Quartz Crystal Microbalance for Bioanalytical Applications

Janshoff, Andreas; Steinem, Claudia

doi:10.1002/1616-8984(200105)9:1<313::aid-seup313>3.0.co;2-e

Cited by 60 publications

(37 citation statements)

References 144 publications

(218 reference statements)

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“…We observed the above colorimetric change (data not shown here but in the Supporting Information file). The presence of scFv-cys on the QCM sensor surface was further verified by cyclic voltammetry (CV; Figure 5a) and electrochemical impedance (Figure 5b, Nyquist plots 6 ] in the solution and the electrode occurs either by tunneling through the monolayer (e.g., immobilized scFvcys) or at a defect in the monolayer. Therefore, the extent of surface passivation to electron transfer is a useful measure of defects in the monolayer.…”

Section: Characterization Of the Scfv Sam Layersmentioning

confidence: 82%

“…Therefore, the extent of surface passivation to electron transfer is a useful measure of defects in the monolayer. As shown in Figure 5a, CV of the bare gold surface gave ideal K 4 Fe(CN) 6 /K 3 Fe(CN) 6 reversible redox peaks. The faradic current was dramatically attenuated on the scFv-modified surface.…”

Section: Characterization Of the Scfv Sam Layersmentioning

confidence: 88%

“…Platinum wire and a saturated calomel electrode (SCE) were used as counter and reference electrodes, respectively. Cyclic voltammetry and electrochemical impedance spectroscopy were carried out in a solution of 0.1 M NaClO 4 containing 1 mM K 3 Fe(CN) 6 / K 4 Fe(CN) 6 using a PARSTAT 2263 advanced electrochemical system (Princeton Applied Research).…”

Section: Electrochemical Characterizationmentioning

confidence: 99%

“…The presence of scFv-cys on the QCM sensor surface was further verified by cyclic voltammetry (CV; Figure 5a) and electrochemical impedance (Figure 5b of these methods confirmed the existence of surface scFv self-assembled monolayers or the binding of surface-immobilized scFv to its corresponding antigen. A K 4 Fe(CN) 6 /K 3 Fe(CN) 6 solution was used as an electrochemical probe to test the integrity of the scFv-cys SAM on the gold surface. Electron transfer between a species [e.g., K 4 Fe(CN) 6 /K 3 Fe(CN) 6 ] in the solution and the electrode occurs either by tunneling through the monolayer (e.g., immobilized scFvcys) or at a defect in the monolayer.…”

Section: Characterization Of the Scfv Sam Layersmentioning

confidence: 99%

“…A K 4 Fe(CN) 6 /K 3 Fe(CN) 6 solution was used as an electrochemical probe to test the integrity of the scFv-cys SAM on the gold surface. Electron transfer between a species [e.g., K 4 Fe(CN) 6 /K 3 Fe(CN) 6 ] in the solution and the electrode occurs either by tunneling through the monolayer (e.g., immobilized scFvcys) or at a defect in the monolayer. Therefore, the extent of surface passivation to electron transfer is a useful measure of defects in the monolayer.…”

Section: Characterization Of the Scfv Sam Layersmentioning

confidence: 99%

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Single-Chain Fragment Variable Antibody Piezoimmunosensors

