Advances in sensor technology have allowed the significant progress in the monitoring of noxious compounds in the sea, providing real-time detection so as to prevent risks associated with the diffusion and dispersion ...Advances in sensor technology have allowed the significant progress in the monitoring of noxious compounds in the sea, providing real-time detection so as to prevent risks associated with the diffusion and dispersion of toxic substances in the environment. An important element in the overall picture is the harmful algal blooms which pose serious threats to marine ecosystems through the production of toxins that accumulate in filter-feeders and ultimately impact both human health and fisheries. Domoic acid is a neurotoxic amino acid produced by marine planktonic diatoms of the genus Pseudo-nitzschia. Here we monitored domoic acid production by natural Pseudo-nitzschia populations in phytoplankton samples collected along the Middle Tyrrhenian coast, over the course of one year, using selective immunosensors based on screenprinted electrodes, using differential pulse voltammetry as the electrochemical technique, to yield quantitative outputs. In this work, disposable devices have been applied for monitoring the production of domoic acid on algal extracts and the results have been validated by conventional high pressure liquid chromatography-ultraviolet detection methods. The data obtained revealed the presence of domoic acid in Italian phytoplankton, especially in coastal impacted areas, highlighting the potential risk of toxin entering into marine food webs and the environment. Immunosensors based on screen-printed electrodes prove to be effective tools for annual monitoring of domoic acid in seawater samples, thus providing a reliable early warning system relative to health and economic impact of algal toxins.展开更多
A simple technique for sensitive detection of heroine based on surface- plasmonresonance has been theoretically and experimentally investigated. The experiment was realized by using an anti-MO monoclonal antibody and ...A simple technique for sensitive detection of heroine based on surface- plasmonresonance has been theoretically and experimentally investigated. The experiment was realized by using an anti-MO monoclonal antibody and a morphine (MO)-bovine serum albumin (MOBSA) conjugate (antigen). The reason for using MO-BSA in the detection of heroine was also discussed. MO-BSA was immobilized on a gold thin film of SPR sensor chip by physical adsorption. The configuration of the device is allowed to be further miniaturized, which is required for the construction of a portable SPR device in the application of in-situ analysis.展开更多
Celiac disease is a permanent intolerance to gluten proteins of wheat, rye, barley, and oats in genetically susceptible individuals. The clinical picture is characterized by inflammation and damage of the small intest...Celiac disease is a permanent intolerance to gluten proteins of wheat, rye, barley, and oats in genetically susceptible individuals. The clinical picture is characterized by inflammation and damage of the small intestinal mucosa and malabsorption of essential nutrients. Therapeutically, a lifelong strict gluten-free diet is necessary. The diagnosis of celiac disease is complex and includes symptomatology, serology, small intestinal histology, and genetic status. Serological testing plays a central role within the diagnostic procedure and is based on the measurement of disease-specific antibodies against gluten proteins (antigen) and tissue transglutaminase (autoantigen). Immunofluorescence detection and enzyme-linked immunosorbent assays are currently most often applied for antibody testing. However, these tests are expensive and time-consuming. Therefore, simple and rapid alternative methods have been developed during the last years, and electro-chemical immunosensors seem to be the most promising analytical tools. The architecture of these sensors may comprise the following elements: working and reference electrodes, covalent or noncovalent binding of the antigen to the surface of the working electrode by means of a functional monolayer, and blocking of unreacted binding sites. The analytical procedure is initiated by adding the analyte (serum antibodies) and an analyte-specific second antibody, which is usually labeled with an enzyme. The special reaction of the enzyme with an appropriate substrate results in a product that initiates a current that can be measured by different electrical methods. A number of different electrochemical immunosensors variable in different electrodes, binding systems, secondary antibodies, and current measurements have been developed. Most of them have been tested with real human serum samples of celiac patients and healthy individuals, and some of them reached disease sensitivity and specificity comparable with traditional analytical systems. Thus, electrochemical immunosensors can be promising alternatives to existing diagnostic tests in the future. They are simple, reliable, robust, user-friendly, and cost-effective tools with short operation times.展开更多
An effective electrochemical signal amplification strategy based on enzyme membrane modification and redox probe immobilization was proposed to construct an amperometric immunosensor.L-cysteine@ferrocene functionalize...An effective electrochemical signal amplification strategy based on enzyme membrane modification and redox probe immobilization was proposed to construct an amperometric immunosensor.L-cysteine@ferrocene functionalized chitosan,which possessed not only efficient redox-activity but also excellent film-forming ability,was coated on the bare glass carbon electrode. Moreover,the thiol groups(SH)in the ferrocenyl compound were used for gold nanoparticles immobilization via the strong bonding interaction,which could further be utilized for the immobilization of antibody biomolecules with well-retained bioactivities.Finally,glucose oxidase(GOD)as the enzyme membrane was employed to block the possible remaining active sites and avoid the nonspecific adsorption.With the excellent electrocatalytic properties of GOD towards glucose,the amplification of antigen-antibody interaction and the enhanced sensitivity could be achieved.Under the optimal conditions,the linear range of the proposed immunosensor for the determination of carcinoembryonic antigen(CEA)was from 0.05 to 100 ng/mL with a detection limit of 0.02 ng/mL(S/N=3).Moreover,the immunosensor exhibited good selectivity,stability and reproducibility, which provided a promising potential for clinical immunoassay.展开更多
