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.

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.

Determination of Paclitaxel Solubility in Carbon Dioxide Using Quartz Crystal Microbalance

A quartz crystal microbalance （QCM） is used to determine the phase equilibrium of paclitaxel-carbon dioxide system in the pressure range of 0-11 MPa and at temperatures of 35 °C,40 °C and 45 °C.The experimental results indicated that gaseous CO2 could be absorbed poorly into paclitaxel.The swelling of paclitaxel film in CO2 was observed before paclitaxel dissolved into supercritical carbon dioxide （ScCO2） with the increase of pressure.It was found that ScCO2 was not a good solvent for paclitaxel.The mole fraction of paclitaxel in ScCO2 was in the range of （4.5×10-9）-（7.8×10-9） under all our experimental conditions.Therefore,a much higher pressure than the CO2 supercritical point and/or a cosolvent must be used in any processes wherever paclitaxel dissolution in ScCO2 is required.

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.

Real-Time Characterization of Fibrinogen Interaction with Modified Titanium Dioxide Film by Quartz Crystal Microbalance with Dissipation

The adsorption of fibrinogen can be used as a quick indicator of surface haemocompatibility because of its prominent role in coagulation and platelet adhesion. In this work the molecular interaction between fibrinogen and a modified titanium oxide surface/platelet has been studied by quartz crystal microbalanee with dissipation （QCM-D） in situ. In order to further characterize the conformation of adsorbed fibrinogen, αC and γ-chain antibody were used to check the orientation and denaturation of fibrinogen on solid surface. QCM-D investiga- tions revealed the fibrinogen have the trend to adsorb on hydropllilic surface in a side-on orientation by positively charged αC domains, which would reduce the exposure of platelet bonding site on γ chain and enable less platelet adhesion and be activated. These obser- vations suggest that certain conformations of adsorbed fibrinogen are less platelet adhesive than others, which opens a possibility for creating a non-platelet adhesive substrates.

In situ Investigation on Layer-by-Layer Deposition of Polyelectrolytes by Quartz Crystal Microbalance

The effect of salt concentration on layer-by-layer deposition of poly（sodium 4-styrene sulfonate） （PSSS）/poly（vinylbenzyl trimethylammonium chloride） （PVTC） was investigated by use of quartz crystal microbalance with dissipation （QCM-D）. The changes in frequency and dissipation demonstrate that the addition of NaC1 leads the thickness of PSSS/PVTC multilayer to increase. The deposition of PSSS/PVTC is dominated by surface charge overcompensation level at lower salt concentrations. However, it is mainly determined by the interpenetration of polyelectrolytes at a higher salt concentration, as reflected in the oscillation of dissipation change.

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.

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.

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.

Polyvinylpyrrolidone/graphene oxide thin films coated on quartz crystal microbalance electrode for NH_3 detection at room temperature

In this paper, composite film based on polyvinylpyrrolidone(PVP)/graphene oxide(GO) was fabricated by spray method on AT-cut 9.986 MHz quartz crystal microbalance(QCM) for NH_3 sensing. The thin films were characterized by scanning electron microscope(SEM), Fourier transform infrared spectroscopy(FTIR) and ultraviolet-visible spectroscopy(UV-VIS) to investigate the morphologies and the composition contents, respectively. The experimental results reveal that PVP/GO based sensor holds higher sensitivity, larger responsiveness and smaller baseline drift than those based on pure PVP at room temperature. Besides, the prepared sensor exhibits greater response to NH_3 than other gases such as CO, CO_2 and NO_2 at the same concentration. The good linearity, reproducibility and stability demonstrate the practicability of PVP/GO hybrid film in detecting NH_3.

The change in thickness of the solidified liquid layer rather than the immobilized mass determines the frequency response of a quartz crystal microbalance

The "solidified liquid layer" model has been examined using a quartz crystal microbalance(QCM) with a polymeric matrix.The model is shown to give a reasonable explanation for the following experimental observations:(i) The opposite response of the QCM and surface plasmon resonance(SPR) for the activation process;(ii) the marked difference in the responses for IgG/anti-IgG interaction between QCM and SPR.Theoretical analysis and experimental results indicated that QCM is sensitive to the thickness change of the "solidified liquid layer" but not the mass of captured biomolecules(i.e.,the immobilized mass),implying caution must be taken in interpreting QCM results.

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

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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.

