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Esterification of Self-Assembled Carboxylic-Acid-Terminated Thiol Monolayers in Acid Environment: A Time-Dependent Study
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
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2010 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 2, 821-829 p.Article in journal (Refereed) Published
Abstract [en]

This contribution reports on the influence of acids oil the quality of carboxylic-acid-terminated self-assembled monolayers (SAMs) on gold prepared from ethanolic solution of HS-(CH2)(15)-COOH and HS-(CH2)(11)CONH-(EG)(6)CH2-COOH. Null ellipsometry, contact angle goniometry, and infrared reflection-absorption spectroscopy are used to monitor the physical and chemical changes occurring within the SAMs upon acid post treatment; after incubation with acids present in the solution: and after incubation in aged acid containing solutions. The presence of acid has a positive effect oil the crystallinity, packing, and orientation Of the Supporting alkyl and ethylene glycol Subunits of the SAM. Our Studies also confirm previous findings stating that the carboxylic groups are rapidly converted into ethyl ester groups in the presence of hydrochloric acid in the incubation solution. It is also evident that the conversion occurs in the presence of the weaker acid, acetic acid, although at a much slower rate than that for hydrochloric acid. This is a new observation that has not been reported on before. The physical and chemical characterization is also complemented with a functional bioaffinity study. The functional evaluation revealed that the present model system was surprisingly insensitive to the degree of esterification of the carboxylic acid groups, but that 4 weeks of storage of the two investigated thiols in hydrochloric acid containing ethanol resulted in SAMs that were completely inactive with respect to immobilization and subsequent binding of the antigen. It was encouraging to note that the nonspecific binding of both antigen and antibody was extremely low oil the two SAMs, regardless of the relative amount of ethyl esters on the surface.

Place, publisher, year, edition, pages
2010. Vol. 26, no 2, 821-829 p.
National Category
Engineering and Technology Natural Sciences
URN: urn:nbn:se:uu:diva-137945DOI: 10.1021/la902255jISI: 000273403400029OAI: oai:DiVA.org:uu-137945DiVA: diva2:378992
Available from: 2010-12-16 Created: 2010-12-16 Last updated: 2014-11-25Bibliographically approved
In thesis
1. Development of Electroacoustic Sensors for Biomolecular Interaction Analysis
Open this publication in new window or tab >>Development of Electroacoustic Sensors for Biomolecular Interaction Analysis
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biomolecular interaction analysis to determine the kinetics and affinity between interacting partners is important for the fundamental understanding of biology, as well as for the development of new pharmaceutical substances. A quartz crystal microbalance instrument suitable for kinetics and affinity analyses of interaction events was developed. The functionality of the sensor system was demonstrated by development of an assay for relative affinity determination of lectin-carbohydrate interactions.

Sensor surfaces allowing for effective immobilization of one interacting partner is a key functionality of a biosensor. Here, three different surfaces and immobilization methods were studied. First, optimized preparation conditions for sensor surfaces based on carboxyl-terminated self assembled monolayers were developed and were demonstrated to provide highly functional biosensor surfaces with low non-specific binding. Second, a method allowing for immobilization of very acidic biomolecules based on the use of an electric field was developed and evaluated. The electric field made it possible to immobilize the highly acidic C-peptide on a carboxylated surface. Third, a method for antibody immobilization on a carboxyl surface was optimized and the influence of immobilization pH on the immobilization level and antigen binding capacity was thoroughly assessed. The method showed high reproducibility for a set of antibodies and allowed for antibody immobilization also at low pH.

Three broadly different strategies to increase the sensitivity of electroacoustic sensors were explored. A QCM sensor with small resonator electrodes and reduced flow cell dimensions was demonstrated to improve the mass transport rate to the sensor surface. The use of polymers on QCM sensor surfaces to enhance the sensor response was shown to increase the response of an antibody-antigen model system more than ten-fold. Moreover, the application of high frequency thin film bulk acoustic resonators for biosensing was evaluated with respect to sensing range from the surface. The linear detection range of the thin film resonator was determined to be more than sufficient for biosensor applications involving, for instance, antibody-antigen interactions. Finally, a setup for combined frequency and resistance measurements was developed and was found to provide time resolved data suitable for kinetics determination.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 68 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 658
biosensor, protein interactions, kinetics, affinity, QCM, quartz crystal microbalance, piezoelectric resonators, dissipation, motional resistance
National Category
Other Industrial Biotechnology Analytical Chemistry
Research subject
Engineering Science with specialization in Microsystems Technology
urn:nbn:se:uu:diva-107211 (URN)978-91-554-7572-7 (ISBN)
Public defence
2009-09-11, Å80101, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:30 (English)
Available from: 2009-08-20 Created: 2009-07-29 Last updated: 2014-11-25Bibliographically approved

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