ambient Mass Spectrometry Using SU-8 as Dielectric Layer" Micromachines 9, no. 12: 649. https://doi.org/10.3390/mi9120649
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