In this study, we have for the first time preformed the facile substrate-enhanced electroless deposition(SEED) of metal nanoparticles onto monolithic graphene@Ni foams for construction of disposable three-dimensional(...In this study, we have for the first time preformed the facile substrate-enhanced electroless deposition(SEED) of metal nanoparticles onto monolithic graphene@Ni foams for construction of disposable three-dimensional(3 D) electrochemical immunosensors. Specifically, we firstly used the SEED method to deposit gold nanoparticles(AuNPs) onto the graphene@Ni foam for immobilization of antibody(Ab1). This is followed by a second step SEED deposition to produce silver nanoparticles(AgNPs) for electrochemical stripping detection. Using a-fetoprotein antigen(AFP) as a module analyte, the newly-developed sensor showed a wide linear response, ranging from 5.0 pg/mL to 5.0 ng/mL and a low detection limit down to 2.3 pg/mL. The newly-developed 3 D-immunosensor is sensitive, reliable,and easy to be fabricated, showing great potential for clinic applications.展开更多
Although diverse signal-amplified methods have been committed to improve the sensitivity of surface plasmon resonance(SPR)biosensing,introducing convenient and robust signal amplification strategy into SPR biosensing ...Although diverse signal-amplified methods have been committed to improve the sensitivity of surface plasmon resonance(SPR)biosensing,introducing convenient and robust signal amplification strategy into SPR biosensing remains challenging.Here,a novel nanozyme-triggered polymerization amplification strategy was proposed for constructing highly sensitive surface plasmon resonance(SPR)immunosensor.In detail,Au@Pd core-shell nanooctahedra nanozyme with superior peroxidase(POD)-like activity was synthesized and utilized as a label probe.Simultaneously,Au@Pd core-shell nanooctahedra nanozyme can catalyze the decomposition of H_(2)O_(2)to form hydroxyl radicals(·OH)that triggers the polymerization of aniline to form polyaniline attaching on the surface of sensor chip,significantly amplifying SPR responses.The sensitivity of SPR immunosensor was enhanced by nanozyme-triggered polymerization amplification strategy.Using human immunoglobulin G(HIgG)as a model,the constructed SPR immunosensor obtains a wide linear range of 0.005–1.0μg/m L with low detection limit of 0.106 ng/m L.This research provides new sights on establishing sensitive SPR immunosensor and may evokes more inspiration for developing signal amplification methods based on nanozyme in biosensing.展开更多
Herein,a novel label-free electrochemical immunosensor was fabricated via immobilizing specific anti-β-lactoglobulin(β-LG)antibodies(Abs)onto an integrated electrode of gold nanoparticles(AuNPs)/Prussian blue(PB)/cu...Herein,a novel label-free electrochemical immunosensor was fabricated via immobilizing specific anti-β-lactoglobulin(β-LG)antibodies(Abs)onto an integrated electrode of gold nanoparticles(AuNPs)/Prussian blue(PB)/cubic Ia3d structured mesoporous carbon(CMK-8).This immunosensor allowed for the quantitative detection of the major milk allergenβ-LG.CMK-8 with excellent electrical conductivity and uniformly adjustable pore structure was modified on the glassy carbon electrode(GCE)and served as the sensitive substrate for the electro-polymerization of PB,forming the redox-active layer.AuNPs were subsequently electrochemically deposited on PB/CMK-8/GCE to improve the electrical conductivity and utilized as the connector for Abs immobilization.Duringβ-LG detection,the Abs-modified AuNPs/PB/CMK-8/GCE exhibited a significant reduction in differential pulse voltammetry current signal when exposed toβ-LG,displaying an inverse dose-dependent relationship.The developed electrochemical immunosensor demonstrated good detection performance forβ-LG,with a wider linear range of 0.01-100 ng/mL and a lower detection limit of 4.72 pg/mL.Meanwhile,the sensor exhibited remarkable repeatability,reproducibility,stability and anti-interference capabilities,which was further applied to detectβ-LG in dairy food,achieving satisfactory recoveries(89.2%-98.8%)and lower relative standard deviation(£3.1%).Therefore,this innovative electrochemical method for food allergen detection holds great potential application in food safety determination and evaluation.展开更多
Hepatitis C is a liver disease that is transmitted through contact with the blood of an infected person. An estimated 150 million individuals worldwide have been chronically infected with the hepatitis C virus(HCV). H...Hepatitis C is a liver disease that is transmitted through contact with the blood of an infected person. An estimated 150 million individuals worldwide have been chronically infected with the hepatitis C virus(HCV). Hepatitis C shows significant genetic variation in the global population, due to the high rate of viral RNA mutation. There are six variants of the virus(HCV genotypes 1, 2, 3, 4, 5, and 6), with 15 recorded subtypes that vary in prevalence across different regions of the world. A variety of devices are used to diagnose hepatitis C, including HCV antibody test, HCV viral load test, HCV genotype test and liver biopsy. Rapid, inexpensive, sensitive, and robust analytical devices are therefore essential for effective diagnosis and monitoring of disease treatment. This review provides an overview of current electrochemical immunosensor and genosensortechnologies employed in HCV detection.There are a limited number of publications showing electrochemical biosensors being used for the detection of HCV.Due to their simplicity,specificity,and reliability,electrochemical biosensor devices have potential clinical applications in several viral infections.展开更多
[Objective] The aim is to develop the piezoelectric immunosensor to detect H9-subtype avian influenza virus（AIV）.[Method] The immunosensor chip was constructed by self-assembling mercaptopmpionic acid（MPA） to be m...[Objective] The aim is to develop the piezoelectric immunosensor to detect H9-subtype avian influenza virus（AIV）.[Method] The immunosensor chip was constructed by self-assembling mercaptopmpionic acid（MPA） to be monolayer on the silver-coated electrode of quartz crystal and coupling the monoclonal antibody to H9 subtype AIV with N-ethy-N＇-（3-dimethyl aminopropyl）carbodiimide hydrochloride（EDC） and N-hydroxysuccinimide（NHS）.The immunosensor to detect H9 subtype AIV was established.[Result] The results showed that the immunosensor displayed better specificity to H9 AIV and had no response to H5AIV and NDV when it was used for detection.The sensitivity test indicated the detection sensitivity for the H9 subtype AIV could reach 20-100 EID50.[Conclusion] The research provided a foundation for further research on the immunosensor for detecting AIV and it could be a new approach to detect other related viruses.展开更多
Antibiotics are a category of chemical compounds used to treat bacterial infections and are widely applied in cultivation,animal husbandry,aquaculture,and pharmacy.Currently,residual antibiotics and their metabolites ...Antibiotics are a category of chemical compounds used to treat bacterial infections and are widely applied in cultivation,animal husbandry,aquaculture,and pharmacy.Currently,residual antibiotics and their metabolites pose a potential risk of allergic reactions,bacterial resistance,and increased cancer incidence.Residual antibiotics and the resulting bacterial antibiotic resistance have been recognized as a global challenge that has attracted increasing attention.Therefore,monitoring antibiotics is a critical way to limit the ecological risks from antibiotic pollution.Accordingly,it is desirable to devise new analytical platforms to achieve efficient antibiotic detection with excellent sensitivity and specificity.Quantum dots(QDs)are regarded as an ideal material for use in the development of antibiotic detection biosensors.In this review,we characterize different types of QDs,such as silicon,chalcogenide,carbon,and other doped QDs,and summarize the trends in QD-based antibiotic detection.QD-based sensing applications are classified according to their recognition strategies,including molecularly imprinted polymers(MIPs),aptamers,and immunosensors.We discuss the advantages of QD-derived antibiotic sensors,including low cost,good sensitivity,excellent stability,and fast response,and illustrate the current challenges in this field.展开更多