et al. 2005

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In this paper, we describe a novel nonlabeled biosensor with high diagnostic potential for rapid and sensitive detection of antigens in complex biological samples. The biosensor comprises a piezoimmunosensor (PZ) displaying a specially constructed recombinant antibody on its surface. The recombinant single-chain fragment variable (scFv) antibody contained a cysteine within the linker amino acid sequence used to join the scFv variable heavy and light chains. The presence of cysteine induced the scFv construct to self-assemble as a densely packed rigid monolayer on the gold surface of a quartz crystal microbalance. scFv molecules in this self-assembled mono-layer (SAM) exhibited a defined orientation and high areal densities, with scFv-modified microbalance surfaces displaying 35 times as many variable antigen-binding sites per square centimeter as surfaces modified with whole antibody. Experimental data show that the scFv SAM PZ is superior to Fab fragment, Fab fragment containing a free sulfhydryl group (i.e., Fab-SH), and whole antibody PZs regarding sensitivity and specificity. Because of their small uniform size (MW ≈ 27000) and the ease with which they can be modified using genetic engineering, scFv's have significant advantages over whole antibodies in microbalance biosensor systems. We demonstrate here that the use of scFv containing a cysteine within the scFv linker sequence (i.e., scFv-cys) for preparation of biosensor surfaces markedly increases the density of available antigen-binding sites, yielding a system that is highly selective, rapid, and capable of detecting low concentrations of antigens in complex samples.Biosensor systems that detect biological and chemical agents have important medical, environmental, public safety, and defense applications. An ideal biosensor would be sensitive, rapid, reliable, robust, and inexpensive. Piezoimmunosensors (PZs) are a type of biosensor utilizing antibodies and a quartz crystal microbalance (QCM) to detect minute changes in mass as antigens bind to the antibodies on the QCM surface. 1,2 Although their diagnostic potential is theoretically quite high, in practice, the usefulness of PZs has been limited by the fact that typical IgG antibodies can trap or nonspecifically bind irrelevant molecules, thus yielding false positive signals in assays. Additionally, there remains some skepticism concerning their applicability as biosensors due to the complexity of the physical properties of biofilms in a liquid that make it difficult to establish an explicit relationship between the added mass and a change in the resonant frequency. The QCM gives a direct response signal that characterizes a binding event between an antibody layer, immobilized on the surface of the QCM or other transducers, and the antigen to be detected. The mass change on the QCM surface is estimated using the Sauerbrey equation, 3 Δf = −2Δmnf 0 2 /[A(µ q ρ q ) 1/2 ], where n is the overtone number, µ q is the shear modulus of the quartz [2.947 × 10 11 g/(cm·s 2 )], ρ q is the density of the ...

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Section: Characterization Of the Scfv Sam Layersmentioning

confidence: 82%

Section: Characterization Of the Scfv Sam Layersmentioning

confidence: 88%

Section: Electrochemical Characterizationmentioning

confidence: 99%

Section: Characterization Of the Scfv Sam Layersmentioning

confidence: 99%

Section: Characterization Of the Scfv Sam Layersmentioning

confidence: 99%

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Single-Chain Fragment Variable Antibody Piezoimmunosensors

et al. 2005

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Quartz Crystal Microbalance for Bioanalytical Applications

Janshoff

Steinem

2003

ChemInform

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Strategies for Label-Free Optical Detection

Gauglitz

Proll

Biosensing for the 21st Century

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A large number of methods using direct detection with label-free systems are known. They compete with the well-introduced fluorescence-based methods. However, recent applications take advantage of label-free detection in protein-protein interactions, high-throughput screening, and high-content screening. These new applications require new strategies for biosensors. It becomes more and more obvious that neither the transduction principle nor the recognition elements for the biomolecular interaction process alone determine the quality of the biosensor. Accordingly, the biosensor system has to be considered as a whole. This chapter focuses on strategies to optimize the detection platform and the biomolecular recognition layer. It concentrates on direct detection methods, with special focus on optical transduction. Since even this restriction still leaves a large number of methods, only microrefractometric and microreflectometric methods using planar transducers have been selected for a detailed description and a listing of applications. However, since many review articles on the physical principles exist, the description is kept short. Other methods are just mentioned in brief and for comparison. The outlook and the applications demonstrate the future perspectives of direct optical detection in bioanalytics.

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Quartz Crystal Microbalance for Bioanalytical Applications

Cited by 60 publications

References 144 publications

Single-Chain Fragment Variable Antibody Piezoimmunosensors

Single-Chain Fragment Variable Antibody Piezoimmunosensors

Quartz Crystal Microbalance for Bioanalytical Applications

Strategies for Label-Free Optical Detection

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