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Nucleic acid amplification reactions such as polymerase chain reaction (PCR), which uses a DNA polymerase to amplify individual double-stranded DNA fragments, are a useful technique for visualizing the presence of specific genomes. Although the fluorescent labeling method is mainly used with DNA amplification, other detection methods should be considered for further improvements, such as miniaturization and cost reduction, of reaction-monitoring devices. In this study, the quartz-crystal microbalance (QCM) method, which can measure nanogram-order masses, was applied for the real-time detection of DNA fragments in a solution with nucleic acids. This was combined with an isothermal nucleic acid amplification reaction based on the recombinase polymerase amplification (RPA) method, which allowed DNA amplification at a constant temperature. When the DNA amplification reaction was initiated on a QCM sensor plate with an immobilized primer DNA strand, a significant increase in mass was observed compared to when the primer DNA was not immobilized. QCM was shown to be sufficiently sensitive for the in situ detection of amplified DNA fragments. Combining a portable QCM device and RPA offers a sensitive point-of-care method for detecting nucleic acids. [ABSTRACT FROM AUTHOR]

In this work, the development of a novel method for the detection of mercury (II) ions in wastewater using a mercury ion-imprinted polymer (IIP) combined with a quartz crystal microbalance (QCM) is described. The IIP was successfully synthesized via the polymerization of a of a novel fluorescein- and 2-aminophenol-functionalized methacrylic acid monomer, which was noted to have high binding affinity to mercury (II) ions. This polymer was subsequently coated on a QCM chip to create an IIP-QCM sensor. This sensor was established to have high selectivity and good sensitivity to mercury (II) ions, and had a limit of detection (LOD) of 14.17 ppb, a limit of quantification (LOQ) of 42.94 ppb, a signal-to-noise ratio (S/N) of 4.29, good repeatability, and a working range of 42.94 ppb to 2 ppm. The sensor was also able to analyze tap water and wastewater samples. The IIP-QCM is, therefore, promising as a highly selective, cost-effective, and rapid mercury ion sensor for applications involving the detection of mercury in wastewater. [ABSTRACT FROM AUTHOR]

Nucleic acid amplification reactions such as polymerase chain reaction (PCR), which uses a DNA polymerase to amplify individual double-stranded DNA fragments, are a useful technique for visualizing the presence of specific genomes. Although the fluorescent labeling method is mainly used with DNA amplification, other detection methods should be considered for further improvements, such as miniaturization and cost reduction, of reaction-monitoring devices. In this study, the quartz-crystal microbalance (QCM) method, which can measure nanogram-order masses, was applied for the real-time detection of DNA fragments in a solution with nucleic acids. This was combined with an isothermal nucleic acid amplification reaction based on the recombinase polymerase amplification (RPA) method, which allowed DNA amplification at a constant temperature. When the DNA amplification reaction was initiated on a QCM sensor plate with an immobilized primer DNA strand, a significant increase in mass was observed compared to when the primer DNA was not immobilized. QCM was shown to be sufficiently sensitive for the in situ detection of amplified DNA fragments. Combining a portable QCM device and RPA offers a sensitive point-of-care method for detecting nucleic acids.

In this work, the development of a novel method for the detection of mercury (II) ions in wastewater using a mercury ion-imprinted polymer (IIP) combined with a quartz crystal microbalance (QCM) is described. The IIP was successfully synthesized via the polymerization of a of a novel fluorescein- and 2-aminophenol-functionalized methacrylic acid monomer, which was noted to have high binding affinity to mercury (II) ions. This polymer was subsequently coated on a QCM chip to create an IIP-QCM sensor. This sensor was established to have high selectivity and good sensitivity to mercury (II) ions, and had a limit of detection (LOD) of 14.17 ppb, a limit of quantification (LOQ) of 42.94 ppb, a signal-to-noise ratio (S/N) of 4.29, good repeatability, and a working range of 42.94 ppb to 2 ppm. The sensor was also able to analyze tap water and wastewater samples. The IIP-QCM is, therefore, promising as a highly selective, cost-effective, and rapid mercury ion sensor for applications involving the detection of mercury in wastewater.

