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  • 1.
    Anderson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Development of Electroacoustic Sensors for Biomolecular Interaction Analysis2009Doctoral 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.

  • 2.
    Anderson, Henrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jönsson, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Vestling, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Lindberg, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Aastrup, Teodor
    Quartz crystal microbalance sensor design: I. Experimental study of sensor response and performance2007In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 123, no 1, p. 27-34Article in journal (Refereed)
    Abstract [en]

    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.

  • 3.
    Anderson, Henrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Wingqvist, Gunilla
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Weissbach, Thomas
    Attana AB, Stockholm.
    Wallinder, Daniel
    Attana AB, Stockholm.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ingemarsson, Björn
    Attana AB, Stockholm.
    Systematic investigation of biomolecular interactions using combined frequency and motional resistance measurements2011In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 153, no 1, p. 135-144Article in journal (Refereed)
    Abstract [en]

    The resonance frequency of acoustic biosensors is today used as a label-free technique for detecting mass changes on sensor surfaces. In combination with an appropriate continuous flow system it has earlier been used for affinity and kinetic rate determination. Here, we assess the potential of a modified acoustic biosensor, monitoring also the real-time dissipation through the resistance of the sensor, to obtain additional kinetic information related to the structure and conformation of the molecules on the surface. Actual interaction studies, including an attempt to determine avidity, are presented along with thorough verification of the experimental setup utilizing true viscous load exposure together with protein and DNA immobilizations. True viscous loads show a linear relationship between resistance and frequency as expected. However, in the interaction studies between antibodies and proteins, as well as in the immobilization of DNA and proteins, higher surface concentrations of interacting molecules led to a decrease (i.e. deviation from the linear trend) in the differential resistance to frequency ratio. This is interpreted as increased surface rigidity at higher surface concentrations of immobilized molecules. Consequently, studies that aim at obtaining biological binding information, such as avidity, from real-time resistance and dissipation data should be conducted at low surface concentrations. In addition, the differential resistance to frequency relationship was found to be highly dependent on the rigidity of the preceding layer(s) of immobilized molecules. This dependence can be utilized to obtain a higher signal-to-noise ratio for resistance measurement by using low surface densities of immobilized interaction partners.

  • 4.
    Dunér, Gunnar
    et al.
    Department of Chemistry, KTH.
    Anderson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Myrskog, Annica
    IFM, Linköping University.
    Hedlund, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Aastrup, Teodor
    Attana AB.
    Ramström, Olof
    Department of Chemistry, KTH.
    Surface-Confined Photopolymerization of pH-Responsive Acrylamide/Acrylate Brushes on Polymer Thin Films2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 14, p. 7559-7564Article in journal (Refereed)
    Abstract [en]

    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 polymerizationmethod 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 highlysensitive to external acid/base stimuli. Large oscillation frequency shifts were detected when the brushes were exposedto buffer solutions of different pH. The dynamic behavior of the resulting polymeric brushes was evaluated, and theextent of expansion and contraction of the films was monitored by the QCM setup in situ in real time. The resultingresponses were rapid, and the effects were fully reversible. Low pH resulted in full contractions of the films, whereashigher pH yielded maximal expansion in order to minimize repulsion around the charged acrylate centers. The surfacesalso proved to be very robust because the responsiveness was reproducible over many cycles of repeated expansionand contraction. Using ellipsometry, copolymer layers were estimated to be ∼220 nm in a collapsed state and ∼340nm in the expanded state, effectively increasing the thickness of the film by 55%.

  • 5.
    Dunér, Gunnar
    et al.
    Department of Chemistry, KTH.
    Anderson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Attana AB.
    Pei, Zhichao
    Attana AB.
    Ingemarsson, Björn
    Attana AB.
    Aastrup, Teodor
    Attana AB.
    Ramström, Olof
    Department of Chemistry, KTH.
    Signal Enhancement in Ligand-Receptor Interactions using Dynamic Polymers at Quartz Crystal Microbalance Surfaces2016In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 141, no 13, p. 3993-3996Article in journal (Refereed)
    Abstract [en]

    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.

  • 6. Melles, E
    et al.
    Andersson, Henrik
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Wallinder, D
    Shafgat, J
    Bergman, T
    Aastrup, T
    Jörnvall, H
    Electroimmobilization of proinsulin C-peptide to a quartz crystal microbalance sensor chip for protein affinity purification2005In: Anal Biochem, Vol. 341, no 1, p. 89-93Article in journal (Refereed)
  • 7. Pei, Z.
    et al.
    Aastrup, T.
    Anderson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Lehn, J. M.
    Ramström, O.
    Quartz crystal microbalance bioaffinity sensor for rapid identification of glycosyldisulfide lectin inhibitors from a dynamic combinatorial library2006In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 22, no 1, p. 42-48Article in journal (Refereed)
    Abstract [en]

    Carbohydrate-lectin,interactions were probed with dynamic combinatorial libraries, using the plant lectin Concanavalin A as target species. The dynamic combinatorial libraries were generated from a pool of thiol components through reversible thiol-disulfide interchange, and screened using a simple and efficient method based on a quartz crystal microbalance setup. It was found that dimers based on 1-thio- and 6-thin-mannose analogues were the most active inhibitors. Furthermore, the results clearly show that the 6-thio-mannose possess unique characteristics compared to its oxygen-containing counterpart.

  • 8. Pei, Z
    et al.
    Aastrup, T
    Andersson, Henrik
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Ramström, O
    Redox-Responsive and Calcium-Dependent Switching of Glycosyldisulfide Interactions with Concanavalin A2005In: Bioorg Med Chem Lett, Vol. 15, no 11, p. 2707-2710Article in journal (Refereed)
  • 9. Pei, Z
    et al.
    Andersson, Henrik
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Aastrup, T
    Ramström, O
    Study of real-time lectin-carbohydrate interactions on the surface of a quartz crystal microbalance2005In: Biosensors & Bioelectronics, Vol. 21, p. 60-66Article in journal (Refereed)
  • 10.
    Pei, Zhichao
    et al.
    Attana AB.
    Anderson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Myrskog, Annica
    IFM, Linköping University.
    Dunèr, Gunnar
    Attana AB.
    Ingemarsson, Björn
    Attana AB.
    Aastrup, Teodor
    Attana AB.
    Optimizing immobilization on two-dimensional carboxyl surface: pH dependence of antibody orientation and antigen binding capacity2010In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 398, no 2, p. 161-168Article in journal (Refereed)
    Abstract [en]

    The performance of immunosensors is highly dependent on the amount of immobilized antibodies and their remaining antigen binding capacity. In this work, a method for immobilization of antibodies on a two dimensional carboxyl surface has been optimized using quartz crystal microbalance biosensors. We have shown that successful immobilization is highly dependent on surface pKa, antibody pI and pH of immobilization buffer. By use of EDC/sulfo-NHS activation reagents, the effect of the intrinsic surface pKa is avoided and immobilization also at very low pH has been made possible which is of importance for immobilization of acidic proteins. Generic immobilization conditions were demonstrated on a panel of antibodies which resulted in an average coefficient of variation of 4% for the immobilization of these antibodies.

    Antigen binding capacity as a function of immobilization pH was studied. In most cases the antigen binding capacity followed the immobilization response. However, the antigen to antibody binding ratio differed between the antibodies investigated, and for one of the antibodies, the antigen binding capacity was significantly lower than expected from immobilization in a certain pH range. Tests with anti-Fc and anti-Fab antibodies on different antibody surfaces showed that the orientation of the antibodies on the surface had a profound effect on the antigen binding capacity of the immobilized antibodies.

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