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Objective To develop a quantitative,highly sensitive,low detection limit and fast endotoxin(ET) biosensing detection system by utilizing the piezoelectric crystal's damping effect(non-mass effect) in the liquid phase environment.Methods The sensor probe of better performance (eliminating the quality load effects and improving the liquid solid coupling effect) was obtained by using the smoothing processing and hydrophilic processing of a quartz crystal sensor probe surface,thus the stability and repeatability of measurement were increased and the low detection limit of measurement was decreased.The whole measurement system was made into a miniature and automated endotoxin detection system by using CPLD device and LabView software to realize the automatic collection,and analysis and results display of measurement data.Results The good linear relationship existed between different concentrations of endotoxin and the stable value of frequency shift.Conclusion By the established data of frequency shift,the endotoxin concentration can be obtained accurately and conveniently.
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The mesoporous manganese dioxide (MnO2) materials were synthesized by the calcinations of manganese carbonate (MnCO3) precursors in air atmosphere at 300, 350 and 400℃. The slurries of MnO2 and binder were sprayed on the quartz electrodes. Quartz crystal microbalance (QCM) was conducted with cyclic voltammetry to analyze the electrochemical behaviors of the three MnO2 samples in 0.1 mol/L sodium sulfate (Na2SO4). The mass of the three samples were generally increased during potential cycling, especially in the first stage, which suggested that an irreversible reaction process occurred. The as-synthesized MnO2 at 300℃ had the better electrochemical stability and capacity retentivity. The three materials were assembled to (-) active carbon/MnO2 (+) supercapacitors and the charge-discharge tests were conducted. The results showed that 35％-40％ capacity loss was occurred in the initial cycling, and the total discharge capacities of MnO2 formed at 300℃, 350℃, 400℃ were 15.9, 12.9, 11.7 mA h/g, respectively. The detection results of QCM method were consistent with that of the charge-discharge tests, suggesting that this QCM method could be used for distinguishing the electrochemical performance of mesoporous MnO2 materials.
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Un paso crucial en el desarrollo de un inmunosensor piezoeléctrico para la detección de tuberculosis (TB), es la selección y obtención de los inmunoreactivos empleados en el inmunoensayo y la estrategia para la biofuncionalización del transductor. Diversos estudios han reportado el uso del antígeno proteico 38kDa (Ag38kDa) de Mycobacterium tuberculosis (Mtb) como un buen biomarcador de la enfermedad y el cumplimiento de las características físicas y bioquímicas para ser inmovilizado por monocapas autoensambladas (SAMs), en la superficie del electrodo de oro de cristales piezoeléctricos. Un inmunosensor piezoeléctrico desarrollado a partir de un antígeno nativo purificado de Mtb podría ser un método alternativo simple para la detección de Mtb con ventajas de rapidez y reusabilidad, contribuyendo al control y el tratamiento oportuno de la enfermedad. En este estudio se presenta el proceso de purificación del Ag38kDa a partir de proteínas de secreción filtradas de cultivo (CFP) de Mtb para ser usado como inmunoreactivo con potencial aplicación en la detección de Mtb con inmunosensores piezoeléctricos. Se obtuvieron cristales funcionalizados mediante la técnica modificada de monocapas autoensambladas (SAMs), con el antígeno nativo purificado y CFP. Las superficies biofuncionalizadas fueron caracterizadas cualitativamente con microscopía de fuerza atómica (AFM) para validar las condiciones de optimización del protocolo de inmovilización con antígenos de secreción de Mtb. Estos cristales modificados pueden ser acoplados a un sistema de caracterización de un inmunosensor piezoeléctrico para la detección de Mtb mediante un inmunoensayo competitivo directo.
