Inhibitory effect of organometallic framework composite nanomaterial ZIF8@ZIF67 on different pathogenic microorganisms of silkworms

The domestic silkworm (Bombyx mori) is of considerable economic importance, but is highly susceptible to various pathogens, which leads to substantial losses in sericulture. Nanomaterials, particularly metal-organic frameworks (MOFs), have shown promise in antibacterial applications due to their broad-spectrum activity and low toxicity. This study presented the synthesis, characterization, and antibacterial evaluation of MOF-based nanomaterials, specifically ZIF8, ZIF67, and their composite ZIF8@ZIF67, for their potential as antibacterial agents against silkworm pathogens. Our findings revealed that the composite material ZIF8@ZIF67 demonstrates better antibacterial efficacy against Bacillus cereus and Serratia marcescens in vitro than pristine ZIF8 and ZIF67, with minimal inhibitory concentrations of 2.5 μg/mL and 3.0 μg/mL, respectively. Furthermore, cytotoxicity assays indicate that neither ZIF8 at 100 μg/mL nor ZIF67 and ZIF8@ZIF67 at 200 μg/mL adversely affected the viability of BmN cells. At the same time, under these concentrations, the proliferation of Nosema bombycis at both 48 h and 72 h post-infection was significantly inhibited. Moreover, supplementation of 300 μg/g ZIF8@ZIF67 to silkworm larvae significantly enhanced their survival rates upon infection with the bacteria above without adversely affecting silkworm growth or cocoon weight. The underlying mechanisms of action may include disruption of bacterial cell membranes, induction of oxidative stress via generation of reactive oxygen species (ROS), and initiation of apoptosis. The biocompatibility and non-toxicity of ZIF8@ZIF67 and its antibacterial efficacy suggest its potential as a safe and effective agent for silkworm disease control. Conclusively, our research offers important insights for advancing MOFs-based nanomaterials for potential antibacterial treatment in silkworms or other insects.