Abstract: Extracellular vesicles (EVs) are lipid bilayer vesicles secreted by almost all cells at the nanometer to micrometer scale, and they carry various active molecules such as proteins, nucleic acids, and lipids. As signaling molecules, EVs can deliver contents containing biological information to target cells to make them exert their specific functions. Milk contains various beneficial bioactive molecules, among which milk-derived EVs (M-EVs) are regarded as an ideal source of EVs due to their high bioavailability, low immunogenicity, digestive tolerance, and commercial production performance. Additionally, M-EVs can endure harsh acidic conditions in the stomach and degradation scenarios in the intestine, and cross the biological barriers to reach their target tissues, making them ideal carriers for the targeted delivery of health-promoting or therapeutic bioactive substances. However, due to the complexity of milk components, further research is needed to clarify the relationship between specific components and functions of M-EVs and standardize their extraction process, thereby promoting the application of M-EVs. This article provides an overview of the formation pathways, compositional characteristics, extraction, and delivery methods of M-EVs. In addition, the advantages and challenges of M-EVs as natural nanocarriers for active substances are discussed and the prospects of M-EV research are deciphered. The review aims to provide a new direction for developing new functional foods based on M-EVs as an oral drug delivery system.

Key words: milk; extracellular vesicles; bioactive substances; delivery vector