Quartz Crystal Microbalance Surface Research Articles

A Quartz Crystal Microbalance-Based Sensor System Coated with Functional Polymers for SO<SUB>2</SUB> and NO<SUB>2</SUB> Detection

In this work, a quartz crystal microbalance (QCM)-based adsorption sensor system with high sensitivity, selectivity, and reproducibility is designed and fabricated. The functional polymers such as polypyrrole, poly(3,4-ethylenedioxythiophene) (PEDOT), and polystyrene are coated on 8 MHz AT-cut quartz crystal surfaces as sensing materials for SO2 and NO2. All sensing materials on the QCM surface are characterized experimentally by SEM and AFM. The frequency shifts of the QCM by adsorption and desorption of gases are measured and analyzed to assess the practical applicability of the sensor system. The overall results show that the QCM coated with polypyrrole is highly selective for SO2 gas and that coated with PEDOT is for NO2. It is proven that the QCM-based adsorption sensor system is possible for monitoring SO2 and NO2 gases in the mixture of ppm level.

Diagnosis and genotyping of Plasmodium falciparum by a DNA biosensor based on quartz crystal microbalance (QCM)

Malaria infection with Plasmodium falciparum is an important basic health problem in the tropical and sub-tropical countries. The standard diagnostic method is blood film examination to visualize parasite morphology. However, in cases of low parasitemia or mixed infection with very low cryptic species, microscopy is not sensitive enough. Therefore, molecular techniques have been widely employed. A label-free DNA biosensor based on quartz crystal microbalance (QCM) to diagnose and genotype P. falciparum was developed. Avidin-biotin interaction was used to coat the specific biotinylated probe on the gold surface of QCM. The gene encoding merozoite surface protein 2 (msp2) was amplified and the PCR products were then cut with restriction enzyme (MwoI). Enzymatic cutting made the PCR products suitable for QCM development. Hybridization between probe and enzymatic cutting DNA fragments resulted in frequency changes of the QCM. The newly developed QCM was tested for its diagnosis ability using both malaria laboratory strains and clinical isolates. The biosensor was sensitive at the sub-nanogram level, specific for only P. falciparum detection, no cross-reaction with P. vivax, and stable at room temperature for up to 6 months. Selection of msp2 as a target gene and a geno-typing marker made the QCM potentially useful for falciparum diagnosis simultaneously with genotyping. Potency was tested by genotyping two allelic families of P. falciparum, FC27 and IC1, using malaria laboratory strains, K1 and 3D7, respectively. The dual function QCM was successfully developed with high sensitivity and specificity, and was cost-effective, stable and field adaptable.

Pyrene-Modified Quartz Crystal Microbalance for the Detection of Polynitroaromatic Compounds

The synthesis of a dithiol-functionalized pyrene derivative is reported, together with studies of interactions between this receptor (and other related pyrenes) and nitroaromatic compounds (NACs), in both solution and in the solid state. Spectroscopic analysis in solution and X-ray crystallographic analysis of cocrystals of pyrene and NACs in the solid state indicate that supramolecular interactions lead to the formation of defined π-π stacked complexes. The dithiol-functionalized pyrene derivative can be used to modify the surface of a gold quartz crystal microbalance (QCM) to create a unique π-electron rich surface, which is able to interact with electron poor aromatic compounds. For example, exposure of the modified QCM surface to the nitroaromatic compound 2,4-dinitrotoluene (DNT) in solution results in a reduction in the resonant frequency of the QCM as a result of supramolecular interactions between the electron-rich pyrenyl surface layer and the electron-poor DNT molecules. These results suggest the potential use of such modified QCM surfaces for the detection of explosive NACs.

