Rapid identification of spinal ventral and dorsal roots using a quartz crystal microbalance

The fast and accurate identification of nerve tracts is critical for successful nerve anastomosis. Taking advantage of differences in acetylcholinesterase content between the spinal ventral and dorsal roots, we developed a novel quartz crystal microbalance method to distinguish between these nerves based on acetylcholinesterase antibody reactivity. The acetylcholinesterase antibody was immobilized on the electrode surface of a quartz crystal microbalance and reacted with the acetylcholinesterase in sample solution. The formed antigen and antibody complexes added to the mass of the electrode inducing a change in frequency of the electrode. The spinal ventral and dorsal roots were distinguished by the change in frequency. The ventral and dorsal roots were cut into 1 to 2-mm long segments and then soaked in 250 pL PBS. Acetylcholinesterase antibody was immobilized on the quartz crystal microbalance gold electrode surface. The results revealed that in 10 minutes, both spinal ventral and dorsal roots induced a frequency change; however, the frequency change induced by the ventral roots was notably higher than that induced by the dorsal roots. No change was induced by bovine serum albumin or PBS. These results clearly demonstrate that a quartz crystal microbalance sensor can be used as a rapid, highly sensitive and accurate detection tool for the quick identification of spinal nerve roots intraoperatively.

Development of a QCM (Quartz Crystal Microbalance) Biosensor to the Detection of Aflatoxin B1

In this study, we have used a direct immunoassay where the simple binding between antigen and an antibody is detected. Immunoassays were performed in a drop system, monitoring the frequency decrease of the quartz-crystal microbalance device because of mass increasing during immunoreaction. The QCM sensor was coated on both sides by gold electrodes, only one side of the crystal (liquid side) was in contact with the solution;the other side (contact side) was always dry. We tested a piezoelectric immunosensor for aflatoxin B1 (AFLA-B1) mycotoxin detection through the immo- bilization of DSP-anti-AFLAB1 antibody (AFLA-B1-Ab anti AFLAB1) on gold-coated quartz crystals (AT-cut/5 MHz). The DSP (3,3’-Dithiodipropionic-acid-di-N-hydroxysuccinimide ester) was used for the covalent attachment of the proteins. The piezoelectric crystal electrodes were pretreated by DSP for 15 min, rinsed with water and dried in a gentle flow of nitrogen gas. Then the DSP-coated crystals were installed in a sample holder and exposed to the anti-AFLAB1 antibody and to the AFLA-BI. Frequency and resistance shifts (Δf and ΔR) were measured simultaneously. Δf versus AFLA-BI concentrations in the range of 0.5 - 10 ppb exhibited a perfect linear correlation with a coefficient of above 0.998.

Quartz Crystal Microbalances for Evaluating Gas Motion Differences between Dichlorosilane and Trichlorosilane in Ambient Hydrogen in a Slim Vertical Cold Wall Chemical Vapor Deposition Reactor

A dichlorosilane gas and a trichlorosilane gas in ambient hydrogen were evaluated to show their different gas flow motions in a slim vertical cold wall chemical vapor deposition reactor for the Minimal Fab system. This evaluation was performed for improving and controlling the film qualities and the productivities, using two quartz crystal microbalances (QCM) installed at the inlet and exhaust of the chamber by taking into account that the QCM frequency corresponds to the real time changes in the gas properties. Typically, the time period approaching from the inlet to the exhaust was shorter for the trichlorosilane gas than that for the dichlorosilane gas. The trichlorosilane gas was shown to move like plug flow, while the dichlorosilane gas seemed to be well mixed in the entire chamber.

