# Surface Plasmon Resonance as a Potential Diagnostic Tool for the Detection of CXC Chemokine Receptor 4 (CXCR4) on Extracellular Vesicles

## TL;DR

This study shows that surface plasmon resonance can detect CXCR4 on extracellular vesicles, offering a new diagnostic tool for cancer and other diseases.

## Contribution

A novel SPR-based method is developed for label-free, real-time profiling of CXCR4 on extracellular vesicles.

## Key findings

- SPR technology successfully detected CXCR4 on EVs with a strong correlation to flow cytometry results.
- SPR molecular fingerprints revealed varying levels of CD9, CD63, CD81, and CXCR4 on EVs from different cancer cell lines.
- The SPR biosensor can profile EVs in buffer and cell culture supernatant with 10% EV-depleted serum.

## Abstract

This study leverages surface plasmon resonance (SPR) BiacoreTM technology to unveil the diagnostic potential of detecting CXCR4 on extracellular vesicles (EVs). Despite its recognized potential as a cancer biomarker, the presence of CXCR4 on EVs remains underexplored for diagnostic purposes. Using reference material (rEVs), a standardized label-free and real-time SPR biosensor is established to molecularly profile CXCR4-positive EVs. The binding interactions between immobilized antibodies and EVs isolated from different cancer cell lines revealed a unique SPR molecular fingerprint (SPR-MFP) consisting of varying expression levels of the CD9, CD63 and CD81 EV biomarkers, as well as CXCR4. There was a strong correlation between CXCR4 expression on the cellular membrane measured by flow cytometry (FCM) and the CXCR4 SPR signal of purified EVs, indicating that the chemokine receptor is actively transferred to the extracellular space. The BiacoreTM biosensor is able to directly detect and molecularly profile EVs in buffer and spiked in cell culture supernatant supplemented with 10% EV-depleted serum. Altogether, our findings illuminate the potential of SPR BiacoreTM technology in EV-related research as well as reveal the diagnostic potential of EV-associated CXCR4, offering valuable insights and paving the way for medical applications in diseases associated with aberrant CXCR4 expression.