The selection and procurance of the immunoreagents used in the immunoassay and biofunctionalisation transducer strategy, are a key in the piezoelectric immunosensor development for the detection of tuberculosis (TB). Many have reported the use of 38kDa protein antigen (Ag38kDa) from Mycobacterium tuberculosis (Mtb) such as good biomarker of TB disease and compliance with physical and biochemical characteristics to be immobilized by self-assembled monolayers (SAMs), in the gold electrode of piezoelectrics crystals surfaces. A piezoelectric immunosensor developed from purified native antigens of Mtb may be an alternative simple method for detection of Mtb with speed and reusable advantages, contributing to the control and early treatment of disease. In this paper, the purification process of Ag38kDa Mtb from secretory proteins filtered culture (CFP) from Mtb is presented as an immunoreactive with potential application in the detection of Mtb by piezoelectric immunosensors. Functionalized crystals were obtained by using the modified self-assembled monolayers (SAMs) technique, with purified native antigen and CFP. The functionalized surfaces were qualitatively characterized using atomic force microscopy (AFM) in order to validate the immobilization protocol optimal conditions for secretion antigens from Mtb. These modified crystals may be coupled to piezoelectric immunosensor characterization system for detecting of Mtb by a direct competition immunoassay.
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Boronic acids and their derivatives have been widely used in carbohydrate-sensitive materials because they can selectively bind 1,2-and 1,3-diol compounds, including sugars, to form cyclic boronate esters. In this work, pheylboronic acid ( PBA) moieties were grafted onto the backbone of poly( acrylic acid) ( PAA) through the condensation reaction between aminopheyl-boronic acid and carboxylic acid group of PAA in the presence of EDC/NHS, designed as PAA-PBA. Then the resulting PAA-PBA were assembled with poly ( ethyleneimine) ( PEI) to form PAA-PBA multilayer films. The sensing performance of the PEI/PAA-PBA film to carbohydrate (> 50 μg/mL ) , including glucose, fructose, mannose and galactose, has been investigated by combination of the complementary techniques of quartz crystal microbalance ( QCM ) and atomic force microscopy ( AFM) . It was demonstrated that the multilayer showed higher sensitivity to fructose than glucose, mannose and galactose. The interferences of ascorbic acid, uric acid and dopamine to the recognition of glucose can be avoided and the multilayer sensor with excellent long term stability can be recycled by changing pH value of buffer solutions. This system may be potential in realization of high selectivity and high sensitivity sensing system for probing carbohydrate.
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In order to solve the problems of present quartz crystal microbalance ( QCM ) measuring instruments, such as high demand for crystal cutting technology and uncomprehensive measurements for crystal parameters, a modified quadrature demodulation-based method was proposed with broadband adaptive response capacity and high frequency resolution. Moreover, it is also capable of measuring both resonant frequencies and dissipation factor D synchronously and continuously. Experimental results at room temperature indicated that the adaptive frequency range was 1-9 MHz while the frequency resolution was less than 1 Hz, measured resonance frequency shifts of crystals in the range scale linearly with the equal thickness increments of poly acrylic acid ( PAA) membrane on the working electrode, and with the volatilization of different solvent factor D is measured continuously and effectively along the time axis. To sum up, compared with traditional ones, this new method has lower material cost and more obtained parameters.
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A simple and sensitive method was developed for the detection of mercury ions with quartz crystal microbalance(QCM), based on the specific thymine(T)-Hg2+-T structure and gold nanoparticles. The gold nanoparticles were prepared by the citrate reduction method. In a self-assembled way, the particle surface was modified with the probe oligonucleotides which were partially replaced by 6-Mercaptohexan-1-ol to reduce the steric hindrance of hybridization. The sensitivity was optimized by the oligonucleotide with a strand length of 9bp and a T number of 7. The linear range was 5.0-100 nmol/L with a detection limit of 2.0 nmol/L. And Ca2+, Mg2+ and other metal ions had no significant interferences. This method was successfully applied for the detection of Hg2+in environmental water samples, with RSD less than 2.9% and recoveries of 97.3%-101.2%.
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Radio frequency identification sensor network, a technique integrating radio frequency identification (RFID) with wireless sensor network (WSN), is introduced. The basic structure of RFID sensor network is analyzed at first. Then components of RFID sensor and relevant supporting techniques including thin film battery, quartz crystal microbalance (QCM) and surface acoustic wave (SAW) are discussed. Research status and foregrounds of both domestic and international researches are introduced as well as applications in different fields.
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Piezoelectric sensor is a kind of chemosensor,which utilizes the changes of quality to measure data.It is widely applied to the measurement of temperature,quality,intensity of strength and acceleration.Now it is also widely applied in the biomedical area.This paper is mainly about the fundamental principle,structure and the applications of the piezoelectric sensor.
