Multi-functional biomedical applications of nanoencapsulated herbal essential oils: polymer-based encapsulation strategies and key biological properties

Herbal essential oils (HEOs) possess broad-spectrum biological activity but their biomedical translation is limited by volatility, poor aqueous solubility, chemical instability, and compositional variability. This review critically synthesizes recent advances in polymer-based nanoencapsulation as a strategy to modulate the physicochemical and biological behavior of HEOs. Delivery platforms including polymeric nanoparticles, nanoemulsions, hydrogels/nanogels, electrospun nanofibers, and hybrid assemblies are analyzed with emphasis on structure–function relationships. Particular attention is given to how polymer selection governs mucoadhesion, degradability, release kinetics, cellular interaction, and compatibility with hydrophobic phytoconstituents. Across diverse biomedical contexts, encapsulation consistently alters exposure profiles and improves therapeutic indices relative to free oils, enhancing antimicrobial and antibiofilm performance, modulating inflammatory and oxidative pathways, promoting wound repair, and increasing selective cytotoxicity in cancer models. These effects are linked to improved physicochemical stabilization, controlled release behavior, and architecture-dependent cellular uptake mechanisms. Despite substantial progress, translational barriers remain, including limited long-term in vivo safety data, challenges in chemotype standardization, batch-to-batch variability, and constraints in GMP-compliant scale-up. Future development will depend on integrating rigorous quality control, scalable manufacturing technologies, and data-driven formulation design to establish clinically and industrially viable HEO-based nanotherapeutic systems.