Quartz crystal microbalance (QCM) as a device for the screening of phage libraries

An immunosensing system based on a quartz crystal microbalance (QCM) is presented for the selection of both antigen specific recombinant antibodies and antigen specific human pancreatic secretory trypsin inhibitor (hPSTI) mutants isolated from large phage libraries. The QCM was integrated into a flow injection analysis system for the straightforward analysis of large sample numbers. Measurements were performed using a biotinylated antigen immobilized by streptavidin onto the gold surface of the quartz crystal and phages displaying recombinant antibodies or hPSTI mutants. The results obtained by the QCM were in accordance to those of a well established enzyme linked immunosorbent assay (ELISA). Therefore, the QCM is well suited for the detection of single high affinity clones isolated from large phage display libraries.     

Quartz tuning fork biosensor.

The use of quartz tuning forks for biosensor applications is investigated. The basis of the sensor is to coat the tuning fork surfaces with specific biomolecules and measure subsequent mass loading from the selective binding of complementary analytes. Two experimental set-ups are evaluated, direct mechanical excitation and self-excitation. Mechanical excitation is achieved by mounting the fork on a piezoelectric plate and it is found that the change in oscillation amplitude on adsorption can be monitored to give the change in mass. However, a major drawback is that the sensitivity is determined by the Q-factor, which varies significantly between different sensors and different experimental arrangements. In self-excitation mode, tuning fork motion is activated and detected by placing the fork within a tuned circuit. Using self-excitation mode, anti-human IgG modified tuning forks can sense the binding of human IgG in the range of 5-100 microg ml(-1). The significance of this study is that quartz tuning forks are routinely made using standard microfabrication process, thus suggesting the possibility of facile microfabrication of arrays of quartz sensors.     

压电石英晶体免疫传感器

近年来压电石英晶体免疫传感器作为一种新型生物传感器发展迅速,该文对其检测原理、材料选择、振荡模式选择及再生使用进行了详细介绍,并介绍了其在微生物检测、病毒和蛋白质检测,环境监测方面的具体应用。     

Quartz crystal microbalance-based measurements of shear-induced senescence in human embryonic kidney cells

Fluid shear and other mechanical forces play an important role in the normal biophysical, biochemical, and gene regulatory responses of vertebrate tissue that are reflected in the expression of normal cell differentiation, growth, and function. Despite some promising work reported on the application of the quartz crystal microbalance (QCM) to both prokaryote and eukaryote cells over the last decade, QCM has yet to be successfully applied to cells in culture under conditions of flow-induced shear. In this study, high sensitivity QCM in conjunction with fluid modelling was used to monitor the onset of senescence in immortalised human embryonic kidney cells under laminar shear stresses of between 0.04 and 335 dyne/cm(2). The feasibility of this approach as a means of quantification and characterisation of cell physiological response and adhesion are explored and discussed.     

Quartz fibers as templates for biopolymers

The polymerization of silica in water solution to form quartz fibers proceeds by a dehydration process, analogous to condensation polymerization in organic high-polymers, in which monomeric Si(OH)₄ groups unite through Si–O–Si bonds with the elimination of H₂O. The resulting fibers are structurally polar along the direction of elongation, are enantiomorphous, and generally shown stereospecific twisting around the direction of elongation. In these regards the fibers are analogues of biopolymers such as RNA and DNA. Quartz also possesses specific adsorptive relations to a wide range of organic substances including monomer amino acids, short-chain polypeptides, and proteins. These involve hydrogen-bonding between (OH) or silanoi groups on the surface of the quartz with active side-groups on the organic molecules and in part are epitaxial through dimensional coincidences in the interface.Geochemical evidence indicates that quartz was deposited in the early Precambrian ocean either by direct crystallization from seawater or by recrystallization of amorphous silica. What is of interest is the possible role of quartz fibers as a template and co-polymer in the passage of biomonomers in the pre-biotic ocean to the long-chain biopolymers such as nucleic acids and proteins that are involved in life processes.     