Method for detection of Hg2+ based on the specific thymine–Hg2+–thymine interaction in the DNA hybridization on the surface of quartz crystal microbalance

A simple and sensitive method was developed for the detection of mercury ions with quartz crystal microbalance (QCM), based on the specific thymine-Hg(2+)-thymine (T-Hg(2+)-T) interaction and gold nanoparticle-mediated signal amplification. To enhance the sensitivity of detection a sandwich hybridization approach was adopted in this work. The QCM gold surface was modified with the probe SH-oligonucleotides (Oligo-1) and 6-Mercapto-1-hexanol to form an active surface for the hybridization of a longer ss-DNA (Oligo-2), and then Oligo-3 hybridazated with an excess and matching part of Oligo-2. In all oligonucleotides, there existed T bases. In the presence of Hg(2+) ions, special T-Hg(2+)-T reaction greatly enhanced the hybridization of oligonucleotides and detection sensitivity. The gold nanoparticle (Au NPs) amplifier method further increased the sensitivity of detection. A detection sensitivity of 5nM Hg(2+) was obtained in the QCM system, whereas other coexisting metal ions (such as Ni(2+), Mg(2+), Co(2+), Cr(3+), Pb(2+), Cd(2+), Mn(2+), Ba(2+)) had no significant interference. This method reveals a new approach for the manufacture of a kind of simple and low cost sensors for the Hg(2+) detection.

Surface molecular imprints of WGA lectin as artificial receptors for mass-sensitive binding studies

Wheat germ agglutinin (WGA) lectin is a model compound for the interaction between viruses and cells during infection events and thus an interesting analyte for mass-sensitive sensing to study these interaction phenomena. Scanning tunneling microscopy studies reveal that surface molecular imprinting leads to cavities having the dimensions of WGA dimers. These reincorporate WGA from phosphate-buffered saline between 1 and 160 μg/ml. Whereas the quartz crystal microbalance (QCM) frequency for molecularly imprinted polymer (MIP)-coated electrodes decreases, indicating uptake of the analyte, their nonimprinted counterparts yield positive, concentration-dependent frequency shifts characteristic for slip of the analyte on the QCM surface. The MIPs achieve selectivity factors towards bovine serum albumin of roughly 4 at higher protein concentrations. Brunauer-Emmett-Teller analysis reveals that binding is favored by 29 kJ/mol until the adsorption of up to ten monolayers on the MIP, whereas above this range the value is lower. Together with the binding behavior of MIP and nonimprinted polymers, this indicates that the MIP acts as a nucleus for multilayer deposition onto the surface.

Sensitive and selective DNA detection based on the combination of hairpin-type probe with endonuclease/GNP signal amplification using quartz-crystal-microbalance transduction

In order to develop a highly sensitive and selective piezoelectric transducer for the detection of DNA, the bio-recognizing probe is for the first time designed by introducing a hairpin structure and a recognition site for EcoRI into an oligonucleotide sequence and signal amplifiers are prepared by modifying gold nanoparticles (GNPs) with biomolecules, deepening the application and understanding of biomaterials. The piezoelectric transducer is prepared by immobilizing designed hairpin recognition probe onto the quartz-crystal-microbalance (QCM). In the absence of target DNA, the hairpin probe is removed from the QCM surface after exposure to endonuclease, inhibiting the subsequent signaling reaction. In contrast, introduction of target DNA can open the hairpin probe due to the probe/target hybridization, dissociating the cleavable double-stranded portion. In this case, even if being treated with endonuclease, the integrated hairpin probe is maintained. Subsequent introduction of GNPs modified with detection probes that can hybridize to the terminal sequence of hairpin probe results in a many-folds increase of the frequency response. Utilizing the proposed transduction scheme, the reliable target DNA detection can be accomplished. The detection limit of 2 pM and dynamic response range for target DNA from 2 to 300 pM are obtained. Furthermore, single-base mismatched DNAs can be easily identified. The developed proof-of-principle of a novel piezoelectric transduction scheme is expected to establish a potential platform for the disease-associated mutation analysis and DNA hybridization detection in biotechnology and medical diagnostics.

