Nanoparticle bead magnetic beads

By using the micro/nanoparticles and magnetic beads, the homogenous immimoassay without the separation of whole blood can be manipulated. However, the detection sensitivity is limited due to the complex whole blood enviromnent. For the heterogeneous immunoassay, the commercial... 

Micro- and nanobeads with magnetic properties have recently become popular since these tools can be manipulated, e.g., collected in the region of interest. Magnetite nanoparticles are introduced in order to render the polymeric beads magnetic. Preparation and application of magnetic beads will be discussed in more detail in Sect 5.5. 

Whenever the commercially available particles do not match the operator s requirements, a variety of possibilities exist in order to modify the particles from company suppliers. Similarly to other doped beads the dyes [92] or quantum dots [107, 108] can be physically entrapped into magnetic beads by swelling or are covalently bound to the surface of the particles. If localization of the dye on the particle surface is desired or if the polarity of dye and/or matrix polymer does not allow the irreversible entrapment of the dye in the bulk polymer, a covalent attachment of the dye is preferable [109, 110]. Even the covalent binding of whole fluorescent nanoparticles to magnetic microparticles is possible, as shown by Kinosita and co-workers who investigated the rotation of molecular motors [111]. 

Fig. 38.2. Particle-based electrochemical immunoassay protocol. (A) Introduction of antibody-modified magnetic beads to magnet/carbon paste electrochemical transducer surface (B) binding of the IgG antigen to the antibodies on the magnetic beads (C) capture of the gold nanoparticle labelled secondary antibodies (D) electrochemical stripping detection of AuNPs. Reprinted with permission from Ref. [72].

Another recent study highlighting a redox-active label employs metal colloids to signal target-probe hybridization. Magnetic beads derivatized with single-stranded DNA probe sequences were used to capture target and reporter sequences that had been labeled with nanoparticles composed of ZnS, PbS, or CdS. The beads were then physically removed from the analyte solution, and the particles were dissolved in acid. After adsorption of these ions onto solid electrodes, stripping voltammetry was used to quantify the... 

Key words Gold nanoparticles, DNA analysis, Magnetic beads, Cystic fibrosis, Genosensor, Electrochemical detection... 

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