Liquid biopsy is a method of collecting blood or other body fluids for the analysis of molecular alterations, tumor cells, and metabolites. Recently, urine liquid biopsy has gained in importance because of its less invasive sampling. Urine samples, in comparison to blood, allow more real-time monitoring, especially for cancer patients. Nevertheless, urine can rapidly hydrolyzed in a short time, which can result in the production of a large amount of ammonia and degradation of urine components requiring fast processing or stabilization.

Urines were collected from 5 healthy volunteers. Each participant provided 10 mL aliquots of urine, that were stabilized in PAXgene Urine Liquid Biopsy Tubes at room temperature or maintained non-stabilized at 4°C up to preliminary centrifugation procedures. Exosomes were isolated from stabilized and non-stabilized urines by ultracentrifugation. Biophysical characterization by AFM and DLS, protein analysis by Western-Blot, and RNA isolation were carried out in exosomes from stabilized and non-stabilized urines at the time of collection and after 7 days of storage.

Protein detection showed a higher amount of proteins at the time of collection in non-stabilized samples in comparison to stabilized ones, but after 7 days, the profile reversed which indicates a degradation of proteins in unstabilized samples. AFM analysis confirmed the presence of exosomes both in stabilized and non-stabilized samples at t=0 and after 7 days. After 7 days an increase in aggregates (particles larger than 200 nm in diameter) was observed both in stabilized and non-stabilized urine. In stabilized samples, a higher number of particles/ vesicles than in the non-stabilized samples was detected as a possible sign of decay in the latter ones.

PAXgene Urine Liquid Biopsy Tubes showed to be a multi-purpose collection device for urine liquid biopsy allowing the sampling of urine at room temperature for exosome isolation even after 7 days of storage at room temperature.