Precision Engineering of Extracellular Vesicles as Programmable Carriers for mRNA Therapeutics.

Messenger RNA (mRNA) therapeutics have rapidly evolved into a transformative modality for treating infectious diseases, cancer, and genetic disorders; however, the clinical translation of these therapeutics remains limited by the need for safe, efficient, and tissue-specific delivery vehicles. Subsequently, extracellular vesicles (EVs) have emerged as a promising next-generation platform due to the associated endogenous biogenesis, intrinsic biocompatibility, low immunogenicity, and natural ability to traverse biological barriers. Thus, this review provides a comprehensive evaluation of the major engineering strategies enabling EV-based mRNA delivery, including exogenous loading methods, endogenous genetic engineering, physical microenvironment-driven enhancement, and hybrid EV-synthetic nanoparticle systems. Moreover, this review summarizes advances in electroporation, lipid-mediated fusion, and chemical/physical loading techniques; programmable endogenous loading platforms leveraging EV-sorting proteins and RNA-binding domains; cargo release mechanisms employing self-cleaving, protease-sensitivity, and optogenetic modules; device- and substrate-based approaches that modulate EV biogenesis and cargo composition. We further highlight emerging hybrid EV systems-particularly fusogenic cubosome-EV constructs-that achieve near-quantitative mRNA encapsulation and improved biodistribution, including enhanced penetration across the blood-brain barrier. Finally, we discuss technological bottlenecks and translational considerations, including scalability, batch variability, long-term mRNA stability, and regulatory challenges associated with biologically derived carriers. Collectively, this review outlines the current landscape and future directions for precision engineering of EVs as programmable, clinically viable carriers for mRNA therapeutics.