Quartz crystal microbalance immunosensors for environmental monitoring

This paper presents discussion of quartz crystal microbalance (QCM) immunosensors for environmental monitoring. Factors limiting the practical application of antibodies to analytical problems are also presented. Among several candidates for the QCM immunosensor device, selected QCM devices and oscillating circuits were tested thoroughly and developed to obtain highly stable and sensitive frequency signals. The biointerface of QCM immunosensor was designed and controlled to immobilize antibody on the QCM surface, to reduce non-specific binding and to suppress denaturation of immobilizing antibody by self-assembled monolayer technique and artificial phospholipid (2-methacryloyloxyethyl phosphorylcholine (MPC)) polymer. MPC polymer as a antibody-stabilizing reagent was added to reduce non-specific binding of the antigen solution and stabilize the immunologic activity of the antibody-immobilized QCM. In addition, it provides examples for detection and quantitation of environmental samples using QCM immunosensors. The analytical results for fly ash extracted samples of dioxins using the QCM immunosensor indicated a good relationship with GC/MS methods. The integrating protocols of the competitive immunoassay and signal-enhancing step are for detecting low molecular analytes with extremely low detection limits using an QCM immunosensor. Furthermore, its detect limitation was extended from 0.1 to 0.01 ng/ml by the signal-enhancing step when the anti-bisphenol-A antibody conjugated MPC polymeric nanoparticles was used. The QCM immunosensor method has demonstrated its effectiveness as an alternative screening method for environmental monitoring because these results were compared with results obtained through environmental monitoring methods such as ELISA and GC/MS.     

Quartz fibers as templates for biopolymers.

The polymerization of silica in water solution to form quartz fibers proceeds by a dehydration process, analogous to condensation polymerization in organic high-polymers, in which monomeric Si(OH)4 groups unite through Si--O--Si bonds with the elimination of H2O. The resulting fibers are structurally polar along the direction of elongation, are enantiomorphous, and generally show stereospecific twisting around the direction of elongation. In these regards the fibers are analogues of biopolymers such as RNA and DNA. Quartz also possesses specific adsorptive relations to a wide range of organic substances including monomer amino acids, short-chain polypeptides, and proteins. These involve hydrogen-bonding between (OH) or silanol groups on the surface of the quartz with active side-groups on the organic molecules, and in part are epitaxial through dimensional coincidences in the interface. Geochemical evidence indicates that quartz was deposited in the early Precambrian ocean either by direct crystallization from seawater or by recrystallization of amorphous silica. What is of interest is the possible role of quartz fibers as a template and co-polymer in the passage of biomonomers in the pre-biotic ocean to the long-chain biopolymers such as nucleic acids and proteins that are involved in life processes.     

Degradation of Glycine and Alanine on Irradiated Quartz

Recent researches suggest participation of minerals in the formation of life under primordial conditions. Among all of the minerals, quartz seems to be one of the most probable to take part in such processes. However, an external source of energy is needed, e.g. electric discharge. A device simulating the proposed conditions was designed and was used to simulate prebiotic conditions. Investigation of processes occurring during the stimulation of quartz with electric discharge was studied by means of Ultraviolet–visible (UV–VIS) spectroscopy, in order to monitor the generation kinetics of free radicals. Additionally, infrared spectroscopy was applied to identify chemical reaction products created in a solution of alanine or glycine, in the presence of quartz treated with electric discharge. Formation of increased amounts of free radicals, compared to experiments performed without quartz and/or amino acid, is reported, along with identification of possible degradation products of alanine. No synthetic reactions were observed.     

Quartz crystal microbalance for the determination of daminozide using molecularly imprinted polymers as recognition element

As the daminozide (DM) and its metabolite have been identified to be potentially carcinogenic, rapid detection method for them is necessary for food safety. A type of piezoelectric crystal sensor has been prepared by using a molecularly imprinted polymer (MIP) as recognition element. The molecularly imprinted polymer was prepared by hot-induced precipitation polymerization, and then the polymer particles were fixed on the surface of the electrode. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to evaluate the obtained imprinted polymer particles and the MIP sensitive film coated on the electrode. The results showed that a typical time-response curve of the MIP-coated crystal to the DM solution had been given, frequency shifts versus logarithm changes of DM showed good linear correlation within the concentration range of 1.0x10(-9) to 10(-6) mg/mL (y=11.38 lg x+115.45, r=0.9872) and 1.0x10(-6) to 10(-1) mg/mL (y=25.22lgx+209.44, r=0.9938), respectively. The detection limit was 5.0x10(-8) mg/mL (S/N=3), which is lower than that of conventional methods. Further, computer simulation technology was employed to investigate the interaction between methacrylic acid and DM for elucidating the recognition mechanism. The influencing factor pH has also been investigated. The injection experiments of DM structurally related compounds indicated that the obtained sensor has high sensitivity, excellent selectivity, low cost, good reproducibility, and reusable property by combining with piezoelectric crystal and molecularly imprinted polymer.     