Direct introduction of a hydrazide group into a quartz crystal microbalance surface with dodecanoic hydrazide embedded in a hybrid bilayer membrane

Hydrazide group has a potential of immobilizing an antibody on a sensor surface in a way that ensures an optimal orientation and efficiency of the antibody. However, a multi-step chemical process, required for the preparation of a hydrazide group, is a barrier to its extensive application. This paper describes a new method to introduce a hydrazide group to a sensor surface by a one-step process using dodecanoic hydrazide. The method is based on an ability of the dodecanoic hydrazide to be incorporated into a hybrid bilayer membrane (HBM) layer, thereby presenting its hydrazide group to the surface. Liposome containing dodecanoic hydrazide was added to a hydrophobic self-assembled monolayer surface of a quartz crystal microbalance for the formation of a HBM. Then, the hydrazide group, presented in the surface of the HBM layer, was utilized for the oriented immobilization of an antibody via its carbohydrate moiety which was partially oxidized prior to the conjugation reaction. Activity and stable status of the incorporated dodecanoic hydrazide was revealed by the efficiency and reproducibility of the resulting immunosensor chip.

Quartz crystal microbalance as a sensing active element for rupture scanning within frequency band

A new method based on the use of quartz crystal microbalance (QCM) as an active sensing element is developed, optimized and tested in a model system to measure the rupture force and deduce size distribution of nanoparticles. As suggested by model predictions, the QCM is shaped as a strip. The ratio of rupture signals at the second and the third harmonics versus the geometric position of a body on QCM surface is investigated theoretically. Recommendations concerning the use of the method for measuring the nanoparticle size distribution are presented. It is shown experimentally for an ensemble of test particles with a characteristic size within 20–30 nm that the proposed method allows one to determine particle size distribution. On the basis of the position and value of the measured rupture signal, a histogram of particle size distribution and percentage of each size fraction were determined. The main merits of the bond-rupture method are its rapid response, simplicity and the ability to discriminate between specific and non-specific interactions. The method is highly sensitive with respect to mass (the sensitivity is generally dependent on the chemical nature of receptor and analyte and may reach 8 × 10 −14 g mm −2) and applicable to measuring rupture forces either for weak bonds, for example hydrogen bonds, or for strong covalent bonds (10 −11–10 −9 N). This procedure may become a good alternative for the existing methods, such as AFM or optical methods of determining biological objects, and win a broad range of applications both in laboratory research and in biosensing for various purposes. Possible applications include medicine, diagnostics, environmental or agricultural monitoring.

Surface imprinted macroporous film for high performance protein recognition in combination with quartz crystal microbalance

Macroporous protein imprinted films (porous-MIP) have been fabricated on the surface of quartz crystal microbalance (QCM) using methyl methacrylate (MMA) as main monomer and trimethylolpropane trimethacrylate (TRIM) as a cross-linker. Macropores were generated by employing calcium carbonate nanoparticles as porogen. The imprinted special surface area and the quantity of the imprinted sites were increased by the formation of macropores on the films. Since the macropores were interconnected in structure, the mass transport and accessibility of protein to the active sites through the material were not affected. In comparison with the nonporous imprinted (nonporous-MIP) films, the porous-MIP films exhibited better affinity and selectivity to template, the binding capacity and mass sensitivity of the biosensor were enhanced. The rigid skeleton structure made the films durable in the recycled tests. The strategy proposed here is generally applicable for constructing high performance biosensor devices.