Quartz-crystal microbalance (QCM) is a technique that can measure nanogram-order masses. When a receptor is immobilized on the sensor surface of a QCM device, the device can detect chemical molecules captured by the mass change. Although QCM devices have been applied to biosensors that detect biomolecules without labels for biomolecular interaction analysis, most highly sensitive QCM devices are benchtop devices. We considered the fabrication of an IC card-sized QCM device that is both portable and battery-powered. Its miniaturization was achieved by repurposing electronic components and film batteries from smartphones and wearable devices. To demonstrate the applicability of the card-sized QCM device as a biosensor, DNA-detection experiments were performed. The card-sized QCM device could detect specific 10-mer DNA chains while discerning single-base differences with a sensitivity similar to that of a conventional benchtop device. The card-sized QCM device can be used in laboratories and in various other fields as a mass sensor. [ABSTRACT FROM AUTHOR]

Quartz-crystal microbalance (QCM) is a technique that can measure nanogram-order masses. When a receptor is immobilized on the sensor surface of a QCM device, the device can detect chemical molecules captured by the mass change. Although QCM devices have been applied to biosensors that detect biomolecules without labels for biomolecular interaction analysis, most highly sensitive QCM devices are benchtop devices. We considered the fabrication of an IC card-sized QCM device that is both portable and battery-powered. Its miniaturization was achieved by repurposing electronic components and film batteries from smartphones and wearable devices. To demonstrate the applicability of the card-sized QCM device as a biosensor, DNA-detection experiments were performed. The card-sized QCM device could detect specific 10-mer DNA chains while discerning single-base differences with a sensitivity similar to that of a conventional benchtop device. The card-sized QCM device can be used in laboratories and in various other fields as a mass sensor.

This study presents experimental data on water content in CO 2 , methane, and their mixtures. A new saturation process was developed using a PVT cell connected to a variable-volume cylinder filled with deionized water. Dry gas with a known composition was injected into the cylinder, and the temperature and pressure conditions were adjusted accordingly. The water content of the saturated gas was then analyzed using a quartz-crystal microbalance (QCM). Various mixtures with different CO 2 and methane mole ratios were investigated at different pressures for a given temperature. The PC-SAFT and CPA equations of state were applied to correlate the moisture data. The association scheme employed included 2B, 3B, and 4C types, considering the cross-association between water and CO 2. The results for pure methane showed that the water content increased as the pressure decreased across all pressure ranges. However, for pure CO 2 above 70 bar, the water content increased due to the condensation behavior of CO 2. The same trend was observed for mixtures, where the water content increased with increasing pressure for CO 2 mole fractions above 0.74. For all the systems studied, the PC-SAFT and CPA equations of state successfully correlated the water content data using a single constant binary interaction parameter and considering the cross-association between water and CO 2. • Water content measurement, especially at high CO2 concentrations, is challenging. • The hydrate formation, integral to flow assurance, relies on water condensation. • New technique and procedure and new experimental data of water content measurements. • PC-SAFT and CPA can describe the data well, considering water-CO2 cross-association. [ABSTRACT FROM AUTHOR]

The two‐step conversion process consisting of metal halide deposition followed by conversion to hybrid perovskite has been successfully applied toward producing high‐quality solar cells of the archetypal MAPbI3 hybrid perovskite, but the conversion of other halide perovskites, such as the lower bandgap FAPbI3, is more challenging and tends to be hampered by the formation of hexagonal nonperovskite polymorph of FAPbI3, requiring Cs addition and/or extensive thermal annealing. Here, an efficient room‐temperature conversion route of PbI2 into the α‐FAPbI3 perovskite phase without the use of cesium is demonstrated. Using in situ grazing incidence wide‐angle X‐ray scattering (GIWAXS) and quartz crystal microbalance with dissipation (QCM‐D), the conversion behaviors of the PbI2 precursor from its different states are compared. α‐FAPbI3 forms spontaneously and efficiently at room temperature from P2 (ordered solvated polymorphs with DMF) without hexagonal phase formation and leads to complete conversion after thermal annealing. The average power conversion efficiency (PCE) of the fabricated solar cells is greatly improved from 16.0(±0.32)% (conversion from annealed PbI2) to 17.23(±0.28)% (from solvated PbI2) with a champion device PCE > 18% due to reduction of carrier recombination rate. This work provides new design rules toward the room‐temperature phase transformation and processing of hybrid perovskite films based on FA+ cation without the need for Cs+ or mixed halide formulation. [ABSTRACT FROM AUTHOR]

Herein, we report on the use of a combined setup of quartz-crystal microbalance, with dissipation monitoring and spectroscopic ellipsometry, to comprehensively investigate the covalent immobilization of an enzyme to a polymer layer. All steps of the covalent reaction of the model enzyme glucose oxidase with the poly(acrylic acid) brush by carbodiimide chemistry, were monitored in-situ. Data were analyzed using optical and viscoelastic modeling. A nearly complete collapse of the polymer chains was found upon activation of the carboxylic acid groups with N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide and N-Hydroxysuccinimide. The reaction with the amine groups of the enzyme occurs simultaneously with re-hydration of the polymer layer. Significantly more enzyme was immobilized on the surface compared to physical adsorption at similar conditions, at the same pH. It was found that the pH responsive swelling behavior was almost not affected by the presence of the enzyme.

