Optical resonance-enhanced absorption-based near-field immunochip biosensor for allergen detection

An optical immunochip biosensor has been developed as a rapid method for allergen detection in complex food matrixes, and its application evaluated for the detection of the egg white allergens, ovalbumin and ovomucoid. The optical near-field phenomenon underlying the basic principle of the sensor design is called resonance-enhanced absorption (REA), which utilizes gold nanoparticles (Au NPs) as signal transducers in a highly sensitive interferometric setup. Using this approach, a novel, simple, and rapid colorimetric solid-phase immunoassay on a planar chip substrate was realized in direct and sandwich assay formats, with a detection system that does not require any instrumentation for readout. Semiquantitative immunochemical responses are directly visible to the naked eye of the analyst. The biosensor shows concentration-dependent color development by capturing antibody-functionalized Au NPs on allergen-coated chips and has a detection limit of 1 ng/mL. To establish a rapid method, we took advantage of the physicochemical microenvironment of the Au NP-antibody bioconjugate to be bound directly over an interacting poly(styrene-methyl methacrylate) interlayer by an immobilized antigen. In the direct assay format, a coating time with allergen of only 5 min under "soft" nondenaturing conditions was sufficient for accurate reproducibility and sensitivity. In conclusion, the REA-based immunochip sensor is easy to fabricate, is reproducible and selective in its performance, has minimal technical requirements, and will enable high-throughput screening of affinity binding interactions in technological and medical applications.     

Potential application of hemoglobin as an alternative to peroxidase in a phenol biosensor

This work describes a new amperometric biosensor for detecting phenolic compounds. The sensor was designed by immobilizing Hemoglobin (Hb) in a sol-gel matrix onto a carbon electrode. Using the peroxidase activity of Hb, the phenolic compound can be reduced in the presence of H₂O₂. The biosensor's performance in phenolic compound detection was based on mediated electron transfer by Hb. The direct electron transfer of Hb can be avoided by use of the sol-gel matrix. The proposed biosensor presents a very sensitive response for phenolic compounds at an applied potential of 0.0 mV vs. Ag/AgCl. The parameters of the fabrication process for the electrode were optimized. Experimental conditions influencing the biosensor performance, such as pH and potential, were investigated and assessed. Various types of phenolic compounds were detected. Among them, using the optimized conditions, a linearity for the detection of the phenol was observed from 5 μM to 50 μM. Biosensor response levels after 30 days were at more than 80% of their initial response readings level. The response time of the biosensor was about 10 s.     

长程表面等离子体共振技术在检测大肠杆菌浓度中的应用研究

建立了一种基于长程表面等离子体共振技术检测大肠杆菌浓度的方法及系统。基于此,制备了能够产生长程表面等离子体共振效应的双层膜传感芯片,并在实验上将长程表面等离子体共振(LSPR)和传统表面等离子体共振(CSPR)两种生物传感器的性能进行了对比。结果表明LSPR生物传感器共振曲线的平均半高宽比CSPR传感器共振曲线的平均半高宽窄1.79倍,且其灵敏度是CSPR的2倍。由此,证实了基于LSPR的生物传感器对大肠杆菌浓度的改变更加敏感。此外,该方法分辨率高,试剂用量少,有效克服分界面所带来的影响,并能够对大肠杆菌进行实时检测。     

Magnetic nanoparticle-enhanced biosensor based on grating-coupled surface plasmon resonance

A highly sensitive surface plasmon resonance (SPR) biosensor employing magnetic nanoparticle (MNP) assays is presented. In the reported approach, MNPs simultaneously served as "vehicles" for rapid delivery of target analyte from a sample to the sensor surface and as labels increasing the measured refractive index changes that are associated with the binding of target analyte. An optical setup based on grating-coupled surface plasmon resonance (GC-SPR) was used with a magnetic field gradient applied through the sensor chip for manipulating with MNPs on its surface. Iron oxide MNPs and a sensor surface with metallic diffraction grating were modified with antibodies that specifically recognize different epitopes of the analyte of interest. The sensitivity of the biosensor was investigated as a function of mass transport of the analyte to the sensor surface driven by diffusion (free analyte) or by the magnetic field gradient (analyte bound to MNPs). Immunoassay-based detection of β human chorionic gonadotropin (βhCG) was implemented to evaluate the sensitivity of the MNP-enhanced GC-SPR biosensor scheme. The results reveal that the sensitivity of βhCG detection was improved by 4 orders of magnitude compared with the regular SPR sensor with direct detection format, and a limit of detection below pM was achieved.     

