Synthesis, characterization and evaluation of ZIF-8/CMC composites loaded with eugenol for sustained antimicrobial activity

Abstract

Past efforts to synthesize antimicrobial materials have relied on the antibacterial effects of metal and metal oxide nanoparticles, proving costly and raising concerns about unexplored health implications. In this study, a Zn-based metal organic framework (ZIF-8) was synthesized hydrothermally (at 18 °C and 75 °C). This ZIF-8 was characterized using various techniques, including SEM, EDS, Raman, FTIR, XRD, and TGA, before being incorporated into a cellulose matrix along with eugenol to modify the composite’s antimicrobial properties. The effect of ZIF-8 loading on the cellulose composite’s properties was studied, varying concentrations of zinc salt during synthesis. ZIF-8 was successfully embedded onto the cellulose surface, with dense coverage of ZIF-8 particles. The results demonstrated that eugenol’s incorporation into the ZIF-8-cellulose composite significantly enhanced its antimicrobial properties. Optimized composites (with 3% eugenol and 13.13% Zn(NO₃)₂ loading during MOF synthesis) produced inhibition halos of 29.97 mm against E. coli and 27.59 mm against S. aureus. MIC values for S. aureus were 64 µg/mL (with or without eugenol). For E. coli, the MIC was 128 µg/mL without eugenol, decreasing to 64 µg/mL with eugenol. The MBC for the composite without eugenol was 1024 µg/mL for both bacteria, dramatically dropping to 128 µg/mL with eugenol. Eugenol release showed a rapid initial burst followed by sustained, diffusion-controlled kinetics. This effect was attributed to the synergistic action of eugenol and the ZnO moieties present in the ZIF-8 structure and the cellulose matrix. The study highlights the potential of ZIF-8-based composite materials for various antimicrobial applications.