Extracellular vesicles (EVs) are natural carriers of biomolecules that play central roles in cell-to-cell communications. Based on this, there have been various attempts to use EVs as therapeutic drug carriers. From chemical reagents to nucleic acids, various macromolecules were successfully loaded into EVs; however, loading of proteins with high molecular weight has been huddled with several problems. Purification of recombinant proteins is expensive and time consuming, and easily results in modification of proteins due to physical or chemical forces. Also, the loading efficiency of conventional methods is too low for most proteins. We have recently proposed a new method, the so-called exosomes for protein loading via optically reversible protein-protein interaction (EXPLORs), to overcome the limitations. Since EXPLORs are produced by actively loading of intracellular proteins into EVs using blue light without protein purification steps, we demonstrated that the EXPLOR technique significantly improves the loading and delivery efficiency of therapeutic proteins. In further
All multicellular organisms develop various ways for exchange of various biomolecules, including not only small chemicals, but also nucleic acids and proteins. As major carriers of biomolecules, extracellular vesicles (EVs) play central roles in intercellular communication. EVs are spherical nano-size particles surrounded by a lipid bilayer, and further classified based on the physical and biochemical properties. Representatively, microvesicles derived from plasma membrane are 100–1,000 nm, and exosomes originating from intracellular multivesicular bodies (MVBs) are 50–200 nm in size. EVs can be simply isolated by ultracentrifugation, size exclusion chromatography or ultrafiltration, and can be easily distinguished by primarily size, and by detecting the surface markers such as tetraspanins in secondary screening.
EV-based drug delivery was originally attempted for small chemical drugs such as curcumin, a well-known anti-inflammatory drug, after loading into exosomes (Dongmei Sun
Simultaneously, several methods for intracellular protein delivery using EVs have also been tried (Fig. 1). Unlike chemical drugs or nucleic acids, proteins cannot passively penetrate cellular membranes. Furthermore, proteins are easily modified by the physical and chemical environment, limiting the applicability of EV-based delivery of proteins with therapeutic potentials. In 2011, one group reported that highly oligomeric proteins can be targeted to exosomes by plasma membrane anchors (Shen B
Exosomes for protein loading via optically reversible protein-protein interaction (EXPLORs) are novel protein carriers developed for overcoming the limitations of conventional EV-based protein delivery. The EXPLOR technology was designed such that the protein drug can be actively and transiently docked into the exosomes by blue light illumination. For that, cryptochrome 2 (CRY2), a photoreceptor of
In conclusion, we have recently developed a novel EV–based protein carrier EXPLOR that can deliver therapeutic proteins efficiently
This research was supported by KAIST Institute for the BioCentury, Cancer Metastasis Control Center (Grant Number: N11160071).