Controlling adsorption of proteins onto medical devices is a key issue for implant-related infections. As self-assembled monolayers (SAMs) on titanium oxide represent a good model to study the surface-protein interactions, TiO 2 surface properties were modified by grafting bisphosphonate molecules terminated with hydrophilic poly(ethylene glycol) groups and hydrophobic perfluoropolyether ones, respectively. Characterisation of the surface chemistry and surface topography of the modified surfaces was performed using XPS and atomic force microscopy (AFM). Quartz-crystal microbalance with dissipation (QCM-D) was used to determine the mass of adsorbed proteins as well as its kinetics. Poly(ethylene glycol)-terminated SAMs were the most effective surfaces to limit the adsorption of both BSA and fibrinogen in comparison to perfluorinated-terminated SAMs and non-modified TiO 2 surfaces, as expected. The adsorption was not reversible in the case of BSA, while a partial reversibility was observed with Fg, most probably due to multilayers of proteins. The grafted surfaces adsorbed about the same quantity of proteins in terms of molecules per surface area, most probably in monolayer or island-like groups of adsorbed proteins. The adsorption on pristine TiO 2 reveals a more important, non-specific adsorption of proteins. [ABSTRACT FROM AUTHOR]

Electrowetting-on-dielectric (EWOD) has been widely exploited as an actuating force to manipulate liquids by surface tension and modulation of the contact angle on a microscale. To evaluate EWOD, an optical measurement of the droplet contact angle is conventional, but is constrained by the optical properties of the liquid, especially when two liquid phases (e.g., water in oil) are involved. We developed a non-optical method to study EWOD using a quartz-crystal microbalance (QCM). A QCM provides a promising technique for mass sensing, and has been developed for the study of liquid viscosity, density and contact angle. In this research, a QCM was employed to generate EWOD and concurrently to measure the variation of the contact angle. The contact angle of droplets of water in air and in oil was evaluated. The voltage-dependent oil film between a water droplet and the QCM surface was sensed. A modified QCM model considering a voltage-dependent oil film was derived for the analysis of the contact angle.

Cell specific ligand molecules are attached to polyethylene glycol (PEG) modified nanoparticles to enhance the drug delivery efficiency. The tethered PEG would interfere in ligand recognition as well as providing biocompatibility to the nanoparticles. The denser PEG can give the greater biocompatibility, while should more hamper the ligand recognition. Therefor it is important to tune PEG density at an appropriate amount to compensate these two factors. In this study, we prepared a series of nanoparticles composed of α-mannose-bearing lipid, dioleoyltrimethyl ammoniumpropane (DOTAP) and 1,2-distearoyl- sn -glycero -3-phosphoethanolamine- N -[methoxy(polyethylene glycol)-2000] (DSPE-PEG 2000 ). The nanoparticles were characterized with dynamic light scattering (DLS), field flow fractionation (FFF), small angle X-ray scattering (SAXS), and quartz-crystal microbalance (QCM). Based on the structural parameter obtained from DLS, SAXS, and FFF, we determined the PEG crowding parameter ( σ ) quantitatively; when σ = 1.0 , the PEG chain occupies the same value on the surface as when the chain is present in the unperturbed state, and at σ = 1.0 , the PEG chains start to contact each other. We found that the recognition ability had the maximum around σ ∼ 0.75 and there was the critical composition at σ = 1.0 for which the recognition was drastically reduced. The present results demonstrated that quantitative characterization and controlling the PEG density are key to designing effective targeting delivery system. [ABSTRACT FROM AUTHOR]

