To overcome the limited environmental stability of carvacrol (CAR) and the lack of pathogen responsive behavior in conventional delivery systems, a pectin gated metal organic framework (MOF) nanocarrier (CAR@MOF@PEC) was developed to enable stabilized and enzyme-activated delivery of CAR through a degradable polysaccharide gatekeeper. The nanoparticles had a mean hydrodynamic diameter of 256 nm and a CAR loading of 6.8%. In vitro release studies revealed that pectinase increased the cumulative release rate by about 2-fold relative to an enzyme-free control, supporting an enzyme degradable gating barrier, and baseline release was also pH-dependent. CAR@MOF@PEC inhibited Xanthomonas oryzae pv. oryzae (Xoo) with an EC50 of 4.41 mg·L–1, lower than that of technical grade CAR at an equivalent CAR dose, whereas CAR soluble concentrate (CAR@SL) showed the lowest EC50. An agar diffusion assay further confirmed clear concentration dependent inhibition zones across formulations, supporting a consistent antibacterial phenotype. Rice seed germination and early seedling growth assays indicated no detectable phytotoxicity at the tested doses. In acute aquatic toxicity assays, CAR@MOF@PEC exhibited an LC50 of 47.68 mg·L–1 in zebrafish, at least 10-fold higher than that of CAR@SL. In cell assays, CAR@MOF@PEC produced significantly greater viability than CAR@SL, with apoptosis levels close to those of the baseline. These results demonstrate an enzyme gated nanomaterial platform that integrates porous MOFs with a polysaccharide gatekeeper to enable on demand release and an improved safety profile, supporting broader use of plant derived essential oils for antimicrobial applications.
Mo et al. (Tue,) studied this question.