Exosome: Super Player in Drug Delivery

Millions of tiny bubbles, released from cells and packaged with molecular mail, are racing through your bloodstream right now. Called exosomes, these lipid vesicles shuttle proteins and genetic information between both neighboring and distant cells.

Long been used as an early diagnosic biomarker of tumor, exosome, in recent researches, has been found to be able to perform well in efficiently delivering different kinds of cargo to the target cell.

what are exosomes?

Exosomes are extracellular vesicles that are released from cells upon fusion of an intermediate endocytic compartment, the multivesicular body (MVB), with the plasma membrane.

Exosomes were discovered in 1983 and officially named in 1987. Although they were known as cell waste at that time, later studies have shown that exosomes contain cell-specific proteins, liposomes, and nucleic acids, and can transmit information from one cell to another as signal molecules.

Compared with normal cells, tumor cells secrete a larger number of exosomes, which can be collected and used as a target for early screening of tumors. In addition, recent research also positioned exosomes to become a widespread tool for drug delivery.

What makes exosomes efficient drug delivery tools?

First of all, the size of exosomes (typically 10-100 nm) makes them an attractive candidate for drug delivery in cancer, which are large enough to avoid renal clearance, yet small enough to escape being absorbed by the reticuloendothelial system.

Besides, exosomes are composed of a lipid bilayer, which forms an aqueous inner compartment and lipophilic outer layer. This structure enables the loading of both hydrophobic and hydrophilic materials into exosomes.

Then, as one of cell products, exosomes’ drug delivery can escape phagocytosis or degradation of macrophages, and can also circulate in the body for a long time to maintain the effect. The ability to deliver specific drugs to the central nervous system is a significant advantage of exosomes.

What is new in exosomes-based drug delivery research?

On 27 November, 2019, Rao Lei's group at Chengdu Medical College published an article in NANO MICRO Small, which reported the use of engineered exosomes to treat type 2 diabetes mellitus (T2DM) targeting pancreas.

This study designed a simple, fast, and efficient method to construct a SPION-modified exosome in which SPION carried BAY55-9837, and this is called BAY-exosome-SPION. This research shows that exosomes as a drug carrier can prolong the T1/2 of BAY55-9837, thereby reducing the number of injections. At the same time, the exosome-SPION can rapidly increase the drug concentration in the target site (pancreatic β cells) in response to the increase of plasma glucose. Therefore, BAY-exosome-SPION may be a potential candidate for the treatment of T2DM.

The application potential of exosomes in clinics has been continuously expanded, and rapid progress has been made on exosomes-based diagnostic methods and drug development for major diseases such as cancer, diabetes, cardiovascular and neurodegenerative diseases. However, the current research on exosomes still has a long way to go. With the rapid development of related technologies and the combination with liquid biopsy, precision medicine and regenerative medicine, the market for exosomes is expected to grow significantly.