Quartz Crystal Microbalance Sensor Deposited with LB Films of Functional Polymers for the Detection of Phenols in Vapour Phase

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Electrochemical Quartz Crystal Microbalance(EQCM) Characterization of Electrodeposition and Catalytic Activity of Pd-based Electrocatalysts for Ethanol Oxidation

Pd was electrochemically deposited on gold-coated quartz crystals at nanogram-level. The coulombic efficiency and initial nucleation and growth mechanism of potentiostatic Pd deposition were investigated via in situ electrochemical quartz crystal microbalance（EQCM）. The coulombic efficieneies are 84%, 93% and 95% for Pd deposition at 0.3, 0.2 and 0.1 V（vs. SCE）, respectively. The results of chronoamperometric measurements show that the Pd deposition proceeded by an instantaneous nucleation（at 0.3 V） or progressive nucleation（at 0.2 and 0.1 V） in a three-dimensional（3D） growth mode. The catalytic activity of Pd-based electrocatalyst for ethanol oxidation was characterized in an alkaline solution. It was found that the highest mass activity for ethanol oxidation on Pd-based electrocatalyst is 1.8× 10^4 A/（g Pd） deposited at 0.3 V for 5 s.

Charge Transport Processes of Immobilized Heteropolyanions at Self-assembled Monolayer Modified Gold Electrode by Electrochemical Quartz Crystal Microbalance Measurement

The in situ electrochemical quartz crystal microbalance（EQCM） technique was used to investigate the ion transport of immobilized heteropolyanions at a self-assembled monolayer（SAM） modified gold electrode during electrochemical redox process.A mixed transfer method was presented to analyse the abnormal change of resonant frequency based on the simultaneous insertion/extraction of different ions.The results indicate that the migration of HSO4-anions was indispensable in the redox process of the heteropolyanions in a 1 mol/L H2SO4 solution and played a key role in the abnormal change of the resonant frequency.Such a change was attributed to different packing densities derived by means of differently immobilized methods.

Hybrid temperature effect on a quartz crystal microbalance resonator in aqueous solutions

The quartz crystal microbalance（QCM） is an important tool that can sense nanogram changes in mass. The hybrid temperature effect on a QCM resonator in aqueous solutions leads to unconvincing detection results. Control of the temperature effect is one of the keys when using the QCM for high precision measurements. Based on the Sauerbrey＇s and Kanazawa＇s theories, we proposed a method for enhancing the accuracy of the QCM measurement, which takes into account not only the thermal variations of viscosity and density but also the thermal behavior of the QCM resonator. We presented an improved Sauerbrey equation that can be used to effectively compensate the drift of the QCM resonator. These results will play a significant role when applying the QCM at the room temperature.

Fabrication and evaluation of a portable and reproducible quartz crystal microbalance immunochip for label-free detection ofβ-lactoglobulin allergen in milk products

In this study,a label-free,portable and reproducible immunochip based on quartz crystal microbalance(QCM)was developed for the qualitative detection ofβ-lactoglobulin(β-LG),an allergen,in milk products.Experimental parameters in the fabrication and regeneration procedure such as pH of the coupling microenvironment,amount of anti-β-LG antibody and regeneration reagent were optimized in detail.Under optimal conditions,the proposed QCM immunochip exhibited good recognition of β-LG,with a calibration curve of ΔF=12.877 C_(β-LG)^(0.4809)(R^(2)=0.9982)and limit of detection of 0.04μg/mL.Additionally,this portable QCM immunochip had good stability,high specificity,and no obvious cross-reaction to three other milk proteins(α-casein,α-lactalbumin,and lactoferrin).It could compete a qualitative measurement within5 min,and could be reused at least ten times.In the β-LG analysis of actual milk samples,the developed QCM immunochip yielded reliable and accurate results,which correlated strongly with those from the standard HPLC method(R^(2)=0.9969).Thus,the portable,stable,and reproducible QCM immunochip developed in this study allowed the rapid,cost-effectively and sensitively measure theβ-LG in milk products.

