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In this study, multiple particle binding-liposomes (MPB-Lips), encapsulating the luminophore tris(2′,2-bipyridyl)ruthenium (II) complex ([Ru(bpy)3]2+), were developed as an electrochemiluminescence (ECL) signal amplifier and were applied to detect the model analyte streptavidin (SA) using the indirect competitive ECL method. The MPB-Lips were prepared by mixing various ratios of two different liposomes—one containing a phospholipid with a primary amine group and a biotinyl group (BIO/NH2-Lip) and one containing a phospholipid with an N-hydroxysuccinimide group (NHS-Lip) to allow binding between particles via amide bonds. Quartz crystal microbalance analysis using SA-modified gold-coated quartz crystals showed that the frequency shift values of MPB-Lips gradually decreased in the order BIO/NH2-Lip:NHS-Lip = 1:0 < 1:1 < 1:3 < 1:5. This indicated that MPB-Lips were successfully formed. The indirect competitive ECL method using SA-modified gold electrodes showed that the 1:5-Lip system had greater sensitivity than the 1:0-Lip system—the limit of detection and quantification values for the systems were 1.84 and 6.30 μg mL−1 for 1:0-Lip, and 1.20 and 1.74 μg mL−1 for 1:5-Lip. Finally, the recovery of SA spiked in fetal bovine serum samples using the 1:5-Lip system showed good accuracy and precision with a recovery rate of 83–106% and relative standard deviation of 4–14%. Our study demonstrated that the MPB-Lips system was an effective and useful ECL amplifier and the ECL method using MPB-Lips could be applied to detect an analyte in a real sample. [ABSTRACT FROM AUTHOR]

The surfaces of solids (gold, silver, and polymers) have been modified with adsorption layers of various compounds. Optimal modification conditions have been determined using the methods of contact angle measuring and quartz crystal microbalance. The degree of surface coverage with the adsorption layer has been calculated and the data obtained have been compared with the results of the direct measurements of adsorption. The surface energy of the modifying layers has been determined and the potential application fields of the modified solids as functional materials have been demonstrated. [ABSTRACT FROM AUTHOR]

Triazine pesticide (atrazine and its derivatives) detection sensors have been developed to thoroughly check for the presence of these chemicals and ultimately prevent their exposure to humans. Sensitive coatings were designed by utilizing molecular imprinting technology, which aims to create artificial receptors for the detection of chlorotriazine pesticides with gravimetric transducers. Initially, imprinted polymers were developed, using acrylate and methacrylate monomers containing hydrophilic and hydrophobic side chains, specifically for atrazine, which shares a basic heterocyclic triazine structure with its structural analogs. By adjusting the ratio of the acid to the cross-linker and introducing acrylate ester as a copolymer, optimal non-covalent interactions were achieved with the hydrophobic core of triazine molecules and their amino groups. A maximum sensor response of 546 Hz (frequency shift/layer height equal to 87.36) was observed for a sensitive coating composed of 46% methacrylic acid and 54% ethylene glycol dimethacrylate, with a demonstrated layer height of 250 nm (6.25 kHz). The molecularly imprinted copolymer demonstrated fully reversible sensor responses, not only for atrazine but also for its metabolites, like des-ethyl atrazine, and structural analogs, such as propazine and terbuthylazine. The efficiency of modified molecularly imprinted polymers for targeted analytes was tested by combining them with a universally applicable quartz crystal microbalance transducer. The stable selectivity pattern of the developed sensor provides an excellent basis for a pattern recognition procedure. [ABSTRACT FROM AUTHOR]

[Display omitted] The interactions of viral fusion peptides from influenza (E4K and Ac-E4K) and human immunodeficiency virus (gp41 and Ac-gp41) with planar lipid bilayers and monolayers was investigated herein. A combination of surface-sensitive techniques, including quartz crystal microbalance with dissipation (QCM-D), Langmuir-Blodgett area-pressure isotherms with Micro-Brewster angle microscopy, and neutron reflectometry, was employed. Differences in the interactions of the viral fusion peptides with lipid bilayers featuring ordered and disordered phases, as well as lipid rafts, were revealed. The HIV fusion peptide (gp41) exhibited strong binding to the DOPC/DOPS bilayer, comprising a liquid disordered phase, with neutron reflectometry (NR) showing interaction with the bilayer's headgroup area. Conversely, negligible binding was observed with lipid bilayers in a liquid ordered phase. Notably, the influenza peptide (E4K) demonstrated slower binding kinetics with DOPC/DOPS bilayers and distinct interactions compared to gp41, as observed through QCM-D. This suggests different mechanisms of interaction with the lipid bilayers: one peptide interacts more within the headgroup region, while the other is more involved in transmembrane interactions. These findings hold implications for understanding viral fusion mechanisms and developing antimicrobials and antivirals targeting membrane interactions. The differential binding behaviours of the viral fusion peptides underscore the importance of considering membrane composition and properties in therapeutic strategy design. [ABSTRACT FROM AUTHOR]

This study investigated the effect of a magnetic field on the crystal deposition of treated seawater to determine the mechanism of calcium carbonate deposition on the quartz surface. Several samples of standard seawater (43 g/L) were circulated through a permanent magnetic field of 0.16 T at a fixed temperature, pH, and flow rate. Scaling experiments showed that magnetic treatment of seawater enhanced the precipitation of calcium carbonate and that two superposed phases were deposited. A first layer formed with crystals of aragonite covering the whole surface of the quartz, and then a second phase of calcite was deposited. In the untreated solutions, only homogeneous agglomerates of aragonite were deposited. [ABSTRACT FROM AUTHOR]

