Figure 1.

Sources of exosomes and their therapeutic advantages for drug delivery. Exosomes can be generated from almost all types of cells. Those are relevant to therapeutics fall into three main categories, i.e., cells, body fluids, and food. There are four major cell sources for exosome generation, i.e., human embryonic kidney (HEK) cells, mesenchymal stem cells (MSCs), immune cells, and cancer cells. Exosomes of HEK cell origin are immunologically inert without safety concerns, have high transfection efficiency, and can deliver drugs to various target tissues. Exosomes derived from MSCs can be easily obtained from a variety of human tissues and expanded ex vivo in large scale. Exosomes originated from immune cells can enhance the anticancer efficacy of its entrapped drugs by boosting the immunity. Exosomes derived from cancer cells have the tropism toward their parental cells and thus can be used as Trojan horses to target these malignant cells. Exosomes derived from blood have a low risk of unexpected mutations, are easily acquirable, and have higher transfection efficiency. Exosomes isolated from other body fluids such as urine, saliva, and amniotic fluids can be used as parental cell sample carriers for disease diagnosis. Exosomes derived from food such as milk and edible plants are stable under acidic conditions that can be orally delivered and massively produced.