A piezoelectric immunosensor for the detection of cortisol

A piezoelectric crystal immunosensor has been developed for the detection and determination of cortisol. Cortisol antibody was layered onto the gold electrodes of a 10 MHz piezoelectric crystal which was pre-coated with either protein A or gluteraldehyde. Crystals pre-coated with protein A showed the best results with respect to stability and sensitivity. The sensor was successfully used for the determination of cortisol in standard solutions from 36-3628 micrograms/L (part per billion). The advantages of the proposed sensor include simplicity, short analysis time, cost effectiveness and selectivity. The results demonstrate the feasibility of cortisol assay in clinical testing and in drug monitoring.     

Flow Injection Piezoelectric Determination of Brix in Sugar Cane Juice and in the Alcoholic Fermentation Process

Abstract

A flow injection piezoelectric procedure is proposed for the determination of brix (total solids dissolved) in the alcoholic fermentation process. A piezoelectric Perspex cell was constructed to fit one of the gold electrodes of a 10 MHz crystal and this sensor was adapted to a flow injection system. The analytical curve is linear over the brix range from 0.5 to 20.0% with a detection limit of 0.3%. Seventy results can be obtained per hour and the relative standard deviation was less than 1.45% for a solution containing 6% of brix (n=15). Applications of this method for the determination of brix in sugar cane juice and in an alcoholic fermentation bench show satisfactory results in comparison with refractometric and densimetric methods, respectively.     

A Rapid Method for Determination of Growth of Thiobacillus Ferrooxidans by Series Piezoelectric Quartz Crystal

ABSTRACT

A rapid and simple method for monitoring the growth of Thiobacillus ferrooxidans is put forward by using a series piezoelectric quartz crystal (SPQC). The SPQC was applied to continuously determine the variation of frequency shift during the culture of Thiobacillus ferrooxidans, with a conductive electrode as the probe. The frequency shift as a function of time agrees with a typical 'S - shape' model, a piezoelectric sensor responding well to the growth of Thiobacillus ferrooxidans. The fundamentals for determination of the bacterial growth activity using the SPQC is also described; the frequency shift is only dependent on the electrical conductivity of the solution and the dielectric constant.     

A Novel QCM-based Biosensor for Detection of Microorganisms Producing Hydrogen Sulfide

Abstract

A novel piezoelectric quartz crystal microbalance (QCM) device with gas permeable membrane is proposed for the detection of microorganisms producing hydrogen sulfide (H₂S). The detection theory is based on the adsorption of hydrogen sulfide onto the silver electrode of the piezoelectric crystal sensor, which causes a dramatic decrease in the resonant frequency of QCM. A 100 Hz frequency shift is chosen as the criteria value to judge the presence of microorganisms producing H₂S. Factors affecting detection were investigated. Desiccant is of great practical importance in sensor response. This new biosensor can be a potential candidate for detecting bacteria which produce hydrogen sulfide.     

Resin and fatty-acid analysis by solid-phase extraction coupled to atmospheric pressure chemical ionization–mass spectrometry

Abstract

DNA biosensors are realised immobilising a DNA structure on a suitable transducer to obtain selective information. In this paper we show how the determination of low-molecular weight compounds with affinity for DNA was measured by their effect on the oxidation signal of the guanine peak of calf thymus DNA immobilised on the electrode sensor and investigated by chronopotentiometric analysis. The DNA biosensor is able to detect known intercalating and groove binding compounds. Applicability to river water samples was demostrated.

Moreover, a piezoelectric sensor coupled to a short oligonucleotide can be used as detector of the hybridisation reaction. We show as a model the detection of a specific mutation in apolipoprotein E (ApoE) gene.

Biotinylated 23-mer probes were immobilised on the streptavidin coated gold surface of a quartz crystal; the protein was covalently bound to the thiol/dextran modified gold surface. The device was able to distinguish different synthetic oligonucleotides. The hybridisation reaction was also performed using real samples of DNA extracted from human blood and amplified by Polymerase chain reaction PCR. The extension of such procedure to samples of environmental interest is discussed.     

A Piezoelectric Quartz Crystal Biosensor as a Direct Affinity Sensor

Abstract

A microprocessor controlled piezoelectric detector as sensor was employed to monitor in real time protein adsorption and immunoreactions using piezoelectric quartz crystals (AT-cut) with a basic resonant frequency of 10 MHz. The adsorbed protein was an immunoglobulin (h-lg G); in the immunosensing a covalent immobilized molecule (the pesticide 2,4-D) formed the receptor for the immobilized ligand sample (Mab anti-2,4-D) in a competitive assay.     