AbstractA theoretical model of a quartz crystal microbalance carrying a layer of substrate and an array of micropillars based on the classical and modified Timoshenko beam theory was established. By choosing specific substrate thickness and micropillar height, this composite sensor approaches the coupled resonance state, and thus significantly improving the mass sensitivity. The intentionally designed sensor is extremely sensitive to tiny mass. However, with increasing mass, the mass sensitivity decreases sharply and then tends to be constant. The frequency shifts calculated by two models have some differences, but their mass sensitivity is almost the same. [ABSTRACT FROM AUTHOR]

Supercritical Impregnation methods are becoming popular in the development of food packaging materials. Bulk functional improvements of cellulose substrates using this method may be influenced by interfacial interactions between the impregnated solutes and cellulose. Hence, an interfacial adsorption kinetics study of solute molecules onto the substrate can provide insight on bulk property development, leading to an optimized packaging material with improved functionality. Paper substrates were impregnated with two food-grade waxes: Alkyl Ketene Dimer (AKD) and Carnauba Wax (CW). Hydrophobic development was monitored over a 3-week period. A quartz crystal microbalance (QCM-D) was used to determine interfacial characteristics and behavior of each wax with cellulose, and adsorption kinetics were quantified to compare the mass transfer processes of each wax at the interface. AKD significantly contributed to the substrate's hydrophobic development over time. CW generated mildly hydrophobic substrates only when heated. AKD strongly adhered to the cellulose fibers at the interface, and demonstrated a 3-stage kinetic adsorption process, tentatively assigned (i) diffusion through the solvent; (ii) diffusion through the substrate; and (iii) attachment onto the fibers. CW readily washed off the cellulose surface, demonstrating only the first adsorption process. The different chemical structures also impacted these behaviors, as did concentration and temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] Conjugating biomolecules, such as antibodies, to bioconjugate moieties on lipid surfaces is a powerful tool for engineering the surface of diverse biomaterials, including cells and nanoparticles. We developed supported lipid bilayers (SLBs) presenting well-defined spatial distributions of functional moieties as models for precisely engineered functional biomolecular-lipid surfaces. We used quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM) to determine how vesicles containing a mixture of 1,2-dipalmitoyl- sn - glycero -3-phosphatidylcholine (DPPC) and 1,2-distearoyl- sn - glycero -3-phosphoethanolamine-N-[azido(polyethylene glycol)-2000] (DSPE-PEG-N 3) form SLBs as a function of the lipid phase transition temperature (T m). Above the DPPC T m , DPPC/DSPE-PEG-N 3 vesicles form SLBs with functional azide moieties on SiO 2 substrates via vesicle fusion. Below this T m , DPPC/DSPE-PEG-N 3 vesicles attach to SiO 2 intact. Intact DPPC/DSPE-PEG-N 3 vesicles on the SiO 2 surfaces fuse and rupture to form SLBs when temperature is brought above the DPPC T m. AFM studies show uniform and complete DPPC/DSPE-PEG-N 3 SLB coverage of SiO 2 surfaces for different DSPE-PEG-N 3 concentrations. As the DSPE-PEG-N 3 concentration increases from 0.01 to 6 mol%, the intermolecular spacing of DSPE-PEG-N 3 in the SLBs decreases from 4.6 to 1.0 nm. The PEG moiety undergoes a mushroom to brush transition as DSPE-PEG-N 3 concentration varies from 0.1 to 2.0 mol%. Via copper-free click reaction, IgG was conjugated to SLB surfaces with 4.6 nm or 1.3 nm inter-DSPE-PEG-N 3 spacing. QCM-D and AFM data show; 1) uniform and complete IgG layers of similar mass and thickness on the two types of SLB; 2) a higher-viscosity/less rigid IgG layer on the SLB with 4.6 nm inter-DSPE-PEG-N 3 spacing. Our studies provide a blueprint for SLBs modeling spatial control of functional macromolecules on lipid surfaces, including surfaces of lipid nanoparticles and cells. [ABSTRACT FROM AUTHOR]

Quartz Crystal Microbalances (QCMs) are versatile sensors employed in various fields, from environmental monitoring to biomedical applications, owing mainly to their very high sensitivity. However, the assessment of their metrological performance, including the impact of conditioning circuits, digital processing algorithms, and working conditions, is a complex and novel area of study. The purpose of this work is to investigate and understand the measurement errors associated with different QCM measurement techniques, specifically focusing on the influence of conditioning electronic circuits. Through a tailored and novel experimental setup, two measurement architectures—a Quartz Crystal Microbalance with dissipation monitoring (QCM-D) system and an oscillator-based QCM-R system—were compared under the same mechanical load conditions. Through rigorous experimentation and signal processing techniques, the study elucidated the complexities of accurately assessing QCM parameters, especially in liquid environments and under large mechanical loads. The comparison between the two different techniques allows for highlighting the critical aspects of the measurement techniques. The experimental results were discussed and interpreted based on models allowing for a deep understanding of the measurement problems encountered with QCM-based measurement systems. The performance of the different techniques was derived, showing that while the QCM-D technique exhibited higher accuracy, the QCM-R technique offered greater precision with a simpler design. This research advances our understanding of QCM-based measurements, providing insights for designing robust measurement systems adaptable to diverse conditions, thus enhancing their effectiveness in various applications. [ABSTRACT FROM AUTHOR]

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Abstract The development and application of Electrochemical Quartz Crystal Microbalance (EQCM) sensing to study metal electroplating, especially for energy storage purposes, are reviewed. The roles of EQCM in describing electrode/electrolyte interface dynamics, such as the electric double‐layer build‐up, ionic/molecular adsorption, metal nucleation, and growth, are addressed. Modeling of the QCM sensor is introduced and its importance is emphasized. Challenges of metal electrode use, including side reactions and dendrite formation, along with their mitigation strategies are reviewed. Numerous factors affecting the electroplating processes, such as electrolyte composition, additives, temperature, and current density, and their influence on the electroplated metals’ mass, structural, and mechanical characteristics are discussed. Looking forward, the need for deeper fundamental understanding and advancing simulations of the QCM signal response as a result of electroplating metal nanostructures is stressed. Further development and integration of innovative EQCM‐strategies will provide unique future means to fundamentally understand and optimize metal electroplating for energy storage and application alike.