Quartz crystal microbalance investigation of the interaction of bacterial toxins with ganglioside containing solid supported membranes

The binding of cholera toxin, tetanus toxin and pertussis toxin to ganglioside containing solid supported membranes has been investigated by quartz crystal microbalance measurements. The bilayers were prepared by fusion of phospholipid-vesicles on a hydrophobic monolayer of octanethiol chemisorbed on one gold electrode placed on the 5 MHz AT-cut quartz crystal. The ability of the gangliosides G_M1, G_M3, G_D1a, G_D1b, G_T1b and asialo-G_M1 to act as suitable receptors for the different toxins was tested by measuring the changes of quartz resonance frequencies. To obtain the binding constants of each ligand-receptor-couple Langmuir-isotherms were successfully fitted to the experimental adsorption isotherms. Cholera toxin shows a high affinity for G_M1 (K_a = 1.8 ⋅ 10⁸M^–1), a lower one for asialo-G_M1 (K_a = 1.0 ⋅ 10⁷ M^–1) and no affinity for G_M3. The C-fragment of tetanus toxin binds to ganglioside G_D1a, G_D1b and G_T1b containing membranes with similar affinity (K_a∼10⁶ M^–1), while no binding was observed with G_M3. Pertussis toxin binds to membranes containing the ganglioside G_D1a with a binding constant of K_a = 1.6 ⋅ 10⁶ M^–1, but only if large amounts (40 mol%) of G_D1a are present. The maximum frequency shift caused by the protein adsorption depends strongly on the molecular structure of the receptor. This is clearly demonstrated by an observed maximum frequency decrease of 99 Hz for the adsorption of the C-fragment of tetanus toxin to G_D1b. In contrast to this large frequency decrease, which was unexpectedly high with respect to Sauerbrey's equation, implying pure mass loading, a maximum shift of only 28 Hz was detected after adsorption of the C-fragment of tetanus toxin to G_D1a. Received: 14 January 1997 / Accepted: 15 April 1997     

Analysis of Perforin Assembly by Quartz Crystal Microbalance Reveals a Role for Cholesterol and Calcium-independent Membrane Binding

Perforin is an essential component in the cytotoxic lymphocyte-mediated cell death pathway. The traditional view holds that perforin monomers assemble into pores in the target cell membrane via a calcium-dependent process and facilitate translocation of cytotoxic proteases into the cytoplasm to induce apoptosis. Although many studies have examined the structure and role of perforin, the mechanics of pore assembly and granzyme delivery remain unclear. Here we have employed quartz crystal microbalance with dissipation monitoring (QCM-D) to investigate binding and assembly of perforin on lipid membranes, and show that perforin monomers bind to the membrane in a cooperative manner. We also found that cholesterol influences perforin binding and activity on intact cells and model membranes. Finally, contrary to current thinking, perforin efficiently binds membranes in the absence of calcium. When calcium is added to perforin already on the membrane, the QCM-D response changes significantly, indicating that perforin becomes membranolytic only after calcium binding.     