Polystyrene spheres coated with gold nanoparticles for detection of DNA

A novel method has been developed here utilizing gold-modified polystyrene spheres (PS@Au) as carriers for the investigation of DNA hybridization. The immobilization ability of DNA probes on the PS@Au was investigated by a quartz crystal microbalance (QCM). More gold nanoparticles (AuNPs) were conjugated to the QCM surface in the form of PS@Au as compared with the AuNPs alone. The influence of PS, AuNPs population and size on the DNA probe fixation, and hybridization has been investigated. The results show that more AuNPs were achievable onto the QCM surface and could greatly increase the immobilization amount further hybridization amount of DNA. There was an optimal surface curvature for the probe DNA absorption. The curvature about 12 nm was more suited to the adsorption of probe DNA which could lead to the detection limit further down to 10(-12) M. These results demonstrate that the introduction of PS@Au, with polystyrene spheres as the medium between the QCM surface and the AuNPs, could achieve modified QCM surfaces and increase its detection ability for a better DNA assay and a novel platform for the fabrication of DNA sensors.

Applying the Quartz Crystal Microbalance Technique to Detect the Epithelial Cell Tight Junction Integrality of Caco-2 Cells

This paper describes a method that utilizes the quartz crystal microbalance (QCM) technique to measure the tight junction of the Caco-2 cell. The Caco-2 cells are placed on the QCM surface for cell growth and tight junction measurements. We found that the QCM resonance frequency changes less when a better tight cell junction is formed. The quantity of QCM frequency change is less than 100 Hz as the tight junction cell integrality is completed up to 15 days. The QCM and traditional detection system transepithelial electrical resistance were similar as the cell growth affects the two systems over time.

A microfluidic system with surface modified piezoelectric sensor for trapping and detection of cancer cells

We present a microfluidic system with integrated surface modified piezoelectric sensor for trapping and label-free detection of target samples that can be used for cancer diagnosis. To introduce active magnetic force control to the piezoelectric sensor and obtain a fast regenerative system, a nickel pillar array was patterned onto the surface of quartz crystal microbalance. The functionalities of the system were tested by trapping suspended superparamagnetic micro-beads (SPMBs) in fluids onto the nickel pillar array with a manually controlled magnetic field and by detecting the accumulated mass from the resonant characterization of the piezoelectric sensor at the same time. The results showed the efficiency of the system in manipulating the SPMBs and the sensitivity of the device was of 5 Hz mm 2/ng. With surface-functionalized SPMBs, the microfluidic system succeeded in trapping and detecting target cancer cells. A549 cancer cells were captured on the nickel pillar array with WGA protein-functionalized SPMBs and detected with a total mass of 90.6 ng. With its simplicity, low production cost and high efficiency, this new device configuration would be useful for the future point-of-care clinical applications.

Studying mechanical microcontacts of fine particles with the quartz crystal microbalance

To study micromechanical adhesion, glass particles were deposited on a quartz crystal microbalance (QCM). Beforehand, a 160 nm-thick film of polystyrene (PS) had been spin-coated on the gold surface of the QCM. Shifts in the resonance frequency were monitored versus the oscillation amplitude. The aim was to analyse how QCM experiments reflect the state of adhesion. During oscillation, the motion of the particles and the induced frequency shift of the QCM are governed by a balance between inertial and contact forces. In order to vary the relative strength of the two, the diameter of the particles was varied between 5 and 20 μm. The adherence of the particles could be increased by annealing the PS film at 150 °C. Annealing led to the formation of a PS meniscus. For a semi-quantitative interpretation we have to take into account that the particles show a distribution of coupling constants. The vibration of the QCM changes the micromechanical contact between QCM surface and particles. There is an instantaneous and a long-term effect. Instantaneously, the oscillation induces partial slip. Under an oscillating load, part of the contact ruptures, which decreases the effective stiffness of the contact. In addition, there are long-term memory effects. The vibration of the QCM can lead to a consolidation and an increased coupling. However, it can also break the contact and even lead to detachment. Particles deform the PS surface and induce damage due to inertial forces.