The quartz crystal microbalance (QCM) biosensor is one of the devices that enables label‐free evaluation of biomolecular reactions. Commercial QCM biosensors have less than 10 channels for detection and are not suitable for the screening. The sensitivity of the QCM biosensor increases as the quartz thickness becomes thinner; however, the limit of thinning is 60–330 μm. In this study, applying micromachining technology, a QCM sensor array chip of 15 mm square that had 100 ultra‐thin quartz resonators (2.5 μm) that were operated wirelessly was developed. And we succeeded in detecting the resonance spectrum through the device evaluation. © 2024 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

A fast and accurate identification of Listeria monocytogenes. A new quartz crystal microbalance (QCM) aptasensor was designed for the specific and rapid detection of L. monocytogenes. Before detection of the target bacterium from samples in the QCM aptasensor, a magnetic pre-enrichment system was used to eliminate any contaminant in the samples. The prepared magnetic system was characterized using ATR-FTIR, SEM, VSM, BET, and analytical methods. The saturation magnetization values of the Fe3O4, Fe3O4@PDA, and Fe3O4@PDA@DAPEG particles were 57.2, 40.8, and 36.4 emu/g, respectively. The same aptamer was also immobilized on the QCM crystal integrated into QCM flow cell and utilized to quantitatively detect L. monocytogenes cells from the samples. It was found that a specific aptamer-magnetic pre-concentration system efficiently captured L. monocytogenes cells in a short time (approximately 10 min). The Fe3O4@PDA@DA-PEG-Apt particles provided selective isolation of L. monocytogenes from the bacteria-spiked media up to 91.8%. The immobilized aptamer content of the magnetic particles was 5834 µg/g using 500 ng Apt/mL. The QCM aptasensor showed a very high range of analytical performance to the target bacterium from 1.0 × 102 and 1.0 × 107 CFU/mL. The limit of detection (LOD) and limit of quantitation (LOQ) were 148 and 448 CFU/mL, respectively, from the feeding of the QCM aptasensor flow cell with the eluent of the magnetic pre-concentration system. The reproducibility of the aptasensor was more than 95%. The aptasensor was very specific to L. monocytogenes compared to the other Listeria species (i.e., L. ivanovii, L. innocua, and L. seeligeri) or other tested bacteria such as Staphylococcus aureus, Escherichia coli, and Bacillus subtilis. The QCM aptasensor was regenerated with NaOH solution, and the system was reused many times. [ABSTRACT FROM AUTHOR]

The three decades of experience with piezoelectric devices applied in the field of bioanalytical chemistry are shared. After introduction to principles and suitable measuring approaches, active and passive methods based on oscillators and impedance analysis, respectively, the focus is directed towards biosensing approaches. Immunosensing examples are provided, followed by other affinity sensing approaches based on hybridization of nucleic acids, aptamers, monitoring of enzyme activities, and detection of pathogenic microbes. The combination of piezosensors with cell lines and testing of drugs is highlighted, including mechanically active cells. The combination of piezosensors with other measuring techniques providing original hybrid devices is briefly discussed. [ABSTRACT FROM AUTHOR]

Dimethoate (DIM) as an organophosphorus pesticide is widely utilized especially in the cultivation of vegetables and fruits due to its killing effect on harmful insects. However, unconscious use of DIM in large amounts can also cause serious health problems. For these reasons, rapid and reliable detection of DIM from food samples is significant. In this study, a novel quartz crystal microbalance (QCM) sensor based on erbium molybdate incorporating sulfur-doped graphitic carbon nitride (EM/S-g-C3N4) and a molecularly imprinting polymer (MIP) was designed for DIM detection in apple juice samples. Firstly, an EM/S-g-C3N4 nanocomposite with high purity was prepared under hydrothermal conditions at high temperatures over a long period of time. After the modification of the EM/S-g-C3N4 nanocomposite on a QCM chip, the polymerization solution including N,N′-azobisisobutyronitrile (AIBN) as an initiator, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, methacryloylamidoglutamic acid (MAGA) as a monomer, and DIM as an analyte was prepared. Then, the polymerization solution was dropped on an EM/S-g-C3N4 nanocomposite modified QCM chip and an ultraviolet polymerization process was applied for the formation of the DIM-imprinted polymers on the EM/S-g-C3N4 nanocomposite modified QCM chip. After the polymerization treatment, some characterization studies, including electrochemical, microscopic, and spectroscopic methods, were performed to illuminate the surface properties of the nanocomposite and the prepared QCM sensor. The values of the limit of quantification (LOQ) and the detection limit (LOD) of the prepared QCM sensor were as 1.0 × 10−9 M and 3.3 × 10−10 M, respectively. In addition, high selectivity, stability, reproducibility, and repeatability of the developed sensor was observed, providing highly reliable analysis results. Finally, thanks to the prepared sensor, it may be possible to detect pesticides from different food and environmental samples in the future. [ABSTRACT FROM AUTHOR]

