Amplification of microsphere-based microarrays using catalyzed reporter deposition

Area of Science:

• Biotechnology
• Analytical Chemistry
• Immunology

Background:

• Luminex flow cytometry is a versatile platform for multiplexed immunoassays.
• Optimizing signal generation is key to improving assay sensitivity and detection limits.
• Tyramide signal amplification (TSA) offers a potential method for signal enhancement.

Purpose of the Study:

• To evaluate and compare the assay sensitivities of three distinct fluorescent signal generation schemes on a Luminex flow cytometer.
• To assess the efficacy of tyramide signal amplification (TSA) in improving toxin detection limits.
• To determine the impact of assay-specific optimization on TSA performance, particularly in multiplexed assays.

Main Methods:

• Three signal generation schemes were tested: Cy3-labeled antibodies, biotinylated tracers with streptavidin-R-phycoerythrin, and biotinylated tracers with avidin-peroxidase and TSA.
• Antigen capture was performed using immobilized antibodies on microspheres.
• Bound targets were quantified using fluorescently labeled detection antibodies or signal amplification techniques.

Main Results:

• TSA improved performance up to 100-fold in three individual toxin assays compared to Cy3-antibody detection.
• Streptavidin-R-phycoerythrin provided equivalent sensitivities to TSA in some cases.
• TSA demonstrated dramatic increases in sensitivity at low concentrations, simplifying positive sample identification for ricin, cholera toxin, and staphylococcal enterotoxin B.
• No improvement was observed for botulinum toxoid A assays with TSA.
• Multiplexed assays showed lower improvements (3-10 fold) with TSA, and increased variability was noted for botulinum toxoid.

Conclusions:

• TSA is a highly effective signal amplification strategy for enhancing Luminex-based toxin detection assays, significantly improving sensitivity and simplifying positive identification.
• The effectiveness of TSA is assay-dependent, with notable variations observed across different toxins and assay formats.
• Assay-specific optimization is critical for maximizing the benefits of TSA, particularly when adapting the method for multiplexed detection to mitigate potential increases in variability and ensure reliable performance.