Synthesis and Characterization of Zinc Oxide Nanoparticles Functionalized with Ellagic Acid: Antibacterial and Antibiofilm Properties and Effect on the Expression of Biofilm Related Genes in Pseudomonas aeruginosa

Biofilm formation contributes to drug-resistant phenotype in P. aeruginosa. In patients with cystic fibrosis, the biofilm made by P. aeruginosa, which is mainly alginate, causes resistance to phagocytosis, as well as increased antibiotic resistance and chronicity of the disease. This work aimed to synthesize Zinc oxide nanoparticles (NPs) functionalized with (3-Chloropropyl) trimethoxysilane (CPTMS) and conjugated with ellagic acid (EA) (ZnO@CPTMS-EA NPs) and characterize their effects on P. aeruginosa growth and expression of some biofilm-related genes. Planktonic growth inhibition was investigated by broth microdilution method, and the antibiofilm property was evaluated by crystal violet staining assay. The effects of ZnO@CPTMS-EA NPs on the expression of the algD, pelA and pslA genes were studied by real-time PCR assay. The synthesized ZnO@CPTMS-EA NPs were spherical, in a size range of 17-35 nm and with Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray diffraction (XRD) characterization that indicated correct synthesis of the particles. The zeta potential and Dynamic Light Scattering (DLS) size of the particles were - 14.1 mV and 191 nm, respectively and the particles showed thermal stability at temperatures up to 200 degrees C. The minimum inhibitory concentration of ZnO and EA for P. aeruginosa strains was 3.75 mg/mL, while ZnO@CPTMS-EA NPs inhibited bacterial growth at 0.11 mg/mL. Treatment of clinical P. aeruginosa with EA and ZnO NPs reduced biofilm formation to 92.2 and 58.0%, respectively, while treatment with ZnO@CPTMS-EA NPs decreased biofilm formation to 48.5%. Real-time PCR showed that treatment of clinical P. aeruginosa strains with ZnO@CPTMS-EA NPs significantly reduced the expression of the algD, pelA and pslA to 0.43, 0.57 and 0.60 folds, respectively, which were significantly lower than in EA-treated bacteria. This work reports antibiofilm properties of ZnO@CPTMS-EA NPs, which can be largely used to prevent nosocomial infections caused by P. aeruginosa in the disinfection of hospital instruments and equipment.