Exosomes are free floating membrane-bound vesicles, 30 – 120 nm in diameter, found in blood. They have been excreted from live biological cells of all types and contain proteins, lipids, mRNA, and microRNA.
Exosomes may also be found in urine and other biological fluids. Once thought to play a role in how cells get rid of waste, it has now become clear that exosomes are often released from cells deliberately as signal carriers or other means of communication with other cells. In this way, exosomes can transfer molecules, thereby influencing immune responses and other processes.
Cell-free DNA are nucleic acids found in the bloodstream, circulating freely from cells. They are thought to arise from cells that have died with their contents released into blood. These cells may include the breakdown or death of normal cells, abnormal cells, or pathogens. Most of the cfDNA in the blood is fragmented and has a median size range of 160 – 180 bp. cfDNA has been shown to be increased in cancer patients and other disease states. But, for metastatic disease, circulating tumor DNA can amount to less than 0.1% of the total cfDNA content found in blood. Current research is being conducted to determine if cfDNA can be used for the diagnosis of many cancer related diseases and for tracking genetic changes that can guide therapy decisions.