The pathological changes in the brain of Parkinson’s disease (PD) patients precede the onset of symptoms by decades. Nevertheless, the diagnosis is based on these symptoms which only occur after irreversible cell loss is already present. Therefore, biomarkers with the ability to predict, diagnose and follow-up disease are essential, but they are still lacking in the field. Accumulating evidence indicates that extracellular vesicles (EVs) represent a highly interesting biomarker source, amongst others due to their capacity to cross gut and brain barriers, their presence in easily accessible body fluids including blood and the fact that EV composition mirrors their cellular origin. Furthermore, bacterial EVs (bEVs) have shown to reflect microbial dysbiosis which is evident in PD patients. In this project, we will investigate the biomarker potential of (b)EVs in PD. The EVs will be isolated from biofluids that can be collected via a non-invasive collection procedure, which is of major importance from a biomarker perspective. Hereby, the selection of EV subtypes and biofluids is tailored to knowledge about the disease pathogenesis. As such, we will analyze the amount, size and protein content of EVs separated from plasma, nasal fluid and saliva as well as bEVs separated from plasma and faeces of PD patients and healthy controls. The primary study outcome is to identify EV-related biomarkers that differentiate PD patients from healthy controls. Additionally, the identified biomarker candidates will be correlated with a broad range of disease symptoms and evaluated for their potential to follow-up a treatment response. Ultimately, we aim to identify a biomarker (profile) that is able to aid disease diagnosis and monitor disease progression as well as treatment response, together improving disease management.