Discovery of Microalgae Extracellular Vesicles

Extracellular vesicles are endogenous nano-size vesicles secreted by cells, ranging from 30–200 nm in diameter enveloped in a lipid bilayer membrane, which carry nucleic acids, proteins, lipids and metabolites, etc. Extracellular vesicles are the main tools of intercellular communication, which are involved in the exchange of materials between cells. Extracellular vesicles can be secreted by a variety of cells under normal and pathological conditions, which mainly come from the polyvesicles formed by intracellular lysosomal particles and are released into the extracellular matrix after fusion of the extracellular membrane and cell membrane of the polyvesicles. Because of its low immunogenicity, non-toxic side effects, strong targeting, capacity of crossing the blood-brain barrier and other characteristics, it has been regarded as potential drug carrier. In 2013, the Nobel Prize in Physiology and Medicine was awarded to three scientists related to the study of external vesicles. Since then, the academic and industrial circles have set off an upsurge of extracellular vesicles research and development, application and commercialization.

Extracellular vesicles from plant cells are rich in unique active components, small in size and capable in tissue penetration. Most of them can be taken and directly absorbed into the intestine. For example, ginseng vesicles are conducive to the differentiation of stem cells into nerve cells, and ginger vesicles can regulate intestinal flora and alleviate colitis. Microalgae are the oldest single-celled plants on Earth. There are nearly 300,000 kinds of microalgae widely distributed in oceans, lakes, rivers, deserts, plateaus, glaciers and other places, with unique regional characteristics. During the evolution of the 3 billion Earth, microalgae have always been able to thrive as single cells on the Earth, which is inseparable from their extraordinary growth and self-repair ability.

Microalgal extracellular vesicles are new biomedical active materials with higher safety and stability. Microalgae have multiple advantages in the production of extracellular vesicles, such as simple culture process, controllable, cheap, fast growth, high output of the vesicles and easy to be engineered. In previous studies, microalgal extracellular vesicles were found to be easily internalized by cells. In animal models, they were found to be directly absorbed through the gut and enriched in specific tissues. After entering the cytoplasm, it can last for several days, which is conducive to long-term sustained drug release.

In addition, microalgal extracellular vesicles are expected to load a variety of drugs, which improve the stability of molecules, slow release, oral adaptability, etc., solving the existing drug administration obstacles. Therefore, the development of microalgae extracellular vesicles has high feasibility in clinical transformation and industrialization.