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

Abstract

Herbal essential oils (HEOs) exhibit potent antimicrobial, anti-inflammatory, antioxi-dant, and anticancer properties, yet their biomedical translation remains constrained by high volatility, poor aqueous solubility, rapid degradation, and chemical variabil-ity. This review provides a critical synthesis of advances in polymer-based nanoen-capsulation-encompassing nanospheres, nanoemulsions, hydrogels/nanogels, elec-trospun nanofibers, and hybrid systems-as a strategy to stabilize HEOs, enhance bio-availability, and enable controlled or targeted release. Polymer selection (e.g., chitosan, PLGA, alginate, PEG, gelatin) is examined in relation to mucoadhesive behavior, bio-degradability, release kinetics, and compatibility with hydrophobic phytoconstituents. Key findings demonstrate that nanoencapsulated HEOs consistently outperform free oils across multiple biomedical applications, including enhanced antimicrobial and an-ti-biofilm efficacy, improved antiinflammatory and antioxidant responses, accelerated wound healing, and greater selective cytotoxicity in cancer models through apoptotic and oxidative stress-mediated mechanisms. Mechanistic insights link these outcomes to improved cellular uptake, physicochemical stabilization, and synergistic interactions between polymer matrices and HEO constituents. Despite these advances, major translational challenges persist, including limited in vivo safety data, difficulties in standardizing natural oil chemotypes, batch-to-batch variability, and significant barri-ers to GMP-compliant scale-up.Emerging opportunities such as smart responsive nanocarriers, 3D-printed biomedical constructs, and AI-guided formulation optimiza-tion offer promising paths toward clinically realizable HEO-based nanotherapeutics.