Gold nanocage-based lateral flow immunoassay for immunoglobulin G

The authors describe a gold nanocage-based lateral flow strip biosensor (LFSB) for low-cost and sensitive detection of IgG. This protein was used as a model analyte to demonstrate the proof-of-concept. The method combines the unique optical properties of gold nanocages (GNCs) with highly efficient chromatographic separation. A sandwich-type of immunoreactions occurs on the GNC-based LFSB which has the attractive features of avoiding multiple incubation, separation, and washing steps. The captured GNCs on the purple test zone and control zone of the biosensor are producing characteristic purple bands, and this enables IgG even to be visually detected. Quantitatation was accomplished by reading the intensities of the bands with a portable strip reader. The LFSB fabrication and assay parameters were optimized. The biosensor displays a linear response in the 0.5 to 50 ng?mL^?1 IgG concentration range, and it has a 15 min assay time. The detection limit is 0.1 ng?mL^?1 of IgG, which is 2.5 times lower than that when using a gold nanoparticle-based LFSB. In our perception, this assay has a wide potential for the detection of other proteins and species for which respective antibodies are available.

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Graphical abstract Gold nanocages have been used as a sensitive tag to prepare lateral flow strip biosensors for sensitive detection of immunoglobulin G.

     

流动注射化学发光免疫分析检测猪肉中的盐酸克伦特罗残留

设计了一种快速检测猪肉中盐酸克伦特罗的流动注射-化学发光免疫分析方法.采用过氧化脲作为luminol-CH<,4>N<,2>O·H<,2>O<,2>-HRP化学发光体系氧化剂,联苯硼酸作为增强剂,流动注射化学发光法检测竞争免疫反应后的上清酶标复合物.在最优条件下,测定克伦特罗的线性范围0.05～9μg/L(r=0.99...     

流动注射化学发光免疫分析研究I. 血清中乙型肝炎表面抗原的测定

我们首次以键合有抗体的多孔玻璃作为固相免疫分析的免疫反应器, 以化学发光作为最终检测手段, 建立了一种新的、高效率的免疫分析技术-流动注射化学发光免疫分析技术。实验表明: 采用该技术可使单次测定时间从ELISA(Enzyme-linked Immunosorbent Assay)法的二十多小时降至二十分钟, 且所有操作均可在微机控制下自动完成。用该方法对人血清中乙型肝炎表面抗原的测定结果与ELISA法所得结果一致, 对同一样品连续九次测定的相对标准偏差为7.2%。因此, 该方法具有自动化程度高、分析速度快、稳定性好的优点。     

Sequential injection chemiluminescence immunoassay for anionic surfactants using magnetic microbeads immobilized with an antibody

A rapid and sensitive immunoassay for the determination of linear alkylbenzene sulfonates (LAS) is described. The method involves a sequential injection analysis (SIA) system equipped with a chemiluminescence detector and a neodymium magnet. Magnetic beads, to which an anti-LAS monoclonal antibody was immobilized, were used as a solid support in an immunoassay. The introduction, trapping and release of the magnetic beads in the flow cell were controlled by means of a neodymium magnet and adjusting the flow of the carrier solution. The immunoassay was based on an indirect competitive immunoreaction of an anti-LAS monoclonal antibody on the magnetic beads and the LAS sample and horseradish peroxidase (HRP)-labeled LAS, and was based on the subsequent chemiluminscence reaction of HRP with hydrogen peroxide and p-iodophenol, in a luminol solution. The anti-LAS antibody was immobilized on the beads by coupling the antibody with the magnetic beads after activation of a carboxylate moiety on the surface of magnetic beads that had been coated with a polylactic acid film. The antibody immobilized magnetic beads were introduced, and trapped in the flow cell equipped with the neodymium magnet, an LAS solution containing HRP-labeled LAS at constant concentration and the luminol solution were sequentially introduced into the flow cell based on an SIA programmed sequence. Chemiluminescence emission was monitored by means of a photon counting unit located at the upper side of the flow cell by collecting the emitted light with a lens. A typical sigmoid calibration curve was obtained, when the logarithm of the concentration of LAS was plotted against the chemiluminescence intensity using various concentrations of standard LAS samples (0-500 ppb) under optimum conditions. The time required for analysis is less than 15 min.     

流动注射化学发光法测定青霉素G钾

在甲醛的存在下,酸性KMnO4与青霉素G钾能够产生很强的化学发光,从而建立了KMnO4-甲醛-青霉素G钾化学发光体系来测定青霉素G钾.青霉素G钾的测定线性范围为2.0×10-7～1.0×10-5 g/mL,方法的检出限为1.4×10-7 g/mL,对4.0×10-7 g/mL的青霉素G钾进行11次平行测定,相对标准偏差为1.0%,用此法测定青霉素G钾取得了较好的结果.     

