Magnetic particles detection labels

Assay for human immunodeficiency virus type 1 (HIV-1) proviral DNA in peripheral blood monuclear cells can be performed by PCR followed by detection of PCR products by electrochemiluminescence-labeled oligonucleotide probe [Tris-bipyridine ruthenium (II) complex]. Since one of the PCR primers is biotin-labeled at the 5 end, facile capture of the PCR product-probe complex can be accomplished on streptavidin-conjugated magnetic particles, prior to analysis in an electrochemiluminescence analyzer (S3). 

We have identified four important biological application areas for magnetic particle handling in microfluidic systems cell handling and separation, nucleic acid processing and detection, immunoassays, and catalysis. We showed that specific magnetic labeling permits to select or deplete certain... 

A different approach based on the use of an enzyme as a traditional amplifying label and aptamer-functionalized magnetic beads has been developed and applied to the detection of thrombin directly into human plasma (Centi et al., 2007b). The assay is based on electrochemical transduction coupled to magnetic particles,... 

Figure 8.3 Sandwich assay developed for thrombin using two different aptamers, magnetic particles, and enzymatic amplification. Two selected aptamers binding thrombin in two different, nonoverlapping sites are used. The protein captured by the first aptamer fixed onto magnetic particles is detected after addition of the second biotinylated aptamer and of streptavidin labeled with an enzyme (alkaline phosphatase). Detection of the product generated by the enzymatic reaction is achieved by differential pulse voltammetry onto screen-printed electrodes onto which the magnetic nanoparticles are deposited and kept in contact through a magnet. [From (Centi et al., 2007b).]...

There is an increasing need for higher sensitivity and specificity of detection for biosensors. Magnetic particles, by the use of the magnetoresistive (MR) effect, have been developed as labels for biosensing. These magnetic biosensors have... 

Biosensors Using Magnetics, Fig. 1 Schematic of magnetically labeled biomolecule detection in a biosensor. Target bimnolecules bound with a magnetic particle interact with magnetraesistive sensor-bound counter biomolecules to be detected... 

Nanostmctured sensors coated with SWCNT forests and AuNP films were used to fabricate sandwich immunoassays for prostate cancer biomarker PSA [10,43,46,64]. As in Fig. 1.2a, conventional secondary antibodies (Ab2) conjugated with enzyme label HRP were used, as well as carbon nanotubes (CNT) or magnetic particles conjugated with Ab2 (Fig. 1.2c,g). These heavily labeled detection particles [69] can replace singly-labeled HRP-Ab2 in immunoassays to greatly enhance sensitivity. 

We also reported a AuNP immunosensor for detection of IL-6 with a DL of 10 pg mL in calf serum without using labeled magnetic particles [71]. A comparison under the same assay conditions using human IL-6 cancer biomarker in calf semm revealed that the AuNP immunosensor offers a threefold better detection limit than SWCNT forest immunosensors. In another strategy we used 0.5 pm multi-labeled polymeric beads (polybeads-HRP-Ab2) to achieve a DL of 10 pg mL for MMP-3 [72] in calf serum. 

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