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A simplified method for capillary embedment into microfluidic devices exemplified by sol-gel based preconcentration
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
2007 (English)In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 28, no 24, 4758-4764 p.Article in journal (Refereed) Published
Abstract [en]

We here describe an alternative method of embedding ftinctionalized capillaries into microdevices fabricated in PDMS. The capillaries have square-shaped outer dimensions and fit into elastic PDMS channel networks of similar dimensions. By modifying the capillary off-chip, the technique makes it possible to integrate a new chip function without risking contamination of already existing chemically patterned areas because of new reagent solutions. Leak-free insertion of these capillaries has earlier been reported, where a thin layer of uncured PDMS bonded the capillary to the microchannel and the lid structure. In this new approach, oxygen plasma is used to bond the square capillary to the PDMS, eliminating the risk of dogging the microsystem with uncured prepolymer. The new embedding technique was exemplified and evaluated by inserting a square capillary piece containing monolithic sol-gel for sample preconcentration application. The assembled microdevice was run with mass spectrometric detection, showing that peptides were preconcentrated without leakage from either the sol-gel itself or around the inserted capillary. Repeated preconcentration runs showed migration times better than 3% for all peptides. We believe that the presented microchip assembling technique greatly simplifies the insertion of functionalized capillary pieces, e.g., an initial preconcentrator to a PDMS device containing other downstream modules.

Place, publisher, year, edition, pages
2007. Vol. 28, no 24, 4758-4764 p.
Keyword [en]
microfluidics, PDMS, preconcentration, sol-gel
National Category
Chemical Sciences Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-95128DOI: 10.1002/elps.200700221ISI: 000252465600028PubMedID: 18008304OAI: oai:DiVA.org:uu-95128DiVA: diva2:169219
Available from: 2006-11-17 Created: 2006-11-17 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Microfluidics in Surface Modified PDMS: Towards Miniaturized Diagnostic Tools
Open this publication in new window or tab >>Microfluidics in Surface Modified PDMS: Towards Miniaturized Diagnostic Tools
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There is a strong trend in fabricating miniaturized total analytical systems, µTAS, for various biochemical and cell biology applications. These miniaturized systems could e.g. gain better separation performances, be faster, consume less expensive reagents and be used for studies that are difficult to access in the macro world. Disposable µTAS eliminate the risk of carry-over and can be fabricated to a low cost.

This work focused on the development of µTAS modules with the intentional use for miniaturized diagnostics. Modules for blood separation, desalting, enrichment, separation and ESI-MS detection were successfully fabricated. Surface coatings were additionally developed and evaluated for applications in µTAS with complex biological samples. The first heparin coating could be easily immobilized in a one-step-process, whereas the second heparin coating was aimed to form a hydrophilic surface that was able to draw blood or plasma samples into a microfluidic system by capillary forces.

The last mentioned heparin surface was further utilized when developing a chip-based sensor for performing CD4-count in human blood, an important marker to determine the stage of an HIV-infection.

All devices in this work were fabricated in PDMS, an elastomeric polymer with the advantage of rapid and less expensive prototyping of the microfabricated master. It was shown that PDMS could be considered as the material of choice for future commercial µTAS. The devices were intentionally produced using a low grade of fabrication complexity. It was however demonstrated that even with low complexity, it is possible to integrate several functional chip modules into a single microfluidic device.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 52 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 241
Keyword
Materials science, µTAS, micro total analysis system, PDMS, poly(dimethylsiloxane), microfluidics, heparin, blood filtration, on-chip, ESI-MS, desalting, QCM-D, biocompatible, CD4, capillary flow, lab-on-chip, microfabrication, enrichment, point-of-care, hydrophilic, oxidation, Materialvetenskap
Identifiers
urn:nbn:se:uu:diva-7270 (URN)91-554-6716-4 (ISBN)
Public defence
2006-12-08, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:30
Opponent
Supervisors
Available from: 2006-11-17 Created: 2006-11-17Bibliographically approved
2. Column Development in Capillary Electrophoresis and Electrochromatography for Bioanalytical Applications
Open this publication in new window or tab >>Column Development in Capillary Electrophoresis and Electrochromatography for Bioanalytical Applications
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Analysis of biological samples can be a difficult task. This thesis covers a broad aspect of the analytical areas of capillary electrophoresis (CE) and capillary electrochromatography (CEC) in combination with mass spectrometry (MS) that are of great importance for achieving fast, accurate and sensitive bioanalyses. A significantly time reduced and automated system for sample cleanup was developed to greatly simplify the pretreatment process of biological samples with a complex matrix. Desalting and preconcentration of species in urine was conducted and the limit of detection for the antidepressant escitalopram was lowered 10 times. This extraction devise was also successfully incorporated in a chip based platform for the possibility to be a part of multidimensional separation systems. The reduced risk of sample loss leads to improved detection limits, which are usually one the most challenging parts when working with bioanalyses.

In the area of separation, a monomer surface with tailored hydrophobicity was developed to achieve rapid, high efficient separations of complex mixtures. Within five minutes a tryptic digest of a protein could be separated and then identified by a Mascot search.

The applications addressed have been focused on medical conditions which are of highest interest for both physicians and patients. A high throughput analysis of the kynurenine metabolites with CE-MS offers a new method to rapidly examine samples from patients with neurological disorders.

A screening study of possible biomarkers for the two different types of appendicitis, gangraenous and phlegmonous was conducted. Indicative patterns were found for both pre and post surgery of the two types of inflammation as well as between them. The divergences were traced back to the MS peaks obtained in the CE- and CEC-MS setups as possible biomarkers for the two forms of appendicitis. A preliminary study of polycystic ovary syndrome also offered some valuable results for future biomarker identification.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 54 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 216
Keyword
Analytical chemistry, Capillary electrophoresis (CE), Capillary electrochromatography (CEC), Mass spectrometry (MS), Bioanalysis, Sample pretreatment, Sol-gel, Analytisk kemi
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-7124 (URN)91-554-6644-3 (ISBN)
Public defence
2006-10-06, B22, BMC, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2006-09-15 Created: 2006-09-15 Last updated: 2012-02-08Bibliographically approved

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