The opportunistic pathogen, Pseudomonas aeruginosa, uses different mechanisms as well as biofilm production to acquired antibiotic resistance. The polysaccharide synthesis locus (psl) genes play an important role in P. aeruginosa biofilm formation. Therefore, targeting the expression of psl genes can be a suitable strategy to prevent the formation of biofilms by antibiotic-resistant strains. Today, advances in nanotechnology provide a novel potential strategy to combat antibiotic-resistant bacteria. Here, the Ag nanoparticles (Ag NPs) synthesized using a chemical co-precipitation method and, after conjugation with thiosemicarbazide, their effect on the biofilm-forming ability studied in P. aeruginosa isolates. Chemical properties of synthesized nanoparticles determined by scanning and transmission electron microscopy (SEM and TEM), Fourier transform infrared spectroscopy (FTIR), Diffuse Reflectance Spectroscopy (DRS), X-ray diffraction (XRD), and energy dispersive X-Ray spectroscopy (EDS). The results confirmed the spherical/cubic morphology, solution stability, and good dispersion of Ag@Glu–TSC NPs with an average size of 40–60 nm. In addition, minimum inhibitory concentration (MIC) values of functionalized Ag NPs were at least 2-fold lower than the Ag NPs (alone). The quantitative PCR data analysis showed a decrease in the expression of the pslA gene in the presence of Ag@Glu–TSC NPs, up to 60% that was associated with a reduction of biofilm formation compared to control. In conclusion, the Ag@Glu–TSC NPs can be considered as a new inhibitor of biofilm production in antibiotic-resistant bacteria.