Platinum nanoparticle modified polyaniline-functionalized boron nitride nanotubes for amperometric glucose enzyme biosensor

A novel amperometric biosensor based on the BNNTs-Pani-Pt hybrids with Pt nanoparticle homogeneously decorated on polyaniline (Pani)-wrapped boron nitride nanotubes (BNNTs), was developed. It is shown that π interactions take place between BNNTs and polyaniline (Pani) located at N atoms from BNNTs and C atoms from Pani, resulting in the water solubility for the Pani wrapped BNNTs hybrids. The developed glucose biosensor displayed high sensitivity and stability, good reproducibility, anti-interference ability, especially excellent acid stability and heat resistance. The resulted BNNTs-Pani-Pt hybrid amperometric glucose biosensor exhibited a fast response time (within 3 s) and a linear calibration range from 0.01 to 5.5 mM with a high sensitivity and low detection limit of 19.02 mA M(-1) cm(-2) and 0.18 μM glucose (S/N = 3). Surprisedly, the relative activity of the GC/BNNTs-Pani-Pt-GOD electrode keeps almost no change in a range from pH 3 to 7. Futhermore, the BNNTs-Pani-Pt hybrid biosensor maintains a high GOD enzymatic activity even at a relatively high temperature of 60 °C. This might be attributed to the effect of electrostatic field and hydrophobia of BNNTs. The unique acid stability and heat resistance of this sensor indicate great promising application in numerous industrial and biotechnological operations involving harsh conditions.     

Carbon paste biosensor for phenol detection of impregnated tissue: modification of selectivity by using β-cyclodextrin-containing PVA membrane

In order to detect and quantify with a biosensor the phenol contents in animal tissue (salmon flesh) by simple contact, we have undertaken experimental study on nonwoven cellulose fibers soaked with phenolic compounds. An electrochemical biosensor made of carbon paste and tyrosinase mixed together with electropolymerized pyrrole was elaborated. Phenol detection was realized by electrochemical reduction of quinones produced by the tyrosinase activity. The biosensor was first optimized based on enzyme loading and nature of the carbon paste. A semipermeable membrane containing cyclodextrin moieties was deposited on the biosensor in order to test its sensitivity for phenol detection. Finally, the biosensor was put in contact with phenol absorbing cellulose fibers. Results showed that the relaxation time response of the sensor was relevant of phenol concentration.     

Mixed ceria-based metal oxides biosensor for operation in oxygen restrictive environments

The unique catalytic, electrochemical, and oxygen storage properties of ceria and mixed ceria/titania hybrid composites were used to fabricate a new type of electrochemical enzyme biosensor. These materials provided increased analytical performance and possibilities for operation in oxygen-free conditions of an oxidase enzyme biosensor using tyrosinase as a model example. The investigation of the enzymatic reaction in the presence and absence of oxygen was first carried out using cyclic voltammetry. The results were used to identify the role of each metal oxide in the immobilization matrix and fabricate a simple amperometric tyrosinase biosensor for the detection of phenol and dopamine. The biosensor was optimized and characterized with respect to response time, detection limit, linear concentration range, sensitivity, and kinetic parameters. The detection limit for phenol was in the nanomolar range, with a detection limit of 9.0 x 10(-9) M and a sensitivity of 86 mA M(-1) in the presence of oxygen and of 5.6 x 10(-9) M and a sensitivity of 65 mA M(-1) in the absence of oxygen. The optimized biosensor also showed selective determination of the neurotransmitter dopamine with a detection limit of 3.4 x 10(-8) M and a sensitivity of 14.9 mA M(-1) in the presence of oxygen and of 4.2 x 10(-8) M and 14.8 mA M(-1) in the absence of oxygen. This strategy shows promise for increasing the sensitivity of oxidase enzyme sensors and provides opportunities for operation in oxygen limited conditions. It can also be extended for the development of other enzyme biosensors.     

