| 1. |
- Aastrup, Teodor
(författare)
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In situ investigations of the metal/atmophere interface
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents a new experimental setup for surfaceanalysis studies, incorporating chemical information frominfrared reflection absorption spectroscopy (IRAS) andquantitative information from quartz crystal microbalance(QCM). The integrated IRAS/QCM surface analysis system enablesin situstudies to be conducted of the metal/atmosphereinteraction on a sub-monolayer level. In combination withtopographical information from tapping mode atomic forcemicroscopy (TM-AFM), it was possible to follow the formation ofcorrosion products providing information about chemicalidentity, quantity and lateral distribution. The newlydeveloped system was used to study the influence of relativehumidity (RH) and levels of sulfur dioxide (SO2), ozone (O3)and nitrogen dioxide (NO2) down to concentrations of subparts-per-million (ppm), on the initial stages of atmosphericcorrosion of copper.Exposure to RH led to the formation of small grains ofcuprous oxide (Cu2O), with an average diameter of approximately40 nm. The grain nucleation rate increased with increasing RHdue to the increasing amount of physisorbed water on thesurface.Exposure to RH and SO2 led to the formation of coppersulfite (CuSO3•xH2O) species as well as reduction in therate of Cu2O formation. The formation of CuSO3•xH2Ooccurred through the dissolution and consecutive precipitationof surface-bound copper sulfite complexes.The roles of O3 and NO2 in the SO2-induced atmosphericcorrosion of copper was also investigated. O3 was found to havea two-fold effect, resulting in the oxidation of the coppersulfite species to copper sulfate and the enhancement of Cu2Oformation. NO2 promoted the oxidation of copper sulfitespecies, though less efficiently than O3, and reduced Cu2Oformation. In addition, copper nitrate formation wasobserved.IRAS was also used to investigate the interaction betweenSO2 and surfaces made of platinum and palladium. Sulfuric acidformation was observed on both metals, showing the importanceof the surface on the formation of the metal/atmospherereaction products.Keywords:Atmospheric corrosion, IR-spectroscopy, IRAS,QCM, AFM, SO2, O3, NO2, Cu.
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| 2. |
- Abellan-Flos, Marta, et al.
(författare)
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QCM sensing of multivalent interactions between lectins and well-defined glycosylated nanoplatforms
- 2019
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Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 139
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Tidskriftsartikel (refereegranskat)abstract
- Quartz crystal microbalance (QCM) methodology has been adopted to unravel important factors contributing to the "cluster glycoside effect" observed in carbohydrate-lectin interactions. Well-defined, glycosylated nanostructures of precise sizes, geometries and functionalization patterns were designed and synthesized, and applied to analysis of the interaction kinetics and thermodynamics with immobilized lectins. The nanostructures were based on Borromean rings, dodecaamine cages, and fullerenes, each of which carrying a defined number of carbohydrate ligands at precise locations. The synthesis of the Borromeates and dodecaamine cages was easily adjustable due to the modular assembly of the structures, resulting in variations in presentation mode. The binding properties of the glycosylated nanoplatforms were evaluated using flow-through QCM technology, as well as hemagglutination inhibition assays, and compared with dodecaglycosylated fullerenes and a monovalent reference. With the QCM setup, the association and dissociation rate constants and the associated equilibrium constants of the interactions could be estimated, and the results used to delineate the multivalency effects of the lectin-nanostructure interactions.
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| 3. |
- Anderson, Henrik, et al.
(författare)
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Quartz crystal microbalance sensor design : I. Experimental study of sensor response and performance
- 2007
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 123:1, s. 27-34
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates a novel quartz crystal microbalance (QCM) biosensor with a small and rectangular flow cell along with a correspondingly shaped crystal electrode. The sensor was evaluated with impedance analysis and compared to standard circular sensor crystals and sensor crystals with small circular electrodes. Comparative QCM measurements on an antibody–antigen interaction system were carried out on the rectangular and standard circular sensor systems. Impedance analysis and subsequent data extraction of the three different sensor crystals showed that the smaller sensors had significantly higher Q-values in air, but that liquid load on the electrodes lowered the Q-values radically for all crystals. Under liquid load, Q-values for the standard circular and the rectangular sensors were similar whereas the Q-value for the small circular sensor was 50% higher. QCM experiments showed that the QCM system with rectangular crystal electrodes was fully functional in a liquid environment. The rectangular system showed higher and more rapid responses for series of antibody injections, albeit at a higher noise level than the standard system. The study elucidates a significant potential for improvement of sensor performance by optimising the sensor electrode size and shape together with the flow cell geometry.
