Intracellular drug delivery by exosomes: Present condition and future perspectives

Nanotechnology plays a crucial part in the detection, diagnosis, andtreatment of a wide variety of human diseases including cancer. The recentdecades have witnessed a rapid development of nanocarriers as drug deliverysystem. Using nanocarriers have several pharmacokinetics and safety profiles inaddition to the increased bioavailability of the entrapped molecules. However,there are several obstacles in attaining the goal of successful clinicaltranslation of nanocarrier-based drug delivery system because of the safety,stability and delivery efficiency of nanocarriers. In this scenario, exosomecould be an excellent alternative to conventional drug delivery agents. Exosomesare bi-layered nanovesicles of 40-100 nm diameter and contain differentbioactive molecules including microRNAs, mRNAs, DNA fragments, and proteins.Exosomes are actively released by healthy cells in the extracellular matrix andcan be taken up by the surrounding or distant cells. Due to their inherentability to carry bioactive molecules, exosomes emerged as a versatile drugvehicle and have attracted the attention of many researchers. The most impressivecharacteristics of exosomes are nanosized, non-immunogenic due to similarcomposition as body’s own cells, high biocompatibility, readily bioavailable,ability to penetrate biological barriers, and encapsulation of various cargowhich significantly distinguish them from other conventional nanocarriers. Itis important to note that recently exosome-based nanocarriers containing smalldrug molecules and bioactive macromolecules have been developed for thetreatment of several prevalent diseases such as cancer, central nervous systemdisorders, and other degenerative diseases. Nanocarriers based on exosomes haveenormous prospects in overcoming several difficulties faced in gene and drugdelivery. This article will briefly highlight the advancement as well as thechallenges of exosome-based nanocarriers as drug delivery system. In addition,it will also discuss the future perspectives of exosome-based drug deliverysystem. Special attention will be placed on the exosomal biogenesis, releasemechanisms, and advantages of using exosomes containing special cargo, as adrug delivery system, in treating obstinate diseases. The aim is to offer newinsights for exploring exosomes in the emerging field of drug delivery.