Iris kashmiriana Mediated Synthesis of Gold Nanoparticles: Characterization and Its Antibacterial Implications on Dental Appliances

In this study, we have synthesized gold nanoparticles (AuNPs) employing a green synthesis method using Iris kashmiriana rhizome extract. The physicochemical characterization of the as-synthesized nanoparticles was done by UV–visible spectroscopy, DLS, zeta potential analyzer, FTIR spectroscopy, and electron microscopy (TEM and SEM). The antimicrobial properties of as-synthesized AuNPs against Gram-positive and Gram-negative bacteria were evaluated by the Minimum Inhibitory Concentration (MIC) and agar well diffusion assays. After that, we performed the live/dead assay, reactive oxygen species (ROS) assay, antibiofilm, and anti-adherence assays. In UV–visible absorption spectra, a noticeable peak was observed at 585 nm, which confirmed the synthesis of AuNPs. The nanoparticles were approximately 80 nm in size and spherical in shape, as revealed from TEM and SEM analyses. The as-synthesized nanoparticles displayed potent antimicrobial properties, as was evident from their MIC and agar well diffusion assays against various bacterial isolates, viz. E. coli , S. aureus , P. aeruginosa , and S. mutans . Their ability to kill bacteria was confirmed from the results of live/dead assay. The results of the ROS assay were affirmative, substantiating it to be their mechanism of action. We also found that these nanoparticles possessed antibiofilm and anti-adherence properties. To leverage this aspect of the nanoparticles, we chose S. mutans for the further experimentation and application part of our study. S. mutans is the causative agent of dental caries and tooth decay. We evaluated the antibacterial potential of as-formed AuNPs on dental appliances (like orthodontic wires and brackets). The topography of the AuNP-coated and uncoated orthodontic wires was also analyzed by scanning electron microscopy (SEM). We concluded from the experimental results that the as-formed AuNPs possessing antimicrobial, antibiofilm, and anti-adherence properties inhibit the prevalence and growth of bacteria on and around the dental appliances coated with the nanoparticles. These characteristics of the as-synthesized nanoparticles can be further explored and validated for clinical use.