Triazine pesticide (atrazine and its derivatives) detection sensors have been developed to thoroughly check for the presence of these chemicals and ultimately prevent their exposure to humans. Sensitive coatings were designed by utilizing molecular imprinting technology, which aims to create artificial receptors for the detection of chlorotriazine pesticides with gravimetric transducers. Initially, imprinted polymers were developed, using acrylate and methacrylate monomers containing hydrophilic and hydrophobic side chains, specifically for atrazine, which shares a basic heterocyclic triazine structure with its structural analogs. By adjusting the ratio of the acid to the cross-linker and introducing acrylate ester as a copolymer, optimal non-covalent interactions were achieved with the hydrophobic core of triazine molecules and their amino groups. A maximum sensor response of 546 Hz (frequency shift/layer height equal to 87.36) was observed for a sensitive coating composed of 46% methacrylic acid and 54% ethylene glycol dimethacrylate, with a demonstrated layer height of 250 nm (6.25 kHz). The molecularly imprinted copolymer demonstrated fully reversible sensor responses, not only for atrazine but also for its metabolites, like des-ethyl atrazine, and structural analogs, such as propazine and terbuthylazine. The efficiency of modified molecularly imprinted polymers for targeted analytes was tested by combining them with a universally applicable quartz crystal microbalance transducer. The stable selectivity pattern of the developed sensor provides an excellent basis for a pattern recognition procedure.

Amine gases and formaldehyde (HCHO) have been used as typical indicators to monitor the quality of marine fish products. However, current detection methods are time-consuming and complicated to preprocess and have limitations such as high technicality requirements. Therefore, developing a sensor capable of simultaneously detecting multiple amine gases and HCHO with high performance in a simple way remains a significant challenge. In this paper, trimethylamine (TMA), dimethylamine (DMA), ammonia gas (NH3), and HCHO were tested by a quartz crystal microbalance (QCM) gas sensor modified with a UiO-66/multi-walled carbon nanotube (MWCNT) nanocomposite. The sensor was operated at room temperature (25 °C) and fixed humidity (35% RH), and the results showed that the limits of detection of the QCM gas sensor for TMA, DMA, NH3, and HCHO were 0.32, 0.52, 1.02, and 2.4 μmoL L–1, respectively. At the same time, our sensor could be reused more than ten times without degradation of sensor signals and showed high stability even after a long storage period of up to 2 months. The adsorption mechanism of the UiO-66/MWCNT nanocomposite-based QCM gas sensor toward the target gases was simulated. Ultimately, salmon meat was examined using the sensor that had been prepared, and the detection outcomes were contrasted with the findings from the Kjeldahl nitrogen determination. The results indicated that refrigerated salmon began emitting target gases on the second day and gradually increased thereafter. By the fifth day, the concentration of the target gases reached the point of complete spoilage. Our platform may be a promising platform for basic research and versatile practical applications in food quality assessments. [ABSTRACT FROM AUTHOR]

Interfaces of glassy materials such as thin films, blends, and composites create strong unidirectional gradients to the local heterogeneous dynamics that can be used to elucidate the length scales and mechanisms associated with the dynamic heterogeneity of glasses. We focus on bilayer films of two different polymers with very different glass transition temperatures (Tg) where previous work has demonstrated a long-range (~200 nm) profile in local Tg(z) is established between immiscible glassy and rubbery polymer domains when the polymer-polymer interface is formed to equilibrium. Here, we demonstrate that an equally long-ranged gradient in local modulus ...(z) is established when the polymer-polymer interface (≈5 nm) is formed between domains of glassy polystyrene (PS) and rubbery poly(butadiene) (PB), consistent with previous reports of a broad Tg(z) profile in this system. A continuum physics model for the shear wave propagation caused by a quartz crystal microbalance across a PB/PS bilayer film is used to measure the viscoelastic properties of the bilayer during the evolution of the PB/PS interface showing the development of a broad gradient in local modulus ...(z) spanning ≈180 nm between the glassy and rubbery domains of PS and PB. We suggest these broad profiles in Tg(z) and ...(z) arise from a coupling of the spectrum of vibrational modes across the polymer-polymer interface as a result of acoustic impedance matching of sound waves with λ ~ 5 nm during interface broadening that can then trigger density fluctuations in the neighboring domain. [ABSTRACT FROM AUTHOR]

Introduction: Atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy. Personal genome analyses have revealed numerous aHUS‐causing variants, mainly complement‐related genes. However, not all aHUS‐causing variants have been functionally validated. Methods: An exome sequence analysis of a Japanese multiplex family composed of three patients diagnosed with aHUS in infancy and showing frequent relapses clustered in a dominant transmission mode was performed. Protein interaction between the C3d and C‐terminal domains of factor H was analyzed using a quartz crystal microbalance. Results: Following filtering by heterozygous variants, amino acid substitutions, and allele frequency, the analysis revealed eight rare variants shared by the affected individuals. Variant prioritization listed C3 p.W1034R as the most likely candidate gene mutation in the affected individuals, despite being classified as a variant of uncertain significance. Binding of recombinant C3d harboring 1034R to recombinant short consensus repeats 15 to 20 of factor H was significantly suppressed compared with that of C3 with 1034W. Conclusion: C3 p.W1034R results in an inherited form of aHUS that often presents with recurrent episodes, possibly because of impaired interactions between the C3d and C‐terminal domains of factor H. Following comprehensive genomic analysis, functional validation of C3 p.W1034R strengthens the molecular basis for aHUS pathophysiology. [ABSTRACT FROM AUTHOR]

