Quartz Crystal Microbalance System Research Articles

Quantification of Enzymatic Biofilm Removal Using the Sauerbrey Equation: Application to the Case of Pseudomonas protegens.

A methodology for the quantitative analysis of enzymatic removal of biofilms (BF) was developed, based on a quartz crystal microbalance (QCM) under stationary conditions. This was applied to the case of Pseudomonas protegens (PP) BFs, through a series of five enzymes, whose removal activity was screened using the presented methodology. The procedure is based on the following: when BFs can be modeled as rigid materials, QCM can be used as a balance under stationary conditions for determining the BFs mass reduction by enzymatic removal. For considering a BF as a rigid model, energy dissipation effects, associated with viscoelastic properties of the BF, must be negligible. Hence, a QCM system with detection of dissipation (referred to as QCM with dissipation) was used for evaluating the energy losses, which, in fact, resulted in negligible energy losses in the case of dehydrated PP BFs, validating the application of the Sauerbrey equation for the change of mass calculations. The stationary methodology reduces operating times and simplifies data analysis in comparison to dynamic approaches based on flow setups, which requires the incorporation of dissipation effects due to the liquid media. By carrying out QCM, glycosidase-type enzymes showed BF removal higher than 80% at enzyme concentration 50 ppm, reaching removal over 90% in the cases of amylase and cellulase/xylanase enzymes. The highest removal percentage produced a reduction from about 15 to 1 μg in the BF mass. Amylase enzyme was tested from below 50 to 1 ppm, reaching around 60% of removal at 1 ppm. The obtained results were supported by other instrumental techniques such as Raman spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, atomic force microscopy, high performance anion exchange chromatography, thermogravimetric analysis, and differential scanning calorimetry. The removal quantifications obtained with QCM were compared with those obtained by well-established screening techniques (UV-vis spectrophotometry using crystal violet and agar diffusion test). The proposed methodology expands the possibility of using a quartz microbalance to perform enzymatic activity screening.

Design and development of a portable low-cost QCM-based system for liquid biosensing

Quartz crystal microbalance (QCM) is a versatile sensing platform that has gained increasing attention for its use in bioapplications due to its high sensitivity, real-time measurement capabilities, and label-free detection. This article presents a portable QCM system for liquid biosensing that uses a modified Hartley oscillator to drive 14 mm-diameter commercial QCM sensors. The system is designed to be low-cost, easy to use, and highly sensitive, making it ideal for various bioapplications. A new flow cell design to deliver samples to the surface of the sensor has been designed, fabricated, and tested. For portability and miniaturization purposes, a micropump-based pumping system is used in the current system. The system has a built-in temperature controller allowing for accurate frequency measurements. In addition, the system can be used in benchtop mode. The capability of the present system to be used in liquid biosensing is demonstrated through an experimental test for sensitivity to changes in the viscosity of glycerol samples. It was found to have a sensitivity of 263.51 Hz/mPa.s using a 10 MHz QCM sensor. Future work regarding potential applications was suggested.Graphical

Formaldehyde gas sensors based on a quartz crystal microbalance modified with aniline-doped polyvinyl acetate nanofibers.

Real-time detection of formaldehyde in the atmosphere remains challenging. The available gaseous formaldehyde sensing methods offer limited sensitivity, selectivity, and robustness. We modified a quartz crystal microbalance (QCM) system for selective detection of formaldehyde in air. The QCM surface was functionalized with polyvinyl acetate (PVAc) nanofibers and doped with 2, 4, and 6 wt% aniline to improve the selectivity and sensitivity of the sensor. The chemical content and morphological structure of PVAc nanofibers doped with aniline were confirmed by Fourier-transform infrared (FTIR) spectroscopy, energy-dispersive X-ray (EDX) spectroscopy, and scanning electron microscopy (SEM). The results showed that the modified QCM sensor had a sensitivity of 0.056 Hz ppm-1 with a response and recovery times of 200 s and 90 s, respectively. It gave limits of detection (LOD) and limit of quantification (LOQ) of 28 ppm and 96 ppm, respectively. Moreover, the modified QCM was selective towards formaldehyde compared to the other gases. The current workplace exposure limit (WEL) for formaldehyde is 2 ppm, with a time-weighted average over eight hours. Future work will focus on improving the reported QCM sensor to meet the required LOD for formaldehyde detection in the environment and industrial sites.