We report on the build-up and the intrinsic properties of polyelectrolyte multilayer films from poly- l -lysine and glycosaminoglycans (GAGs) with different sulfation degree, i.e. different charge. We used three complementary techniques, namely electrokinetic analysis (EKA), quartz-crystal microbalance with dissipation (QCM-D) and surface plasmon resonance (SPR), to characterize the assembly process and to assess the properties of the obtained films. EKA elucidated the contribution of the polymers charged groups to the net surface charge of the films and suggested that the assembly process is not solely driven by electrostatic interactions. The combined analysis of QCM-D and SPR data demonstrated that the mechanical properties of the films are dependent on the polymer charge: sulfated GAGs (heparin and chondroitin sulfate) form elastic films while hyaluronan (no sulfation) assembles into multilayer constructs with viscous behavior. The contribution of the water content to these distinct regimes is also discussed. Finally, we show that rather complete characterization of the film properties is possible by SPR employing the two-wavelength and two-media approach: thickness, adsorbed mass, refractive index, and interaction kinetics of the assembly process can be studied by SPR alone. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) with branched and cyclic substituents are seldom studied in the literature, and as such there are little to no data characterizing their thermophysical properties. ILs with branched and cyclic substituents are just as convenient to synthesize and study as their counterparts with linear substituents, but the effects of these substituents on IL properties are not yet well-defined due to the preference for linear substituents. Standard molar vaporization enthalpies of six imidazolium based ionic liquids [Rmim][NTf 2 ] with iso-alkyl and cyclic substituents (R = iso-propyl, iso-butyl, sec-butyl, methylcyclopropyl, cyclopentyl and methylcyclohexyl) were derived from quartz-crystal microbalance (QCM) method. Enthalpies of vaporization measured at elevated temperatures have been adjusted to the reference temperature 298 K and tested for consistency by comparison with the homomorphy alkane, alkylbenzenes and alkyl-imidazoles. It was found that vaporization enthalpies of ILs with the iso-alkyl and cyclic groups are generally on the same level within (±2 to 3) kJ · mol −1 significantly compared to the analogous ILs with the imidazolium cation substituted with the linear alkyl substituents of the same chain length. These findings are useful for the quick estimation of vaporization enthalpies of various substituted IL cations (e.g. pyrrolidinium, ammonium, pyridinium, etc.). [ABSTRACT FROM AUTHOR]

Reversible Li-ion intercalation into composite Li-ion battery (LIB) electrodes is often accompanied by significant dimensional electrode changes (deformation) resulting in significant deterioration of the cycling performance. Viscoelastic properties of polymeric binders affected by intercalation-induced deformation of composite LIB electrodes have never been probed in situ on operating electrochemical cells. Here, we introduce a newly developed noninvasive method, namely electrochemical quartz-crystal microbalance with dissipation monitoring (EQCM-D), for in situ monitoring of elastic properties of polymeric binders during charging of LIB electrodes. As such, we find EQCM-D as a uniquely suitable tool to track the binder's structural rigidity/softness in composite Li insertion electrodes in real-time by the characteristic increase/decrease of the dissipation factor during the charging-discharging process. The binders partially swollen in aprotic solutions demonstrate intermediate viscoelastic charge-rate-dependent behavior, revealing rigid/soft behavior at high/low charging rates, respectively. The method can be adjusted for continuous monitoring of elastic properties of the polymeric binders over the entire LIB electrodes cycling life. [ABSTRACT FROM AUTHOR]

Integrating nanotechnology into useable devices requires a combination of bottom up and top down methodology. Often the techniques to measure and control these different components are entirely different, so methods that can analyse the nanoscale component in situ are of increasing importance. Here we describe a strategy that employs a self-assembling monolayer of engineered protein chimeras to display an array of oriented antibodies (IgG) on a microelectronic device for the label free detection of influenza nucleoprotein. The structural and functional properties of the bio-interface were characterised by a range of physical techniques including surface plasmon resonance, quartz-crystal microbalance and neutron reflectometry. This combination of methods reveals a 13.5 nm thick engineered-monolayer that (i) self-assembles on gold surfaces, (ii) captures IgG with high affinity in a defined orientation and (iii) specifically recognises the influenza A nucleoprotein. Furthermore we also show that this non-covalent self-assembled structure can render the dissociation of bound IgG irreversible by chemical crosslinking in situ without affecting the IgG function. The methods can thus describe in detail the transition from soluble engineered molecules with nanometre dimensions to an array that demonstrates the principles of a working influenza sensor. [ABSTRACT FROM AUTHOR]

Quartz-crystal microbalance (QCM) is a technique that can measure nanogram-order masses. When a receptor is immobilized on the sensor surface of a QCM device, the device can detect chemical molecules captured by the mass change. Although QCM devices have been applied to biosensors that detect biomolecules without labels for biomolecular interaction analysis, most highly sensitive QCM devices are benchtop devices. We considered the fabrication of an IC card-sized QCM device that is both portable and battery-powered. Its miniaturization was achieved by repurposing electronic components and film batteries from smartphones and wearable devices. To demonstrate the applicability of the card-sized QCM device as a biosensor, DNA-detection experiments were performed. The card-sized QCM device could detect specific 10-mer DNA chains while discerning single-base differences with a sensitivity similar to that of a conventional benchtop device. The card-sized QCM device can be used in laboratories and in various other fields as a mass sensor.