Impedance measurements play a critical role in analyzing the electrical behavior of piezoelectric biosensors in general. Antenna analyzers are engineered to measure the specific case of input impedance for antenna systems. In this study small form factor antenna analyzer is repurposed to work as driving circuit for a Quartz Crystal Microbalance (QCM) biosensor in combination with a single board computer as an indication of how small and portable an impedance measuring system can be made, while allowing monitoring of important parameters of series and parallel resonance frequencies together with dissipation factor. A QCM crystal with a 10 MHz fundamental resonance frequency is employed to determine the limit of detection of the system in Bovine Serum Albumin (BSA) and glycerol solutions. Dissipation factor and phase angle were monitored during the experiments. Limit of detection is 20 µg/ml BSA in phosphate buffer saline (PBS) and 250 µl of glycerol in 100 ml of deionized water. [ABSTRACT FROM AUTHOR]

[Display omitted] The structure and interaction of ionic liquids (ILs) influence their interfacial composition, and their arrangement (i.e. , electric double-layer (EDL) structure), can be controlled by an electric field. Here, we employed a quartz crystal microbalance (QCM) to study the electrical response of two non-halogenated phosphonium orthoborate ILs, dissolved in a polar solvent at the interface. The response is influenced by the applied voltage, the structure of the ions, and the solvent polarizability. One IL showed anomalous electro-responsivity, suggesting a self-assembly bilayer structure of the IL cation at the gold interface, which transitions to a typical EDL structure at higher positive potential. Neutron reflectivity (NR) confirmed this interfacial structuring and compositional changes at the electrified gold surface. A cation-dominated self-assembly structure is observed for negative and neutral voltages, which abruptly transitions to an anion-rich interfacial layer at positive voltages. An interphase transition explains the electro-responsive behaviour of self-assembling IL/carrier systems, pertinent for ILs in advanced tribological and electrochemical contexts. [ABSTRACT FROM AUTHOR]

A gas sensor array was developed and evaluated using four high-frequency quartz crystal microbalance devices (with a 30 MHz resonant frequency in fundamental mode). The QCM devices were coated with ethyl cellulose (EC), polymethylmethacrylate (PMMA), Apiezon L (ApL), and Apiezon T (ApT) sensing films, and deposited by the ultrasonic atomization method. The objective of this research was to propose a non-invasive technique for acetone biomarker detection, which is associated with diabetes mellitus disease. The gas sensor array was exposed to methanol, ethanol, isopropanol, and acetone biomarkers in four different concentrations, corresponding to 1, 5, 10, and 15 µL, at temperature of 22 °C and relative humidity of 20%. These samples were used because human breath contains them and they are used for disease detection. Moreover, the gas sensor responses were analyzed using principal component analysis and discriminant analysis, achieving the classification of the acetone biomarker with a 100% membership percentage when its concentration varies from 327 to 4908 ppm, and its identification from methanol, ethanol, and isopropanol. [ABSTRACT FROM AUTHOR]

Amphipathic copolymers are useful materials for nanomedicine, owing to their ability to self‐assemble into nanoparticles, act as surfactants for inorganic materials, or for their favorable interactions with lipid membranes. Despite their widespread use, there is still a range of questions about the physicochemical properties that are necessary to drive their interactions at biological interfaces. To fully understand these interactions requires a diverse range of complementary analytical techniques. In this work, a library of neutral amphipathic methacrylate copolymers is synthesized by reversible addition‐fragmentation chain‐transfer polymerization (RAFT) polymerization, to investigate the effect of polymer composition and nature of the hydrophobic comonomer on interactions with model lipid membranes. These materials are shown to interact with Langmuir lipid monolayers, and neutron reflectometry demonstrates that hydrophobic interactions lead to the polymers intercalating with the monolayers. More complex models of lipid bilayers are studied using an in situ quartz crystal microbalance (QCM) model and shows while the composition and hydrophobic comonomer affect the stability of these interactions, there is no effect on the viscoelasticity of the lipid membranes. The in‐depth understanding of these interfacial interactions afforded by this suite of analytical tools will allow for more complex copolymers to be studied, providing a greater understanding of key processes in nanomedicine, such as cellular entry and endosomal escape. [ABSTRACT FROM AUTHOR]

Molecular dynamic modeling and various experimental techniques, including multi-angle dynamic light scattering (MADLS), streaming potential, optical waveguide light spectroscopy (OWLS), quartz crystal microbalance with dissipation (QCM), and atomic force microscopy (AFM), were applied to determine the basic physicochemical parameters of fibroblast growth factor 21 in electrolyte solutions. The protein size and shape, cross-section area, dependence of the nominal charge on pH, and isoelectric point of 5.3 were acquired. These data enabled the interpretation of the adsorption kinetics of FGF 21 on bare and macrocation-covered silica investigated by OWLS and QCM. It was confirmed that the protein molecules irreversibly adsorbed on the latter substrate, forming layers with controlled coverage up to 0.8 mg m−2, while their adsorption on bare silica was much smaller. The viability of two cell lines, CHO-K1 and L-929, on both bare and macrocation/FGF 21-covered substrates was also determined. It is postulated that the acquired results can serve as useful reference systems for designing complexes that can extend the half-life of FGF 21 in its active state. [ABSTRACT FROM AUTHOR]

