Homogeneous immunoassay advantage

The advantages of homogenous immunoassays are simple formats and rapid data output producing user-friendly and cost-effective products. Technical challenges to consider, however, are the necessity to remove or minimize background interference from the reagents and nonspecific binding reactions. 

The main advantage of a homogeneous immunoassay, compared to a heterogeneous immunoassay, is the absence of a separation step. This translates into a simpler procedure and easier automation. However, homogeneous assays are typically less sensitive and more susceptible to sample interferences which are removed in a separation step. 

Figure 13.2 Principles of (a) time-resolved spectroscopy, (h) heterogeneous immunoassays, and (c) homogeneous immunoassays [1]. (Reproduced from J.C.G Bunzli and C. Piguet, Taking advantage of luminescent lanthanide ions, Chemical Society Reviews, 34, 1048—1077, 2005, by permission of The Royal Society of Chemistry.)...

Separation-free, homogeneous immunoassay protocols offer several advantages in comparison to heterogeneous methods. Because no separation is involved, the number of procedural steps is decreased, which decreases the time required per assay. Additionally, because the physical transfer step is avoided, potential sample loss related to this step is eliminated. Drugs with low molecular weights (amphetamines, digoxin) are commonly measured by separation-free homogeneous immunoassay protocols. ... 

Mathis G, Socquet F, Viguier M, Darbouret B (1997) Homogeneous immunoassays using rare earth cryptates and time resolved fluorescence principles and specific advantages for tumor markers. Anticancer Res 17 3011-3014... 

Like in RILAs, an advantage of fluorescence detection is the possibility of developing homogeneous FILAs using direct or indirect (competitive or displacement) approaches. The fluorescence polarization immunoassay (PFIA) and their homolog fluorescence polarization immuno-like assay (PFILA) are two of the most widely used procedures in homogeneous fluoroassays. Both are based on the principle that fluorescence polarization gives a direct measure of the bound/free ratio of the labeled analyte (tracer) without the need for their separation [23, 28]. 

Optical immunoassays have a number of advantages over radioimmunoassays (Table 3), mainly because the reagents are stable and homogeneous assays can be produced simply. Various labels can... 

The MAbs and EIA we have developed provide a means of detecting avermectins at the level of sensitivity now possible with HPLC and gas chromatography. The EIA employs standard methods, and it is stable, reproducible, and economical. The solvent tolerance exhibited by the MAbs makes the assay compatible with methods for recovering residues of these very hydrophobic compounds. Monoclonal antibodies have the well-known advantages of defined affinity, specificity, and potentially infinite supply. The IgGi subclass of all of the avermectin MAbs makes them easy to purify to near-homogeneity by well-documented methods. This could facilitate tests of their usefulness in other immunoassay formats. 

FPls have advantages and disadvantages. FPls do not require multiple antigenic sites, as is needed with heterogeneous capture immunoassays, as detected in sec-tionl9.9.A FPls can be performed in a homogeneous format and may not require separation steps. However,... 

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