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| 4. |
- Duner, Gunnar, et al.
(författare)
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Signal Enhancement in Ligand-Receptor Interactions using Dynamic Polymers at Quartz Crystal Microbalance Surfaces
- 2016
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 141:13, s. 3993-3996
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Tidskriftsartikel (refereegranskat)abstract
- The potential for signal amplification on QCM sensors by use of in situ polymerized poly(acrylic acid) brushes has been studied. A biotin derivative was immobilized on these surfaces and the interaction with anti-biotin Fabs was evaluated. Interaction data was found to be specific for the studied binding events, and the level of non-specific binding was shown to be low. The surface was proven to be suitable for regeneration, of importance for biomolecular interaction analysis and repetitive immunoassays.For comparison, the same interaction system was tested using commercial sensor surfaces with carboxylated self-assembled monolayers. The poly(acrylic acid) surface showed a dramatic increase in signal response with more than ten times the signal of the carboxylated self-assembled monolayer surface. Thus, the present study shows that polymers can be successfully applied to amplify responses on QCM sensors, valuable for studies of interactions between receptors and low molecular weight compounds.
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| 5. |
- Dunér, Gunnar, et al.
(författare)
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Surface-confined photopolymerization of pH-responsive acrylamide/acrylate brushes on polymer thin films
- 2008
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 24:14, s. 7559-7564
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic acrylamide/acrylate polymeric brushes were synthesized at gold-plated quartz crystal surfaces. The crystals were initially coated with polystyrene-type thin films, derivatized with photolabile iniferter groups, and subsequently subjected to photoinitiated polymerization in acrylamide/acrylate monomer feeds. This surface-confined polymerization method enabled direct photocontrol over the polymerization, as followed by increased frequency responses of the crystal oscillations in a quartz crystal microbalance (QCM). The produced polymer layers were also found to be highly sensitive to external acid/base stimuli. Large oscillation frequency shifts were detected when the brushes were exposed to buffer solutions of different pH. The dynamic behavior of the resulting polymeric brushes was evaluated, and the extent of expansion and contraction of the films was monitored by the QCM setup in situ in real time. The resulting responses were rapid, and the effects were fully reversible. Low pH resulted in full contractions of the films, whereas higher pH yielded maximal expansion in order to minimize repulsion around the charged acrylate centers. The surfaces also proved to be very robust because the responsiveness was reproducible over many cycles of repeated expansion and contraction. Using ellipsometry, copolymer layers were estimated to be similar to 220 nm in a collapsed state and similar to 340 nm in the expanded state, effectively increasing the thickness of the film by 55%.
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| 6. |
- Durall, Claudia, et al.
(författare)
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Robust QCM-Based Sensing and Assay Formats in Commercialized Systems
- 2023
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Ingår i: Springer Series on Chemical Sensors and Biosensors. - : Springer.
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Bokkapitel (refereegranskat)abstract
- Attana’s Quartz Crystal Microbalance (QCM) analytical instruments have been developed to study in vitro biological interactions, mimicking the in vivo conditions. Attana’s superior technology for kinetic interaction studies allows to perform different assays, including biochemical, crude, sera, cell, and tissue-based, in vitro diagnostic and material chemistry assays, in real time and label free. With the focus to validate, select, and optimize drug candidates prior to clinical trials, Attana has helped pharmaceutical companies to increase their efficiency and profitability. In addition, the Attana instruments and services have been used in many other applications and research as described in this chapter.
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| 7. |
- Elmlund, Louise, et al.
(författare)
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Biotin selective polymer nano-films
- 2014
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Ingår i: Journal of Nanobiotechnology. - : Springer Science and Business Media LLC. - 1477-3155. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Background: The interaction between biotin and avidin is utilized in a wide range of assay and diagnostic systems. A robust material capable of binding biotin should offer scope in the development of reusable assay materials and biosensor recognition elements. Results: Biotin-selective thin (3-5 nm) films have been fabricated on hexadecanethiol self assembled monolayer (SAM) coated Au/quartz resonators. The films were prepared based upon a molecular imprinting strategy where N, N'-methylenebisacrylamide and 2-acrylamido-2-methylpropanesulfonic acid were copolymerized and grafted to the SAM-coated surface in the presence of biotin methyl ester using photoinitiation with physisorbed benzophenone. The biotinyl moiety selectivity of the resonators efficiently differentiated biotinylated peptidic or carbohydrate structures from their native counterparts. Conclusions: Molecularly imprinted ultra thin films can be used for the selective recognition of biotinylated structures in a quartz crystal microbalance sensing platform. These films are stable for periods of at least a month. This strategy should prove of interest for use in other sensing and assay systems.