Highlights: [•] A β-glucan called schizophyllan (SPG) forms a complex with polynucleotides. [•] We found that SPG/ODN complex was recognized by β-glucan receptor. [•] The complex with phosphodiester backbone was recognized in the same manner as SPG. [•] The complex with phosphorothioate backbone had multi-binding sites to the receptor. [ABSTRACT FROM AUTHOR]

Implant-related infections are a major challenge in clinical routine because of severe complications, for example infective endocarditis (IE). The purpose of this study was to investigate the real-time interaction of S. gordonii with proteins and cells important in the development of IE, in a flow system, by use of a quartz-crystal microbalance (QCM). Acoustic sensors were biologically modified by preconditioning with sterile saliva, platelet-poor plasma (PPP), or platelet-rich plasma (PRP), followed then by perfusion of a bacterial suspension. After perfusion, additional fluorescence and scanning electron microscopic (SEM) studies were performed. The surface structure of S. gordonii was analyzed by atomic force microscopy (AFM). Compared with S. gordonii adhesion on the abiotic sensor surface following normal mass loading indicated by a frequency decrease, adhesion on saliva, PPP, or PRP-conditioned sensors resulted in an increase in frequency. Furthermore, adhesion induced slightly increased damping signals for saliva and PPP-coated sensors but a decrease upon bacterial adhesion to PRP, indicating the formation of a more rigid biofilm. Microscopic analysis confirmed the formation of dense and vital bacterial layers and the aggregation of platelets and bacteria. In conclusion, our study shows that the complex patterns of QCM output data observed are strongly dependent on the biological substrate and adhesion mechanisms of S. gordonii. Overall, QCM sheds new light on the pathways of such severe infections as IE. [ABSTRACT FROM AUTHOR]

Abstract: New experimental data for [C n1 Pyrr][NTf2] family with odd and even chain length of the methyl-pyrrolidinium cation, based on the concurring results from quartz crystal microbalance and thermogravimetry, have been used for validation of procedures for extrapolation of vaporization enthalpies to the reference temperature 298K. A simple method based on the liquid heat capacities was recommended. We have shown that vaporization enthalpies at 298K are linearly dependant on the alkyl chain length with the CH2 group contribution to the vaporization enthalpy around 4.0kJ·mol−1, which was shown to be common for different ILs homologous series. [Copyright &y& Elsevier]

Abstract: Virtual and experimental affinity binding properties of 5 different peptides (cysteinylglycine, glutathione, Cys–Ile–His–Asn–Pro, Cys–Ile–Gln–Pro–Val, Cys–Arg–Gln–Val–Phe) vs. 14 volatile compounds belonging to relevant chemical classes were evaluated. The peptides were selected in order to have a large variability in physicochemical characteristics (including length). In virtual screening a rapid and cost-effective computational methodology for predicting binding scores of small peptide receptors vs. volatile compounds is proposed. Flexibility was considered for both ligands and peptides and each peptide conformer was treated as a possible receptor, generating a dedicated box and then running a docking process vs. all possible conformers of the 14 volatile compounds. The 5 peptides were covalently bound to gold nanoparticles and deposited onto 20 MHz quartz crystal microbalances to realize gas sensors. Gas sensing confirmed that each of the peptide conferred to the gold nanoparticles a particular selectivity pattern able to discriminate the 14 volatile compounds. The largest response was obtained for the pentapeptides Cys–Ile–His–Asn–Pro and Cys–Ile–Gln–Pro–Val while low response was achieved for the dipeptide. The comparative study, carried using a two-tailed T test, demonstrated that virtual screening was able to predict reliably the sensing ability of the pentapeptides. The dipeptide receptor exhibited 29% of virtual-experimental matching vs. 71% of glutathione and up to 93% for the pentapeptides. This virtual screening approach was proved to be a promising tool in predicting the behaviour of sensors array for gas detection. [Copyright &y& Elsevier]

Electrogravimetric analysis was performed on the consumption of the neurotransmitter Acetylcholine (ACh) by Acetylcholinesterase (AChE) in situ and in real time. Michaelis-Menten assumption was achieved by using an enzyme micro-reactor in which the total enzyme was anchored in a quartz crystal microbalance chip (QCM-chip) with a strategically engineered self-assembled monolayer (SAM) of alkanethiols, which can prevent diffusion-controlled or spatially restricted kinetics. The real-time frequency changes indicated the rate of the products formation from enzymatic reaction. The QCM-chip was tested showing that it could demonstrate AChE inhibition by physostigmine. [ABSTRACT FROM PUBLISHER]