Analysis of HepG2 cell response to a wide concentration range of mitomycin C using a multichannel quartz crystal microbalance system with a microscope

The morphological response of HepG2 cells to mitomycin C was analyzed using a multichannel quartz crystal microbalance system equipped with a home-built movable microscope that enables the simultaneous acquisition of cell images and measurements of eight-channel quartz crystal microbalance. After 24 h of cell seeding, mitomycin C was injected into the culture medium. During the attachment process, the resonant frequency decreased, and the curves fitted well with the first-order lag response. Analysis of the response to mitomycin C revealed that the resonant frequency response curves varied with mitomycin C concentration. When the mitomycin C concentration was <10 μmol L−1, the delay time was observed before the increase in resonant frequency. When the mitomycin C concentration was extremely low, an additional decrease in resonant frequency was observed in the middle of the delay time that fitted well with the cumulative log-normal distribution curve. The resonant frequency response curves after the delay time fitted well with the cumulative log-normal distribution curves. The delay time and mean cumulative log-normal distribution time for the increase in resonant frequency correlated with the mitomycin C concentration; however, the mean time for the additional decrease in the resonant frequency did not show a statistically significant difference as a function of mitomycin C concentration. For mitomycin C concentrations of >20 μmol L−1, the response to the change in resonant frequency was rapid, and the response curves fitted well with the first-order lag response. The first-order lag response indicates that the response occurred simultaneously for all cells. The results showed that the time constant was independent of the tested mitomycin C concentration between 20 and 100 μmol L−1. These results suggested that different cell death processes occurred by mitomycin C. The findings of this study suggest that the system can be used to investigate cell death in adherent cells.

A Quartz Crystal Microbalance (QCM) Study on the Formation of Aqueous κ-Carrageenan-Chitosan Composite Bilayers with NaCl and Graphene Oxide

Biomaterials and thin biofilms play a fundamental role in the medical, food and pharmaceutical industries. The Quartz crystal microbalance (QCM) measurement technique is one of the attractive techniques which have been used for monitoring the thin-film formation process. In the current work described here, κ-carrageenan and chitosan solutions were used for the layer-by-layer (LBL) deposition of polyelectrolyte multilayers (PEMs) on the gold surface of a 5 MHz AT-cut (thickness-shear mode) quartz crystal in a flow module. A sensitive QCM system was designed to detect 0.1 Hz differences in the resonance frequency (Δf) and 10−7 changes in the energy dissipation (ΔD) values, which are the measures of the deposited mass and the film rigidity, respectively. Negatively charged carrageenan and positively charged chitosan biomolecules in the solutions were used to build up sequential and very thin bilayers on the modified gold surface. The effects of NaCl and graphene oxide (GO) addition on the mass of the deposited films were also investigated. Intermolecular interactions between the biopolymer chains, Na+ cations and GO sheets were explained by interactions between molecules, such as electrostatic forces and hydrogen bondings.

Biased quartz crystal microbalance method for studies of chemical vapor deposition surface chemistry induced by plasma electrons.

A recently presented chemical vapor deposition (CVD) method involves using plasma electrons as reducing agents for deposition of metals. The plasma electrons are attracted to the substrate surface by a positive substrate bias. Here, we present how a standard quartz crystal microbalance (QCM) system can be modified to allow applying a DC bias to the QCM sensor to attract plasma electrons to it and thereby also enable in situ growth monitoring during the electron-assisted CVD method. We show initial results from mass gain evolution over time during deposition of iron films using the biased QCM and how the biased QCM can be used for process development and provide insight into the surface chemistry by time-resolving the CVD method. Post-deposition analyses of the QCM crystals by cross-section electron microscopy and high-resolution x-ray photoelectron spectroscopy show that the QCM crystals are coated by an iron-containing film and thus function as substrates in the CVD process. A comparison of the areal mass density given by the QCM crystal and the areal mass density from elastic recoil detection analysis and Rutherford backscattering spectrometry was done to verify the function of the QCM setup. Time-resolved CVD experiments show that this biased QCM method holds great promise as one of the tools for understanding the surface chemistry of the newly developed CVD method.

Design of surface nanostructures for chirality sensing based on quartz crystal microbalance.

