Assessment of olive leaf extract–mediated chitosan–silver nanocomposites as antibacterial and biocorrosion mitigation agents

A chitosan (CHT)–Ag nanocomposite was prepared using olive leaf extract (OLE) as the reducing and capping agent and AgNO₃ as the precursor. Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (TEM), field emission scanning electron microscopy, X-ray diffraction (XRD), ultraviolet-visible (UV–Vis) spectrophotometry, and energy-dispersive X-ray spectroscopy (EDS) were used to characterize the OLE-mediated chitosan–Ag nanocomposites. The TEM results indicate that the CHT–Ag nanocomposites are spherical and range in diameter from 3.7 to 18.1 nm. The Ag nanoparticles in the nanocomposites are crystalline, as confirmed by XRD and TEM. The Ag nanoparticles are polydispersed in the chitosan matrix and are very stable. The zeta potential of the CHT–Ag nanocomposites fluctuates with pH; the maximum value (+ 50 mV) was achieved at pH 2. The antibacterial activity of the CHT–Ag nanocomposite was tested against gram-positive (B. licheniformis, B. cereus, S. haemolyticus, M. luteus) and gram-negative (E. coli, P. citronellolis, P. aeruginosa, Sphingobacterium sp., B. japonicum, and R. pickettii) bacteria using cup plating. Significant inhibition was reported against the tested bacteria strains. Compared to amoxicillin and ciprofloxacin, the OLE-mediated CHT–Ag nanocomposite inhibits all bacteria strains with MIC and MBC concentrations ranging from 0.001 to 0.1%. S. haemolyticus and P. aeruginosa were unaffected by amoxicillin and ciprofloxacin. In addition, the CHT–Ag nanocomposite prevents the growth of sulfate-reducing bacteria (SRB) and the biocorrosion of steel coupons. The order of biocorrosion mitigation efficacy is CHT_2.0–Ag (88.87%) > CHT_1.0–Ag (67.74%) > CHT_0.5–Ag (51.51%). The CHT–Ag nanocomposites have lower values than QUATS (93.58%), a known biocide. The CHT–Ag nanocomposites exhibit promising antibacterial and biocorrosion-mitigating properties, making them a potential antibacterial agent for biomedical and packaging applications. Graphical abstract: (Figure presented.).