An impedance immunosensor based on O-phenylenediamine modified gold electrode for the determination of phytohormone abscisic acid(ABA) was proposed.The operating pH,absorption time,absorption temperature and concentra...An impedance immunosensor based on O-phenylenediamine modified gold electrode for the determination of phytohormone abscisic acid(ABA) was proposed.The operating pH,absorption time,absorption temperature and concentration of anti-ABA antibody were investigated to optimize the analytical performance.The calibration curve for the determination of ABA was obtained from this impedance immunosensor under optimal conditions.The results showed that the detection limit at about 1 ng/mL in the range of 10-5000 ng/mL...展开更多
A novel multilayer film based on Au nanoparticles(AuNPs) and polyaniline/carboxylated multiwall carbon nanotubes-chitosan nanocomposite(PANI/MWCNTs/CS) was exploited to fabricate a highly sensitive immunosensor for de...A novel multilayer film based on Au nanoparticles(AuNPs) and polyaniline/carboxylated multiwall carbon nanotubes-chitosan nanocomposite(PANI/MWCNTs/CS) was exploited to fabricate a highly sensitive immunosensor for detecting chlorpyrifos. PANI-coated MWCNTs were prepared by in situ chemical polymerization and carboxylated MWCNTs played an important role in obtaining the thin and uniform coating of PANI resulting in the improved immunosensor response. Au NPs were used as a linker to immobilize chlorpyrifos antibody. The performance of the immunosensor was characterized by means of cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS) and scanning electron microscopy(SEM), respectively. All variables involved in the preparation process and analytical performance of the immunosensor were optimized.Under optimal conditions(antibody concentration: 5 μg/mL, working buffer pH: 6.5, incubation time: 40 min,incubation temperature: 25℃), the immunosensor exhibited a wide linear range from 0.1 to 40× 10^(-6)mg/mL and from 40 × 10^(-6)mg/mL to 500 × 10^(-6)mg/mL, and with a detection limit of 0.06 × 10^(-6)mg/mL, which provided a valuable tool for the chlorpyrifos detection in real samples.展开更多
A sensitive and specific immunosensor for the detection of the hormones cortisol and lactate in human or animal biological fluids, such as sweat and saliva, was devised using the label-free electrochemical chronoamper...A sensitive and specific immunosensor for the detection of the hormones cortisol and lactate in human or animal biological fluids, such as sweat and saliva, was devised using the label-free electrochemical chronoamperometric technique. By using these fluids instead of blood,the biosensor becomes noninvasive and is less stressful to the end user, who may be a small child or a farm animal.Electroreduced graphene oxide(e-RGO) was used as a synergistic platform for signal amplification and template for bioconjugation for the sensing mechanism on a screenprinted electrode. The cortisol and lactate antibodies were bioconjugated to the e-RGO using covalent carbodiimide chemistry. Label-free electrochemical chronoamperometric detection was used to analyze the response to the desired biomolecules over the wide detection range. A detection limit of 0.1 ng mL^(-1) for cortisol and 0.1 mM for lactate was established and a correlation between concentration and current was observed. A portable, handheld potentiostat assembled with Bluetooth communication and battery operation enables the developed system for point-of-care applications. A sandwich-like structure containing the sensing mechanisms as a prototype was designed to secure the biosensor to skin and use capillary action to draw sweat or other fluids toward the sensing mechanism. Overall, the immunosensor shows remarkable specificity, sensitivity as well as the noninvasive and point-of-care capabilities and allows the biosensor to be used as a versatile sensing platform in both developed and developing countries.展开更多
Convenient,rapid,and accurate detection of cardiac troponin I(cTnI)is crucial in early diagnosis of acute myocardial infarction(AMI).A paper-based electrochemical immunosensor is a promising choice in this field,becau...Convenient,rapid,and accurate detection of cardiac troponin I(cTnI)is crucial in early diagnosis of acute myocardial infarction(AMI).A paper-based electrochemical immunosensor is a promising choice in this field,because of the flexibility,porosity,and cost-efficacy of the paper.However,paper is poor in electronic conductivity and surface functionality.Herein,we report a paper-based electrochemical immunosensor for the label-free detection of cTnI with the working electrode modified by MXene(Ti_(3)C_(2))nanosheets.In order to immobilize the bio-receptor(anti-cTnI)on the MXene-modified working electrode,the MXene nanosheets were functionalized by aminosilane,and the functionalized MXene was immobilized onto the surface of the working electrode through Nafion.The large surface area of the MXene nanosheets facilitates the immobilization of antibodies,and the excellent conductivity facilitates the electron transfer between the electrochemical species and the underlying electrode surface.As a result,the paper-based immunosensor could detect cTnI within a wide range of 5-100 ng/mL with a detection limit of 0.58 ng/mL.The immunosensor also shows outstanding selectivity and good repeatability.Our MXene-modified paper-based electrochemical immunosensor enables fast and sensitive detection of cTnI,which may be used in real-time and cost-efficient monitoring of AMI diseases in clinics.展开更多
An electrochemical immunosensor was developed for ultrasensitive detection of microcystin-LR in water. MIL-101, a porous metal-organic frameworks(MOFs) material based on trivalent chromium skeleton were synthesized by...An electrochemical immunosensor was developed for ultrasensitive detection of microcystin-LR in water. MIL-101, a porous metal-organic frameworks(MOFs) material based on trivalent chromium skeleton were synthesized by hydrothermal synthesis method, and loaded with Au nanoparticles(Au NPs) to prepare Au NPs@MIL-101 composite materials which were used as a marker to label anti microcystin-LR(Anti-MC-LR). The composite materials have strong catalytic properties to the oxidation of ascorbic acid. Anti-MC-LR was immobilized on glassy carbon electrode surface using electrodeposition graphene oxide(GO) as an immobilization matrix to construct a competitive microcystin-LR immunosensor. The electrochemical immunosensor display linear relationship in the range of 0.05 ng/mL-75 μg/mL with linear correlation coefficient of 0.9951 and detection limit of 0.02 ng/mL(S/N = 3). This sensor was used to detect microcystin-LR in the water sample. The recovery was 102.43%,which is satisfied. The good testing results indicate the sensor has a great prospect in practical application.展开更多