Abstract: A quartz-crystal microbalance (QCM) technique was applied to analyze the effects of site-directed mutagenesis of soybean β-amylase (SBA) by using an amylose-immobilized 27-MHz QCM in buffer solution. We followed directly and quantitatively the formation and decomposition of an enzyme-substrate (ES) complex as frequency changes (mass changes) on the QCM plate. It has been predicted from X-ray crystallography of SBA that two carboxyl groups, Glu186 and Glu380, are the crucial residues for the catalytic hydrolysis of α-1,4-glycoside linkage, and the side chain Thr342 on the inner loop structure bends the glycoside at subsites −1 and +1 of the substrate, thereby accelerating the hydrolysis. When SBA wild-type (WT) was employed, the frequency increased (mass decreased) simply because of the hydrolysis of the substrate on the QCM plate. When T342S and T342A mutants having small side chains with no hydrogen bond on the inner loop were employed, the frequency change showed a sigmoidal curve pointing to an increase in ES complex formation and hydrolysis of the substrate. When E186A and E380A mutants were employed, the frequency decreases (mass increases) showed only enzyme binding to the substrate ES complex formation, but not hydrolysis. From curve fitting of these different patterns of frequency changes, we obtained all kinetic parameters for each step of the enzyme binding to the substrate (k on), the enzyme release from the ES complex (k off), and the catalytic rate constant (k cat) for WT and mutants. From the frequency change patterns of the substrate-immobilized QCM we evaluated how mutations of the enzyme affect k on, k off, and k cat values for ES complex formation and decomposition. We also evaluated the effects of accelerators and inhibitors on enzymes from the frequency change pattern. [Copyright &y& Elsevier]

Using a highly sensitive flow-type 27 MHz quartz crystal microbalance, we could detect a small mass change during stepwise and alternating one-sugar transfer of glucuronic acid (GlcA) and N-acetylgalactosamine (GalNAc) to an acceptor, catalyzed by chondroitin polymerase from Escherichia coli strain K4 (K4CP), and analyze the elongation mechanism of K4CP. K4CP was found to bind strongly to a chondroitin acceptor ( Kd=0.97 μ M). Although the binding affinity and the catalytic rate constant for each monomer were considerably different, the apparent catalytic efficiency ( kcat/ Km) was similar (6.3×104 M−1 s−1 for GlcA transfer and 3.4×104 M−1 s−1 for the GalNAc transfer). This is reasonable for the smooth alternating elongation of GlcA and GalNAc on the acceptor. This is the first study to report the determination of kinetic parameters for enzymatic, alternated, sugar elongation. [ABSTRACT FROM AUTHOR]

Abstract: Adsorption behaviors of recombinant E-cadherin-IgG Fc (E-cad-Fc) fusion protein and mutated E-cad-Fcs on the polystyrene (PS) surface were investigated using a 27MHz quartz-crystal microbalance (QCM) and ELISA. The amount of adsorbed E-cad-Fc on PS surface was increased with an increase of E-cad-Fc concentration as a Langmuir-type in a monolayer. Adsorbed E-cad-Fc on PS surface was stable even after washing if calcium ions are absent in the washing solution due to the calcium ion dependence in the adsorption. E-cadherin homophilic adhesion among E-cadherins during adsorption of E-cad-Fc was involved. Deglycosylation of the E-cad in the E-cad-Fc did not affect adsorption of E-cad-Fc on the PS surface although deglycosylation of the E-cad in the E-cad-Fc enhanced cell adhesion compared with E-cad-Fc. [Copyright &y& Elsevier]

Abstract: We monitored real-time DNA transcription by T7 RNAP using a 27-MHz DNA-immobilized quartz-crystal microbalance (QCM) in buffer solution to investigate the stepwise reaction of transcription. We designed a template double-stranded DNA that consisted of a T7 promoter, a stall position (15bp downstream from the promoter), and a 73-bp transcription region. Based on the frequency (mass) changes of the template-immobilized QCM in response to the addition of T7 RNAP and monomers of NTP, we obtained the kinetic parameters of each step of the T7 RNAP reactions: the enzyme-binding rate (k on) to and the dissociation rate (k off) from the promoter, the proceeding rate (k for) from the promoter to the forward stall position, the polymerization rate (k cat) of RNA along DNA, and the release rate (k r) from the end of the template DNA. We found that k cat (120s−1) was extremely large compared with k off (0.014s−1), k for (0.062s−1), and k r (0.014s−1), revealing that the rate-limiting steps of T7 RNAP involve the binding to the promoter, the movement to the stall position, and the release from DNA. These kinetic parameters were compared with values for other DNA-binding enzymes. [Copyright &y& Elsevier]

