Double Digital Assay for Single Extracellular Vesicle and Single Molecule Detection

Area of Science:

• Biotechnology
• Molecular Diagnostics
• Nanotechnology

Background:

• Extracellular vesicles (EVs) show potential as disease biomarkers.
• Current EV detection methods face challenges due to low biomarker abundance and complex EV properties.

Purpose of the Study:

• To develop a highly sensitive assay for absolute quantification of molecules from single EVs.
• To overcome limitations in detecting low-abundance biomarkers on individual EVs.

Main Methods:

• A double digital assay integrated with tyramide signal amplification (TSA) for enhanced fluorescent readout.
• Utilized microfluidic technology for single EV compartmentalization and digital partitioning.
• Applied the assay to quantify PD-L1 proteins on single EVs from melanoma cells.

Main Results:

• Demonstrated successful compartmentalization and digital partitioning of single EVs.
• Achieved absolute quantification of individual molecules from single EVs.
• Quantified approximately 2.7 PD-L1 molecules per EV in melanoma-derived EVs.

Conclusions:

• The developed assay enables precise quantification of rare, low-abundance protein molecules from single EVs.
• This technology is applicable for profiling cancer biomarkers, aiding in prognosis and therapy response assessment.
• The findings facilitate a deeper understanding of EV heterogeneity and the discovery of novel EV-based biomarkers.