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Objective To design a system for the detection of coagulation factors using piezoelectric quartz crystal (PQC) sensors and to introduce its operating principle and the main components. Methods The contrary piezoelectric response of quartz crystal was used. Based on the fuzzy and decoupling control, a singlechip computer was used for constant temperature and constant humidity control and frequency count. The plasma coagulation time was measured for the purpose of determination of the activities and contents of the coagulation factors. Results The system was convenient, precise, and consistent for the detection of the coagulation factors. Conclusion PQC sensors with high accuracy and low cost can be used in the detection of coagulation factors and has a bright future in clinical practice.
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Objective To develop a new type of piezoelectric quartz crystal microbalance DNA sensor based on lambda exonuclease to detect Staphylococcus aureus (S. aureus) and optimize the main detection conditions. Methods After the DNA was extracted from the stain of S. aureus and the target fragment was amplified with self-designed universal primers, the PCR products were treated with Lambda exonuclease and visualized by agarose gel electrophoresis with ethidium bromide followed by a gel documentation system analysis. Then the products with or without exonuclease digestion were added into our piezoelectric quartz crystal microbalance DNA sensor for hybridization. The temperature and time of hybridization were optimized respectively. The specificity and sensitivity of our detection system were evaluated. Results The optimal temperature for hybridization was 35℃ and the optimal time was 60 min. The sensitivity of the lambda exonuclease based DNA sensor was better than that of common DNA sensor. The lowest detection limit of this new type quartz crystal microbalance system was 1.0?104 CFU/ml. Conclusion The lambda exonuclease based quartz crystal microbalance system we designed has the advantages of high efficiency in hybridization, easy to operate, and good response performance. Thus it can be applied to detect S. aureus infections.
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Objective To develop a portable analyzer which can rapidly detect antigen of type B hepatitis,antibody of HIV and H5N1 in blood samples.Methods The micro-processor of STC89C52 was adopted as the controlling core in the system.Based on an embedded technology,the analyzer can rapidly detect the antigen of type B hepatitis,antibody of HIV and H5N1 by processing the synchronic frequency of quartz crystal micro-array and by sensitivity of quality on the surface of quartz crystal with special identification between antibody and antigen.Results The system has the advantages of high sensitivity,better sample-specific characteristics,convenient portability and multi-parameter simultaneous detection.Conclusion The piezoelectric analyzer exceeds the traditional reagent method and serves for institution of scientific research and hospital widely.
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Objective To compare 2 methods to immobilize probes on the surface of gold membrane and select the better one for aptamer immobilization of aptamer-based piezoelectric quartz crystal sensor. Methods Anti-IgE aptamers were immobilized on the gold surface of piezoelectric quartz crystal sensor with thiol method or biotin-avidin method. The changes of frequency were compared in reactions with different concentrations of IgE. Results Biotin-avidin method obtained higher frequency changes in the reactions of IgE, lower limit of detection and wider liner range than thiol method. For biotin-avidin method, there was significant linear correlation between frequency changes and the concentration of IgE with the correlation coefficient of 0.994 5. Conclusion The thiol method which is proved effective for probe immobilization on gene sensor is unfit for aptamer immobilization. Biotin-avidin method has a better ability to immobilize probe on the surfaces of aptamer-based piezoelectric quartz crystal sensor.
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In order to investigate the possibility of analysis of single strand DNA by using DNA biosensor, we developed a quartz crystal DNA biosensor and studied its performances. The single strand DNA probe was immobilized on the surface of gold filled quartz crystal by biotin immunoreaction. The DNA biosensors were used to detect the complete complementary and single base mismatch complementary single strand DNA in solution. The DNA biosensors were regenerated with 0 1mol/L HCl after hybridization. The hybridization sensitivity of quartz crystal DNA biosensor is 10ng/ml. In the range of 5～40ng/ml, there was a linear correlation between responding signals and concentrations of complementary single strand DNA with a high specificity. The DNA biosensor could be repeatedly used over 5 times by using 0 1mol/L HCl for regeneration.