Codes multiplex

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. 

Han M, Gao X, Su JZ, Nie SM (2001). Quantum-dot-tagged microbeads for multiplexed optical coding of biomolecules. Nature Biotechnol. 19 631-635. 

A multiplexed immrmoassay has likewise been introduced based upon the ArrayPlate format in which antibody-oligonucleotide conjugates are assembled by hybridization to complementary capture probes. Beckman Coulter introduced the A MicroArray System in March 2004. The A squared or A (array of arrays) approach involves the printing of a capture oligonucleotide "zip code" in the bottom of a rounded square 96-well... 

Luminex is also a bead-based, non-separation technology using the Luminex colour-coded beads and detection systems (Luminex 100 IS or Luminex HT ). The readers used for this assay format are based on the principle of flow cytometry. The system enables assays to be multiplexed, i.e. allowing different analytes to be monitored simultaneously. The Luminex HT system is compatible with 96- and 384-well microplates14 but throughput of the reader is still a limiting factor for large-scale HTS. 

In sandwich immunoassays, a pair of antibodies binds to different epitopes of an analyte and one of the antibodies (the so-called capture antibody ) is immobihzed on the substrate. The second antibody is labeled with a probe (e.g. a fluorescent dye), it allows detection of the analyte molecules that bind to the capture antibody. We use this approach when the antigen is a well-characterized protein. Multiplexing is possible by immobilizing the capture antibodies in an array or on individually coded beads for medium- to low-volume amounts of biological liquids. The submicroliter version of this approach, in which capture antibodies are immobilized in stripes and the sample is guided to the capture sites by means of microfluidic networks, is described in Section 3.1 of this chapter. 

Qin L, Banholzer MJ, Millstone JE, Mirkin CA (2007) Nanodisk codes. Nano Lett 7 3849 StoermerRL, Cederquist KB, McEarland SK, Sha MY, Penn SG, Keating CD (2006) Coupling molecular beacons to barcoded metal nanowires for multiplexed, sealed chamber DNA bioassays. J Am Chem Soc 128 16892... 

Raman spectroscopy can be used to detect normal modes of target molecules and also to monitor spectra of Raman labels that are used for one of the spectroscopic bar-codes. Raman bands in the vibrational Raman spectmm have intrinsically narrow bandwidths of ca. 10 cm, which, for example, correspond to less than 0.5 nm width in the visible region below 800 nm. The fluorescence of dye molecules has a broad bandwidth of 100 nm more or less. Hence, spectral overlap between fluorescence bands is inevitable and limits their use for multiplexed analysis. Quantum dots (QDs) have narrower bandwidth than dye-based fluorescence but stUl have broad bands that are several tens of nanometers. Light scattering of noble metal nanoparticles caused by surface plasmon resonance is also... 

Irudayaraj et al. have reported the multiplex detection of up to eight different non-fluorescent nanoparticles functionalized with one sequence of DNA [61]. In this approach, a thiolated sequence of DNA was used to functionalize the surface of gold nanoparticles and then non-fluorescent Raman reporters were added to the surface of the nanoparticle to code them with a SERS signal. It was reported that multiplex detection of two, four, and eight differently labeled nanoparticles could be detected in one analysis. However, only one DNA sequence was used in this study to label all the different flavors of nanoparticles and the detection of a specific, target DNA sequence by SERS was not reported. However, it was possible to observe the change in surface plasmon by UV-Vis spectroscopy when two batches of nanoparticles functionalized with complementary sequences were hybridized together. 

This was further extended to allow the multiplex detection of two different target sequences of DNA using two different Raman reporter dyes to code for different probe sequences on the nanoparticles. In this advancement, three batches of... 

Non-dispersive multiplex spectrometers include Hadamard transformation spectrometers and Fourier transform spectrometers and are particularly useful for the case of very stable sources. In both cases the information, such as intensities at various wavelengths, is coded by a multiplex system, so that it can be recorded with a conventional detector. A suitable transformation is then used to reconstruct the wavelength dependence of the information. In Hadamard spectrometry use is made of a codation of the spectrum produced by recombining the information with the aid of a slit mask which is moved along the spectrum [66],... 

There are two types of microarray platforms - standard and liquid microarrays. The standard microarrays are those on which assays are carried out on a shared substrate containing a spatially resolved and indexed series of biological elements. Conversely, the liquid microarrays utilize many particles or beads to carry out multiplexed assays, wherein each particle contains a biological element and is identified with a unique characteristic (e.g., code) [55]. 

Stoeva, S.I., Lee, J.S., Smith, J.E., Rosen, S.T. and Mirkin, C.A. (2006) Multiplexed detection of protein cancer markers with biobar-coded nanoparticle probes. J. Am. Chem. Soc. 128,8378-8379... 

Fig. 2 shows the balanced luminescence spectra taken from the aqueous dispersions of two-color tagged spheres with 3 different ratios of the well-separated emission peaks. The relative amount of each kind of nanocrystals encapsulated depends on the number of particles in the solution, as it was proven by almost linear relationship between the luminescence intensity of a single color in the two-color tagged spheres and the concentration of the correspondent CdTe nanocrystals in solution. This allows the control of the relative emission intensity ratios at different wavelengths and can be used in addition to the luminescence color to create microspheres carrying unique multiplexed codes. 

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