Exploiting the role of milk extracellular vesicles: a comprehensive analysis on isolation methods, characterization, surface modifications, and their therapeutic applications.

Milk EVs (MEVs) are a class of extracellular vesicles (EVs) that have attracted significant attention for their potential as natural nanocarriers in drug delivery. These nanosized vesicles (30 - 150 nm) are composed of a lipid bilayer that encapsulates proteins, nucleic acids, and lipids. The biogenesis of EVs involves a tightly regulated "endocytosis-fusion-secretion" pathway, and they are secreted by diverse cells into physiological fluids (blood, urine, and saliva). The isolation and characterization methods of MEVs are essential to achieve high purity, structural integrity, size distribution, and biomolecular composition. Efficient drug loading strategies such as passive diffusion, electroporation, and sonication enable the incorporation of therapeutic molecules. Surface modifications such as PEGylation, ligand conjugation, and genetic engineering further enhance the targeting efficiency, circulation stability, and therapeutic efficacy. Given their biocompatibility, low immunogenicity, and natural ability to traverse biological barriers, MEVs offer a scalable, and non-toxic platform for targeted drug delivery such as span cancer therapy, neurodegenerative disease treatment, and immune modulation. However, further research is needed to optimize MEV-based therapeutics, ensuring their efficacy and safety through rigorous clinical trials. This review explores the biogenesis, composition, isolation, characterization, drug-loading strategies, surface modifications, and therapeutic applications of MEVs, highlighting their emerging role in nanomedicine.