Gum-Assisted Magnesium Oxide Nanoparticles Using Guar Extract Focusing on Their Bioactivities

The study aims to fabricate eco-friendly, biogenic magnesium oxide nanoparticles (MgO NPs) mediated by ethanol-guar gum extract, which acts as both a reducing and coating/stabilizing agent. The prepared MgO NPs were first synthesized and characterized by various analytical techniques, including UV-visible, FTIR spectroscopy, SEM-energy-dispersive X-ray spectroscopy (EDS) mapping, and X-ray diffraction (XRD) crystallography. Bioactivity studies included antibacterial studies focusing on the inhibition of a dental caries-causing pathogen, Enterococcus faecalis, by MIC, MBC, well diffusion (WD) agar, antibiofilm, and time-kill (TK) assays. Furthermore, the antioxidant activity and cytotoxicity of MgO NPs were examined. A bacterial adherence study was conducted as the main aim by exposing the bacteria to human teeth in vitro. Findings demonstrated that biogenic MgO NPs were successfully synthesized with flaky morphologies, with an average size of 20-30 nm and the desired purity. FTIR showed possible functional groups, confirming the involvement of guar metabolites in NP formation. The XRD pattern elucidated the crystalline phase of MgO NPs to be a cubic (FCC) periclase structure with a crystallite size of 16.5 nm. Antibacterial experiments showed that MgO NPs had a moderate effect on Enterococcus faecalis, with MIC and MBC of 32 and 64 µg/mL, respectively. In contrast, chlorhexidine (CHX), doxycycline (Dox), and sodium hypochlorite (NaClO) were more effective, while the guar extract showed the weakest inhibition; additionally, antibiofilm assessments were followed by antibacterial outcomes. However, cytotoxicity studies exhibited the least toxicity for MgO NPs compared with other compounds. The dental adherence test also showed that MgO NPs can inhibit bacterial interactions with the dental surface without inhibiting bacterial growth at sub-MIC concentrations. Meanwhile, other groups killed them rapidly before they could adhere to teeth. Here, biocompatibility and long-term antibacterial effectiveness were advantages of biogenic MgO NPs over other compounds that have been shown to be toxic to the host over long-term consumption. Therefore, guar extract-mediated MgO NPs demonstrated that they can be a favorable alternative for biofilm control in dental health without toxicity to related tissues in the oral cavity.