Cardiac troponin T detection using polymers coated quartz crystal microbalance as a cost-effective immunosensor

Cardiac troponin T (cTnT) detection has been the focus of increased interest due to its role in myocardial infarction diagnosis. In this study, we report a relatively low coat technique to detect cTnT using a quartz crystal microbalance (QCM) sensor. A sensitive detection is achieved by introducing a QCM surface with a carboxylic polyvinyl chloride immobilization layer. The surface morphologies of this polymer film under varied deposition thickness have been investigated by field emission scanning electron microscopy and atomic force microscopy. A cTnT detection result from a modified QCM surface can be obtained within a short response time by a direct detection of the immunoreaction and a direct conversion of mass accumulation into a frequency shift, representing a measurable electrical signal. The relationship between the cTnT concentration and the response current from a QCM sensor shows detectability at the concentration of cTnT as low as 5 ng/ml.

Quartz crystal microbalance with β-cyclodextrin/TiO2 composite films coupled with chemometrics for the simultaneous determination of urinary 1- and 2-naphthol

Abstract A novel sensitive method was presented for the simultaneous determination of 1-naphthol (1-NAP) and 2-naphthol (2-NAP) in human urine samples. This method is based on the combination of the high sensitivity of quartz crystal microbalance (QCM) and excellent predictive ability of chemometrics. Nanocrystalline TiO 2 films were used as substrates for immobilizing β-cyclodextrin (β-CD) onto the QCM surface. The sensing layer consisting of β-CD and nanocrystalline TiO 2 particles was characterized by X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TG) and IR spectroscopy. In the Britton–Robinson (B–R) buffer solution of pH 6.37, frequency shift (Δ F ) of the QCM was directly proportional to the concentration of 1-NAP and 2-NAP as 1.0 × 10 −6 to 1.3 × 10 −4 mol L −1 , and 1.0 × 10 −6 to 1.2 × 10 −4 mol L −1 , respectively. The correlation coefficients were 0.993 for 1-NAP, and 0.990 for 2-NAP. The limits of detection (LOD) were found to be 8.362 × 10 −7 mol L −1 for 1-NAP and 2.146 × 10 −7 mol L −1 for 2-NAP. The proposed method has been successfully applied for detecting 1-NAP and 2-NAP in human urine with a satisfactory result. The QCM with β-CD/TiO 2 composite films coupled with chemometrics can lead to significant improvements in the sensor performance, and would be benefit to extend the scope of application of QCM and chemometrics.

Preventing Nonspecific Adsorption on Polymer Brush Covered Gold Electrodes Using a Modified ATRP Initiator

Biological systems have a tendency to adsorb nonspecifically onto a solid substrate, thus reducing the efficacy of the interface being used in biorecognition. This nonspecific adsorption is a common problem in the development of biosensors as it typically reduces the efficacy of the sensor platform. In this manuscript we report the synthesis of an oligo(ethylene glycol) (OEG) containing ATRP (atom transfer radical polymerization) thiol initiator and demonstrate the role of this initiator in preventing nonspecific adsorption of IgG antibodies on chemically functionalized gold electrode surfaces using cyclic voltammetry. A new synthetic route for the synthesis of the new ATRP thiol initiator in high yields has been reported. Surface initiated poly(acrylic acid) brushes grown off the gold surface with modified OEG containing and conventional ATRP thiol initiators were chemically modified with 2,4-dinitrophenyl (DNP) groups. Amperometric studies were carried out on gold electrodes modified with DNP-PAA brushes using DNP-specific and nonspecific IgG antibodies. The cyclic voltammograms of an osmium redox mediator recorded over time suggest that the chemical modification of the gold electrodes with DNP-PAA brushes using the OEG-containing ATRP initiator is much more effective in preventing nonspecific adsorption of antibodies than polymer brushes grown from the conventional initiator. Finally, we confirmed these results with the quartz crystal microbalance (QCM) technique by quantitatively evaluating the adsorption of nonspecific IgG antibodies on DNP-PAA functionalized QCM surfaces. The use of this modified ATRP thiol initiator to chemically functionalize macro/microelectrode surfaces will help develop reproducible, reliable, and robust electrochemical biosensors with minimized nonspecific adsorption.

