Nanocrystal labeling

FIGURE 14.5 Multiprotein electrical detection protocol based on different inorganic colloid nanocrystal tracers, (a) Introduction of antibody-modified magnetic beads (b) binding of the antigens to the antibodies on the magnetic beads (c) capture of the nanocrystal-labeled secondary antibodies (d) dissolution of nanocrystals and electrochemical stripping detection (reproduced from [29] with permission). 

The concept is demonstrated for a simultaneous immunoassay of (32-microglobulin, IgG, bovine serum albumin, and C-reactive protein in connection with ZnS, CdS, PbS, and CuS colloidal crystals, respectively (Fig. 14.6). These nanocrystal labels exhibit similar sensitivity. Such electrochemical coding could be readily multiplexed and scaled up in multiwell microtiter plates to allow simultaneous parallel detection of numerous proteins or samples and is expected to open new opportunities for protein diagnostics and biosecurity. 

FIGURE 14.6 Typical stripping voltammograms for (a) nanocrystal-labeled antibodies and (b-f) magnetic bead-Ab-Ag-Ab-nanocrystal complexes, (b) Response for a solution containing dissolved ZnS anti-/32-microglobulin, PbS-anti-BSA, and CdS-anti-IgG conjugates (reproduced from [29] with permission). 

Resch-Genger U, Grabolle M, Nitschke R, Nann T (2010) Nanocrystals and nanoparticles vs. molecular fluorescent labels as reporters for bioanalysis and the life sciences. A critical comparison. In Demchenko AP (ed) Advanced Fluorescence Reporters in Chemistry and Biology II. Springer Ser Fluoresc 9 3—40... 

Water-soluble QDs now are available from a number of manufacturers (Invitrogen, Evident Technologies, and Crystalplex). Each supplier uses their own proprietary methods of surface pacification to create biocompatible particles. Even coated QD clusters are available that contain hundreds of particles bound together in a polymer matrix (Crystalplex). These form intensely bright labels for biomolecules, because the nanocrystals do not quench when clustered together at high density. 

Nanocrystals and Nanoparticles Versus Molecular Fluorescent Labels as Reporters for Bioanalysis and the Life Sciences ... 

Nanocrystals and Nanoparticles Versus Molecular Fluorescent Labels... 

The thermal and photochemical stability of both organic dyes and nanocrystals are influenced by an extremely broad variety of conditions that need to be considered excitation wavelength and intensity, matrix or microenvironment, label concentration, and, in the case of nanoparticles, surface chemistry. Therefore, the individual study of the stability of a chromophore under the conditions required can usually not be avoided. 

Grabolle M, Kapusta P, Nann T, Shu X, Ziegler J, Resch-Genger U (2009) Fluorescence lifetime multiplexing with nanocrystals and organic labels. Anal Chem 81 7807-7813... 

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