Carboxylated β-Cyclodextrin-Based Drug-Loaded Nanodelivery System for the Control of Kiwifruit Soft Rot

Kiwifruit soft rot is one of the most destructive postharvest diseases, causing substantial economic losses during storage. In this study, carboxymethyl-β-cyclodextrin (CM-β-CD) nanospheres were synthesized through carboxymethylation with chloroacetic acid. Carvacrol (CAR) was subsequently incorporated into the nanospheres through impregnation to produce CAR@CM-β-CD. Scanning and transmission electron microscopy revealed that CAR@CM-β-CD predominantly formed spherical or quasi-spherical particles with relatively smooth surfaces. Dynamic light scattering analysis showed an average hydrodynamic diameter of 278.9 nm and a polydispersity index of 0.128. The formulation showed sustained release for 112 h, indicating favorable controlled-release performance. Thermogravimetric analysis showed that CAR@CM-β-CD in TGA was enhanced char residue at 800 °C, indicating improved high-temperature stability through carbonization. CAR@CM-β-CD exhibited improved but incomplete wettability and spreading on the tested surface. In vitro plate antifungal assays revealed strong antifungal activity, with a half-maximal effective concentration (EC 50 ) of 54.8 mg/L. The drug-loading (DL) capacity reached 13.46%. Cytocompatibility tests using human bronchial epithelial BEAS-2B cells showed high cell viability (> 81.59%) at 100 mg/L and a much lower apoptosis rate than carbendazim. Through morphological analyses and staining assays of the hyphae, we elucidated the antifungal mechanism of CAR@CM-β-CD. Collectively, these results suggest that CAR@CM-β-CD is a promising and effective controlled-release antimicrobial formulation for postharvest preservation of kiwifruit.