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Biomimetic surfaces: Preparation, characterization and application
Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [sv]

I denna avhandling beskrivs tillverkning, karaktärisering och tillämpning av ett antal biomimetiska ytor. Biomimetik är att härma naturen och grundtanken är att titta på hur naturen löst liknande problemställningar. Två olika typer av modellsystem med inspiration från naturen har tagits fram för framtida tillämpningar inom bioanalys, biosensorer samt antifrysmaterial. Det ena typen av modellsystem innefattar fosforylerade ytor och det andra består av ytor som härmar antifrys(glyko)proteiner. Ytorna tillverkades av monolager av självorganiserande svavelorganiska molekyler och karaktäriserades före tillämpning med hjälp av ellipsometri, IR-spektroskopi, kontaktvinkelmätning och röntgenfotoelektronspektroskopi.

Modellsystemen för att studera vattenfrysning på ytor inspirerades av antifrys(glyko)proteiner som bl.a. kan hittas i polarfiskar. Två modellsystem utvecklades och studerades med avseende på frysning av kondenserat vatten. Det ena designades att härma den aktiva domänen hos ett antifrysglykoproteiner (AFGP) och det andra härmade typ I antifrysproteiner (AFP I). Frysstudierna visade på signifi-kanta skillnader för AFGP-modellen jämfört med ett (OH/CH3) referenssystem med jämförbar vätbarhet, men inte för AFP Imodellen. Vattnet frös vid högre temperatur för AFGPmodellen.

Modellsystemen med fosforylerade ytor inspirerades av fosforylering och biomineralisering. Två system utvecklades, ett med långa och ett med korta alkylkedjor på aminosyraanalogerna, både med och utan fosfatgrupp. En ny metod användes med skyddsgrupper på fosfaterna hos de långa analogerna innan bildandet av monolager. Skyddsgrupperna togs bort efter bildandet av monolager. Dessa monolager undersöktes också med elektrokemiska metoder och signifikant högre kapacitans observerades för de fosforylerade monolageren jämfört med de icke fosforylerade.

Abstract [en]

This thesis describes the preparation, characterization and application of a few biomimetic surfaces. Biomimetics is a modern development of the ancient Greek concept of mimesis, i.e. man-made imitation of nature. The emphasis has been on the preparation and characterization of two types of model systems with properties inspired by nature with future applications in bioanalysis, biosensors and antifreeze materials. One type of model system involves phosphorylated surfaces; the other consists of surfaces mimicking antifreeze (glyco)proteins. The surfaces were made by chemisorbing organosulfur substances to a gold surface into monomolecular layers, so called self-assembled monolayers (SAMs). The physicochemical properties of the SAMs were thoroughly characterized with null ellipsometry, contact angle goniometry, x-ray photoelectron spectroscopy and infrared spectroscopy prior to application.

The work on antifreeze surfaces was inspired by the structural properties of antifreeze (glyco)proteins, which can be found in polar fish. Two model systems were developed and studied with respect to ice nucleation of condensed water layers. One was designed to mimic the active domain of antifreeze glycoproteins (AFGP) and the other mimicked type I antifreeze proteins (AFP I). Subsequent ice nucleation studies showed a significant difference between the AFGP model and a (OH/CH3) reference system displaying identical wetting properties, whereas the AFP I model was indistinguishable from the reference system.

The model systems with phosphorylated surfaces were inspired from phosphorylations and biomineralization. Two systems were developed, short- and long-chained amino acid analogues, with and without a phosphate group. A novel approach with protected groups before attachment to gold were developed for the long-chained analogues. The protective groups could be removed successfully after assembly. The long-chained SAMs were evaluated with electrochemical methods and significantly higher capacitance values were observed for the phosphorylated SAMs compared to the non-phosphorylated.

Place, publisher, year, edition, pages
Institutionen för fysik, kemi och biologi , 2007. , 84 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1069
Keyword [en]
Self-assembled monolayers, biomimetic surfaces, phosphates, antifreeze, surface spectroscopy
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:liu:diva-8492ISBN: 978-91-85715-99-2 (print)OAI: oai:DiVA.org:liu-8492DiVA: diva2:23268
Public defence
2007-03-30, Planck, Fysikhuset, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2009-04-23
List of papers
1. A new route to the formation of biomimetic phosphate assemblies on gold: Synthesis and characterization
Open this publication in new window or tab >>A new route to the formation of biomimetic phosphate assemblies on gold: Synthesis and characterization
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2006 (English)In: Journal of Colloid and Interface Science, ISSN 1095-7103, Vol. 295, no 1, 41-49 p.Article in journal (Refereed) Published
Abstract [en]

A biomimetic model system based on long-chain alkanethiols tailored with serine, threonine and tyrosine side-chain groups is created as a platform for the study of phosphorylated amino acids. The phosphorylated analogues are synthesized with protective tert-butyl groups that after assembly on thin polycrystalline gold films are removed in an acidic deprotection solution to form the corresponding phosphate self-assembled monolayers (SAMs). The SAMs are thoroughly characterized with null ellipsometry, contact angle goniometry, infrared reflection–absorption spectroscopy and X-ray photoelectron spectroscopy. The assembly and the subsequent deprotection process are optimized with respect to molecular orientation and chain conformation by varying the incubation time and the exposure time to the deprotection solution. The high quality of the generated SAMs suggests that the present assembly/deprotection approach is an attractive alternative when traditional synthetic routes become demanding because of solubility problems.