In this experimental study the differential sputtering yield and total sputtering yield of ion thruster grid materials (Mo and C/C composite) under low-energy ion bombardment has been investigated. A novel combinable aluminum arch array is developed to determine the spatial distributions of sputtered atoms in different azimuthal angles. The quartz crystal microbalance (QCM) method is used to validate the typical distribution profile of sputtered atoms at the 180° azimuthal angle. The distribution characteristics of sputtered atoms as well as the specific regions of maximum differential sputtering yield under different incident energies, incident angles and ion species (Xe, Kr, Ar) have been discussed. The sputtering resistance performance of C/C composite materials have been compared with Mo metal by measuring the total sputtering yield. The spatial distributions of C/C differential sputtering yield are found highly anisotropic even under normal incidence, a multi-region discontinuous distribution characteristic of maximum differential sputtering yield have been observed in C/C composite material. The experimental results about the spatial distribution of sputtered atoms are of great importance for establishing the sputter-redeposition models of grid apertures to accurately predict the evolution of grid morphology and lifetime of ion thruster. • Incident ion species affect differential sputter yield distribution profiles. • Incident energies affect distribution range of maximum differential sputter yield. • Ejection angle range of y max is not depending on the incident angles. • Sputtrer distribution profiles of C/C material is highly anisotropic. [ABSTRACT FROM AUTHOR]

Rapid and accurate serological analysis of SARS-CoV-2 antibodies is important for assessing immune protection from vaccination or infection of individuals and for projecting virus spread within a population. The quartz crystal microbalance (QCM) is a label-free flow-based sensor platform that offers an opportunity to detect the binding of a fluid-phase ligand to an immobilized target molecule in real time. A QCM-based assay was developed for the detection of SARS-CoV-2 antibody binding and evaluated for assay reproducibility. The assay was cross-compared to the Roche electrochemiluminescence assay (ECLIA) Elecsys® Anti-SARS-CoV-2 serology test kit and YHLO's chemiluminescence immunoassay (CLIA). The day-to-day reproducibility of the assay had a correlation of r2 = 0.99, p < 0.001. The assay linearity was r2 = 0.96, p < 0.001, for dilution in both serum and buffer. In the cross-comparison analysis of 119 human serum samples, 59 were positive in the Roche, 52 in the YHLO, and 48 in the QCM immunoassay. Despite differences in the detection method and antigen used for antibody capture, there was good coherence between the assays, 80–100% for positive and 96–100% for negative test results. In summation, the QCM-based SARS-CoV-2 IgG immunoassay showed high reproducibility and linearity, along with good coherence with the ELISA-based assays. Still, factors including antibody titer and antigen-binding affinity may differentially affect the various assays' responses. [ABSTRACT FROM AUTHOR]

The adsorption of cationic and anionic polyelectrolytes (PEs) from aqueous solutions on the polystyrene surface is studied by quartz crystal microbalance (QCM) and contact angle measurements. It is shown that, despite the multilayer nature of adsorption, only a monolayer of PE macromolecules is firmly retained on the polymer surface, and the polystyrene surface is hydrophilized. It is shown that with the complete monolayer filling of the surface, the degree of modification of the polystyrene surface does not depend on the nature of the studied PEs, and the modifying monolayers provide the value of the polystyrene/water interfacial energy, which indicates the potential biocompatibility of the material based on the modified polystyrene. [ABSTRACT FROM AUTHOR]

Various aniline sensing materials have excellent properties based on quartz crystal microbalance (QCM) transducer, but their synthesis processes are complex. Herein, commercial calcium silicate hydrate nanosheets (CSH-S) was utilized for facile fabrication of aniline sensor based on QCM platform. This sensor was capable of detecting 0.1 ppm aniline, and the response time (14 s) and recovery time (16 s) were short. Besides, the devices could restore sensitivity after 30 days, demonstrating excellent stability. In addition, variable temperature experiment combined with simulation calculation methods were carried out to study the adsorption of aniline on CSH-S surfaces, then the sensing mechanism was revealed. This work opens up a rapid and convenient method for detecting gaseous aniline.

This study investigates the enzymatic degradation processes of different classes of polyhydroxyalkanoates (PHAs), a group of biopolymers naturally synthesized by various microorganisms. Medium chain length PHAs (mcl-PHAs) are distinguished biopolymers due to their biodegradability and diverse material properties. Using quartz crystal microbalance measurements as a valuable tool for accurate real-time monitoring of the enzymatic degradation process, the research provides detailed kinetic data, describing the interaction between enzymes and substrates during the enzymatic degradation process. Thin films of poly-3-hydroxybutyrate (PHB) and polyhydroxyoctanoate copolymer (PHO), containing molar fractions of about 84% 3-hydroxyoctanoate and 16% 3-hydroxyhexanoate, were exposed to scl-depolymerases from Pseudomonas lemoignei LMG 2207 and recombinant mcl-depolymerase produced in Escherichia coli DH5α harboring the plasmid pMAD8, respectively. Analyses based on a heterogeneous kinetic model for the polymer degradation indicated a six-fold stronger adsorption equilibrium constant of mcl-depolymerase to PHO. Conversely, the degradation rate constant was approximately twice as high for scl-depolymerases acting on PHB. Finally, the study highlights the differences in enzyme-substrate interactions and degradation mechanisms between the investigated scl- and mcl-PHAs.