By combining several surface analytical tools, we show that an adsorbed layer of the protein H*Protein B prevents the adsorption of secondary proteins bovine serum albumin, casein, or collagen at low-salinity conditions and at pH 8. H*Protein B is an industrially producible fusion protein of the hydrophobin family, known for its high interfacial activity. While applications of hydrophobin have been reported to facilitate adhesion of proteins under different pH conditions, careful analysis by quartz-crystal microbalance and ellipsometry prove that no additional adsorption can be found on top of the H*Protein B layer in this study. Surface analysis by X-ray photoelectron spectroscopy and secondary ion mass spectrometry proves that the hydrophobin layer stays intact even after hours of exposure to solutions of the secondary proteins and that no exchange of proteins can be detected. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: ac impedance and electrochemical quartz crystal microbalance (EQCM) techniques have been applied to analyze the structure of electric double-layer formed at carbon/organic electrolyte solution interface using a sputtered carbon electrode. The mass changes caused by electrochemical adsorption (accumulation) of ions have been estimated in the solutions of propylene carbonate (PC) dissolving tetrafluoroborate (BF4 −) salts of lithium (Li+), tetraethylammonium (TEA+) and tetra-n-butylammonium (TBA+) cations. The observed mass changes during the cathodic polarization in the solutions containing TEA+ and TBA+ were well consistent with those expected by the calculation based on mono-layer adsorption of the cations with giving the consideration to the surface roughness. On the other hand, the mass change observed in the solution containing Li+ salt showed that the solvation of Li+ with three or four molecules of PC would be the charge compensation species at the interface. Comparison of the quantity of the electricity passed during the EQCM measurements with that from theoretical calculation with simple Helmholtz-layer model revealed that the major part of the double-layer capacitance would be based on the electrostatic polarization of the solvent molecule directly adsorbed at the carbon surface. [Copyright &y& Elsevier]

We study the effects of the nonuniform thickness of a thin mass layer on a quartz-crystal microbalance. A theoretical analysis is performed on thickness-shear (TSh) vibration of an AT-cut quartz plate with a nonuniform mass layer. Mindlin's 2-D equation for TSh vibration of a quartz plate is used. An elliptical mass layer with stepped thickness is considered which allows an exact analysis based on the plate equation. Free vibration frequencies and modes are obtained. The effects of the mass layer nonuniformity are examined. Results show that a mass layer thicker at the center tends to confine more modes under the mass layer and push the distribution of the TSh displacement toward the center. [ABSTRACT FROM PUBLISHER]

Abstract: Polyaniline (PANI)-chemically coated the electrode of quartz-crystal microbalance (QCM) has been developed for the determination of phosphoric acid (H3PO4) in the liquid phase. The sensing mechanism is based on the fact that the QCM devices produce a change in the oscillating frequency when the PANI coating the electrode of QCM interacts with different concentration of the acid. This was made during the subsequent redoping–dedoping processes of the PANI film in acid and ammonia solutions, respectively. Also, this was made during the successive redoping in different acid solutions. The QCM sensor demonstrated a rapid response to the acid with an excellent reversibility. A linear response of the sensor for different concentrations of H3PO4 was found in region of ⩽1M. The conductivity at different concentration of the acid was also determined. Finally, pH dependence on the electronic absorption of PANI phosphate film was studied which indicates that the film can be used as a sensor over a wider pH range of 3–12. This is in comparison to a PANI-sulphate film which shows limited pH absorption dependence (5–8). [Copyright &y& Elsevier]

Abstract: Nanotubular polyaniline film was deposited onto the electrode of the quartz-crystal microbalance (QCM). The film in the form of emeraldine base was exposed to a solution of silver nitrate. The reduction for silver ions took place and silver nanoparticles were produced at the film surface. The deposition of silver was monitored by using the QCM and the UV–vis spectroscopy. The morphology of the film before and after the silver deposition was studied by the scanning and transmission electron microscopy. Silver nanoparticles had sizes of about 50–120nm and globular and triangular shape. X-ray diffraction and infrared spectroscopy were used to characterize the structure of the composite. The present approach could be used for noble-metal recovery in waste waters. [Copyright &y& Elsevier]

Abstract: Polyaniline (PANI) emeraldine-base films have been exposed to iodine solutions. The interaction between the films and the iodine solution was studied using the quartz-crystal microbalance (QCM) technique and the UV–visible absorption spectroscopy. The iodine-treated film of emeraldine base was subjected to dedoping process using 0.1 M ammonia solution. The resulting film was exposed again to the previously used iodine solution. Iodine was found to play multiple roles: the ring-iodination of PANI film, the oxidation of PANI to pernigraniline base, and iodine doping to PANI salt. A sensor based on PANI-coated electrode of QCM was developed to monitor the presence of iodine in solution. [Copyright &y& Elsevier]

