A comprehensive assessment of multiplex immunoassay platforms and detection methods is summarized in an interesting 2011 article by Chandra, et al, in Expert Review Proteomics (1). The article, “Protein Microarrays and Novel Detection Platforms” provides interesting information for several reasons.First, it presents an excellent description of the emerging discovery and clinical need for high throughput proteomics, pointing out that traditional 2-D gel and mass spec techniques are not sufficient solutions. It contains a thorough summary of both widely accepted and novel emerging multiplexed immunoassay techniques, assay platforms and detection methodologies. This includes planar arrays along with suspension based bead arrays and detection methods ranging from fluorescent to chromogenic label-based systems and several label free methods. Finally, there is a detailed compendium of the merits and demerits for these respective systems which is particularly interesting. Although this compendium was published as recently as 2011, the evolution of multiplex applications has been significant and the Grace Bio-Labs ArrayCAM Protein Microarray System is an example of the rapid advances that have occurred in the brief timespan since this paper’s publication.
Chadra, et al, conclude the ultimate goal of high-throughput proteomics is whole-proteome assays, which are economically possible only on microarray platforms such as the ArrayCAM. The microarray is currently the only platform capable of screening hundreds (to thousands) of analytes within a single well while retaining spatially separated individual reactions to mitigate non-specific interactions of biological reagents. This point excludes low density platforms such as suspension arrays like flow cytometry and mass spec methods from efficient or economical screening of large density content. Some of the indicated drawbacks of microarray based systems in this article include requirements for chemical modifications of samples, dynamic range of colorimetric detection, detection of low abundance proteins and high cost or complexity of multiple laser epi-fluorescent instrumentation. With the advancement of near IR quantum nanocrystal detection in conjunction with porous nitrocellulose and digital CMOS data acquisition, the ArrayCAM System provides the solution to these typical microarray shortfalls.
Label-free microarray methods present numerous interesting possible solutions. Although these methods are generally less mature than traditional microarrays, the simplicity of the concept is compelling. Presenting a substantial obstacle for general adoption however, is the complexity of instrumentation and cost of these platforms when compared to the extremely low cost ArrayCAM System.
An important general conclusion drawn from this article is that no single platform is suitable for all user applications. Each system has particular strengths and weaknesses and it is necessary for users to select a system optimally suited to their technical and economic needs. With rapidly advancing technologies, important factors to consider when selecting an optimal platform for a particular users needs include cost-per-data point, sensitivity, dynamic range, marker density, binding chemistry and analyte format, data reduction, speed, immunological technique and complexity of use.
The article in full can be found here:
(1)Protein Microarrays and Novel Detection Platforms”, Chandra, et al; Expert Rev Proteomics, 2011;8(1):61-79
- PMID: 21329428