<i>In-Situ</i>Monitoring of Chemical Vapor Deposition from Trichlorosilane Gas and Monomethylsilane Gas Using Langasite Crystal Microbalance

Using the langasite crystal microbalance (LCM), the trends in film thickness produced by means of the chemical vapor deposition using trichlorosilane gas, monomethylsilane gas and their mixed gas were observed at 600?C and evaluated by comparison with the information from a transmission electron microscope (TEM). The crystalline silicon film thickness from trichlorosilane gas was comparable to that of an amorphous silicon carbide film from monomethylsilane gas. The film obtained from the gas mixture was amorphous and was the thinnest in this study. Because the thickness trend obtained by the LCM agreed with that by the TEM, the LCM is shown to be a convenient evaluation tool for the behavior of various film deposition.

Gravimetric Studies of Ni Electrodeposition with Additives from Deep Eutectic Solvents Using Electrochemical Quartz Crystal Microbalance EQCM

The gravimetric analysis of electrodeposited nickel is demonstrated using electrochemical quartz crystal microbalance (EQCM) where the nickel coatings come from a solution of the metal chloride salt separately in either a1choline chloride: 2 ethylene glycol (ethaline) or 1 choline chloride: 2 urea (reline) based ionic liquid. The possibility of adapting the Quartz Crystal Microbalance EQCM (which measures the mass attached to the electrode) to probe kinetics of electrochemically-driven solid state phase transformations has been explored in a Ni electrodeposition in absence and presence of complexing agents ethylene diamine en and acetylacetonate acac from both electrolytes ethaline and reline. The study shows that the current efficiency and the rate of deposition of nickel coatings obtained from ethaline and reline baths in absence of brighteners en and acac are different, and the addition of en and acac to both ionic liquid solutions results in a significant decrease current. And the associated growth rate will also be decreased, suggesting that the en acac stops the formation and growth of Ni nuclei. This suggests that the mechanism of growth is changed.

Application of Nanoparticles in Quartz Crystal Microbalance Biosensors

Nanoparticles are playing an increasingly important role in the development of biosensors. The sensitivity and performance of biosensors are being improved by using Nanoparticles for their construction. The use of these Nanoparticles has allowed the introduction of many new signal transduction technologies in biosensors. In this report, a comprehensive review of application of nanoparticles in Quartz Crystal Microbalance biosensors is presented. The main advantages of QCM in sensing fields include high sensitivity, high stability, fast response and low cost. In addition, it provides label-free detection capability for bio-sensing applications. Firstly, basic QCM’s design and characterization are described. Next, QCM biosensors based on modification of quartz substrate structure and their applications are digested. Nanoparticles and their utilizationin analysis are then illustrated. These include Nanoparticles in bio applications that cover Nanoparticles in Quartz Crystal Microbalance biosensors.

Study of physisorption of volatile anesthetics on phos-pholipid monolayers using a highly sensitive quartz crystal microbalance (HS-QCM)

We have investigated the interactions between phospholipid monolayers and volatile anest-hatics. Two monolayers (dihexadecyl phosphate (DHP) and dipalmitoyl phosphatidyl choline (DPPC) and two anesthetics (halothane and enflurane) were used to observe these interac-tions using a highly sensitive quartz crystal microbalance (HS-QCM). The concentration of each anesthetic in aqueous solution was kept at 4 mM. The frequency of QCM showed no change when halothane was added to the DHP monolayer, however, it responded and de-creased when interaction occurred with DPPC monolayer. In case of enflurane addition the frequency decreased in both the monolayers of DHP and DPPC. The frequency change followed the following order of monolayer-anesthetic interactions: DHP-halothane <DPPC-halothane <DHP-enflurane <DPPC-enflurane. These re-sults showed that the response of anesthetics to the monolayers i.e. the physisorption not only depends on the anesthetic structure, the type of anesthetic hydrate formed, but also the hydrophilic polar group structure of the monolayer or the monolayer/water interface had an important role in physisorption.

