Papers by Keyword: Immunoassay

Abstract: Magnetic nanoparticles (MNP) are efficient molecular carriers for affine molecules. MNP complexes with antibodies can be used for the selective concentration and highly sensitive detection of various compounds. In this paper, development steps of the enzyme immunoassay using MNP are considered in details. Simple method of MNP synthesis and production of conjugates of antibodies with the aggregated MNP using physical sorption is presented. Simple, yet effective, formats of enzyme immunoassay are given. Using aflatoxin B1 detection as an example, possibility of decreasing detection limit up to 2 pg/mL, with a considerable decrease in the assay time, and performing immune interaction in the media with high organic content is shown.

Abstract: An indirect competitive immunoassay using quantum dots (QDs) as the fluorescent label has been developed for detection of melamine in milk products. The method exhibited a response for melamine with IC₅₀ value of 11.3 ng mL^-1 and a detection limit of 0.27 ng mL^-1. Milk and milk powder samples spiked with melamine have been analyzed, and the method provided recoveries ranging from 84.2% to 108.0%, and a CV of 12.8%. The implementation of QDs provides for at least 30 fold improvement of detection limit when compared with optically-based ELISA screening methods that have been reported. The analytical performance in combination with simplicity of sample and antibody preparation provides the basis for a practical method for melamine detection.

Abstract: ZnS semiconductor nanocrystals (NCs) were prepared by ways from primary materials of ZnCl₂ and Na₂S in water solution. Using the synthesized ZnS NCs, a polyclonal antibody-based ZnS-labelled immunosorbent assay for the determination of estriol (E₃) was developed with atomic absorption spectrophotometry (AAS) as a detector. An immunoaffinity column was applied to testify conjugation between antibody and ZnS NCs. The linear range for determination of estriol is 40.0~600.0 ng.mL^-1, and the limit of detection (LOD) is 10.0 ng.mL^-1. Some serum samples have been analyzed with satisfactory results which are in good agreement with those obtained using ELISA. This work suggests the potential application of NCs as biological probes and AAS as detector in nonisotopic immunoassay.

Abstract: Recently, nanomaterial based biosensor application has drawn a lot attention among researchers because of specialty to enhance the sensor signal for increasing the sensitivity for detecting and identification of pathogen, viruses and toxic compound in controlling plant disease outbreak effectively. Rice tungro disease (RTD) causes a major problem in rice production and also will effect in the economic loss in the country. Therefore, early detection system is needed to monitor the disease at the early stage of the infection for preventing the disease outbreak in planting area. Lastly, this paper will discuss the current findings in rapid diagnostics using immunosensors technologies with nanomaterial application in enhancing the sensor signal for increasing the detection sensitivity

Abstract: To generate a group-specific monoclonal antibody (McAb) against danofloxacin (DANO), enrofloxacin (ENR) and ciprofloxacin (CIP), glutaraldehyde was used to link the presentative hapten of CIP to the immunogen and coating antigen, respectively, leaving the common structure of these 3 drugs exposed in both conjugates as a major antigenic site. Consequently, a McAb (6D3) with high cross-reactivity to this three antibiotics has been obtained by using hybridomas technique. In a biotin-avidin mediated enzyme-linked immunosorbent assay, the IC₅₀ values for DANO, ENR and CIP were 5.1, 4.5 and 4.2 ng mL^-1, respectively. The ELISA was used for the detection of spiked DANO and ENR+CIP in milk. The recoveries ranged from 74.1 to 92.4% and coefficients of variation were in a range of 6.6-11.9%. The accuracies and sensitivity of the method were good for simultaneous analysis of the 3 drugs in milk after a simple sample extraction process.

Abstract: In pH 6.6 Na2HPO4-citric acid buffer solution and in the presence of KCl, the nanosilver-labeled rabbit anti-hCG (Ag-RAhCG) was aggregated un-specifically to the aggregations. Upon addition of rhodamine 6G (RhG) molecular probe, it adsorb on the surface of Ag-RAhCG aggregations that exhibited the strongest surface-enhnaced resonance Raman scattering (SERRS) peak at 613 cm-1. In the optimal condition, the decreased SERRS intensity responds linearly with the concentration of hCG over 0.05-1.75 µg/mL. Based on this, a new and simple SERRS method has been proposed for the determination of hCG in serum samples, with satisfactory results.

Abstract: A series of fluorescent methods of analysis and investigation of system based on the use of stilbenes and potentially important in biochemistry, biophysics, biotechnology, and biomedicine were proposed and developed. In these methods, two new types of stilbene molecular probes have been used: (i) fluorescent photochrome molecules and (ii) super molecules containing fluorescent and fluorescent quenching segments. These methods utilize the following photochemical and photophysical phenomena: the fluorescence and phosphorescence quenching, photochrome photoisomerization, and triplet–triplet and singlet–singlet energy transfer. The fluorescence properties of the new probes were intensively exploited as the basis of several methodologies that include a real-time analysis of nitric oxide, immunoassay in solution, investigation of molecular dynamics of biomembranes in a wide range characteristic times, and characterization of sensors for antibodies. These techniques may be adapted to fibro-optic sensoring.

Abstract: In pH 6.6 Na₂HPO₄- citric acid buffer solution and in the presence of KCl, the immunoreaction between hCG and nanosilver-labeled anti-hCG took place, the immunonanosilver-complex was formed and deposited, caused the resonance Rayleigh scattering (RRS) intensity at 510 nm decreased. In the optimal condition, the decreased RRS intensity responds linearly with the concentration of hCG over 0.125-1.75 µg/mL. Based on this, a new and simple RRS method has been proposed for the determination of hCG in serum samples, with satisfactory results.

Abstract: In this work, we demonstrate a simple yet convenient centrifugal microfluidics, or lab-on-a-disc (LOAD) platform for bead-based immunoassays. The disc contains a network of passive valves for sample manipulation and a bead-aggregating barrier structure to instead of commonly used immobilization method. The narrow-channel structure not only provides a geometric barrier for retaining the beads, but also significantly increased fluidic resistance which results in lower flow rate and longer reaction time for each reagent in the reaction chamber. Centrifuge-forced beads densification in the small junction area and signal concentrating allows high signal sensing capability. The acceleration speed is optimized for largest signal-to-noise ratio. The device uses different rotation speed to trigger a cascade of flow events. The integrated platform contains all the necessary functional elements for conducting one-step parallel assays through a sequential protocol. For our test device, the total time required to complete an immunoassay experiment is typically under 6 minutes. Through this work we have also shown that the use of a geometric barrier for the aggregation of signaling beads is an effective approach for the enhancement of optical signals in common immunoassays. This flexible design is suitable for a broad range of bead-based immunoassays with low-cost and high-speed operation.

Abstract: The AuRu nanoalloy (GR) which Au/Ru molar ratio of 32:1 was prepared by the sodium borohydride reduction method. In the condition of pH 6.0, the GR was used to label CA125 antibody (Ab) to obtain an immunonanoprobe for CA125 (GRAb). In pH 7.0 citric acid-Na₂HPO₄ buffer solution, GRAb was aggregated nonspecifically to big clusters, which showed a strong resonance Rayleigh scattering (RRS) peak at 278nm. When CA125 was added, GRAb reacted specifically with CA125 and GR dispersive in the solution, which led to the RRS intensity decreased greatly. The decreased RRS intensity was linear to the concentration of CA125 in the range of 1.3-80 U/mL, a detection limit of 0.81 U/mL. The proposed method was applied to detect CA125, with satisfactory results.