Quartz crystal microbalance (QCM) has been widely used for various sensing applications, including chirality detection due to the high sensitivity to nanogram or picogram mass changes, fast response, real-time detection, easy operation, suitability in different media, and low experimental cost. The sensing performance of QCM is dependent on the surface design of the recognition layers. Various strategies have been employed for studying the relationship between the structural features and the specific detection of chiral isomers. This review provides an overview of the construction of chiral sensing layers by various nanostructures and materials in the QCM system, which include organic molecules, supermolecular assemblies, inorganic nanostructures, and metal surfaces. The sensing mechanisms based on these surface nanostructures and the related potentials for chiral detection by the QCM system are also summarized.

Novel Trend in Development of QCM System Based on Analysis of Adsorption Kinetics

In this work, modern approach was demonstrated which is improving the performance of gas sensors that utilize the quartz crystal microbalance technique. The gas sensors based on quartz crystal microbalance (QCM) are one of the common methods using for gas sensor applications. Although, these QCM sensors posses high sensitivities, its ability to discriminate the target gas still need to develop. It does not have the ability to identify or distinguish the type of gas. The idea of this work depends on investigating and invest the kinetics of the diffusion and adsorption thermodynamics gas molecules to identify gas species. So, the relationship between the parameter of the dynamic adsorption and chemisorption thermodynamic parameter were employed to know the concentration and type of the gases. The sensor was coated Polydimethylsiloxane (PDMS) ultrathin films are prepared via spin coating system, and micro incision via lithographic methods has been created on the PDMS film. In order to enhance the selectivity of the sensor. The outcome data prove the methology was working and considerable. Nevertheless, there are insufficiency. The gas molecules distinction was made possible by analysis the response signal. In particular, observing and taking into account the difference and change in the time constant. Where note a difference in the time constant due to present of the micro-pattern layer.

Effect of Zn(S,O,OH) Buffer Thin Films Formed on CIGS through Different Stages and Reaction Processes in Chemical Bath Deposition: Interpretations from Mechanisms and Transformation Kinetics Perspective

Herein, Zn(S,O,OH) is used as a buffer material for Cu(In,Ga)Se2 (CIGS) solar cells instead of CdS to increase the quantum efficiency and remove toxicity. To control the fine thickness of the Zn(S,O,OH) thin films in the chemical bath deposition (CBD) method, a quartz crystal microbalance (QCM) system is introduced by measuring the frequency change. As the frequency changes are adjusted according to the S/O ratio of the Zn(S,O,OH) buffer (Zn buffer) produced during the reaction, the formed phase and thickness are cross‐validated several times to obtain the accurate thickness. These different S/O ratios can be modified by different deposition mechanisms and reaction processes depending on the reaction rate of material formation. Therefore, to investigate the associated mechanism and reaction process in detail, Zn buffer thin films are formed and characterized using two different Zn sources (zinc sulfate and zinc acetate) that affect the reaction rate due to the anion effect. In addition, the optimal deposition range is obtained by comparing the performances of the solar cells with Zn thin films of the same thickness, deposited through different stages in a continuous CBD reaction. Finally, the effect of Zn buffers using different Zn sources on the interfaces with CIGS is investigated in the band alignment.

Selective isolation and sensitive detection of lysozyme using aptamer based magnetic adsorbent and a new quartz crystal microbalance system

Magnetic chitosan beads and quartz crystal microbalance chip were decorated with lysozyme specific aptamer for isolation and detection of lysozyme, respectively. The lysozyme specific aptamer was immobilized on poly (dopamine) coated magnetic chitosan beads and the chip via Schiff base reaction. The percentage of the removal efficiency and purity of the isolated lysozyme from egg white were 87.6% and 91.8%, respectively. Further, the sensor system was contacted with different concentrations of lysozyme and other test proteins. This sensor system provided a method for the label-free, concentration-dependent, and selective detection of lysozyme with an observed detection limit of 17.9 ± 0.6 ng/mL. The sensor system was very selective and not significantly responded to the other tested proteins such as ovalbumin, trypsin, cytochrome C, and glucose oxidase. The prepared new sensor system showed a good durability and a high sensitivity for determination of lysozyme from solutions and whole egg white.

