Biocompatible chitosan-coated polydatin@ZIF-8 MOF nanostructures: synthesis, drug delivery and enhanced antibacterial properties.

Zeolitic imidazolate framework-8 (ZIF-8) is a promising nanocarrier for drug delivery due to its tunable porosity, biocompatibility, and pH sensitivity. In this study, a one-pot room-temperature synthesis strategy was developed to encapsulate polydatin (PD) within ZIF-8 (PD@ZIF-8), followed by chitosan (CS) coating (PD@ZIF-8/CS) for improved stability and sustained release of this drug delivery system. FTIR, UV-vis, XRD, DLS and TGA characterization confirmed the successful synthesis of PD@ZIF-8/CS. SEM micrographs revealed the rhombic dodecahedral particles (85.2 nm) of ZIF-8, slightly roughened polyhedral particles (115.4 nm) of PD@ZIF-8 and aggregated particles (294.8 nm) of PD@ZIF-8/CS, confirming CS shell formation. DLS analysis showed hydrodynamic diameters of 99.3 ± 2.1 nm, 112.8 ± 3.4 nm, and 251.7 ± 4.6 nm for ZIF-8, PD@ZIF-8 and PD@ZIF-8/CS, respectively, with the zeta potential shifting from +12.6 to -3.9 mV after CS coating. The PD@ZIF-8 system achieved an outstanding drug-loading efficiency (91.34%) and exhibited pH-dependent release, reaching 92.5% release at pH 5.0 and 37 °C within 72 h, while the CS coating reduced the burst release by ∼35% and prolonged t 0 from 18.4 h to 38.6 h, following the Korsmeyer-Peppas model (R 2 = 0.991). The PD@ZIF-8/CS composite displayed potent antibacterial activity (inhibition zones: 24.6 ± 0.4 mm for S. aureus and 21.2 ± 0.3 mm for E. coli; MIC: 6.25 µg mL-1), demonstrating a synergistic effect of PD, ZIF-8 and CS. These findings indicate that PD@ZIF-8/CS is a strong and pH-sensitive nanoplatform that can selectively release the drug in the acidic microenvironment of infection sites, suggesting its potential utility as an antibacterial nanoplatform, pending further biological validation.