[Display omitted] Biomaterials such as collagen and tannic acid (TA) particles are of interest in the development of advanced hybrid biobased systems due to their beneficial therapeutic functionalities and distinctive structural properties. The presence of numerous functional groups makes both TA and collagen pH responsive, enabling them to interact via non-covalent interactions and offer tunable macroscopic properties. The effect of pH on the interactions between collagen and TA particles is explored by adding TA particles at physiological pH to collagen at both acidic and neutral pH. Rheology, isothermal titration calorimetry (ITC), turbidimetric analysis and quartz crystal microbalance with dissipation monitoring (QCM-D) are used to study the effects. Rheology results show significant increase in elastic modulus with an increase in collagen concentration. However, TA particles at physiological pH provide stronger mechanical reinforcement to collagen at pH 4 than collagen at pH 7 due to the formation of a higher extent of electrostatic interaction and hydrogen bonding. ITC results confirm this hypothesis, with larger changes in enthalpy, |Δ H |, observed when collagen is at acidic pH and |Δ H | > | T Δ S | indicating enthalpy-driven collagen-TA interactions. Turbidimetric analysis and QCM-D help to identify structural differences of the collagen-TA complexes and their formation at both pH conditions. [ABSTRACT FROM AUTHOR]

Nanomaterial-based humidity sensors hold great promise for water vapor detection because of their high sensitivity and fast response/recovery. However, the condensation of water in nanomaterial films remains unclear from a physicochemical perspective. Herein, the condensation of water vapor in silica nanoparticle films was physicochemically analyzed to bridge the abovementioned gap. The morphology of surface-adsorbed water molecules was characterized using infrared absorption spectroscopy and soft X-ray absorption spectroscopy, and the effect of RH on the amount of adsorbed water was observed using a quartz crystal microbalance. The adsorbed water was found to exist in liquid- and ice-like states, which contributed to high and low conductivity, respectively. The large change in film impedance above 80% RH was ascribed to the condensation of water between the nanoparticles. Moreover, RH alteration resulted in a colorimetric change in the film's interference fringe. The obtained insights were used to construct a portable device with response and recovery times suitable for the real-time monitoring of water vapor. Thus, this study clarifies the structure of water adsorbed on nanomaterial surfaces and, hence, the action mechanism of the corresponding nanoparticle-based sensors, inspiring further research on the application of various nanomaterials to vapor sensing. [ABSTRACT FROM AUTHOR]

It is vital to develop a quick and reliable approach for nitrobenzene in gas phase detection. In this work, the quartz crystal microbalance (QCM) platform was used to take advantage of the porphyrin-based metal-organic frameworks (MOFs) of PCN-224 as a novel sensing material for the sensitive and selective detection of nitrobenzene vapor. Besides, a quick response time of only 16 s was achieved. Meanwhile, the frequency shift in gas sensor could be proportionally quenched in correlation with the concentration of nitrobenzene vapor. Additionally, this PCN-224-based sensor demonstrated great stability to nitrobenzene vapor. This foreshadowed the huge potential of nitrobenzene detection in gas phase for practical applications in public security. [ABSTRACT FROM AUTHOR]

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To date, numerous aptamer-based biosensing platforms have been developed for sensitive and selective monitoring of target analytes, relying on analyte-induced conformational changes in the aptamer for the quantification of the analyte and the conversion of the binding event into a measurable signal. Despite the impact of these conformational rearrangements on sensor performance, the influence of the environment on the structural conformations of aptamers has rarely been investigated, so the link between parameters directly influencing aptamer folding and the ability of the aptamer to bind to the target analyte remains elusive. Herein, the effect a number of variables have on an aptamer's 3D structure was examined, including the pH of the buffering medium, as well as the anchoring of the aptamer on a solid support, with the use of two label-free techniques. Circular dichroism spectroscopy was utilized to study the conformation of an aptamer in solution along with any changes induced to it by the environment (analyte binding, pH, composition and ionic strength of the buffer solution), while quartz crystal microbalance with dissipation monitoring was employed to investigate the surface-bound aptamer's behavior and performance. Analysis was performed on an aptamer against oxytetracycline, serving as a model system, representative of aptamers selected against small molecule analytes. The obtained results highlight the influence of the environment on the folding and thus analyte-binding capacity of an aptamer and emphasize the need to deploy appropriate surface functionalization protocols in sensor development as a means to minimize the steric obstructions and undesirable interactions of an aptamer with a surface onto which it is tethered. [ABSTRACT FROM AUTHOR]

Blood transfusion, as well as organ transplantation, is only possible after prior blood group (BG) typing and crossmatching. The most important blood group system is that of Landsteiner's ABO classification based on antigen presence on the erythrocyte surfaces. A mass sensitive QCM (quartz crystal microbalance) sensor for BG typing has been developed by utilizing molecular imprinting technology. Polyvinylpyrrolidone (crosslinked with N,N-methylenebisacrylamide) is a favorable coating that was imprinted with erythrocytes of different blood groups. In total, 10 MHz quartz sheets with two resonators, one for MIP (molecularly imprinted polymer) and the other for NIP (non-imprinted polymer) were fabricated and later used for mass-sensitive measurements. The structure of erythrocyte imprints resembles a donut, as identified by AFM (atomic force microscope). All the erythrocytes of the ABO system were chosen as templates and the responses to these selective coatings were evaluated against all blood groups. Each blood group can be characterized by the pattern of responses in an unambiguous way. The results for blood group O are remarkable given that all types of erythrocytes give nearly the same result. This can be easily understood as blood group O does not possess neither antigen A nor antigen B. The responses can be roughly related to the number of respective antigens on the erythrocyte surface. The imprints generate hollows, which are used for reversible recognition of the erythrocytes. This procedure is based on molecular recognition (based on supramolecular strategies), which results from size, shape and enthalpic interactions between host and guest molecules. [ABSTRACT FROM AUTHOR]

