A colorimetric aptasensor based on a hemin/EpCAM aptamer DNAzyme for sensitive exosome detection.

Area of Science:

• Biotechnology
• Nanotechnology
• Analytical Chemistry

Background:

• Exosomes are crucial biomarkers reflecting the tumor microenvironment.
• Aptasensors offer a promising approach for detecting cancer and tumor-derived exosomes.
• EpCAM aptamers are frequently employed for exosome recognition in biosensing applications.

Purpose of the Study:

• To investigate the properties of the EpCAM aptamer under acidic conditions.
• To develop a novel colorimetric aptasensor for sensitive exosome detection.
• To evaluate the sensor's performance in complex biological samples.

Main Methods:

• Characterization of EpCAM aptamer topology, thermal stability, and hemin binding affinity.
• Construction of a hemin/G-quadruplex DNAzyme using an unmodified EpCAM aptamer.
• Catalysis of the TMB-H2O2 system for colorimetric signal generation.
• Assay development for exosome detection and quantification.

Main Results:

• The EpCAM aptamer forms a stable G-quadruplex structure under acidic conditions.
• The developed aptasensor exhibits a colorimetric signal negatively correlated with exosome concentration.
• Achieved a linear detection range of 10^6-10^8 particles/mL with a detection limit of 3.94 × 10^5 particles/mL.
• Demonstrated high specificity and sensitivity for detecting exosomes from breast, liver, and lung cancers in serum samples.

Conclusions:

• The EpCAM aptamer's unique G-quadruplex structure can be leveraged for biosensing.
• The proposed colorimetric aptasensor provides a sensitive and specific method for cancer exosome detection.
• This approach holds potential for early cancer diagnosis and monitoring.