A Miniaturized Quartz Crystal Microbalance (QCM) Measurement Instrument Based on a Phase-Locked Loop Circuit

The quartz crystal microbalance (QCM) has been widely used in laboratory settings as an analytical tool for recognizing and discriminating biological and chemical molecules of interest. As a result, recent studies have shown there to be considerable attention in practical applications of the QCM technique beyond the laboratory. However, most commercial QCM instruments are not suitable for off-laboratory usage. For field-deployable applications and in situ detection, the development of a portable QCM measurement system achieving comparable performance to benchtop instruments is highly desired. In this paper, we describe the development of a fully customizable, miniaturized, battery-powered, and cost-efficient QCM system employing a phase-locked loop (PLL) electronic circuit-based QCM measurement system. The performance of this developed system showed a minimum frequency resolution of approximately 0.22 Hz at 0.1 s measurement time. This novel, miniaturized system successfully demonstrated an ability to detect two common volatile organic compounds (VOCs), methanol and dichloromethane (DCM), and the obtained results were comparable to responses from a commercially available benchtop instrument.

Label-Free Real-Time Detection of HBsAg Using a QCM Immunosensor.

Hepatitis B virus surface antigen (HBsAg) is an important protein in both diagnosis and prevention of hepatitis B infection. In the current study, a piezoelectric immunosensor based on antibody-antigen interaction was designed to detect HBsAg. A quartz crystal microbalance system was employed to detect antibody-antigen interaction. At first, an oscillator was designed to measure the resonant frequency affected by the reactants using IC 74LVC1GX04. Antibody against HBsAg was immobilized on 10 MHz AT-cut quartz crystal. The surface modifications were monitored by atomic force microscopy (AFM) and contact angle measurements. Different concentrations of antibody were used for surface immobilization and the frequency shifts were assessed. The system stability was studied by evaluating the stability of the crystal and the immobilized antibody. The adsorption of antibody onto the crystal was analyzed using AFM and changes in the resonance frequency. Further, a direct immunoassay was performed with this immobilized antibody to identify HBsAg solutions at different concentrations. Finally, specific and non-specific responses were investigated using hepatitis B (HBsAg) and hepatitis C (HCV Ag) antigens, respectively. Antibodies against HBsAg were successfully immobilized on 10 MHz AT-cut quartz crystal. The stability tests of crystal immobilized with antibody and unimmobilized crystal revealed that both forms of crystals were stable. Theoretical and experimental frequency assays were compared. A decrease in the contact angle indicated the hydrophilicity of surface after modifications. AFM images illustrated a more uniform surface after antibody adsorption and the surface roughness (RMS) reduced from 1.13 to 0.99 nm. Changes in the frequency were detected after the physical adsorption of HBsAb on the designed chip. The standard curve of antigen revealed the frequency changes depend on concentration of antigen. Finally, the specificity test confirmed the specificity of the designed biosensor for the detection of HBsAg from HCV Ag. The quantization of immobilized antibody was characterized by the frequency shift of the QCM. The obtained results were compared with ELISA assay. The correlation coefficients of HBsAg dilution between QCM and ELISA was 0.9821. This study is a new step to meet the challenges regarding HBsAg detection. Physical adsorption used in this study was effective as the simplest immobilization method to design a QCM-based immunosensor for HBsAg detection. Facilitated, fast, and simple detection of HBsAg by an antibody-based QCM biosensor is our main objective.

Analysis of HepG2 Cell Response to a Wide Concentration Range of Mitomycin C Using a Multichannel Quartz Crystal Microbalance System With a Microscope

Analysis of HepG2 Cell Response to a Wide Concentration Range of Mitomycin C Using a Multichannel Quartz Crystal Microbalance System With a Microscope

Preparation of Notch-4 Receptor Containing Quartz Crystal Microbalance Biosensor for MDA MB 231 Cancer Cell Detection.