Molecularly imprinted polymers (MIPs) are tailor-made functional composites which selectively recognize and bind the target molecule of interest. MIP composites are products of the massively cross-linked polymer matrices, generated via polymerization, with bio-inspired recognition cavities that are morphologically similar in size, shape and spatial patterns to the target conformation. These features have enabled researchers to expand the field of molecular recognition, more specifically for target with peculiar requirements. Nevertheless, MIPs alone are characterized with weak sensitivity. Besides, nanoparticles (NPs) are remarkably sensitive but also suffer from poor selectivity. Intriguingly, the combination of the two results in a highly sensitive and selective MIP composite. For instance, the conjugation of different functional NPs with MIPs can generate new flexible target capture tools, either a dynamic sensor or a novel drug delivery system. In this regard, although the technology is considered an established and feasible approach, it is still perceived as a burgeoning technology for various fields, which makes it unceasingly worthy reviewing. Therefore, in this review, we attempt to give an update on various custom-made biosensors based on MIPs in combination with various NPs for the detection of mycotoxins, the toxic secondary metabolites of fungi. We first summarize the classification, prevalence, and toxicological characteristics of common mycotoxins. Next, we provide an overview of MIP composites and their characterization, and then segment the role of NPs with respect to common types of MIP-based sensors. At last, conclusions and outlook are discussed. [ABSTRACT FROM AUTHOR]

Quartz Crystal Microbalances (QCMs) are versatile sensors employed in various fields, from environmental monitoring to biomedical applications, owing mainly to their very high sensitivity. However, the assessment of their metrological performance, including the impact of conditioning circuits, digital processing algorithms, and working conditions, is a complex and novel area of study. The purpose of this work is to investigate and understand the measurement errors associated with different QCM measurement techniques, specifically focusing on the influence of conditioning electronic circuits. Through a tailored and novel experimental setup, two measurement architectures—a Quartz Crystal Microbalance with dissipation monitoring (QCM-D) system and an oscillator-based QCM-R system—were compared under the same mechanical load conditions. Through rigorous experimentation and signal processing techniques, the study elucidated the complexities of accurately assessing QCM parameters, especially in liquid environments and under large mechanical loads. The comparison between the two different techniques allows for highlighting the critical aspects of the measurement techniques. The experimental results were discussed and interpreted based on models allowing for a deep understanding of the measurement problems encountered with QCM-based measurement systems. The performance of the different techniques was derived, showing that while the QCM-D technique exhibited higher accuracy, the QCM-R technique offered greater precision with a simpler design. This research advances our understanding of QCM-based measurements, providing insights for designing robust measurement systems adaptable to diverse conditions, thus enhancing their effectiveness in various applications.

Dimethoate (DIM) as an organophosphorus pesticide is widely utilized especially in the cultivation of vegetables and fruits due to its killing effect on harmful insects. However, unconscious use of DIM in large amounts can also cause serious health problems. For these reasons, rapid and reliable detection of DIM from food samples is significant. In this study, a novel quartz crystal microbalance (QCM) sensor based on erbium molybdate incorporating sulfur-doped graphitic carbon nitride (EM/S-g-C3N4) and a molecularly imprinting polymer (MIP) was designed for DIM detection in apple juice samples. Firstly, an EM/S-g-C3N4 nanocomposite with high purity was prepared under hydrothermal conditions at high temperatures over a long period of time. After the modification of the EM/S-g-C3N4 nanocomposite on a QCM chip, the polymerization solution including N,N′-azobisisobutyronitrile (AIBN) as an initiator, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, methacryloylamidoglutamic acid (MAGA) as a monomer, and DIM as an analyte was prepared. Then, the polymerization solution was dropped on an EM/S-g-C3N4 nanocomposite modified QCM chip and an ultraviolet polymerization process was applied for the formation of the DIM-imprinted polymers on the EM/S-g-C3N4 nanocomposite modified QCM chip. After the polymerization treatment, some characterization studies, including electrochemical, microscopic, and spectroscopic methods, were performed to illuminate the surface properties of the nanocomposite and the prepared QCM sensor. The values of the limit of quantification (LOQ) and the detection limit (LOD) of the prepared QCM sensor were as 1.0 × 10−9 M and 3.3 × 10−10 M, respectively. In addition, high selectivity, stability, reproducibility, and repeatability of the developed sensor was observed, providing highly reliable analysis results. Finally, thanks to the prepared sensor, it may be possible to detect pesticides from different food and environmental samples in the future.

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 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.

RAFT aqueous emulsion polymerization of isopropylideneglycerol monomethacrylate (IPGMA) is used to prepare a series of PGEO5MA46‐PIPGMAy nanoparticles, where PGEO5MA is a hydrophilic methacrylic steric stabilizer block bearing pendent cis‐diol groups. TEM studies confirm a spherical morphology while dynamic light scattering (DLS) analysis indicated that the z‐average particle diameter can be adjusted by varying the target degree of polymerization for the core‐forming PIPGMA block. Periodate oxidation is used to convert the cis‐diol groups on PGEO5MA46‐PIPGMA500 and PGEO5MA46‐PIPGMA1000 nanoparticles into the analogous aldehyde‐functionalized nanoparticles, which are then reacted with histidine via reductive amination. In each case, the extent of functionalization is more than 99% as determined by 1H NMR spectroscopy. Aqueous electrophoresis studies indicate that such derivatization converts initially neutral nanoparticles into zwitterionic nanoparticles with an isoelectric point at pH 7. DLS studies confirm that such histidine‐derivatized nanoparticles remain colloidally stable over a wide pH range. A quartz crystal microbalance is employed at 25°C to assess the adsorption of both the cis‐diol‐ and histidine‐functionalized nanoparticles onto planar stainless steel at pH 6. The histidine‐bearing nanoparticles adsorb much more strongly than their cis‐diol counterparts. For the highest adsorbed amount of 70.5 mg m–2, SEM indicates a fractional surface coverage of 0.23 for the adsorbed nanoparticles. [ABSTRACT FROM AUTHOR]