Multi-channel PMMA microfluidic biosensor with integrated IDUAs for electrochemical detection
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A novel multi-channel poly(methyl methacrylate) (PMMA) microfluidic biosensor with interdigitated ultramicroelectrode arrays (IDUAs) for electrochemical detection was developed. The focus of the development was a simple fabrication procedure and the realization of a reliable large IDUA that can provide detection simultaneously to several microchannels. As proof of concept, five microchannels are positioned over a large single IDUA where the channels are parallel with the length of the electrode finger. The IDUAs were fabricated on the PMMA cover piece and bonded to a PMMA substrate containing the microfluidic channels using UV/ozone-assisted thermal bonding. Conditions of device fabrication were optimized realizing a rugged large IDUA within a bonded PMMA device. Gold adhesion to the PMMA, protective coatings, and pressure during bonding were optimized. Its electrochemical performance was studied using amperometric detection of potassium ferri and ferro hexacyanide. Cumulative signals within the same chip showed very good linearity over a range of 0–38 μM (R 2 = 0.98) and a limit of detection of 3.48 μM. The bonding of the device was optimized so that no cross talk between the channels was observed which otherwise would have resulted in unreliable electrochemical responses. The highly reproducible signals achieved were comparable to those obtained with separate single-channel devices. Subsequently, the multi-channel microfluidic chip was applied to a model bioanalytical detection strategy, i.e., the quantification of specific nucleic acid sequences using a sandwich approach. Here, probe-coated paramagnetic beads and probe-tagged liposomes entrapping ferri/ferro hexacyanide as the redox marker were used to bind to a single-stranded DNA sequence. Flow rates of the non-ionic detergent n-octyl-β-d-glucopyranoside for liposome lysis were optimized, and the detection of the target sequences was carried out coulometrically within 250 s and with a limit of detection of 12.5 μM. The robustness of the design and the reliability of the results obtained in comparison to previously published single-channel designs suggest that the multi-channel device offers an excellent opportunity for bioanalytical applications that require multianalyte detection and high-throughput assays.
KeywordsMicrofluidic chip Multi-channel Electrochemical biosensor Ultramicroelectrode PMMA
2-(4-Morpholino)-ethane sulfonic acid
Potassium phosphate buffer
Saline sodium citrate
The authors acknowledge financial support which enabled the research presented. This publication was developed under the auspices of the Cornell University Center for Life Science Enterprise, a New York State Center for Advanced Technology supported by New York State and industrial partners. Also, this publication was supported by a subcontract with Rheonix, Inc. and 1U01 A1082448-01 from the NIH. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of Rheonix nor those of the National Institutes of Health. This work was performed in part at the Cornell NanoScale Science and Technology Facility, a member of the National Nanotechnology Infrastructure Network, which is supported by the National Science Foundation (grant ECS-0335765). NW and WS thank the Thailand Research Fund through the Royal Golden Jubilee Ph.D. program (grant no. PHD/0319/2548) for financial support.