A New Approach to the Development of a Reusable Piezoelectric Crystal Biosensor

Abstract

A reusable piezoelectric crystal immunosensor for human albumin has been developed. The crystal was coated with protein a and then reacted with anti-human albumin antibody. Human albumin in the range 10^?4 mg/ml to 10^?1 mg/ml could be detected by the system. Crystals were regenerated by saturation with albumin and subsequent binding of a new anti-albumin antibody layer. The albumin assay could be repeated up to 5 times using the same crystal.     

Rapid Detection of Escherichia Coliform Using A Series Electrode Piezoelectric Crystal Sensor

Abstract

A series electrode piezoelectric crystal sensor was used to determine Escherichia coliform (E. coli.). This method is simple and rapid, and requires only a single sample dilution. E. coli. in the range of 10 - 10⁶ cells per ml can be estimated by this method. The procedure is a frequency detection time (FDT) method. The factors which affect the determination are discussed. Thirty samples in pure culture were tested by this method and the results fell within the 95% confidence limits of the standard plate count values. A correlation coefficient of 0.93 was obtained between the frequency detection time and logarithm of initial bacterial concentration. This corresponds to the criteria used to evaluate E. coli. with the added advantage of single dilution and more rapid results.     

A Selective Pharmaceutical Analysis Technique with Sensitive Piezoelectric Crystal Quartz Sensors

Abstract

The frequency shift of a piezoelectric crystal sensor showed a linear dependence on the concentration for drugs which can be hydrolyzed in base aqueous solutions, at a given reacting time after the addition of the base, when the base concentration is basically constant during the entire measurement period. The sensitivity of the analysis method was improved, if crystal responses at different reacting times were recorded and utilized to estimate component concentration, when used for determining atropine sulfate in a pharmaceutical compound. The analytical results indicated that the selective and sensitive analytical procedure could be easily applied in true low concentration pharmaceutical analysis.     

A Coated Piezoelectric Crystal Sensor for the Determination of 2, 4-Toluene Diisocyanate in Air

Abstract

2, 4-toluene diisocyanate (TDI) in air was detected and determined by a piezoelectric quartz crystal sensor coated with tetrakis(hydroxyethyl)ethylenediamine (THEED)/dithizone(diphenylthiocarbazone) solution (l:3v/v in acetone). The response curve is linear over the concentration range 3–24 ppb of TDI. The sensor can be used for more than 2 months without loss in sensitivity and presented good reversibility and reproducibility. Of the different possible interferents tested, only SO₂ caused a frequency change.     

Reusable Amperometric Immunosensor for the Determination of Cortisol

Abstract

A novel reusable amperometric immunosensor was developed for the determination of cortisol by co-immobilizing horseradish peroxidase (POD) and cortisol-antibody on a chemically activated affinity membrane which is mounted over the tip of an oxygen electrode. The enzymatic electrocatalytic current response to the respective substrate is inhibited by the association of the antigen to the co-immobilized antibody. The sensor can be regenerated to facilitate several assays by washing with dilute hydrochloric acid solution. The advantages of the sensor include rapid-response, simple analysis methodology and high selectivity. The calibration curve for cortisol is linear in the concentration range of 1 × 10^?7 – 1 × 10^?5M. The optimal conditions of immobilization and pH have been studied. The inhibition of enzymatic activity was confirmed by luminescence measurement utilizing the luminol- H₂O₂-POD system.     

Use of Piezoelectric Crystals as Sensitive and Specific Detectors for So2

Abstract

A general purpose gas chromatograph using a piezoelectric crystal as detector has been constructed and a piezoelectric crystal detector sensitive and selective for sulfur dioxide has been designed and developed. From 1 to 100 ppm of SO₂ can be quickly and easily determined.     

Assay of Sulfur in Organic Liquids Using a Mercury Displacement Method

Abstract

A method for the assay of sulfur in organic liquids is presented. The method utilizes an oxidative combustion process coupled with a piezoelectric crystal detector. The sulfur dioxide evolved upon combustion of the organic liquid is bubbled through a mercurous nitrate solution. The mercury vapor produced is detected by a piezoelectric crystal due to the formation of a mercury amalgam.     

