Tracing Tumor-Derived Exosomal PD-L1 by Dual-Aptamer Activated Proximity-Induced Droplet Digital PCR

Tumor-derived exosomal proteins have emerged as promising biomarkers for cancer diagnosis, but the quantitation accuracy is hindered by large numbers of normal cell-derived exosomes. Herein, we developed a dual-target-specific aptamer recognition activated in situ connection system on exosome membrane combined with droplet digital PCR (ddPCR) (TRACER) for quantitation of tumor-derived exosomal PD-L1 (Exo-(PD-L1)). Leveraging the high binding affinity of aptamers, excellent selectivity of dual-aptamer recognition, and the high sensitivity of ddPCR, this method exhibits significant sensitivity and selectivity for tracing tumor-derived Exo-(PD-L1) in a wash-free manner. Due to the excellent sensitivity, the level of tumor-derived Exo-(PD-L1) detected by TRACER can distinguish cancer patients from healthy donors, and for the first time was identified as a more reliable tumor diagnostic marker than total Exo-(PD-L1). The TRACER strategy holds great potential for converting exosomes into reliable clinical indicators and exploring the biological functions of exosomes.

Automated summary

The TRACER system utilizes a dual-target-specific aptamer recognition activated in situ connection system combined with ddPCR technology to quantitatively detect tumor-derived exosomal PD-L1 in a wash-free manner, showing significant sensitivity and selectivity. This method has the potential to serve as a more reliable tumor diagnostic marker than total Exo-(PD-L1) and to explore the biological functions of exosomes.