Phage-Based Magnetoelastic Wireless Biosensors for Detecting Bacillus Anthracis Spores

A biosensor for the detection of biological warfare agents (Bacillus anthracis spores) was developed that combines the phage display technique with a magnetoelastic wireless detection platform. The affinity-based biosensor utilizes a phage-derived diagnostic probe as the biomolecular recognition element to capture target agents multivalently. Upon binding of the target agent to the sensor surface, the resonance frequency of the magnetoelastic biosensors decreases due to the additional mass of the target agent. Scanning electron microscopy was used to confirm binding of spores to the sensor surface. The sensitivity of the magnetoelastic acoustic sensor was tested to be 130 Hz per order of magnitude of spore concentration with a detection limit of 10³ spores/ml. The specificity of the sensors was tested against spores of other closely related Bacillus species and a large preferential binding to Bacillus anthracis spores was observed. The longevity of the phage based biosensor was compared to traditional antibody based biosensors and found to exhibit a much longer life     

A hydrogen peroxide biosensor based on peroxidase activity of hemoglobin in polymeric film

A Hydrogen peroxide (H2O2) biosensor, based on hemoglobin (Hb) and ortho-phenylenediamine (o-PD) gold electrode, was fabricated. Hb was immobilized onto the electrode surface by electrochemical polymerize method with o-PD. The designed biosensor showed a well defined redox peak which was attributed to the direct electrochemical response of Hb. The immobilized Hb exhibited an excellent electrocatalytical response to the reduction of hydrogen peroxide, enabling the sensitivity determination of H2O2. Factors and performances such as pH, potential, influencing the designed biosensor, were studied carefully. The amperometric detection of H2O2 was carried out at -300 mV in phosphate buffer solution (PBS) (0.1 M) with pH 6.0. This biosensor showed a fast amperometric response (less then 5 s) to H2O2. The levels of the (Relative standard deviation) RSDs (< 3.5%) for the entire analyses reflected a highly reproducible sensor performance. Using the optimized conditions, the detection limit of the biosensor was 1 x 10(-7) M and linear range was from 5 x 10(-6) to 1.25 x 10(-4) M. In addition, this sensor showed long-term stability and good sensitivity.     

Design of the polyacrylonitrile-reduced graphene oxide nanocomposite-based non-enzymatic electrochemical biosensor for glucose detection

With the advantages of developed electronic devices, various biosensor applications have become attractive issues with excellent electrochemical performances against biomarkers and molecules in biomedical applications. In this study, novel polyacrylonitrile (PAN)-reduced graphene oxide (rGO) nanocomposite-based non-enzymatic electrochemical biosensors were prepared to investigate the detection performance of the glucose. The PAN-rGO nanocomposite-based biosensor detected glucose with a high sensitivity and stability due to enhanced redox mechanism arising from rGO additive. PAN-rGO nanocomposite-based biosensor detected glucose in (0.75–12) mM with a high sensitivity of 49 µAmM^?1 cm^?2 (2.5 times higher than PAN-based sensor). Concentration–response graphs correlating the non-enzymatic electrochemical signal to glucose concentration revealed a low limit of detection (LOD) of 0.6 mM within 1-min voltammetric cycle. The selectivity results confirmed a significant preferential response of the proposed PAN-rGO nanocomposite-based biosensor for glucose against possible interfering compounds. The proposed PAN-rGO nanocomposite-based biosensor has a great potential to be used as a nanostructured platform for detection of glucose in phosphate-buffered saline (pH 7.4) solution with high sensitivity, selectivity, stability, reproducibility, and fast response properties.

