Direct Profiling of Extracellular Vesicle Surface Markers in Plasma: A Proof-of-Concept Study

During the last decade, non-invasive methods such as liquid biopsy have increasingly replaced invasive techniques for diagnosing and monitoring diseases. Liquid biopsies are easier to obtain, highly sensitive, cost-effective per sample, and can be used for real-time monitoring, such as tracking drug response. To uncover molecular and cellular characteristics today, blood, saliva, urine, or cerebrospinal fluid are typically analyzed. In this methodological proof-of-concept study, we propose that patient profiling can be facilitated by assessing surface markers on extracellular vesicles (EVs) directly in plasma without prior purification. EV composition reflects the physiological or pathological state of their parent cell, making EVs valuable tools for biomarker discovery and understanding disease mechanisms. Plasma and purified EVs from 30 ischemic stroke patients were analyzed for 17 surface markers using an in-house protein microarray method (EV Array). The findings indicate that measurements on EVs directly in plasma and on purified EVs show similar patterns in expression of surface markers, supporting the feasibility of omitting purification in EV profiling. This knowledge can provide faster monitoring of various diseases, prevent delays in patient profiling, and optimize patient care.