Quantitative measurement of p53-p53 antibody interactions by quartz crystal microbalance: A modelsystem for immunochemical calibration

We are developing methods to quantify antibody interactions that include a quartz crystal microbalance (QCM) system to measure, on a molecular basis, the interaction of p53 and anti-p53 antibodies. Previously, as a model system, we developed a measurement device consisting of p53 protein (human wild type), characterized by mass spectroscopy and immobilized at various concentrations on a glass slide. The device is designed as a control to be used with immunohistochemical (IHC) assays that incorporate commercially available anti-p53 antibodies and probes. In the current study, p53 protein is covalently immobilized on a silicon dioxide-coated quartz crystal and the resonance frequency shift is followed in-situ. The functionalized sensor is then incubated with the anti-p53 antibody, which provides a direct gravimetric measure of the antibody-antigen binding. This previously described method allows the comparison of the surface immobilized protein concentrations with estimates obtained by fluorescence measurement. The p53 functionalized QCM system offers an independent measure of surface immobilized protein concentration and is essential in development of our IHC calibration prototypes. These results provide a benchmark for comparing antibody systems that may be used in developing other molecular diagnostic assays such as immunocytochemical analysis and the detection of biomarker proteins in blood and urine.

Nanodiamond/Ti_(3)C_(2) MXene-coated quartz crystal microbalance humidity sensor with high sensitivity and high quality factor

To address the challenge of achieving both high sensitivity and a high quality factor in quartz crystal microbalance(QCM)humidity sensors,a nanodiamond(ND)/Ti_(3)C_(2)MXene composite-coated QCM humidity sensor was fabricated.The material characteristics of ND,Ti_(3)C_(2)MXene,and ND/Ti_(3)C_(2)MXene composite were analyzed by transmission electron microscopy(TEM)and Fourier transform infrared(FTIR)spectroscopy.The experimental results demonstrated that the hydrophilic ND nanoparticles coated on Ti_(3)C_(2) MXene nanosheet prevented the self-stacking of Ti_(3)C_(2)MXene and enhanced the sensitivity of Ti_(3)C_(2) MXene-based QCM humidity sensor.Moreover,the high mechanical modulus of Ti_(3)C_(2) MXene material helped ND/Ti_(3)C_(2)MXene composite-coated QCM humidity sensor to achieve a high quality factor(>20,000).ND/Ti_(3)C_(2)MXene compositecoated QCM humidity sensor exhibited a sensitivity of 82.45 Hz/%RH,a humidity hysteresis of 1.1%RH,fast response/recovery times,acceptable repeatability,and good stability from 11.3%RH to 97.3%RH.The response mechanism of ND/Ti_(3)C_(2) MXene composite-coated QCM humidity sensor was analyzed in combination with a bi-exponential kinetic adsorption model.Finally,the potential application of ND/Ti_(3)C_(2)MXene composite-coated QCM humidity sensor was demonstrated through its frequency response to wooden blocks with different moisture contents.

Quartz crystal microbalance study of the kinetics of surface initiated polymerization

Surface initiated polymerization (SIP) is a valuable tool in synthesizing functional polymer brushes,yet the kinetic understanding of SIP lags behind the development of its application. We apply quartz crystal microbalance (QCM) to address two issues that are not fully addressed yet play a central role in the rational design of functional polymer brushes,namely quantitative determination of the kinetics and the initiator efficiency (IE) of SIP. SIP are monitored online using QCM. Two quantitative frequencythickness (f-T) relations make the direct determination and comparison of the rate of polymerization possible even for different monomers. Based on the bi-termination model,the kinetics of SIP is simply described by two variables,which are related to two polymerization constants,namely a = 1/(kp,s,app-[M][R·]0) and b = kt,s,app/(kp,s,app[M]). Factors that could alter the kinetics of SIP are studied,including (i) the molecular weight of monomers,(ii) the solvent used,(iii) the initial density of the initiator,(iv) the concentration of monomer,[M],and (v) the catalyst system (ratio among the ingredients,metal,ligands,and additives). The dynamic nature of IE is also described by these two variables,IE = a/(a + bt). Instead of the molecular weight and the polydispersity,we suggest that film thickness,the two kinetic parameters (a and b),and the initial density of the initiator and IE be the parameters that characterize ultrathin polymer brushes. Besides the kinetics study of SIP,the reported method has many other applications,for example,in the fast screening of catalyst system for SIP and other polymerization systems.