Development of solid-phase chemiluminescence immunoassays for digoxin comparing flow injection and sequential injection techniques.

The development of a competitive solid-phase immunoassay for digoxin making use of the acridinium chemiluminescence system is described. Two different instrumental approaches are compared. One is based on a continuous flow system using a peristaltic flow injection analysis pump; the other uses a new sequential injection technique. In both systems a flow cell, consisting of transparent PTFE tubing packed with immobilized antibodies, acts as an immunoreactor. The entire assay, including both the immunoreaction and the chemiluminescence reaction, takes place in this immunoreactor cell. Compared with the flow injection technique, the sequential injection mode showed higher precision, ranging from 2.16 to 5.5% RSD depending on concentration. The total assay time, including regeneration, is less than 8 min with the sequential injection technique. The detection limit for both techniques is in the low femtomole range.     

Homogenous electrogenerated chemiluminescence immunoassay for human immunoglobulin G using N-(aminobutyl)-N-ethylisoluminol as luminescence label at gold nanoparticles modified paraffin-impregnated graphite electrode

A homogeneous electrogenerated chemiluminescence (ECL) immunoassay for human immunoglobulin G (hIgG) has been developed using a N-(aminobutyl)-N-ethylisoluminol (ABEI) as luminescence label at gold nanoparticles modified paraffin-impregnated graphite electrode (PIGE). ECL emission was electrochemically generated from the ABEI-labeled anti-hIgG antibody and markedly increased in the presence of hIgG antigen due to forming a more rigid structure of the ABEI moiety. The concentration of hIgG antigen was determined by the increase of ECL intensity at a gold nanoparticles modified PIGE. It was found that the ECL intensity of ABEI in presence of hydrogen peroxide was dramatically enhanced at gold nanoparticles modified PIGE in neutral aqueous solution and the detection limit of ABEI was 2 x 10(-14)mol/L (S/N=3). The integral ECL intensity was linearly related to the concentration of hIgG antigen from 3.0 x 10(-11) to 1.0 x 10(-9)g/mL with a detection limit of 1 x 10(-11)g/mL (S/N=3). The relative standard deviation was 3.1% at 1.0 x 10(-10)g/mL (n=11). This work demonstrates that the enhancement of the sensitivity of ECL and ECL immunoassay at a nanoparticles modified electrode is a promising strategy.     

Liposome-based flow injection enzyme immunoassay for theophylline

Preliminary results are presented on the development of a sensitive, quantitative immunoassay based on a regenerable, flow injection analysis system incorporating a double-amplification approach. The double amplification is achieved by means of liposome-encapsulated peroxidase enzyme molecules which are released subsequent to a competitive immunological reaction with analyte molecules for immobilized antibodies. The released peroxidase enzymatically cleaves, from an organofluorine substrate, fluoride ions which are then potentiometrically measured. The entire process is carried out in a flow injection analysis system. The competition between the analyte molecules (theophylline) and theophylline-derivatized liposomes for immobilized antibody sites in flow-through immunoreactor column results in unbound liposomes being carried downstream where they are ruptured in the presence of hydrogen peroxide andp-fluorophenol. The peroxidase molecules released react enzymatically to produce fluoride ions which are measured with an ion-selective electrode. The immunoreactor column is then regenerated with a chaotropic agent and the next sample or calibration solution is injected. By means of column regeneration and calibration, accurate quantitation can be achieved; a feature missing from conventional batch-type immunoassays. By means of this liposome/enzyme double-amplification approach, theophylline was determined over a range of concentrations from 0.2 to 4000 ng/ml. The detection limit of 200 pg/ml corresponds to about 100 femtomole of theophylline measured in the 100 l sample injected.Dedicated to Professor W. Simon on the occasion of his 60th birthday     

Sequential injection chemiluminescence immunoassay for nonionic surfactants by using magnetic microbeads

