Development of an Ionic Liquid@Metal-Based Nanocomposite-Loaded Hierarchical Hydrophobic Surface to the Aluminum Substrate for Antibacterial Properties

Designing biomaterials and substrates possessing antibacterial properties is a growing field nowadays. In this context, we have developed benzimidazolium ionic liquids ILs-1­(a–d)-based metal hybrid nanocomposites using various metals such as silver (Ag), gold (Au), and copper (Cu), which were fully characterized by various techniques. Their morphology, elemental composition, crystallinity, and size were studied by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, powder X-ray diffraction, and dynamic light scattering, respectively. Further, the prepared ionic liquids ILs-1­(a–d) and ionic liquid@metal composites were screened for their antibacterial potential against Gram-positive and Gram-negative pathogenic microorganisms via the colony forming unit assay, and their minimum inhibitory concentrations (MICs) were also evaluated. The results obtained from preliminary antibacterial screening demonstrated that these ionic liquid@metal nanocomposites IL-1d@M (M = Ag, Cu, and Au) exhibited potent antibacterial activity in comparison to the ionic liquids ILs-1­(a–d). In particular, the ionic liquid@silver nanocomposites (IL-1d@Ag) showed the most potent activity against both E. coli and S. aureus bacterial strains with MIC = 12 ± 2 and 08 ± 2 μg/mL, respectively. The mechanism of action for antibacterial activity of IL-1d@Ag nanocomposites was investigated through generation of 1O2 (ROS), whereas the morphology of treated pathogenic bacteria was examined through atomic force microscopy and SEM. Furthermore, to utilize this developed material IL-1d@Ag in biomedical applications, the prepared ionic liquid material was fabricated onto a microstructured aluminum (Al) substrate with hierarchically arranged functionalities, and the modified surface was characterized and also evaluated for antibacterial activity. Moreover, the hydrophobicity of the material coated onto the Al substrate was also measured by static water contact angle measurement, which reveals its improved hydrophobic character. Thus, the developed hierarchical hydrophobic coating material possessing long-term antibacterial activity on an Al substrate may minimize the wetting by biological secretions and also prevent the substrate from corrosion.