Extracellular vesicles (EVs) are a heterogeneous population of biological particles released by cells. They represent an attractive source of potential biomarkers for early detection of diseases such as cancer. However, it is critical that sufficient amounts of EVs can be isolated and purified in a robust and reproducible manner. Several isolation methods that seem to produce distinct populations of vesicles exist, making data comparability difficult. While some methods induce cellular stress that may affect both the quantity and function of the EVs produced, others involve expensive reagents or equipment unavailable for many laboratories. Thus, there is a need for a standardized, feasible and cost-effective method for isolation of EVs from cell culture supernatants. Here we present the most common obstacles in the production and isolation of small EVs, and we suggest a combination of relatively simple strategies to avoid these. Three distinct cell lines were used (human oral squamous cell carcinoma (PE/CA-PJ49/E10)), pancreatic adenocarcinoma (BxPC3), and a human melanoma brain metastasis (H3). The addition of 1% exosome-depleted FBS to Advanced culture media enabled for reduced presence of contaminating bovine EVs while still ensuring an acceptable cell proliferation and low cellular stress. Cells were gradually adapted to these new media. Furthermore, using the Integra CELLine AD1000 culture flask we increased the number of cells and thereby EVs in 3D-culture. A combination of ultrafiltration with different molecular weight cut-offs and size-exclusion chromatography was further used for the isolation of a heterogeneous population of small EVs with low protein contamination. The EVs were characterized by nanoparticle tracking analysis, immunoaffinity capture, flow cytometry, Western blot and transmission electron microscopy. We successfully isolated a significant amount of small EVs compatible with exosomes from three distinct cell lines in order to demonstrate reproducibility with cell lines of different origin. The EVs were characterized as CD9 positive with a size between 60–140 nm. We conclude that this new combination of methods is a robust and improved strategy for the isolation of EVs, and in particular small EVs compatible with exosomes, from cell culture media without the use of specialized equipment such as an ultracentrifuge.

The COVID-19 (caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)) epidemic started in Wuhan (Hubei Province, China) in mid-December 2019 and quickly spread across the world as a pandemic. As a key to tracing the disease and to implement strategies aimed at breaking the chain of disease transmission, extensive testing for SARS-CoV-2 was suggested. Although nasopharyngeal/oropharyngeal swabs are the most commonly used biological samples for SARS-CoV-2 diagnosis, they have a number of limitations related to sample collection and healthcare personnel safety. In this context, saliva is emerging as a promising alternative to nasopharyngeal/oropharyngeal swabs for COVID-19 diagnosis and monitoring. Saliva collection, being a non-invasive approach with possibility for self-collection, circumvents to a great extent the limitations associated with the use of nasopharyngeal/oropharyngeal swabs. In addition, various salivary biomarkers including the salivary metabolomics offer a high promise to be useful for better understanding of COVID-19 and possibly in the identification of patients with various degrees of severity, including asymptomatic carriers. This review summarises the clinical and scientific basis for the potential use of saliva for COVID-19 diagnosis and disease monitoring. Additionally, we discuss saliva-based biomarkers and their potential clinical and research applications related to COVID-19.

p75(NTR) was expressed in all OSCCs. p75(NTR) expression and the pattern of invasion were significantly associated with a poor prognosis in OSCCs, and both were better prognostic factors than traditional prognostic parameters. The combination of p75(NTR) expression and the pattern of invasion strongly increased precision in the identification of tumours with poor disease-free survival.