Keyword
SAM; Thiols; Gold; Phosphorylated amino acids; Surface deprotection scheme
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-14334 (URN)10.1016/j.jcis.2005.08.026 (DOI)
Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2010-09-06
2. Electrochemical Evaluation of the Interfacial Capacitance upon Phosphorylation of Amino Acid Analogue Molecular Films
Open this publication in new window or tab >>Electrochemical Evaluation of the Interfacial Capacitance upon Phosphorylation of Amino Acid Analogue Molecular Films
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2001 (English)In: Analytical Chemistry, ISSN 0003-2700, Vol. 73, no 18, 4463-4468 p.Article in journal (Refereed) Published
Abstract [en]

An approach based on electrochemistry to differentiate between phosphorylated and nonphosphorylated amino acid analogues adsorbed on gold is presented. Analogues of serine, threonine, and tyrosine, containing thiohexadecyl headgroups, were synthesized and assembled on gold, and the surface capacitance was evaluated using electrochemical impedance spectroscopy. A procedure for deprotection of tert-butyl phosphate protecting groups, on the monolayer, is also described. Characterizations of the assembled analogues by cyclic voltammetry, infrared spectroscopy, and ellipsometry are used to confirm the insulating properties of the monolayers and the outcome of surface modifications. The results from cyclic voltammetry show good insulating properties for the monolayers even after phosphate deprotection. The infrared measurements reveal well-ordered monolayers, and the thickness from ellipsometry is in good agreement with expectations from molecular modeling. The impedance experiments show a capacitance increase up to 0.6 μF/cm2 as phosphate groups are introduced. The results in this study indicate the possibility of using a surface chemical and impedance spectroscopy approach to detect the kinase/phosphatase activity and kinetics involved in phosphorylation reactions.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-14335 (URN)10.1021/ac010487+ (DOI)
Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2009-05-11
3. Synthesis and Monolayer Characterization of Phosphorylated Amino Acid Analogs
Open this publication in new window or tab >>Synthesis and Monolayer Characterization of Phosphorylated Amino Acid Analogs
2002 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 254, no 2, 322-330 p.Article in journal (Refereed) Published
Abstract [en]

The synthesis of a series of thiols containing phosphorylated and non-phosphorylated serine, threonine, and tyrosine amino acid residues is described. The synthesized molecules, based on 3-mercaptopropionic acid, were assembled onto gold and subsequently characterized using infrared reflection-absorption spectroscopy, ellipsometry, X-ray photoelectron spectroscopy, and contact angle goniometry. The ellipsometric analysis indicates that they form densely packed and well-oriented monolayers on gold, with thicknesses that are in good agreement with estimated values from space-filling models. The bulky and space-demanding phosphorylated threonine analog was, however, found to be an exception. The increase in layer thickness when adding a phosphate group to the threonine is only 35% of that observed for the two other analogs. A detailed infrared examination of the influence of cation coordination to the phosphorylated serine analog using calcium and magnesium reveals structural similarities to those of the inorganic phosphate compound calcium hydroxy apatite. We furthermore discuss the application of these monolayers as soft templates for biomineralization.

Place, publisher, year, edition, pages
Maryland Heights, MO, United States: Academic Press, 2002
Keyword
SAM; phosphorylated amino acid; phosphate layer; alkanethiols; gold; counterion influence
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-14336 (URN)10.1006/jcis.2002.8576 (DOI)000178935400016 ()
Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2017-12-13Bibliographically approved
4. Mimicking the properties of antifreeze glycoproteins: synthesis and characterization of a model system for ice nucleation and antifreeze studies
Open this publication in new window or tab >>Mimicking the properties of antifreeze glycoproteins: synthesis and characterization of a model system for ice nucleation and antifreeze studies
2005 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 33, 15849-15859 p.Article in journal (Refereed) Published
Abstract [en]

Synthesis of β-D-Gal-(1 → 3)-β-D-GalNAc coupled to HOC2H4NHCOC15H30SH is described. This compound was coadsorbed at various proportions with C2H5OC2H4NHCOC15H30SH to form statistically mixed self-assembled monolayers (SAMs) on gold in an attempt to mimic the properties of the active domain in antifreeze glycoproteins (AFGPs). The monolayers were characterized by null ellipsometry, contact angle goniometry, X-ray photoelectron spectroscopy, and infrared reflection−absorption spectroscopy. The disaccharide compound adsorbed preferentially, and SAMs prepared at a solution molar ratio >0.3 displayed total wetting. The mixed SAMs showed well-organized alkyl chains up to a disaccharide surface fraction of 0.8. The amount of gauche conformers in the alkyls increased rapidly above this point, and the monolayers became disordered and less densely packed. Furthermore, the generated mixed SAMs were subjected to water vapor at constant relative humidity and the subsequent ice crystallization on a cooled substrate was monitored via an optical microscope. Interestingly, rapid crystallization occurred within a narrow range of temperatures on mixed SAMs with a high disaccharide content, surface fraction >0.3. The reported crystallization temperatures and the ice layer topography were compared with results obtained for a much simpler reference system composed of −OH/−CH3 terminated n-alkanethiols in order to account for changes in topography of the water/ice layer with surface energy. Although preliminary, the obtained results can be useful in the search for the molecular mechanism behind the antifreeze activity of AFGPs.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-14337 (URN)10.1021/jp050752l (DOI)
Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2017-12-13
5. Biomimetic Surfaces for Ice Interaction Studies
Open this publication in new window or tab >>Biomimetic Surfaces for Ice Interaction Studies
Manuscript (Other academic)
Identifiers
urn:nbn:se:liu:diva-14338 (URN)
Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2010-01-13

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