Piezoelectric Detection of Ricin and Affinity-Purified Goat Anti-ricin Antibody

Abstract

Detection of ricin, in a piezoelectric quartz crystal microbalance format, can be accomplished with the use of capture antibody techniques. These techniques allow for the specific attachment of ricin to immobilized capture antibodies on the quartz crystal transducer area. A reversed format can also be used to detect antibody in solution. In this case, the antigen is immobilized and antibody attaches specifically, thus increasing the overall mass and decreasing the resonant frequency. In this report we describe detection of both ricin and anti-ricin antibody using immunological piezoelectric quartz crystal microbalance techniques.

     

Phosphate Sensor Composed from Immobilized Pyruvate Oxidase and an Oxygen Electrode

Abstract

A phosphate sensor based on amperometric determination was constructed with immobilized pyruvate oxidase and an oxygen electrode. A rapid, simple and sensitive determination of phosphate was performed with the sensor. The determination time was 7min. The linearity range of this sensor was 12 – 80μM.     

Novel Reduction Kinetics Model of Dimethoate (DMA) on the Growth of Pseudomonas aeruginosa

Abstract

A new method for monitoring Pseudomonas aeruginosa growth with dimethoate (DMA) as sole carbon using the series piezoelectric quartz crystal (SPQC) and high-performance liquid chromatography (HPLC) was described. Compared with the general methods, SPQC gives real-time, multidimensional information. The determination limit of HPLC was 1.08 ng. A combined novel response model for Pseudomonas aeruginosa degrading DMA was derived. By fitting DMA reducing data, the value of the reduction rate constant (k) was obtained and in line with the actual trend. The proposed kinetic model was successfully applied to Pseudomonas aeruginosa degrading DMA.     

A Piezoelectric Biosensor For DNA Hybridisation Detection

Abstract

In this paper the realisation of a piezoelectric biosensor for DNA hybridisation detection is reported. A biotinylated 25-mer, was immobilised on a (strept)avidin coated piezoelectric crystal; avidin was covalently bound to the thiol/dextran modified gold surface of the crystal. Hybridisation of the probe with a complementary sequence was detected. The device was able to distinguish among targets of different lengths. Many cycles of measurements could be performed on the same crystal surface regenerating the single strand with HCl (ImM). No signal was detected when the probe reacted with a non complementary sequence. The same experiments were performed immobilising the biotinylated DNA probe on the gold surface coated with avidin by adsorption and the results were compared.     

A New Sensor Method for Studying the Effect of Gentamicin and Cefotaxime Combination Against Escherichia coli

Abstract

A new sensor method based on a multi-channel series piezoelectric quartz crystal (MSPQC) was proposed for studying the effect of gentamicin and cefotaxime combination against Escherichia coli ATCC 25922. The frequency curves under different combination regimens were obtained and compared with each other. When antibiotic had an inhibitory effect to the growth of bacteria, frequency detection time (FDT) would be prolonged. The FDT was used to assess the effect of an antibiotic combination. By using the proposed method, simultaneous administration, different order, and time interval of nonsimultaneous administration were investigated in detail. The MSPQC method can provide the process information in real time. It is simple, rapid, and easy to perform.     

Detection of Sulfur Dioxide Using a Piezoelectric Quartz Crystal Microbalance

Abstract

Sulfur dioxide was detected and determined in air by a piezoelectric quartz crystal sensor coated with 4-aminoantipyrine 1-hydroxyetil-2-heptadecenyl imidazol (amine 220) solution (1:1 v/v in chloroform). The analytical response curve is linear over the concentration range from 0.70 to 5.0 ppm of SO₂. Good linearities (r = 0.9990, 0.9995 and 0.9968) and sensitivities (18.0, 33.4 and 50.7 Hz/ppm) were found, respectively for exposure times of 30, 60 and 90 seconds. The sensor can be used for more than six months without loss in sensitivity and presented good reversibility and reproducibility. Among some possible interferents tested, only nitrogen dioxide and moisture caused major frequency changes.     

Piezoelectric Crystal Biosensor System for Detection of Escherichia Coli

Abstract

A piezoelectric crystal biosensor system was applied to the detection of Escherichia coli. the system consists of an oscillator, a frequency counter, a flow cell and a modified piezoelectric crystal. Anti-E. coli antibody is immobilized on the surface of the crystal. It is used as an E. coli detection by measuring its resonant frequency shift due to a mass change caused by specific binding of the micro organisms to the surface. the frequency shift correlates with an E. coli concentration in the range of 10⁶?10⁸ cells·cm^?3. the resonant frequency shift is increased by further treatment to bind micro-particles modified with anti-E. coli antibody. This method allows us to improve the determination limit to 10⁵ cells · cm^?3.