     

Detection of gold nanoparticles using an immunoglobulin-coated piezoelectric sensor

Since the existence of nanoparticles in our environment has already attracted considerable attention due to their possible toxic impact on biological systems, the field detection of nanoparticles is becoming a technology that will be much in need. We have constructed a piezoelectric sensor with an antibody-coated electrode. The antiserum can bind gold nanoparticles with a high degree of selectivity and sensitivity. The biosensor thus constructed can detect 4, 5, or 6?nm gold nanoparticles (GNPs) depending on the coated antiserum. The sensitivity for the detection of 5?nm GNPs was 10.3 ± 0.9?ng?Hz(-1), with the low limit of detection at 5.5?ng. A quartz crystal microbalance (QCM) sensor was capable of detecting GNPs and other types of nanoparticle, such as ZnO, or Fe(3)O(4). The current study provides, for the first time, a platform for detecting nanoparticles in a convenient, economical manner.     

Surface Plasmon Resonance Biosensor Incorporated in a Michelson Interferometer WithEnhanced Sensitivity

A novel double-pass phase-sensitive surface plasmon resonance (SPR) biosensor based on a Michelson interferometer with differential phase interrogation is presented. The new setup provides an intrinsic resolution enhancement of up to two times in terms of achievable detection sensitivity due to an amplification effect in the SPR phase change when we place the SPR sensor head in the signal arm of the interferometer so that the interrogating optical beam traverses the sensor surface twice. Experimental results obtained from saltwater mixtures and antibody-antigen binding reactions confirmed the expected sensitivity enhancement as compared to the conventional SPR biosensor based on a Mach-Zehnder interferometer     

Development of a microconductometric biosniffer for detection of trimethylamine

The paper describes the development of a conductometric biosensor for detecting trimethylamine (TMA) which is a good parameter for estimating fish freshness. The biosensor consists of two parts: a microconductometric transducer and a structured enzymatic membrane using a flavin-containing monooxygenase 3 (FMO3) which is known for its sensitivity and selectivity for TMA. The process parameters for the fabrication of the biosniffer and various experimental variables such as pH, time of exposure to glutaraldehyde vapour were investigated with regard to their influence on sensitivity and limit of detection. A low detection limit of 2 μg/mL (ppm) and a linear range up to 40 μg/mL (ppm) were obtained. 90% response was reached in less than 10 min.     

Coupling reaction-based ultrasensitive detection of phenolic estrogens using surface-enhanced resonance Raman scattering

Studies have shown that many adverse health effects are associated with human exposure to dietary or environmental estrogens. Therefore, the development of rapid and highly sensitive detection methods for estrogens is very important and necessary to maintain hormonal concentration below the safety limit. Herein, we demonstrate a simple and rapid approach to detect trace amounts of phenolic estrogen based on surface-enhanced resonance Raman scattering (SERRS). Because of a coupling reaction between diazonium ions and the phenolic estrogens, azo compounds are formed with strong SERRS activity, which allows phenolic estrogen recognition at subnanomolar levels in solution. The proposed protocol has multiplexing capability, because each SERRS fingerprint of the azo dyes specifically corresponds to the related estrogen. Moreover, it is universal and highly selective, not only for phenolic estrogens but also for other phenolic molecules, even in complex systems.     

Nanofabrication of bio-self assembled monolayer and its electrochemical property for toxicant detection

Cyclic voltammetry (CV) has been used to investigate the electrochemical behavior of a glutathione (GSH) self assembled monolayer on modified gold electrodes (Bio-SAM). The GSH monolayer exhibits an influence on electrode surface activity. Electrochemically immobilized dsDNA onto a Cyt c/GSH-SAM/Au electrode, which is useful for the fabrication of a nanobiosensing device. The immobilized Cyt c followed by dsDNA immobilized films maintained its surface activity and finally dsDNA/Cyt c/GSH-SAM/Au electrode, targeted for the detection of toxicants. The films were characterized by CV, DPV, and AFM. The differential pulse voltammetry (DPV) technique was applied to detect three kinds of common toxins, 2-aminoanthracene (2-AA), 3-bromobenzanthrone (3-BBA) and bisphenol A (BPhA). The electrochemical signals showed good inverse relationship with the increase of concentrations of toxicants. Our proposed system based on electrochemical method with nanoscale film technology can be applied at highly sensitive biosensor for detecting various toxic chemicals.     