Protein adsorption behaviors on chitosan/poly(ε-caprolactone) blend films studied by quartz crystal microbalance with dissipation monitoring(QCM-D)

Chitosan/poly(ε-caprolactone) (PCL) blend films in different mass ratios were prepared using the chitosan/PCL mixture solutions in 80 vol.-% acetic acid by spin coating. Their surface micromorphologies were assessed by atomic force microscopy (AFM). It was found that the micromorphology of chitosan/PCL blend films was in large extent related to the mass ratio of chitosan. 25 wt% chitosan/PCL blend film presented microphase separation. The protein adsorption of bovine serum albumin (BSA) onto chitosan/PCL blend films was investigated by using quartz crystal microbalance with dissipation monitoring (QCM-D) in real time. The results suggested that the amount of adsorbed BSA on the chitosan/PCL blend films decreased with the addition of chitosan, but the structure and viscoelastic properties of the adsorbed BSA layers were greatly affected by the surface micromorphology of chitosan/PCL blend films. BSA absorbed on the 25 wt% chitosan/PCL blend film with microphase separa- tion showed larger adsorption reversibility, and preferred to form a loose, dissipative layer in comparison with those on other chitosan/PCL blend films without microphase separation.

A CD44-biosensor for evaluating metastatic potential of breast cancer cells based on quartz crystal microbalance

A sensitive CD44-biosensor based on quartz crystal microbalance(QCM) was proposed for evaluating metastatic potential of breast cancer cells by using hyaluronan(HA) functionalized substrate film,polydopamine and polyethyleneimine composite film,for the purpose of capturing CD44-positive cancer cells through specific binding of HA to CD44.Two differently CD44-expressed breast cancer cell lines(MDAMB-231 cells and MCF-7 cells) were put to use as targets for quantitative analysis as well as evaluation of metastatic potential of the cells.The limit of detection for MDA-MB-231(M231) cells and MCF-7 cells were 300 and 1,000 cells mL ~1 respectively.The expression level of CD44 on M231 cells exhibited two times higher than that of MCF-7 cells,indicating of a higher metastatic potential.Moreover,poly-Llysine modified QCM sensor was applied to monitor the stiffness of breast cancer cells that can reflect metastatic potential of cells.The results revealed that the MCF-7 cells were stiffer than M231 cells,implying that the M231 cells possessed higher metastatic potential.The proposed protocol is simple and rapid to evaluate the metastatic potential of cancer cells,in addition to offering a promising diagnostic tool for metastatic cancer.

Vibration analysis of a new polymer quartz piezoelectric crystal sensor for detecting characteristic materials of volatility liquid

We present a new polymer quartz piezoelectric crystal sensor that takes a quartz piezoelectric crystal as the basal material and a nanometer nonmetallic polymer thin film as the surface coating based on the principle of quartz crystal microbalance(QCM). The new sensor can be used to detect the characteristic materials of a volatile liquid. A mechanical model of the new sensor was built, whose structure was a thin circle plate composing of polytef/quartz piezoelectric/polytef. The mechanical model had a diameter of 8 mm and a thickness of 170 μm. The vibration state of the model was simulated by software ANSYS after the physical parameters and the boundary condition of the new sensor were set. According to the results of experiments, we set up a frequency range from 9.995850 MHz to 9.997225 MHz, 17 kinds of frequencies and modes of vibration were obtained within this range. We found a special frequency fspof 9.996358 MHz. When the resonant frequency of the new sensor's mechanical model reached the special frequency, a special phenomenon occurred. In this case, the amplitude of the center point O on the mechanical model reached the maximum value. At the same time, the minimum absolute difference between the simulated frequency based on the ANSYS software and the experimental measured stable frequency was reached. The research showed that the design of the new polymer quartz piezoelectric crystal sensor perfectly conforms to the principle of QCM. A special frequency value fspwas found and subsequently became one of the most important parameters in the new sensor design.

Effect of N-doping-derived solvent adsorption on electrochemical double layer structure and performance of porous carbon

N-doped porous carbon has been extensively investigated for broad electrochemical applications.The performance is significantly impacted by the electrochemical double layer(EDL),which is material dependent and hard to characterize.Limited understanding of doping-derived EDL structure hinders insight into the structure-performance relations and the rational design of high-performance materials.Thus,we analyzed the mass and chemical composition variation of EDL within electrochemical operation by electrochemical quartz crystal microbalance,in-situ X-ray photoelectron spectroscopy,and time-offlight secondary ion mass spectrometry.We found that N-doping triggers specifically adsorbed propylene carbonate solvent in the inner Helmholtz plane(IHP),which prevents ion rearrangement and enhances the migration of cations.However,this specific adsorption accelerated solvent decomposition,rendering rapid performance degradation in practical devices.This work reveals that the surface chemistry of electrodes can cause specific adsorption of solvents and change the EDL structure,which complements the classical EDL theory and provide guidance for practical applications.