A micro amperometric immunosensor with the sensitive area of only 1mm^2 was fabricated on silicon using the technique of Micro-Electro-Mechanical Systems (MEMS).A double exposure of SU-8 photoresist process was develo...A micro amperometric immunosensor with the sensitive area of only 1mm^2 was fabricated on silicon using the technique of Micro-Electro-Mechanical Systems (MEMS).A double exposure of SU-8 photoresist process was developed to create both the sensitive pool and reaction pool.Antibody was immobilized via cross-linking with glutaraldehyde on the sensitive area of the electrode surface,which was electropolymerized with polypyrrole previously.The immunosensor was characterized by detection of human immunoglobulin G (HIgG).The immunosensor displayed a good linear response to HIgG concentrations between 5ng/ml and 255ng/ml and demonstrated a fast response time of 3 minutes.展开更多
By means of the specific immuno-recognition and ultra-sensitive mass detection, a quartz crystal microbalance (QCM) biosensor for Escherichia coli O157:H7 detection was developed in this work. As a suitable surfactant...By means of the specific immuno-recognition and ultra-sensitive mass detection, a quartz crystal microbalance (QCM) biosensor for Escherichia coli O157:H7 detection was developed in this work. As a suitable surfactant, 16-mercaptohexadecanoic acid (MHDA) was introduced onto the Au surface of QCM, and then self-assembled with N-hydroxysuccinimide (NHS) raster as a reactive intermediate to provide an active interface for the specific antibody immobilization. The binding of target bacteria with the immobilized antibodies decreased the sensor’s resonant frequency, and the frequency shift was correlated to the bacterial concentration. The stepwise assembly of the immunosensor was characterized by means of the electrochemical techniques. Using the immersion-dry-immersion procedure, this QCM biosensor could detect 2.0×102 colony forming units (CFU)/ml E. coli O157:H7. In order to reduce the fabrication time, a polyelectrolyte layer-by-layer self-assembly (LBL-SA) method was adopted for fast construction. Finally, the reproducibility of this biosensor was discussed.展开更多
Label-free immunoassay is confronted with a great challenge that its insufficient sensitivity for low concentration analytes,which can be assigned to the low catalytic efficiency of modified materials towards electroa...Label-free immunoassay is confronted with a great challenge that its insufficient sensitivity for low concentration analytes,which can be assigned to the low catalytic efficiency of modified materials towards electroactive molecules.Herein,a universal MOF nanozyme-induced catalytic amplification strategy was proposed for constructing highly sensitive label-free electrochemical immunoassay.Specifically,the synthesized Cu Fe-MOF nanozyme with superior peroxidase(POD)-like activity,regarding as a MOF nanozyme model,can catalyze hydrogen peroxide to produce hydroxyl radicals(·OH),which can efficiently oxidize electroactive probe(such as 1,2-phenylenediamine(o-PD))accompanying with intense electrochemical signals.Modification of MOF nanozyme on the electrode and capture of antibodies for binding target antigens hinder the catalytic process of MOF nanozyme toward o-PD,resulting in a gradual decrease in electrochemical signal with increasing target antigen concentration,enabling quantitative label-free immunoassay.Thus,a highly sensitive label-free immunosensor using MOF nanozyme-induced catalytic amplification achieved effective detection of Immunoglobulin G(Ig G)with a wide linear range of 0.001-50 ng/mL and low detection limit of 0.45 pg/mL.This work proposes a promising nanozyme-induced catalytic amplification strategy for the development of label-free electrochemical immunoassay.展开更多
A new α-fetoprotein-MIP(AFP-MIP) immunosensor based on glass carbon electrode(GCE) modified with polythionine(PTh) and gold nanoparticles(AuNPs) was successfully fabricated for sensitive detection ofα-fetoprotein(AF...A new α-fetoprotein-MIP(AFP-MIP) immunosensor based on glass carbon electrode(GCE) modified with polythionine(PTh) and gold nanoparticles(AuNPs) was successfully fabricated for sensitive detection ofα-fetoprotein(AFP). Through controlling electropolymerization, A "polydopamine(PDA)-AFP" complex was achieved applying AFP as template and dopamine(DA) as imprinted monomers. After elution, the specific cavities can adsorb the target molecules. Using differential pulse voltammetry(DPV) detection,the peak current decreased with the increase in concentration of AFP, and the linear response range of the AFP-MIP immunosensor was from 0.001 ng/mL to 800 ng/mL with the detection limit as low as0.8138 pg/mL. The MIP immunosensor could become a new promising method for the detection of AFP.Furthermore, this MIP sensor was demonstrated in testing AFP in human serum samples with satisfactory results.展开更多
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-crys...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.展开更多
文摘Advances in sensor technology have allowed the significant progress in the monitoring of noxious compounds in the sea, providing real-time detection so as to prevent risks associated with the diffusion and dispersion of toxic substances in the environment. An important element in the overall picture is the harmful algal blooms which pose serious threats to marine ecosystems through the production of toxins that accumulate in filter-feeders and ultimately impact both human health and fisheries. Domoic acid is a neurotoxic amino acid produced by marine planktonic diatoms of the genus Pseudo-nitzschia. Here we monitored domoic acid production by natural Pseudo-nitzschia populations in phytoplankton samples collected along the Middle Tyrrhenian coast, over the course of one year, using selective immunosensors based on screenprinted electrodes, using differential pulse voltammetry as the electrochemical technique, to yield quantitative outputs. In this work, disposable devices have been applied for monitoring the production of domoic acid on algal extracts and the results have been validated by conventional high pressure liquid chromatography-ultraviolet detection methods. The data obtained revealed the presence of domoic acid in Italian phytoplankton, especially in coastal impacted areas, highlighting the potential risk of toxin entering into marine food webs and the environment. Immunosensors based on screen-printed electrodes prove to be effective tools for annual monitoring of domoic acid in seawater samples, thus providing a reliable early warning system relative to health and economic impact of algal toxins.
