Nanoencapsulation Enhances Stability, Release Behavior, and Antimicrobial Properties of Sage and Thyme Essential Oils

The increasing demand for natural bioactive compounds in agriculture, food preservation, and pharmaceuticals has highlighted the need for effective delivery systems to enhance their stability and bioavailability. In this study, we address this challenge by developing and characterizing silica hollow nanospheres (HNSs) and hollow polymer nanocapsules (HPNs) for the encapsulation of essential oils (EOs), specifically those derived from Thyme ( Thymus vulgaris ) and Sage ( Salvia officinalis ). The HNSs were synthesized using tetraethyl orthosilicate (TEOS) via a sol-gel process, while urea-formaldehyde HPNs (UF-HPNs) were fabricated through in-situ polymerization. The qualitative encapsulation efficiency, structural integrity, and release behavior of the EOs were analyzed using Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), and dynamic light scattering (DLS). The results demonstrated that HNSs, particularly those synthesized via in-situ techniques, exhibited superior size uniformity, higher oil loading capacity (4.18 mg/g), and controlled release performance over 102 days. Adsorption studies revealed that HNSs provided higher adsorption capabilities for Thyme EO, aligning with the Freundlich and Temkin isotherm models. Antimicrobial studies revealed that encapsulated Thyme EO exhibited strong antibacterial activity, with MIC values of 4 µL/mL against Escherichia coli ( E. coli ) and 2 µL/mL against Staphylococcus aureus ( S. aureus ), while Sage EO required higher concentrations, with MIC values of 8 µL/mL and 4 µL/mL, respectively. Notably, the encapsulation of Thyme EO in HNSs resulted in enhanced antimicrobial performance compared to HPNs, likely due to the porous silica matrix allowing for sustained EO release. The encapsulated EOs also modulated peroxidase enzyme activity, further supporting their potential for biological applications. These findings suggest that HNS-based encapsulation offers a robust and sustainable approach for enhancing the efficacy of natural antimicrobial agents, making them suitable for industrial applications in biopesticides, food safety, and therapeutic formulations.