Detecting cells on the surface of a silver electrode quartz crystal microbalance using plasma treatment and graft polymerization

This paper utilizes a silver electrode quartz crystal microbalance (QCM) mass sensor to detect the physiology of cells. This study also investigates the plasma surface modification of silver electrode QCMs through deposition of hexamethyldisilazane (HMDSZ) films as a protection film. To improve the cell growth, this paper also performs post-treatments by surface-grafting acrylic acid (AAc), acrylamide (AAm), and oxygen plasma treatment onto the QCM electrodes. Experimental results indicate that plasma deposition is a useful technique to protect the surface of silver electrodes. This technique extends the unpeeling time of silver electrodes from 1 to 7 days. The hydrophilic silver electrode QCM surface modified by AAm exhibited a better storage time effect than other post-treatments.

Biocatalyzed deposition amplification for detection of aflatoxin B 1 based on quartz crystal microbalance

An ultrasensitive piezoelectric method for the detection of the aflatoxin B 1 (AFB 1) based on the indirect competitive immunoassay and the biocatalyzed deposition amplification has been developed. In this method, the quartz crystal surface was coated with a self-assembled monolayer of 3-mercaptopropionic acid (MPA) for covalently immobilization of the BSA-AFB 1 conjugate, which could compete with the free AFB 1 for binding to the anti-AFB 1 antibody (MsIgG). After the competitive immunoreaction, the horseradish peroxidase (HRP) labeled goat anti-mouse IgG (G-Anti-MsIgG) was introduced into the detection cell to combine with the anti-AFB 1 antibody on the crystal surface. The enzyme labeled G-Anti-MsIgG as a biocatalyst could accelerate the oxidation of 4-chloro-1-naphthol by H 2O 2 to yield the insoluble product benzo-4-chlorohexadienone on the surface of quartz crystal microbalance (QCM), resulting in a mass increase that was reflected by a decrease in the resonance frequency of the QCM. The proposed approach could allow for the determination of AFB 1 in the concentration range of 0.01–10.0 ng mL −1. Furthermore, several artificially contaminated milk samples were analyzed with good recoveries obtained, which demonstrated the suitability of the proposed method for detecting AFB 1.

이차항체를 포함하는 수정미소저울 센서 칩을 이용한 사람과 소의 헵토글로빈 측정

In this study, secondary antibody-containing quartz crystal microbalance(QCM) sensor chip was prepared and utilized for the detection of human and bovine haptoglobin. Anti-goat immunoglobulin G antibody, which is a secondary antibody capable of capturing primary antibodies raised in goat, was immobilized through the reaction between hydrazide and aldehyde group prepared on the QCM surface and antibody respectively. The resulting sensor chip showed higher stability in the repeated surface regeneration with acidic dissociation solution as well as requiring lower amount of primary antibody when compared to the protein G sensor chip. The secondary antibody sensor chip was applied for the estimation of bovine and human haptoglobin.

Protein G를 포함하는 수정미소저울 센서 칩과 정제되지 않은 항혈청을 이용한 헵토글로빈과 트랜스페린의 면역분석

Quartz crystal microbalance immunosensor has a capacity to perform a label-free and real time detection of a trace amount of analyte through the specific interaction between antibody and antigen. However, immobilization of antibody molecules on the sensor surface is a troublesome procedure for researchers who are not experienced in chemistry. Protein G has a specific affinity to antibody and would serve as a capturing agent for antibody when immobilized on the sensor surface. In this work, we prepared a protein G sensor chip by immobilizing protein G on the surface of quartz crystal microbalance and examined its capability to detect human haptoglobin or human transferrin with unpurified corresponding antiserum. Specific and dose dependent response was observed when the protein G chip was used for detection of antigens after saturated with antiserum. We also verified several advantageous aspects of the protein G chip such as improved flexibility and sensitivity.