Simultaneous mixture analysis using a dynamic microbial sensor combined with chemometrics

A biosensor consisting of immobilized microbial cells and an oxygen electrode was used in a flow-through system as a microbial sensor flow injection analyzer (FIA). For different organic analytes, the metabolism of vital cells provides individual time-resolved responses with distinct time-dependent amplitudes. Chemometrical data analysis revealed that the individual responses are additive and depend linearly on single analyte concentrations. Based on these observations, simultaneous multicomponent analysis of organic mixtures was carried out in the FIA's time domain with analytical errors of less than 10%. For mixture analysis and monitoring in processes like enzymatic conversions, the described microbial sensor FIA ("dynamic microbial sensor") offers an alternative to expensive analytical equipment.     

Ultraspecific and Highly Sensitive Nucleic Acid Detection by Integrating a DNA Catalytic Network with a Label‐Free Microcavity

Nucleic acid detection with label‐free biosensors circumvents costly fluorophore functionalization steps associated with conventional assays by utilizing transducers of impressive ultimate detection limits. Despite this technological prowess, molecular recognition at a surface limits the biosensors' sensitivity, specificity, and reusability. It is therefore imperative to integrate novel molecular approaches with existing label‐free transducers to overcome those limitations. Here, we demonstrate this concept by integrating a DNA strand displacement circuit with a micron‐scale whispering gallery mode (WGM) microsphere biosensor. The integrated biosensor exhibits at least 25‐fold improved nucleic acid sensitivity, and sets a new record for label‐free microcavity biosensors by detecting 80 pM (32 fmol) of a 22nt oligomer; this improvement results from the catalytic behavior of the circuit. Furthermore, the integrated sensor exhibits extremely high specificity; single nucleotide variants yield 40‐ to 100‐fold lower signal. Finally, the same physical sensor was demonstrated to alternatingly detect 2 different nucleic acid sequences through 5 cycles of detection, showcasing both its reusability and its versatility.     

A planar amperometric creatinine biosensor employing an insoluble oxidizing agent for removing redox-active interferences.

A planar microchip-based creatinine biosensor employing an oxidizing layer (e.g., a PbO2 film), where interfering redox-active substances are broken (i.e., oxidized) to redox-inactive products, was developed to facilitate the microfabrication of the sensor and to provide improved, reliable determination of creatinine in physiological samples. The feasibility of using hydrophilic polyurethanes in permselective barrier membranes for creatinine biosensors and the effect of adding a silanizing agent (adhesion promoter) on the sensor performance (e.g., sensitivity, stability, and lifetime) are described. The proposed creatinine microsensor with a three-layer configuration, i.e., enzyme, protecting, and oxidizing layers, exhibits good electrochemical performance in terms of response time (t95% = 98 s at 100-->200 microM creatinine change), linearity (1-1000 microM, r = 0.9997), detection limit (0.8 microM), and lifetime (approximately 35 days). The creatinine biosensor devised in a differential sensing arrangement that compensates the erroneous results from creatine is considered to be suitable for assay of serum specimens.     

A kinetic study of analyte-receptor binding and dissociation for surface plasmon resonance biosensors applications

A fractal analysis, which takes into account the effect of surface heterogeneity brought about by ligand immobilization on the reaction kinetics in surface plasmon resonance (SPR) biosensors, is presented. The binding and dissociation of estrogen receptors (ERs), ERa and ER/spl alpha/ and ER/spl beta/, in solution to different ligands immobilized on the SPR biosensor is analyzed within the fractal framework. The heterogeneity on the biosensor surface is made quantitative by using a single number, the fractal dimension D/sub f/. The analysis provides physical insights into the binding of these receptors to different ligands and compounds, particularly the endocrine disrupting compounds (EDCs). These EDCs have deleterious effects on humans and on wildlife. Single- and dual-fractal models were employed to fit the ER-binding data obtained from the literature. Values of the binding and dissociation rate coefficient and fractal dimensions were obtained from a regression analysis provided by Corel Quattro Pro, 8.0. Values for the affinity K/sub D/(=k/sub d//k/sub a/) were also calculated. This provides us with some extra flexibility in designing biomolecular assays. The analysis should provide further information on the mode of action and interaction of EDCs with the ERs. This would help in the design of agents and modulators against these EDCs.