A rapid and sensitive immunoassay based on a sequential injection analysis (SIA) using magnetic microbeads for the determination of alkylphenol polyethoxylates (APnEOs) is described. An SIA system was constructed from a syringe pump, a switching valve, a flow-through type immunoreaction cell equipped with a photon counting unit and a neodymium magnet. Magnetic beads, to which an anti-APnEOs monoclonal antibody was immobilized, were used as a solid support in an immunoassay. The introduction, trapping and release of the magnetic beads in and from the immunoreaction cell were controlled by means of a neodymium magnet and adjusting the flow of a carrier solution. The immunoassay was based on an indirect competitive immunoreaction of an anti-APnEOs monoclonal antibody immobilized on the magnetic beads with a sample APnEOs and a horseradish peroxidase (HRP)-labeled APnEOs in the same sample solution, and was based on the subsequent chemiluminscence reaction of HRP on the magnetic microbeads with a luminol solution containing hydrogen peroxide and p-iodophenol. The anti-APnEOs antibody was immobilized on the magnetic microbeads by coupling the antibody with the magnetic beads after activation of a carboxylate moiety on the surface of the magnetic beads that had been coated with a polylactic acid film. The antibody immobilized magnetic beads were introduced in the immunoreaction cell and trapped in it by the neodymium magnet, which was equipped beneath the immunoreaction cell. An APnEOs sample solution containing the HRP-labeled APnEOs at a constant concentration, and a luminol solution containing hydrogen peroxide and p-iodophenol were sequentially introduced into the immunoreaction cell, according to an SIA programmed sequence. Chemiluminescence emission was monitored by means of a photon counting unit located at the upper side of the immunoreaction cell by collecting the emitted light with a lens. A typical sigmoidal calibration curve was obtained, when the logarithm of the concentration of APnEOs was plotted against the chemiluminescence intensity as the number of photons in 100 ms using standard APnEOs sample solutions at various concentrations (0–1000 ppb) under optimum conditions. The lower detection limit defined as IC₈₀ is ca 10 ppb. The time required for analysis is less than 15 min per a sample. The present method was successfully applied to the determination of APnEOs in river water.     

Development of an electrochemical flow injection immunoassay (FIIA) for the real-time monitoring of biospecific interactions

Not only are sensors a revolution in analysis; they themselves are also experiencing a revolution brought about by parallel developments in sensor fabrication techniques and materials, polymer chemistry, signal processing methodologies, the increased use of biomolecular processes as a means of analyte detection, and the coupling of sensors to other techniques such as flow injection analysis. Many of these developments have been incorporated into the present study, which we are undertaking in the development of our immunosensor technology. The system described here utilises screen-printed electrodes which are low-cost, disposable devices that are simple to fabricate. Incorporated into our sensor is the electroactive polymer, polyaniline, which brings about mediatorless redox coupling between the electrode and biomolecular components attached to the polymer surface. This system also utilises enzyme-labelled antibodies as the biomolecular recognition component for the analysis of the test analyte, biotin. The system has also been integrated into a flow injection system. This has led to the monitoring of real-time antibody-antigen interactions using electrochemical methods and foreshadows the development of single-step immunosensors.     

流动注射化学发光法测定人体血清中的胆固醇

流行病学和临床证明,血清中胆固醇含量的高低和人体的心血管疾病等有着十分密切的关系[1],因而血清胆固醇测定可作为肝脏功能、胆汁功能、肠吸收、冠状动脉疾病、甲状腺功能和肾上腺疾病的诊断指征。血清中胆固醇含量的测定方法有分光光度法、酶法、化学发光法、色谱法、气质联     

CE-based noncompetitive immunoassay for immunoglobulin G in bovine colostrum products

A CE-based noncompetitive immunoassay for IgG in bovine colostrum products was established. FITC-labeled protein G (FITC-PrG) was tagged through noncovalent bindings to the Fc region of the mouse monoclonal antibovine IgG (Ab). The FITC-PrG, Ab, and IgG formed a sandwiched immunocomplex FITC-PrG-Ab-IgG under optimal incubation conditions. The immunocomplex was separated and analyzed by CZE with LIF detection in less than 2 min in an uncoated fused-silica capillary. Addition of PEG 20,000 (PEG 20M) in the running buffer significantly suppressed analyte adsorption and thus improved the reproducibility and the resolution. The precision of the method was 5.1% (n = 7). A linear relationship was established for the IgG concentration in the range of 1-5 mg/L with a linear correlation coefficient (r = 0.9917). The LOD was 0.1 mg/L (S/N = 3). The method was successfully applied for the determination of IgG in bovine colostrum products and satisfactory results were achieved.     

Ultrasound-enhanced flow injection chemiluminescence for determination of hydrogen peroxide

A novel ultrasonic flow injection chemiluminescence (FI-CL) manifold for determining hydrogen peroxide (H2O2) has been designed and evaluated. Chemiluminescence obtained from the luminol-H2O2-cobalt(II) reaction was enhanced by applying 120 W of ultrasound for a period of 4 s to the reaction coil in the FI-CL system and this enhancement was verified by comparison with an identical manifold without ultrasound. The system was developed for determining ultra-trace levels of H2O2 and a calibration curve was obtained with a linear portion over the range of 10-200 nmol L(-1) H2O2 (correlation coefficient 0.9945). The detection limit (3sigma) and the quantification limit (LOQ) were found to be 1 x 10(-9) and 3.3 x 10(-9) mol L(-1) respectively and the relative standard deviation was 1.37% for 2 x 10(-7) mol L(-1) H2O2 (n = 10). The method was applied to the determination of trace amounts of H2O2 in purified water and natural water samples without any special pre-treatments.     