文摘A simple technique for sensitive detection of heroine based on surface- plasmonresonance has been theoretically and experimentally investigated. The experiment was realized by using an anti-MO monoclonal antibody and a morphine (MO)-bovine serum albumin (MOBSA) conjugate (antigen). The reason for using MO-BSA in the detection of heroine was also discussed. MO-BSA was immobilized on a gold thin film of SPR sensor chip by physical adsorption. The configuration of the device is allowed to be further miniaturized, which is required for the construction of a portable SPR device in the application of in-situ analysis.
文摘Celiac disease is a permanent intolerance to gluten proteins of wheat, rye, barley, and oats in genetically susceptible individuals. The clinical picture is characterized by inflammation and damage of the small intestinal mucosa and malabsorption of essential nutrients. Therapeutically, a lifelong strict gluten-free diet is necessary. The diagnosis of celiac disease is complex and includes symptomatology, serology, small intestinal histology, and genetic status. Serological testing plays a central role within the diagnostic procedure and is based on the measurement of disease-specific antibodies against gluten proteins (antigen) and tissue transglutaminase (autoantigen). Immunofluorescence detection and enzyme-linked immunosorbent assays are currently most often applied for antibody testing. However, these tests are expensive and time-consuming. Therefore, simple and rapid alternative methods have been developed during the last years, and electro-chemical immunosensors seem to be the most promising analytical tools. The architecture of these sensors may comprise the following elements: working and reference electrodes, covalent or noncovalent binding of the antigen to the surface of the working electrode by means of a functional monolayer, and blocking of unreacted binding sites. The analytical procedure is initiated by adding the analyte (serum antibodies) and an analyte-specific second antibody, which is usually labeled with an enzyme. The special reaction of the enzyme with an appropriate substrate results in a product that initiates a current that can be measured by different electrical methods. A number of different electrochemical immunosensors variable in different electrodes, binding systems, secondary antibodies, and current measurements have been developed. Most of them have been tested with real human serum samples of celiac patients and healthy individuals, and some of them reached disease sensitivity and specificity comparable with traditional analytical systems. Thus, electrochemical immunosensors can be promising alternatives to existing diagnostic tests in the future. They are simple, reliable, robust, user-friendly, and cost-effective tools with short operation times.
基金financially supported by the National Natural Science Foundation of China(20675064)the Ministry of Education of China(708073)+1 种基金the Natural Science Foundation of Chongqing City (CSTC-2009BA1003)High Technology Project Foundation of Southwest University(XSGX 02)
文摘An effective electrochemical signal amplification strategy based on enzyme membrane modification and redox probe immobilization was proposed to construct an amperometric immunosensor.L-cysteine@ferrocene functionalized chitosan,which possessed not only efficient redox-activity but also excellent film-forming ability,was coated on the bare glass carbon electrode. Moreover,the thiol groups(SH)in the ferrocenyl compound were used for gold nanoparticles immobilization via the strong bonding interaction,which could further be utilized for the immobilization of antibody biomolecules with well-retained bioactivities.Finally,glucose oxidase(GOD)as the enzyme membrane was employed to block the possible remaining active sites and avoid the nonspecific adsorption.With the excellent electrocatalytic properties of GOD towards glucose,the amplification of antigen-antibody interaction and the enhanced sensitivity could be achieved.Under the optimal conditions,the linear range of the proposed immunosensor for the determination of carcinoembryonic antigen(CEA)was from 0.05 to 100 ng/mL with a detection limit of 0.02 ng/mL(S/N=3).Moreover,the immunosensor exhibited good selectivity,stability and reproducibility, which provided a promising potential for clinical immunoassay.
基金financially supported by the Natural Science Foundation of Zhejiang Province (LY18H200008)Wenzhou Science and Technology Bureau Project (Y20170203)National Natural Science Foundation of China (51433005)
文摘In this study, we have for the first time preformed the facile substrate-enhanced electroless deposition(SEED) of metal nanoparticles onto monolithic graphene@Ni foams for construction of disposable three-dimensional(3 D) electrochemical immunosensors. Specifically, we firstly used the SEED method to deposit gold nanoparticles(AuNPs) onto the graphene@Ni foam for immobilization of antibody(Ab1). This is followed by a second step SEED deposition to produce silver nanoparticles(AgNPs) for electrochemical stripping detection. Using a-fetoprotein antigen(AFP) as a module analyte, the newly-developed sensor showed a wide linear response, ranging from 5.0 pg/mL to 5.0 ng/mL and a low detection limit down to 2.3 pg/mL. The newly-developed 3 D-immunosensor is sensitive, reliable,and easy to be fabricated, showing great potential for clinic applications.