Quartz crystal microbalance (QCM) is a highly sensitive system thatis used as a biosensor for biomolecules and cells. Detection and characterization of cancer cells in circulation or biopsy samples is of crucial importance for cancer diagnosis. Here, we introduce approaches for breast cancer cell detection via their surface molecules. The sensor system is based on preliminary coating of QCM chip with polymeric nanoparticles to increase the surface area and allow for the attachment of proteins to the chip surface. This is followed by the attachment of a specific protein in order to functionalize the chip. Breast cancer cells and fibroblast cells as control are cultured and applied to this chip. The functionalized QCM system candetect breast cancer cells with high affinity and selectivity. Here, we present the preparation methods of QCM-based sensors for selective detection of MDA MB 231 cancer cells. Selectivity of QCM-based sensor is carried out in the presence of L929 mouse fibroblast cells.

Chiral Recognition on Bare Gold Surfaces by Quartz Crystal Microbalance.

Quartz crystal microbalance (QCM) is one of the powerful tools for the studies of molecular recognition and chiral discrimination. Its efficiency mainly relies on the design of the functional sensitive layer on the electrode surface. However, the organic sensitive layer may easily cause dissipation of oscillation or detachment and weaken the signal transfer during the molecular recognition processes. In this work, we reveal for the first time that the bare metal surface without the organic selector layer has the capability for chiral recognition in the QCM system. During the adsorption of various chiral amino acids, relatively higher selectivity of D-enantiomers on gold (Au) surface was shown by the QCM detection. Based on analyses of the surface crystalline structure and density functional theory calculations, we demonstrate that the chiral nature of Au surface plays an important role in the selective binding of specific D-amino acids. These results may open new insights on chiral detection by QCM system. It will also promote the construction of novel chiral sensing systems with both efficient detection and separation capability.

Development of a Battery-Operated Handheld QCM Measurement Electronics

There continues to be major interest in detection and discrimination of volatile organic compounds (VOCs) because these compounds are pervasive in common environments, such as buildings, factories, and in households, among others. These VOCs can be detrimental to both human health and organisms in the environment. The quartz crystal microbalance (QCM) has become a popular analytical instrument to detect various VOCs [1]. However, most QCM studies are performed in a laboratory setting with cumbersome benchtop instruments. To utilize the QCM technique in a manner that permits researchers to be outside of a laboratory environment, such as VOCs detection on-site and point-of-care testing (POCT), it is important to develop a suitably portable QCM measurement system that maintains acceptable system performance, such as frequency resolution and measurement time, which requires low-power input [2, 3]. To fulfill this demand, we propose a QCM measurement electronic system that uses a phase-locked loop (PLL) circuit as a frequency-to-voltage converter and measures an output voltage level to calculate frequency shifts of the resonator. Our proposed system does not rely on the quality of a clock frequency, which is important in typical frequency counters to improve measurement performance. Instead, a common microcontroller is used to calculate frequency shift. In this work, a portable QCM system based on this strategy was developed, and its performance successfully characterized by measuring changes in system output voltage corresponding to input frequency changes. Temperature dependence of frequency changes was also investigated from 15 to 55 °C. With a resonance frequency of 5 MHz, the system showed a frequency resolution of 0.22 Hz, which is significantly less than a common frequency counter. For validation, we employed Ionic Liquids and a Group of Uniform Materials based on Organic Salts (GUMBOS) as chemosensitive coating materials for VOCs detection [4]. Measurement results of the frequency shift caused by VOCs from the developed system were comparable to those obtained from experiments with a commercial system (QSense Analyzer, Biolin Scientific), which demonstrates the feasibility of applying this electronic strategy for development of a portable QCM measurement system.

Mechanism‐Based Approach of CdS/Cu(In,Ga)Se2 (CIGS) Interfaces for CIGS Solar Cells through Deposition in Different Stages of Continuous Chemical Bath Deposition Reaction: Key to Achieving High Photovoltaic Performance

To accurately obtain an adjustable CdS layer, a quartz crystal microbalance (QCM) system is used in the chemical bath deposition (CBD) method by measuring the frequency change. However, although the thickness of the CdS layers deposited using the QCM system can be accurately adjusted to the same thickness, CdS layers of the same thickness formed in each section of the continuous reaction are expected to have different properties due to the reaction rate and mechanism, ultimately affecting the performance of solar cells. Therefore, 30 nm‐thick CdS layers are formed in the various reaction sections (initial, middle, and late ranges) and their characteristics and performances are examined and compared with the conventional 60 nm‐thick CdS buffer layer. Most Cu(In,Ga)Se2 (CIGS) solar cells with the 30 nm‐thick CdS buffer exhibit a higher efficiency than those with the 60 nm‐thick CdS buffer due to improved J sc. However, the CIGS with the 30 nm CdS formed in the middle range exhibits the lowest photovoltaic performance. To investigate this unexpected result, all the deposited CdS layers are chemically, structurally, and optically examined and the results are explained by a deposition mechanism study. Furthermore, the effect of heat treatment is demonstrated by band alignment.

