Exosomes as next-generation drug carriers: Transforming cancer therapy.
Cancer remains a major global health challenge, with its growing incidence highlighting the critical need for effective and accessible treatments. Current therapeutic approaches, including surgery, chemotherapy, radiation therapy, hormone therapy, and immuno-therapy, are often limited by toxicity, poor targeting, and suboptimal efficacy. These challenges have driven the development of nanotechnology-based strategies aimed at improving tumor selectivity and therapeutic outcomes. Among the most promising are extracellular vesicles, particularly exosomes (30-150 nm), which have garnered significant attention as natural nanocarriers due to their inherent role in intercellular communication and their capacity to encapsulate proteins, nucleic acids, and lipids. Exosomes can be obtained from a wide range of sources, including biological fluids, cell cultures, and unconventional origins such as plants and microorganisms. Of particular interest are milk- and colostrum-derived exosomes, particularly those of bovine origin, have emerged as a promising delivery platform owing to their scalability, biocompatibility, cost-effectiveness and suitability for oral administration. These vesicles possess immunomodulatory properties, demonstrate stability under gastrointestinal conditions, and are readily internalized by intestinal epithelial cells. Furthermore, surface engineering with targeting ligands such as folic acid can enhance tumor specific delivery by exploiting receptor overexpression while minimizing systemic toxicity. This review critically examines exosome sources, isolation and characterization methodologies, cargo-loading strategies, biodistribution, pharmacokinetics, and engineering approaches together with their applications in delivering small-molecule drugs and nucleic acid-based therapeutics to overcome multidrug resistance in cancer. In addition, current challenges related to exosome heterogeneity, manufacturing, quality control, clinical translation, and regulatory considerations are discussed, together with future perspectives for the development of exosome-based therapeutics.