Green-synthesised bimetallic nanomaterials: plant-derived solutions for antibacterial challenges

Background Nosocomial pneumonia caused by multidrug-resistant (MDR) respiratory pathogens remains a major threat to patient safety and hospital biosafety, necessitating the development of sustainable and effective antimicrobial alternatives. Objective This study aimed to synthesise and evaluate the antimicrobial efficacy of green-synthesised palladium–gold bimetallic nanoparticles (Pd–Au BMNPs) and their alginate-encapsulated nanocomposites against MDR respiratory pathogens. Methods Pd–Au BMNPs were synthesised by adopting an eco-friendly approach using aqueous ajwain leaf and clove extracts, followed by alginate encapsulation to form Pd–Au bimetallic alginate nanocomposites. Ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, dynamic light scattering, high-resolution transmission electron microscopy and high-resolution scanning electron microscopy were used to characterise the synthesised materials. Zone of inhibition and minimum inhibitory concentration assays were used to assess antibacterial activity against Streptococcus pneumoniae , Klebsiella pneumoniae , Acinetobacter baumannii , methicillin-resistant Staphylococcus aureus and Haemophilus parainfluenzae . One-way analysis of variance was used to determine statistical significance. Results Pd–Au BMNPs exhibited inhibition zones of 13–14 mm and showed dose-dependent activity, with >93% growth inhibition at 100 µg mL⁻1. Alginate nanocomposites retained comparable activity (11–14 mm). Statistical analysis confirmed significant effects ( p < 0.05). Conclusion Pd–Au nanomaterials demonstrate strong antimicrobial potential against MDR pathogens, supporting their application as biosafe antimicrobial agents, although further validation is required.