Exosomal bioactive molecules: molecular regulation, functional heterogeneity, and translational implications in disease diagnostics and therapeutics.

Exosomes are nanoscale extracellular vesicles that play a pivotal role in cell-to-cell communication by transporting a rich cargo of bioactive molecules, including proteins, lipids, and diverse nucleic acids. Recent discoveries have uncovered the complex molecular machinery behind exosome biogenesis and cargo loading, highlighting the roles of Endosomal Sorting Complex Required for Transport (ESCRT) complexes, lipid domains, RNA-binding proteins, and post-translational modifications. This review presents a comprehensive synthesis of the molecular pathways that regulate exosomal heterogeneity, with a focus on how these mechanisms govern the selective enrichment of biologically active cargo. We also discuss state-of-the-art technologies and omics platforms—such as ExoCarta and machine learning–based classifiers—used to decode exosomal content for diagnostic purposes. The clinical relevance of exosomes is examined through their roles in liquid biopsies for cancer, metabolic, and neurodegenerative diseases, emphasizing biomarker performance in terms of sensitivity and specificity. Furthermore, we explore the therapeutic potential of both native and engineered exosomes for targeted drug delivery, wound healing, and neuroregeneration, and provide insights into ongoing clinical trials. Despite growing interest, translational challenges persist, including standardization of isolation protocols, variability in cargo, targeting specificity, and regulatory constraints. Emerging strategies—ranging from synthetic exosome mimetics to AI-driven diagnostic algorithms—are rapidly reshaping the landscape of exosome-based precision medicine. This review consolidates current knowledge while proposing a forward-looking framework that integrates basic biology, engineering innovation, and clinical application, positioning exosomes as powerful agents in the future of diagnostics and therapeutics.