Assessment of antimicrobial activity of hexagonal boron nitride nanoparticles and its impact on biomolecules

Abstract

The emergence of multidrug-resistant bacteria necessitates exploring alternative antimicrobial strategies, where nanomaterials offer a promising avenue due to their distinct mechanisms of action. Unlike antibiotics, which often induce resistance through various mechanisms, nanomaterials typically exert antibacterial effects via various non-specific mechanism. This study aimed to evaluate the significant antibacterial potential of boron nitride nanosheets (BNNS) and BN/TiO2 nanocomposites, particularly when combined with UV exposure. The results demonstrated that both BNNS and BN/TiO2 composites exhibited significant antibacterial activity, which was further enhanced to 3 log reduction when combined with UV light. Their performance was almost identical with each other but superior to individual BN and TiO2. When applied by spraying onto contaminated PPE surfaces, the efficiency of BNNS solution was almost 80%. TEM analysis revealed that the synthesized BNNS possessed a sheet-like structure with high crystallinity. However, some degree of agglomeration was observed, which could have potentially reduced the material's antibacterial effectiveness by limiting the available surface area. The presence of both BN and TiO2 phases in the XRD pattern confirmed the successful synthesis of the BN/TiO2 nanocomposite. From the Tauc plot, the band gap energy of the composite was determined to be 3.10 eV, which is lower than the bandgap energy of BN and TiO2, indicating the possible enhancement in ROS generation upon UV exposure. The study further revealed effective disruption of essential bacterial components, including DNA, proteins, and amino acids, leading to bacterial death. The Bradford Assay indicated that BNNS and BN/TiO2 alone reduced the protein concentration in E. coli by 20%. The reduction was more pronounced (almost 50%) when the nanomaterials were combined with UV light, suggesting a synergistic effect facilitated by ROS generation. Additionally, BNNS and BN/TiO2 treatments, particularly when combined with UV light, disrupted the amino acid profile of E. coli, causing degradation of several amino acids including threonine, lysine, histidine and phenylalanine. This indicates that oxidative stress induced by ROS plays a crucial role in their antibacterial mechanism. Agarose gel electrophoresis revealed significant DNA fragmentation in E. coli treated with BNNS and BN/TiO2, especially under UV light.