Automated flow immunoassay for detection of food allergen using anion-exchange resin and alkaline phosphatase conjugated immunoglobulin G

A novel automated flow immunoassay system is developed for the detection of wheat protein as a food allergen. A polyclonal immunoglobulin G (IgG) antibody was isolated from serum of a rat with a wheat allergy, then reductively treated using dithiothreitol and covalently coupled to alkaline phosphatase. This conjugate was used in a non-competitive binding assay. The automated system was equipped with an immunoreaction column, an anion-exchange column, a luminescent reaction column and a photodetector. Antibody–antigen complexes were separated from their free conjugate on the basis of a difference in isoelectric point (pI) by an anion-exchange column. This simple technique permits the assay of wheat-protein allergen in 25 min with a reliable detection limit of 5 μg/ml. The anion-exchange column was regenerated by occasional elution with N-methylpiperazine buffer (pH 5.0) containing 0.5 M NaCl, to remove free conjugate. Free conjugate recovered in this manner could be reused up to four times without significant decrease in sensitivity of the immunoassay.     

流动注射化学发光法测定甲氧氯普胺

在酸性条件下，甲醛对高锰酸钾氧化甲氧氯普胺的化学发光反应有很强的增敏作用，据此，建立了流动注射化学发光法测定甲氧氯普胺纳新方法。方法的线性范围为0．4-100μg/mL，检出限为0．2μg/mL，对10μg/mL的甲氧氯普胺标准溶液连续11次测定的相对标准偏差为1．8％。方法已用于药物中甲氧氯普胺含量的测定。     

流动注射-化学发光法测定决明子蒽醌类化合物

基于在碱性条件下,蒽醌对ClO- Luminol化学发光体系的显著抑制作用,结合反向流动注射技术,提出了蒽醌的流动注射 化学发光分析新方法。蒽醌的质量浓度在0.5～100μg mL范围内与化学发光的抑制强度呈良好的线性关系。检出限为0.05μg mL,RSD=1.6%,采样频率为150次 h,回收率为105%～107.5%。     

In vitro monitoring of clindamycin in human urine using flow injection chemiluminescence

A sensitive chemiluminescence method for the determination of clindamycin is presented. The method is based on the inhibitory effect of clindamycin on the chemiluminescence reaction between luminol and myoglobin in a flow-injection system. The decrement in chemiluminescence intensity is linear with the logarithm of the clindamycin concentration over the range of 0.1–70.0 ng mL⁻¹ (r ² = 0.9995), with a detection limit of 0.03 ng mL⁻¹ (3σ). At a flow rate of 2.0 mL min⁻¹, the complete analytical process could be performed within 0.5 min, including sampling and washing, with a relative standard deviation of less than 3.0% (n = 5). The procedure was applied to the determination of clindamycin in human serum and in monitoring the excretion of clindamycin in human urine samples without any pretreatment process. It was found that the excretive clindamycin concentration reached its maximum 3 hours after oral administration. The clindamycin excretive ratio in 9 hours was 10.84% in the body of the volunteer.     

A chemiluminescence flow injection system for nitrite ion determination

A chemiluminescence system is described for the determination of nitrite ion based on new designs for an ozone generator, liquid-gas separator and chemiluminescence reaction cell. The method is based on the gas-phase chemiluminescence reaction between ozone and nitric oxide, which is generated from the reduction of nitrite with iodide in sulfuric acid solution. The efficiency of the system was evaluated by investigation of the analytical performance characteristics of the system for nitrite determination in batch and flow injection procedures. Under optimal conditions, the chemiluminescence response of the system was linear against the nitrite concentration over the range 1 to 1 × 10⁴ ng ml^?1 in the batch procedure and 10 to 5 × 10³ ng ml^?1 in the flow injection procedure, with detection limits of 1 and 10 ng ml^?1, respectively. The method is highly selective and allows for the determination of nitrite in the presence of high concentrations of several cationic, anionic and nitrogen containing species. It has been successfully applied to the analysis of nitrite in natural water and soil extracts.     

A flow injection chemiluminescence system for the determination of isoniazid

A chemiluminescence (CL) flow system is described for the determination of isoniazid based on its enhancement on the chemiluminescence (CL) emission produced upon mixing a hexacyanoferrate(III) solution with an alkaline luminol solution. The system responds linearly to isoniazid concentration in the range 0-1 mg/L with a detection limit (3sigma) of 0.03 microg/L, relative standard deviation (RSD) of 1.2% for 0.1 mg/L isoniazid (n = 11). The system has been successfully applied to the determination of isoniazid in pharmaceutical preparations.