Isolation and Characterization of Salivary Exosomes for Cancer Biomarker Discovery

Exosomes are small extracellular vesicles secreted by cells and are known to play a key role in intercellular communication. Several studies have associated exosomes with various roles in tumorigenesis and explored their potential as a source of biomarkers for diagnosis and prognosis in cancer research. Exosomes can be isolated from several body fluids, including those that are noninvasively accessible, such as human saliva. This book chapter provides a step-by-step detailed description of techniques that are used for the isolation, quantification, and characterization of exosomes from saliva. These include ultracentrifugation for the isolation, nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), and western blot (WB) for characterization of exosomes. The NTA approach explores the Brownian motion and light scattering of particles to predict size and concentration. TEM enables visualization of the exosomes which often present a cup-shaped morphology. Western blot is used to detect commonly expressed exosome-associated proteins. Finally, salivary exosomes isolated using these protocols can further be characterized for downstream analysis according to their cargo (proteins, DNA, RNA, miRNA) and utilized for cancer biomarker discovery.