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The effect of drying on the homogeneity of DBS
KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
KTH, School of Electrical Engineering (EES), Micro and Nanosystems.ORCID iD: 0000-0001-8531-5607
KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
2015 (English)In: Bioanalysis, ISSN 1757-6180, E-ISSN 1757-6199, Vol. 7, no 16, 1977-1985 p.Article in journal (Refereed) Published
Abstract [en]

Background: Inhomogeneous sample distribution in DBS is a problem for accurate quantitative analysis of DBS, and has often been explained by chromatographic effects. Results: We present a model describing formation of inhomogeneous DBS during drying of the spot caused by higher evaporation rates of water at the edge as compared with the center. Color intensity analysis shows that the relative humidity and DBS card position affect the homogeneity of DBS. Conclusion: The so-called coffee-stain effect' explains the typical distribution pattern of analytes with higher concentrations measured along the edge of DBS as compared with the center. The driving mechanism and potential influencing factors should be considered when addressing the inhomogeneity of DBS in the future.

Place, publisher, year, edition, pages
2015. Vol. 7, no 16, 1977-1985 p.
National Category
Biological Sciences
URN: urn:nbn:se:kth:diva-173995DOI: 10.4155/bio.15.135ISI: 000360713600005PubMedID: 26327179ScopusID: 2-s2.0-84940752589OAI: diva2:858200
Stockholm County Council, 20130765EU, European Research Council, 267528

QC 20151001

Available from: 2015-10-01 Created: 2015-09-24 Last updated: 2016-01-22Bibliographically approved
In thesis
1. From Lab to Chip – and back: Polymer microfluidic systems for sample handling in point-of-care diagnostics
Open this publication in new window or tab >>From Lab to Chip – and back: Polymer microfluidic systems for sample handling in point-of-care diagnostics
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis contributes to the development of Lab-on-a-Chip systems that enables reliable, rapid medical diagnostics at the point-of-care. These contributions are focused on microfluidic Lab-on-a-Chip systems for sepsis diagnosis, autonomous sample-to-answer tests, and dried blood spot sampling.

Sepsis is a serious condition with high mortality and high costs for society and healthcare. To facilitate rapid and effective antibiotic treatment, improved sepsis diagnostics is needed. Diagnosis of sepsis requires the processing of relatively large blood volumes, creating a need for novel and effective techniques for the handling of large volume flows and pressures on chip. Components, materials, and manufacturing methods for pneumatically driven Lab-on-a-Chip systems have therefore been developed in this thesis. Microvalves, an essential component in many Lab-on-a-Chip systems have been the focus on several of the advances: a novel elastomeric material (Rubbery Off-Stoichiometric-Thiol-Ene-Epoxy) with low gas and liquid permeability; the first leak-tight vertical membrane microvalves, allowing large channel cross-sections for high volumetric flow throughput; and novel PDMS manufacturing methods enabling their realization. Additionally, two of the new components developed in this thesis focus on separation of bacteria from blood cells based on differences in particle size, and cell wall composition: inertial microfluidic removal of large particles in multiple parallel microchannels with low aspect ratio; and selective lysis of blood cells while keeping bacteria intact. How these components, materials and methods could be used together to achieve faster sepsis diagnostics is also discussed.

Lab-on-a-Chip tests can not only be used for sepsis, but have implications in many point-of-care tests. Disposable and completely autonomous sampleto- answer tests, like pregnancy tests, are capillary driven. Applying such tests in more demanding applications has traditionally been limited by poor material properties of the paper-based products used. A new porous material, called “Synthetic Microfluidic Paper”, has been developed in this thesis. The Synthetic Microfluidic Paper features well-defined geometries consisting of slanted interlocked micropillars. The material is transparent, has a large surface area, large porous fraction, and results in low variability in capillary flowrates. The fact that Synthetic Microfluidic Paper can be produced with multiple pore sizes in the same sheet enables novel concepts for self-aligned spotting of liquids and well-controlled positioning of functional microbeads.

Diagnostic testing can also be achieved by collecting the sample at the point-of-care while performing the analysis elsewhere. Easy collection of finger-prick blood in paper can be performed by a method called dried blood spots. This thesis investigates how the process of drying affects the homogeneity of dried blood spots, which can explain part of the variability that has been measured in the subsequent analysis. To reduce this variability, a microfluidic sampling chip has been developed in this thesis. The chip, which is capillary driven, autonomously collects a specific volume of plasma from a drop of blood, and dry-stores it in paper. After sampling, the chip can be mailed back to a central lab for analysis.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. xiii, 75 p.
TRITA-EE, ISSN 1653-5146 ; 2016:002
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
urn:nbn:se:kth:diva-180740 (URN)978-91-7595-844-6 (ISBN)
Public defence
2016-02-05, F3, Lindstedtsvägen 26, KTH, Stockholm, 09:00 (English)

QC 20160122

Available from: 2016-01-22 Created: 2016-01-22 Last updated: 2016-01-22Bibliographically approved

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