Abstract
To detect and study diseases, research and clinical laboratories must quantify specific biomarkers in the plasma and urine of patients with precision, sensitivity, and cost-effectiveness. Newly developed techniques, such as particle-based immunoassays, must be validated in these terms against standard methods such as enzyme-linked immunosorbent assays (ELISAs). Here, we compare the performance of assays that use hollow polyelectrolyte microcapsules with assays based on solid plastic beads, and with standard microplate immunoassays. The polyelectrolyte microcapsules detect the disease biomarker beta-2 microglobulin with a fifty-fold increase in sensitivity than polystyrene (PS) beads. For sequence-specific nucleic acid detection, the oligonucleotide-coated microcapsules exhibit a two-fold lower increase in sensitivity over PS beads. The microcapsules also detect the presence of a monoclonal antibody in hybridoma supernatant at a fifty-six-fold increase in sensitivity compared to a microplate assay. Overall, polyelectrolyte microcapsule-based assays are more sensitive for the detection of protein and nucleic acid analytes than PS beads and microplate assays, and they are viable alternatives as a platform for the rapid quantitative detection of analytes at very low concentrations.
Highlights
For diagnosis and monitoring of disease, the accurate, sensitive and early measurement of biomarkers is essential
The CaCO3 cores are left in place for all assay manipulations, which makes it easier to centrifuge and wash the particles and are removed with ethylenediaminetetraacetic acid (EDTA) just before reading the assay so that the resulting hollow microcapsules remain in suspension for analysis in the flow cytometer
Available beads made of polystyrene (PS), silica (SiO2), or poly(methylmethacrylate) (PMMA) are currently used for detection of analytes and for multiplexing studies that are read out by flow cytometry [1,25]
Summary
For diagnosis and monitoring of disease, the accurate, sensitive and early measurement of biomarkers is essential. Comparative validation of a microcapsule-based immunoassay for the detection of proteins and nucleic acids we have recently introduced the use of hollow polyelectrolyte microcapsules [9] Their porous surface can be modified with large amounts of antibodies [10,11,12], and their great physicochemical stability aids the development of assays that are fast and robust in a broad range of experimental conditions. The CaCO3 cores are left in place for all assay manipulations, which makes it easier to centrifuge and wash the particles and are removed with ethylenediaminetetraacetic acid (EDTA) just before reading the assay so that the resulting hollow microcapsules remain in suspension (microcapsules have approximately the same density as the buffer) for analysis in the flow cytometer This allows samples to be analyzed for a longer period of time, especially in diagnostics laboratories where many samples are continuously processed. Our results show that polyelectrolyte microcapsule-based immunoassays are robust techniques for protein and nucleic acid detection and can serve the requirements for a sensitive, robust and optical read-out immunoassay [21]
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