Multilayer encapsulation of bioactive terpenes for enhanced long-term biocidal performance.

Abstract

Effective encapsulation of active compounds depends on well-balanced interactions between the guest molecule and the host matrix, which determines loading efficiency, structural integrity, and release kinetics. This work reports the development of a novel hybrid material based on terpene/MCM-41/polycaprolactone (PCL) through a sequential multilayer encapsulation strategy. Menthol or thymol were loaded into MCM-41 mesopores and subsequently microencapsulated within PCL via electrospraying. The structural integrity, chemical stability, and long-term morphological aspect of the hybrid systems were evaluated by optical microscopy, scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). The multilayer encapsulation preserved structural stability over time, whereas control microcapsules containing thymol directly incorporated into PCL underwent progressive deformation and structural collapse. FTIR analysis of the carbonyl and hydroxyl stretching regions revealed -C=O···H-O- hydrogen bonding interactions confirming the molecular miscibility and plasticizing effect of free thymol within the PCL matrix. Microbiological assays against P. aeruginosa validated the long-term biocidal efficacy of the dual-barrier system.