Microfluidic Device-Based In Vivo Detection of PD-L1-Positive Small Extracellular Vesicles and Its Application for Tumor Monitoring

Abstract

Liquid biopsy is of great significance in tumor early diagnosis and treatment stratification. PD-L1-positive small extracellular vesicles (PD-L1 + sEVs) are closely related to tumor growth and immunotherapy response, which are considered valuable liquid biopsy biomarkers. In contrast to conventional in vitro detection, in vivo detection has the ability to improve the detection efficiency and enable continuous or real-time dynamic monitoring. However, in vivo detection of PD-L1 + sEVs has multiple difficulties, such as high cell background, complex blood environments, and lack of a specific and stable detection method. Herein, the in vivo detection of PD-L1 + sEVs method was constructed, which efficiently separated sEVs based on the microfluidic device and quantitatively analyzed PD-L1 + sEVs by aptamer recognition and hybridization chain reaction. The concentration of PD-L1 + sEVs was continuously monitored, and significant differences at different stages of tumor as well as a correlation with tumor volume were found. Diseased and healthy individuals could also be effectively distinguished based on the concentration of PD-L1 + sEVs. The method with good stability, biocompatibility, and detection performance provided a powerful means for in vivo detection of PD-L1 + sEVs, contributing to the clinical diagnosis and treatment of tumor.

Ultrasensitive quantification of PD-L1+ extracellular vesicles in melanoma patient plasma using a parallelized high throughput droplet digital assay

“…We chose to use PD-L1 as the capture antibody and CD81 as the detection antibody for several reasons. First, we found via plate ELISA that even for mel-B7H1-derived EVs, which are known to express PD-L1, 30–32,47 there was greater labeling of CD81 than PD-L1 on the EVs (ESI† Fig. 3).…”

“…28,29 Melanoma cells, especially metastatic ones, release EVs that carry PD-L1. 30–32 PD-L1 molecules expressed on the cell surface interact with the PD-1 receptors highly expressed on T cells, and this interaction protects normal cells from an immune attack by signaling T cells to reduce their activity. 33,34 However, many cancer cells, including melanoma cells, exploit this mechanism by overexpressing PD-L1 to effectively suppress the immune system, promoting the tumor growth and spread.…”