基金supported by National Natural Science Foundation of China(Nos.22474124,21575125)the National Natural Science Foundation of Jiangsu Province(No.BK20221370)+4 种基金Key University Natural Science Foundation of Jiangsu-Province(No.20KJA150004)the Project for Science and Technology of Yangzhou(No.YZ2022074)Project for Yangzhou City and Yangzhou University corporation(No.YZ2023204)the Open Research Fund of State Key Laboratory of Analytical Chemistry for Life Science(No.SKLACLS2405)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX22_3462)。
文摘Although diverse signal-amplified methods have been committed to improve the sensitivity of surface plasmon resonance(SPR)biosensing,introducing convenient and robust signal amplification strategy into SPR biosensing remains challenging.Here,a novel nanozyme-triggered polymerization amplification strategy was proposed for constructing highly sensitive surface plasmon resonance(SPR)immunosensor.In detail,Au@Pd core-shell nanooctahedra nanozyme with superior peroxidase(POD)-like activity was synthesized and utilized as a label probe.Simultaneously,Au@Pd core-shell nanooctahedra nanozyme can catalyze the decomposition of H_(2)O_(2)to form hydroxyl radicals(·OH)that triggers the polymerization of aniline to form polyaniline attaching on the surface of sensor chip,significantly amplifying SPR responses.The sensitivity of SPR immunosensor was enhanced by nanozyme-triggered polymerization amplification strategy.Using human immunoglobulin G(HIgG)as a model,the constructed SPR immunosensor obtains a wide linear range of 0.005–1.0μg/m L with low detection limit of 0.106 ng/m L.This research provides new sights on establishing sensitive SPR immunosensor and may evokes more inspiration for developing signal amplification methods based on nanozyme in biosensing.
基金supported by the National Natural Science Foundation of China(32272416,31972147)Project of Tianjin Science and Technology Plan(22ZYJDSS00030).
文摘Herein,a novel label-free electrochemical immunosensor was fabricated via immobilizing specific anti-β-lactoglobulin(β-LG)antibodies(Abs)onto an integrated electrode of gold nanoparticles(AuNPs)/Prussian blue(PB)/cubic Ia3d structured mesoporous carbon(CMK-8).This immunosensor allowed for the quantitative detection of the major milk allergenβ-LG.CMK-8 with excellent electrical conductivity and uniformly adjustable pore structure was modified on the glassy carbon electrode(GCE)and served as the sensitive substrate for the electro-polymerization of PB,forming the redox-active layer.AuNPs were subsequently electrochemically deposited on PB/CMK-8/GCE to improve the electrical conductivity and utilized as the connector for Abs immobilization.Duringβ-LG detection,the Abs-modified AuNPs/PB/CMK-8/GCE exhibited a significant reduction in differential pulse voltammetry current signal when exposed toβ-LG,displaying an inverse dose-dependent relationship.The developed electrochemical immunosensor demonstrated good detection performance forβ-LG,with a wider linear range of 0.01-100 ng/mL and a lower detection limit of 4.72 pg/mL.Meanwhile,the sensor exhibited remarkable repeatability,reproducibility,stability and anti-interference capabilities,which was further applied to detectβ-LG in dairy food,achieving satisfactory recoveries(89.2%-98.8%)and lower relative standard deviation(£3.1%).Therefore,this innovative electrochemical method for food allergen detection holds great potential application in food safety determination and evaluation.
基金Supported by Brazilian funding agencies(Sao Paulo Research Foundation-FAPESP and National Council for Scientific and Technological Development-CNPq)
文摘Hepatitis C is a liver disease that is transmitted through contact with the blood of an infected person. An estimated 150 million individuals worldwide have been chronically infected with the hepatitis C virus(HCV). Hepatitis C shows significant genetic variation in the global population, due to the high rate of viral RNA mutation. There are six variants of the virus(HCV genotypes 1, 2, 3, 4, 5, and 6), with 15 recorded subtypes that vary in prevalence across different regions of the world. A variety of devices are used to diagnose hepatitis C, including HCV antibody test, HCV viral load test, HCV genotype test and liver biopsy. Rapid, inexpensive, sensitive, and robust analytical devices are therefore essential for effective diagnosis and monitoring of disease treatment. This review provides an overview of current electrochemical immunosensor and genosensortechnologies employed in HCV detection.There are a limited number of publications showing electrochemical biosensors being used for the detection of HCV.Due to their simplicity,specificity,and reliability,electrochemical biosensor devices have potential clinical applications in several viral infections.
基金Supported by the Supporting Program of the"Eleventh Five-year Plan"for Sci&Tech Research of China(2006BAK20A29)Strategical Project for Science and Technology of Guangdong Province(2004A2090102)~~
文摘[Objective] The aim is to develop the piezoelectric immunosensor to detect H9-subtype avian influenza virus（AIV）.[Method] The immunosensor chip was constructed by self-assembling mercaptopmpionic acid（MPA） to be monolayer on the silver-coated electrode of quartz crystal and coupling the monoclonal antibody to H9 subtype AIV with N-ethy-N＇-（3-dimethyl aminopropyl）carbodiimide hydrochloride（EDC） and N-hydroxysuccinimide（NHS）.The immunosensor to detect H9 subtype AIV was established.[Result] The results showed that the immunosensor displayed better specificity to H9 AIV and had no response to H5AIV and NDV when it was used for detection.The sensitivity test indicated the detection sensitivity for the H9 subtype AIV could reach 20-100 EID50.[Conclusion] The research provided a foundation for further research on the immunosensor for detecting AIV and it could be a new approach to detect other related viruses.
基金supported by grants from the National Key Research and Development Project(Project No.:2019YFC1605800)the National Natural Science Foundation of China(Grant Nos.:22006070 and 82103816)+2 种基金the Natural Science Foundation of Jiangsu Province(Grant Nos.:BK20200715,BK20200718,and BK20210538)the Natural Science Foundation of Jiangsu Higher Education Institutions,China(Grant No.:20KJB350010)the Natural Science Fund for Colleges and Universities in Jiangsu Province(Grant No.:19KJB530011).
