120: Inhibitory Effects of Metal-Doped-ZIF-8 Nanoparticles Coated by Hyaluronic Acid Nanoparticles Against Listeria Monocytogenes Biofilms on Stainless Steel and Polyurethane Surfaces

Introduction

Listeria monocytogenes represents a critical hazard in food processing facilities. Advanced strategies that inhibit biofilm formation and promote effective removal are essential for mitigating these risks.

Methods

64.4 mmol C4H6N2 and the mixture of 1.96 mmol Zn(NO3)2.6H2O and 0.84 mmol Cu(NO3)2, (for Cu-ZIF-8), or AgNO3 (for Ag-ZIF-8), respectively, were dissolved in 1.4x103 mmol methanol, in an Erlenmeyer flask. The solutions were poured together and stirred for 24 h at 21°C until dissolved. The mixture was centrifuged at 4500 rpm for 15 min to recover the solid, washed three times with methanol, dried overnight at 80°C, and collected as Cu-ZIF-8 and Ag-ZIF-8 nanoparticles. Nanoparticles were suspended in HA at 1:1 ratio (mg/ml), vortexed until fully dispersed, and collected by centrifugation and washing three times with deionized water. Prior to use, L. monocytogenes culture was activated in TSB by transferring and incubating aerobically for 24 h at 37°C. A single colony was transferred to TSA slant and incubated for 24 h at 37°C then stored at 4°C. AISI 304 stainless steel and polyurethane sheet coupons were placed in 100 mm sterile petri dishes, 30 mL of 109 -log CFU/mL adjusted L. monocytogenes suspended in TSB added on the dishes and incubated for 24 h at 37°C for bacterial attachment and biofilm formation. Antibacterial activity was determined by disk diffusion test, minimum inhibitory (MIC) and minimum bactericidal concentrations (MBC).

Results

Disk diffusion test revealed that Ag-ZIF-8@HA exhibited the largest inhibition zones (17.14 ± 1.33 mm). MIC and MBC results confirmed that Ag-ZIF-8@HA required the lowest concentrations to inhibit bacteria, followed by Cu-ZIF-8@HA and Ag-ZIF-8, while Cu-ZIF-8 was least effective. Incorporation of Cu-ZIF-8 and Ag-ZIF-8 into hyaluronic acid amplifies the antimicrobial properties by targeting bacterial cell membranes and disrupting metabolic functions. This dual-functional system not only inhibits the growth of bacteria, but also benefits from the hydrophilic nature of hyaluronic acid, which aids in biofilm prevention by reducing bacterial adhesion.

Significance

Results underscore the enhanced antibacterial properties of nanoparticles coated by HA, especially with Ag-ZIF-8, due to the synergistic effect of Ag+ complemented by the anti-adhesive and diffusion enhancing properties of hyaluronic acid.

Authors: Huy Loc Nguyen, Rosana G. Moreira, M. Elena Castell-Perz