Low-molecular-weight acid vapors cause aging and destruction in material processing. In this paper, facile fabrication of novel corn-husk-shaped fullerene C60 crystals (CHFCs) through the dynamic liquid–liquid interfacial precipitation method is reported. The CHFCs were grown at the liquid–liquid interface between isopropyl alcohol (IPA) and a saturated solution of C60 in mesitylene under ambient temperature and pressure conditions. The average length, outer diameter, and inner diameter of CHFCs were ca. 2.88 μm, 672 nm, and 473 nm, respectively. X-ray diffraction (XRD) analysis showed the CHFCs exhibit a mixed face-centered cubic (fcc) and hexagonal-close pack (hcp) crystal phases with lattice parameters a = 1.425 nm, V = 2.899 nm3 for fcc phase and a = 2.182 nm, c = 0.936 nm, a/c ratio = 2.33, and V = 3.859 nm3 for hcp phase. The CHFCs possess mesoporous structure as confirmed by transmission electron microscopy (TEM) and nitrogen sorption analysis. The specific surface area and the pore volume were ca. 57.3 m2 g−1 and 0.149 cm3 g−1, respectively, are higher than the nonporous pristine fullerene C60. Quartz crystal microbalance (QCM) sensing results show the excellent sensing performance CHFCs sensitive to acetic acid vapors due to the enhanced diffusion via mesoporous architecture and hollow structure of the CHFCs, demonstrating the potential of the material for the development of a new sensor system for aliphatic acid vapors sensing. [ABSTRACT FROM AUTHOR]

Abstract: Novel low-humidity sensors were fabricated by the in situ photopolymerization of polypyrrole/Ag/TiO2 nanoparticles (PPy/Ag/TiO2 NPs) composite thin films on a quartz-crystal microbalance (QCM). The characterizations of the thin films were analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The sensitivity increased with the doping amount of TiO2 NPs. The PPy/Ag/50wt% of TiO2 NPs composite thin films exhibited excellent sensitivity (0.0246 −ΔHz/Δppmv at 171.1ppmv), linearity (R 2 =0.9576) and a short response time (12s at 55.0ppmv). The low-humidity sensing mechanism was elucidated in terms of surface texture and the nanostructural morphology of the composite materials. Additionally, based on the dynamic analysis of adsorption, the association constants of water vapor molecules with PPy/Ag and PPy/Ag/50wt% TiO2 NPs composite thin films were estimated to be 81.6 and 227.9M−1, respectively, explaining the effect of adding 50wt% TiO2 NPs to PPy/Ag; the sensitivity to low humidity increased as the association constant increased. [Copyright &y& Elsevier]

Abstract: Calreticulin (CRT) is a soluble molecular chaperone of the endoplasmic reticulum. It is a lectin that promotes the folding of proteins carrying N-linked glycans. Recent investigations have revealed that glucosylated high-mannose-type glycans are employed as key elements in this process. Here, we performed quantitative analyses of the interaction of CRT with various disaccharides, including fluorine-substituted analogues using a quartz-crystal microbalance (QCM). These experiments revealed the weak affinity of 2- and 3-fluoroglucose derivatives. On the other hand, 6-fluoroglucose derivatives exhibited a significant affinity, indicating that the role of 6-position of OH is less significant for binding to CRT. We also characterized binding epitope of the Glcα1-3ManαMe to CRT by saturation transfer difference (STD) NMR spectroscopy. It is proposed that 2-, 3-, and 4-positions of Glc and 3-, 4-, and 6-positions of Man are in close contact with CRT binding pocket, while 6-position of Glc and 2-position of Man are not. These finding are in excellent agreement with our QCM experiment. [Copyright &y& Elsevier]

Abstract: Hydrogen storage in single-walled carbon nanotubes (SWCNTs) was investigated by using a dual quartz-crystal microbalance (QCM). The chamber pressure can be adjusted from up to 1 MPa. The dual QCM decreases the frequency fluctuations that originate from environmental variables such as temperature and pressure. Our moisture-free chamber enables us to measure accurately the hydrogen storage capacity in carbon nanotubes. Highly purified SWCNTs store about 0.2 wt% of hydrogen at room temperature under 0.5 MPa through physical adsorption. Our SWCNTs without baking adsorb up to 1 wt% of water, often obscuring the hydrogen storage capacity. Our results suggest that the hydrogen storage capacity relies strongly on the functional groups remaining on the SWCNTs which may enhance the storage capacity. [Copyright &y& Elsevier]

Abstract: The electrical conductivity of polyaniline depends on factors such as degree of oxidation, type of protonation, and dopant weight fraction. The last of these factors is connected with the loss of mass during the deprotonation of polyaniline, and can thus conveniently be determined in situ by the use of a quartz microbalance. This is illustrated in the present paper which concerns the determination of the weight fraction of acid in thin polyaniline films prepared by the chemical oxidation of aniline in the aqueous solutions of sulfuric and phosphoric acids. It is illustrated that the deprotonation–reprotonation processes are fast, complete, and reversible. Polyaniline has sulfate counter-ions in 0.1 M sulfuric acid while, in 0.5–1 M sulfuric acid, hydrogen sulfate counter-ions are present. The quartz microbalance involving polyaniline films can be used in the sensing of the acidity. [Copyright &y& Elsevier]