文摘Antibiotics are a category of chemical compounds used to treat bacterial infections and are widely applied in cultivation,animal husbandry,aquaculture,and pharmacy.Currently,residual antibiotics and their metabolites pose a potential risk of allergic reactions,bacterial resistance,and increased cancer incidence.Residual antibiotics and the resulting bacterial antibiotic resistance have been recognized as a global challenge that has attracted increasing attention.Therefore,monitoring antibiotics is a critical way to limit the ecological risks from antibiotic pollution.Accordingly,it is desirable to devise new analytical platforms to achieve efficient antibiotic detection with excellent sensitivity and specificity.Quantum dots(QDs)are regarded as an ideal material for use in the development of antibiotic detection biosensors.In this review,we characterize different types of QDs,such as silicon,chalcogenide,carbon,and other doped QDs,and summarize the trends in QD-based antibiotic detection.QD-based sensing applications are classified according to their recognition strategies,including molecularly imprinted polymers(MIPs),aptamers,and immunosensors.We discuss the advantages of QD-derived antibiotic sensors,including low cost,good sensitivity,excellent stability,and fast response,and illustrate the current challenges in this field.
基金supported by the National Natural Science Foundation of China(No.90817101,30670190 and 3060049)
文摘An impedance immunosensor based on O-phenylenediamine modified gold electrode for the determination of phytohormone abscisic acid(ABA) was proposed.The operating pH,absorption time,absorption temperature and concentration of anti-ABA antibody were investigated to optimize the analytical performance.The calibration curve for the determination of ABA was obtained from this impedance immunosensor under optimal conditions.The results showed that the detection limit at about 1 ng/mL in the range of 10-5000 ng/mL...
基金supported by the National Natural Science Foundation of China (No. 30972055, 31101286)Agricultural Science and Technology Achievements Transformation Fund Projects of the Ministry of Science and Technology of China (No. 2011GB2C60020)Shandong Provincial Natural Science Foundation, China (No. Q2008D03)
文摘A novel multilayer film based on Au nanoparticles(AuNPs) and polyaniline/carboxylated multiwall carbon nanotubes-chitosan nanocomposite(PANI/MWCNTs/CS) was exploited to fabricate a highly sensitive immunosensor for detecting chlorpyrifos. PANI-coated MWCNTs were prepared by in situ chemical polymerization and carboxylated MWCNTs played an important role in obtaining the thin and uniform coating of PANI resulting in the improved immunosensor response. Au NPs were used as a linker to immobilize chlorpyrifos antibody. The performance of the immunosensor was characterized by means of cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS) and scanning electron microscopy(SEM), respectively. All variables involved in the preparation process and analytical performance of the immunosensor were optimized.Under optimal conditions(antibody concentration: 5 μg/mL, working buffer pH: 6.5, incubation time: 40 min,incubation temperature: 25℃), the immunosensor exhibited a wide linear range from 0.1 to 40× 10^(-6)mg/mL and from 40 × 10^(-6)mg/mL to 500 × 10^(-6)mg/mL, and with a detection limit of 0.06 × 10^(-6)mg/mL, which provided a valuable tool for the chlorpyrifos detection in real samples.
基金the Natural Sciences and Engineering Research Council of Canada (400705) for funding this study
文摘A sensitive and specific immunosensor for the detection of the hormones cortisol and lactate in human or animal biological fluids, such as sweat and saliva, was devised using the label-free electrochemical chronoamperometric technique. By using these fluids instead of blood,the biosensor becomes noninvasive and is less stressful to the end user, who may be a small child or a farm animal.Electroreduced graphene oxide(e-RGO) was used as a synergistic platform for signal amplification and template for bioconjugation for the sensing mechanism on a screenprinted electrode. The cortisol and lactate antibodies were bioconjugated to the e-RGO using covalent carbodiimide chemistry. Label-free electrochemical chronoamperometric detection was used to analyze the response to the desired biomolecules over the wide detection range. A detection limit of 0.1 ng mL^(-1) for cortisol and 0.1 mM for lactate was established and a correlation between concentration and current was observed. A portable, handheld potentiostat assembled with Bluetooth communication and battery operation enables the developed system for point-of-care applications. A sandwich-like structure containing the sensing mechanisms as a prototype was designed to secure the biosensor to skin and use capillary action to draw sweat or other fluids toward the sensing mechanism. Overall, the immunosensor shows remarkable specificity, sensitivity as well as the noninvasive and point-of-care capabilities and allows the biosensor to be used as a versatile sensing platform in both developed and developing countries.
基金financially supported by the National Key R&D Program of China(2017YFA0204700)the Joint Research Funds of Department of Science&Technology of Shaanxi Province and Northwestern Polytechnical University(2020GXLH-Z-021)+1 种基金the China-Sweden Joint Mobility Project(51811530018)the Fundamental Research Funds for the Central Universities.
文摘Convenient,rapid,and accurate detection of cardiac troponin I(cTnI)is crucial in early diagnosis of acute myocardial infarction(AMI).A paper-based electrochemical immunosensor is a promising choice in this field,because of the flexibility,porosity,and cost-efficacy of the paper.However,paper is poor in electronic conductivity and surface functionality.Herein,we report a paper-based electrochemical immunosensor for the label-free detection of cTnI with the working electrode modified by MXene(Ti_(3)C_(2))nanosheets.In order to immobilize the bio-receptor(anti-cTnI)on the MXene-modified working electrode,the MXene nanosheets were functionalized by aminosilane,and the functionalized MXene was immobilized onto the surface of the working electrode through Nafion.The large surface area of the MXene nanosheets facilitates the immobilization of antibodies,and the excellent conductivity facilitates the electron transfer between the electrochemical species and the underlying electrode surface.As a result,the paper-based immunosensor could detect cTnI within a wide range of 5-100 ng/mL with a detection limit of 0.58 ng/mL.The immunosensor also shows outstanding selectivity and good repeatability.Our MXene-modified paper-based electrochemical immunosensor enables fast and sensitive detection of cTnI,which may be used in real-time and cost-efficient monitoring of AMI diseases in clinics.