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| 8. |
- Elmlund, Louise
(författare)
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QCM-based sensing using biological and biomimetic interfaces
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The objective of this thesis was to explore novel approaches for studying molecular recognition at biological and biomimetic surfaces using the quartz crystal microbalance (QCM) biosensor technique. The first two papers focused on the synthesis and study of biotin selective polymer films prepared using the molecularly imprinted polymer (MIP) technique. Control over polymer structure is of importance for sensor reproducibility and sensitivity, and was addressed in Paper I where a simple strategy for fabricating uniform thin biotin imprinted polymer films was employed. In Paper II the binding of biotin moieties to thin (3-5 nm) biomimetic polymer films was examined and consequences for sensor performance discussed. The potential for using QCM as a tool for assessing the binding of small peptides derived from phage display screening was presented Paper III. Here, screening of a phage peptide library against immobilized adenine resulted in candidate peptides that were studied using this technique. In Paper IV a whole cell-based biosensor was developed for studying interactions with cell membrane-incorporated targets. Epithelial cancer cells, SKOV3, were attached to QCM sensor chips and the binding of the monoclonal antibody HerceptinTM was studied. This approach demonstrates the potential of using QCM to study binding to membrane-incorporated targets, an alternative to assays based upon immobilized receptor structures lacking their natural context.
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| 9. |
- Elmlund, Louise, 1981-, et al.
(författare)
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Study of the Interaction of Trastuzumab and SKOV3 Epithelial Cancer Cells Using a Quartz Crystal Microbalance Sensor
- 2015
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Ingår i: Sensors. - : MDPI. - 1424-8220. ; 15:3, s. 5884-5894
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Tidskriftsartikel (refereegranskat)abstract
- Analytical methods founded upon whole cell-based assays are of importance in early stage drug development and in fundamental studies of biomolecular recognition. Here we have studied the binding of the monoclonal antibody trastuzumab to human epidermal growth factor receptor 2 (HER2) on human ovary adenocarcinoma epithelial cancer cells (SKOV3) using quartz crystal microbalance (QCM) technology. An optimized procedure for immobilizing the cells on the chip surface was established with respect to fixation procedure and seeding density. Trastuzumab binding to the cell decorated sensor surface was studied, revealing a mean dissociation constant, K-D, value of 7 +/- 1 nM (standard error of the mean). This study provides a new perspective on the affinity of the antibody-receptor complex presented a more natural context compared to purified receptors. These results demonstrate the potential for using whole cell-based QCM assay in drug development, the screening of HER2 selective antibody-based drug candidates, and for the study of biomolecular recognition. This real time, label free approach for studying interactions with target receptors present in their natural environment afforded sensitive and detailed kinetic information about the binding of the analyte to the target.
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| 10. |
- Forssén, Patrik, 1966-, et al.
(författare)
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Reliable Strategy for Analysis of Complex Biosensor Data
- 2018
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 90:8, s. 5366-5374
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Tidskriftsartikel (refereegranskat)abstract
- When using biosensors, analyte biomolecules of several different concentrations are percolated over a chip with immobilized ligand molecules that form complexes with analytes. However, in many cases of biological interest, e.g., in antibody interactions, complex formation steady-state is not reached. The data measured are so-called sensorgram, one for each analyte concentration, with total complex concentration vs time. Here we present a new four-step strategy for more reliable processing of this complex kinetic binding data and compare it with the standard global fitting procedure. In our strategy, we first calculate a dissociation graph to reveal if there are any heterogeneous interactions. Thereafter, a new numerical algorithm, AIDA, is used to get the number of different complex formation reactions for each analyte concentration level. This information is then used to estimate the corresponding complex formation rate constants by fitting to the measured sensorgram one by one. Finally, all estimated rate constants are plotted and clustered, where each cluster represents a complex formation. Synthetic and experimental data obtained from three different QCM biosensor experimental systems having fast (close to steady-state), moderate, and slow kinetics (far from steady-state) were evaluated using the four-step strategy and standard global fitting. The new strategy allowed us to more reliably estimate the number of different complex formations, especially for cases of complex and slow dissociation kinetics. Moreover, the new strategy proved to be more robust as it enables one to handle system drift, i.e., data from biosensor chips that deteriorate over time.
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