NS1 glycoprotein detection in serum and urine as an electrochemical screening immunosensor for dengue and Zika virus.

The incidence of infection by the dengue virus (DENV) has grown dramatically, reaching 128 countries in tropical and subtropical regions worldwide, with a pattern of hyper-endemicity. DENV is a mosquito-borne disease having four serotypes, one or two circulating in epidemic outbreaks. The diagnosis of DENV is challenging mainly due to the circulation of new viruses with remarkable similarities, such as Zika (ZIKV) that may cause fetal microcephaly. DENV affects 390 million people per year, but these numbers may be higher due to the underreported and misclassified cases. Recently, the NS1 nonstructural protein has been described in serum and urine of DENV and ZIKV patients, suggesting its use as a biomarker for screening since a negative NS1 sample confirms the absence of these infections. Herein, a label-free immunosensor comprising an assembled nanostructured thin film of carbon nanotube-ethylenediamine is described. The advantage of in situ electrosynthesis of polymer film is to allow major control of thickness and conductivity, in addition to designing the reactive groups for functionalization. A quartz crystal microbalance system was used to estimate the thickness of the polymeric film obtained. The anti-NS1 monoclonal antibodies were immobilized to carbon nanotubes by covalent linkage, permitting a high stability during measurements. Analytical responses to NS1 were obtained by differential pulse voltammetry (DPV), showing a linear range from 20 to 800ngmL-1 and reproducibility of 3.0%, with a limit of detection (LOD) of 6.8ngmL- 1. This immunosensor was capable of detecting ZIKV and DENV NS1 in spiked urine and real serum in a clinical range.Graphical abstract.

Finite element analysis on the quartz plate due to the placement of quartz crystal microbalance on printed circuit board

Quartz Crystal Microbalance (QCM) is a high sensitivity piezoelectric sensor that enables it to detect loads in the nanogram order. QCM usually consists of a thin quartz plate with an AT-cut orientation. The sensor resonance frequency and its stability are affected by the sensor parameter and its placement in the reaction cell. Previous studies have shown that the physical parameters and geometric shapes of the QCM sensor greatly affected the sensitivity and stability of the sensor. As the sensor is thin, only in the order of hundredths micrometer, pressure, or force on top of the sensor surface also affects the sensor resonance frequency. In this study, we conducted a deformation analysis due to the placement of QCM on the Printed Circuit Board (PCB). The simulation is done by Finite Element Method using ANSYS 19.2. Variations in the shape of the electrodes on the PCB and O-ring elastic modulus that used in the QCM system has been investigated O-rings that have a smaller elastic modulus that will cause greater deformation. From the two types of PCB electrodes, electrodes in the form of ¾ circular arcs give smaller deformations than electrodes in the form of ½ circular arcs. The deformation occurs in the order of 10−6 m.

Effects of Surface Modification on Adsorption Behavior of Cell and Protein on Titanium Surface by Using Quartz Crystal Microbalance System

Primary stability and osseointegration are major challenges in dental implant treatments, where the material surface properties and wettability are critical in the early formation of hard tissue around the implant. In this study, a quartz crystal microbalance (QCM) was used to measure the nanogram level amount of protein and bone marrow cells adhered to the surfaces of titanium (Ti) surface in real time. The effects of ultraviolet (UV) and atmospheric-pressure plasma treatment to impart surface hydrophilicity to the implant surface were evaluated. The surface treatment methods resulted in a marked decrease in the surface carbon (C) content and increase in the oxygen (O) content, along with super hydrophilicity. The results of QCM measurements showed that adhesion of both adhesive proteins and bone marrow cells was enhanced after surface treatment. Although both methods produced implants with good osseointegration behavior and less reactive oxidative species, the samples treated with atmospheric pressure plasma showed the best overall performance and are recommended for clinical use. It was verified that QCM is an effective method for analyzing the initial adhesion process on dental implants.