基金supported by the National Natural Science Foundation of China(Nos. 21165023,21465026, 21765026, 21605130)the National Key Scientific Program of China(Nos. 2011CB911000,01100205020503104)
文摘An electrochemical immunosensor was developed for ultrasensitive detection of microcystin-LR in water. MIL-101, a porous metal-organic frameworks(MOFs) material based on trivalent chromium skeleton were synthesized by hydrothermal synthesis method, and loaded with Au nanoparticles(Au NPs) to prepare Au NPs@MIL-101 composite materials which were used as a marker to label anti microcystin-LR(Anti-MC-LR). The composite materials have strong catalytic properties to the oxidation of ascorbic acid. Anti-MC-LR was immobilized on glassy carbon electrode surface using electrodeposition graphene oxide(GO) as an immobilization matrix to construct a competitive microcystin-LR immunosensor. The electrochemical immunosensor display linear relationship in the range of 0.05 ng/mL-75 μg/mL with linear correlation coefficient of 0.9951 and detection limit of 0.02 ng/mL(S/N = 3). This sensor was used to detect microcystin-LR in the water sample. The recovery was 102.43%,which is satisfied. The good testing results indicate the sensor has a great prospect in practical application.
基金The authors greatly acknowledge the financial support from the National Natural Science Foundation of China （Grant No. 90307014）
文摘A micro amperometric immunosensor with the sensitive area of only 1mm^2 was fabricated on silicon using the technique of Micro-Electro-Mechanical Systems (MEMS).A double exposure of SU-8 photoresist process was developed to create both the sensitive pool and reaction pool.Antibody was immobilized via cross-linking with glutaraldehyde on the sensitive area of the electrode surface,which was electropolymerized with polypyrrole previously.The immunosensor was characterized by detection of human immunoglobulin G (HIgG).The immunosensor displayed a good linear response to HIgG concentrations between 5ng/ml and 255ng/ml and demonstrated a fast response time of 3 minutes.
基金Project supported by the Talent Foundation of Zhejiang Province (No. R205502)the Program of Education Department of Zhejiang Province (No. 20040197), China
文摘By means of the specific immuno-recognition and ultra-sensitive mass detection, a quartz crystal microbalance (QCM) biosensor for Escherichia coli O157:H7 detection was developed in this work. As a suitable surfactant, 16-mercaptohexadecanoic acid (MHDA) was introduced onto the Au surface of QCM, and then self-assembled with N-hydroxysuccinimide (NHS) raster as a reactive intermediate to provide an active interface for the specific antibody immobilization. The binding of target bacteria with the immobilized antibodies decreased the sensor’s resonant frequency, and the frequency shift was correlated to the bacterial concentration. The stepwise assembly of the immunosensor was characterized by means of the electrochemical techniques. Using the immersion-dry-immersion procedure, this QCM biosensor could detect 2.0×102 colony forming units (CFU)/ml E. coli O157:H7. In order to reduce the fabrication time, a polyelectrolyte layer-by-layer self-assembly (LBL-SA) method was adopted for fast construction. Finally, the reproducibility of this biosensor was discussed.
基金financially supported by National Natural Science Foundation of China(Nos.21575125,82172345 and 81573220)the National Natural Science Foundation of Jiangsu Province(No.BK20221370,BK20221281)+5 种基金Key University Natural Science Foundation of Jiangsu-Province(No.20KJA150004)the Project for Science and Technology of Yangzhou(Nos.YZ2022074,YZ2020076)Project for Yangzhou City and Yangzhou University corporation(No.YZ2023204)Cross cooperation project of Subei Peoples’Hospital of Jiangsu Province(No.SBJC220009)Open Research Fund of State Key Laboratory of Analytical Chemistry for Life Science(No.SKLACLS2405)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX22_3462)。
文摘Label-free immunoassay is confronted with a great challenge that its insufficient sensitivity for low concentration analytes,which can be assigned to the low catalytic efficiency of modified materials towards electroactive molecules.Herein,a universal MOF nanozyme-induced catalytic amplification strategy was proposed for constructing highly sensitive label-free electrochemical immunoassay.Specifically,the synthesized Cu Fe-MOF nanozyme with superior peroxidase(POD)-like activity,regarding as a MOF nanozyme model,can catalyze hydrogen peroxide to produce hydroxyl radicals(·OH),which can efficiently oxidize electroactive probe(such as 1,2-phenylenediamine(o-PD))accompanying with intense electrochemical signals.Modification of MOF nanozyme on the electrode and capture of antibodies for binding target antigens hinder the catalytic process of MOF nanozyme toward o-PD,resulting in a gradual decrease in electrochemical signal with increasing target antigen concentration,enabling quantitative label-free immunoassay.Thus,a highly sensitive label-free immunosensor using MOF nanozyme-induced catalytic amplification achieved effective detection of Immunoglobulin G(Ig G)with a wide linear range of 0.001-50 ng/mL and low detection limit of 0.45 pg/mL.This work proposes a promising nanozyme-induced catalytic amplification strategy for the development of label-free electrochemical immunoassay.
基金the National Natural Science Foundation of China (Nos. 61471168, 61571187)China Postdoctoral Science Foundation (No. 2016T90403)+2 种基金Postdoctoral Science Foundation of Jiangsu Province (No. 1601021A)the Natural Science Foundation of Hunan Province (No. 2017JJ209) Hunan Key Research Project (No. 2017SK2174) for the financial supports
文摘A new α-fetoprotein-MIP(AFP-MIP) immunosensor based on glass carbon electrode(GCE) modified with polythionine(PTh) and gold nanoparticles(AuNPs) was successfully fabricated for sensitive detection ofα-fetoprotein(AFP). Through controlling electropolymerization, A "polydopamine(PDA)-AFP" complex was achieved applying AFP as template and dopamine(DA) as imprinted monomers. After elution, the specific cavities can adsorb the target molecules. Using differential pulse voltammetry(DPV) detection,the peak current decreased with the increase in concentration of AFP, and the linear response range of the AFP-MIP immunosensor was from 0.001 ng/mL to 800 ng/mL with the detection limit as low as0.8138 pg/mL. The MIP immunosensor could become a new promising method for the detection of AFP.Furthermore, this MIP sensor was demonstrated in testing AFP in human serum samples with satisfactory results.
文摘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.