Improving the Shear Strength of Quartz Sand using the Microbial Method

An increase in urban population and the reduced number of suitable lands for construction projects have necessitated the need for ground improvement methods with no environmentally detrimental effects. Microbial-induced calcite precipitation (MICP) is a relatively environmentally friendly method for soil regeneration. In the present paper, X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were performed to investigate the type and method of cement formation in loose quartz sand with different densities stabilized using bacteria. The results showed that the highest content of calcium carbonate cement was produced in the sample with the lowest density. Moreover, after microbial stabilization, the shear strength measured in the direct shear test was increased in the specimen with a lower density. We observed an increase in shear strength from 0.63 kg/cm² before injection for loose sand (γ = 1.5 g/cm³) to 3.92 kg/cm² after injection. In addition, the effect of injection time was investigated and found that shear strength in the two-stage injection per day is greater than that in one- and three-stage injections per day. With prolonging the injection time from one to five days, shear strength was significantly increased from 2.07 to 4.54 kg/cm². Furthermore, prolonging the bacterial treatment period led to a significant increase in the produced carbonate cement and, consequently, enhanced soil shear strength.     

ITO石英晶体电极上不同内皮细胞浓度的粘弹性研究及药物作用评估

用石英晶体微天平(quartz crystal microbalance,QCM)和活细胞成像技术实时监测人脐静脉内皮细胞(HUVEC)在ITO石英晶体电极上的动态粘附响应过程。在ITO晶体电极上加入不同浓度的HUVEC,测定细胞在QCM上谐振频率以及耗散的实时变化。通过ITO电极与光学显微镜的联用,监测了HUVEC在药物处理前后的动态变化过程。用细胞粘弹性指数(QCM的动态电阻变化与频移变化之比,CVI=ΔR/Δf)表征细胞的粘弹性变化,同时通过活细胞成像技术的联用,实时监测细胞的形态变化。结果表明:细胞浓度为10万个/m L时,细胞在ITO电极上铺展完全且粘弹性最大。抑制剂y-27632和激动剂凝血酶thrombin药物处理细胞前后,在显微镜的实时监测下细胞形态变化不明显,但CVI粘弹性指数变化较大,说明QCM信号比光学信号更为敏感,且在药物筛选方面有有很大的应用前景。     

Preparation of Macroporous Epitaxial Quartz Films on Silicon by Chemical Solution Deposition

This work describes the detailed protocol for preparing piezoelectric macroporous epitaxial quartz films on silicon(100) substrates. This is a three-step process based on the preparation of a sol in a one-pot synthesis which is followed by the deposition of a gel film on Si(100) substrates by evaporation induced self-assembly using the dip-coating technique and ends with a thermal treatment of the material to induce the gel crystallization and the growth of the quartz film. The formation of a silica gel is based on the reaction of a tetraethyl orthosilicate and water, catalyzed by HCl, in ethanol. However, the solution contains two additional components that are essential for preparing mesoporous epitaxial quartz films from these silica gels dip-coated on Si. Alkaline earth ions, like Sr²⁺ act as glass melting agents that facilitate the crystallization of silica and in combination with cetyl trimethylammonium bromide (CTAB) amphiphilic template form a phase separation responsible of the macroporosity of the films. The good matching between the quartz and silicon cell parameters is also essential in the stabilization of quartz over other SiO₂ polymorphs and is at the origin of the epitaxial growth.     

Surfactant Protein SP-B Strongly Modifies Surface Collapse of Phospholipid Vesicles: Insights from a Quartz Crystal Microbalance with Dissipation

Pulmonary surfactant protein B (SP-B) facilitates the rapid transfer of phospholipids from bilayer stores into air-liquid interfacial films along the breathing cycle, and contributes to the formation of a surface-associated multilayer reservoir of surfactant to optimize the stability of the respiratory interface. To obtain more insights into the mechanisms underlying this transfer and multilayer formation, we established a simple model system that captures different features of SP-B action. We monitored the formation of supported planar bilayers from the collapse of intact phospholipid vesicles on a silica surface using a technique called quartz crystal microbalance with dissipation, which provides information on changes in membrane thickness and viscosity. At physiologically relevant concentrations, SP-B dramatically alters vesicle collapse. This manifests itself as a reduced buildup of intact vesicles on the surface before collapse, and allows the stepwise buildup of multilayered deposits. Accumulation of lipids in these multilayer deposits requires the presence of SP-B in both the receptor and the arriving membranes, surrounded by a comparable phospholipid charge. Thus, the quartz crystal microbalance with dissipation system provides a useful, simplified way to mimic the effect of surfactant protein on vesicle dynamics and permits a detailed characterization of the parameters governing reorganization of surfactant layers.