Self-assembled graphene oxide/polyethyleneimine films as high-performance quartz crystal microbalance humidity sensors

As humidity is one of the most widely demanded environmental parameters,the precision of its detection is significant.An advanced humidity sensor will improve the validity of the humidity monitoring system.In this study,a facile chemical layer-by-layer self-assembly(CLS)method was developed for fabricating graphene oxide(GO)/polyethyleneimine(PEI)multilayer films.Owing to the chemical bonding between the PEI and GO,and the intrinsic stickiness of the PEI,layered films with different numbers of layers were successfully prepared using the CLS method and confirmed through ultraviolet-visible(UV-Vis)spectroscopy and the mass loading of quartz crystal microbalance(QCM).Morphological measurements revealed that the roughness and thickness of the films increased exponentially with the number of bilayers.The GO/PEI films were deposited on QCM electrodes using the CLS method to produce the humidity sensors.The humidity measurement results showed a high sensitivity(37.84 Hz/%RH)and rapid response/recovery(<5 s/8 s)of the optimal sensor,which was superior to that of recently developed QCM sensors.

Research on the Initial Oxidation of Silver by Electrochemical Quartz Crystal Microbalance

1 Introduction Quartz crystal microbalance (QCM) has been used as a sensitive mass detector in vacuum or gas experiments for a long time, but it was not until the mid-1980s that the electrochemical quartz crystal microbalance (EQCM) was accomplished by combining QCM in liquid phases with electrochemical methods. EQCM consists of an oscillator circuit adequately designed and a slice of piezoelectric quartz crystal. Metal

Electrochemical quartz crystal microbalance study on the two-electrode-system cyclic voltammetric behavior of Prussian blue films

A two-channel electrochemical quartz crystal microbalance (EQCM) was used to investigate the cyclic voltammetric behavior of two Prussian blue (PB) film-modified Au electrodes in a two-electrode con-figuration in aqueous solution. The redox peaks observed in the two-electrode cyclic voltammogram (CV) are assigned to the intrinsic redox transitions among the Everitt's salt, PB, and Prussian yellow for the film itself, the redox process of the Au substrate and the redox process of small-quantity ferri-/ferrocyanide impurities entrapped in the PB film, as also supported by ultraviolet-visible (UV-Vis) spectroelectrochemical data. The profile of the two-electrode solid-state CV for the PB powder sand-wiched between two gold-coated indium-tin oxide (ITO) electrodes is similar to that for two PB-modified Au electrodes in aqueous solution, implying similar origins for the corresponding redox peaks. The two-channel EQCM method is expected to become a highly effective technique for the studies of the two-electrode electrochemical behaviors of many other species/materials.

Adsorption-desorption of Silica Nanoparticles on Poly（ethylene glycol） Brushes Grafted onto Au Substrate Studied by Quartz Crystal Microbalance

The adsorption-desorption of silica nanoparticles（NPs） on poly（ethylene glycol）（PEG） grafted onto gold（Au） substrate was studied by quartz crystal microbalance with dissipation monitoring（QCM-D） technique. The results of frequency and dissipation show that SiO2 NPs can be adsorbed strongly on PEG-SH brushes at pH of 9.6, and a new dense and rigid construction is formed. Adjusting the pH from 9.6 to 12.3 resulted in the desorption of si- lica NPs from the PEG brushes because of a significant weakening of the hydrogen bond between the silica NPs and PEG chains. In addition, the viscoelastic properties of the system during the adsorption-desorption process were also analyzed via the relationship between the normalized frequency（Af/n） and mass. And the corresponding atomic force microscopy（AFM） images also exhibit morphological changes during the above process, consistent with the changes in viscoelasticity.