Early detection of prostate cancer (PC) is largely carried out using assessment of prostate-specific antigen (PSA) level; yet it cannot reliably discriminate between benign pathologies and clinically significant forms of PC. To overcome the current limitations of PSA, new urinary and serum biomarkers have been developed in recent years. Although several biomarkers have been explored in various scenarios and patient settings, to date, specific guidelines with a high level of evidence on the use of these markers are lacking. Recent advances in metabolomic, genomics, and proteomics have made new potential biomarkers available. A number of studies focused on the characterization of the specific PC metabolic phenotype using different experimental approaches has been recently reported; yet, to date, research on metabolomic application for PC has focused on a small group of metabolites that have been known to be related to the prostate gland. Exosomes are extracellular vesicles that are secreted from all mammalian cells and virtually detected in all bio-fluids, thus allowing their use as tumor biomarkers. Thanks to a general improvement of the technical equipment to analyze exosomes, we are able to obtain reliable quantitative and qualitative information useful for clinical application. Although some pilot clinical investigations have proposed potential PC biomarkers, data are still preliminary and non-conclusive.

In physiological environments (e.g. the blood), nanoparticles (NPs) are surrounded by a layer of biomolecules referred to as a ‘protein corona’ (PC). The most tightly NP-bound proteins form the so-called hard corona (HC), the key bio-entity that determines the NP's biological identity and physiological response. To date, NP-HC has been almost exclusively characterized in vitro, while NP–protein interactions under realistic in vivo conditions remain largely unexplored. In this study, we thoroughly characterized the in vivo HC of a NP formulation that forms around lipid nanoparticles with a lipid composition equal to that of clinically used liposomal amphotericin B (AmBisome®) after the recovery of the NPs from the blood circulation of FVB/N mice 10 minutes post intravenous administration. In vitro HC formed by 10 minutes incubation of NPs in FVB/N mouse plasma was used for comparison. Here we show that the biological identity (i.e. size, zeta-potential and aggregation state) of NPs in vivo is significantly different from that acquired in vitro. Furthermore, the variety of protein species in the in vivo HC was considerably larger. The present work has demonstrated that characterization of the in vivo HC is essential to provide an accurate molecular description of the biological identity of NPs in physiological environments.