Synthesis of Silver Nanoparticles Using Carica papaya Leaf Extract and Evaluation of Antibacterial Properties

Green synthesis of metallic nanoparticles using plant extracts represents an environmentally friendly alternative to conventional chemical and physical synthesis routes, offering reduced toxicity and lower production costs. This study reports the green synthesis of silver nanoparticles using aqueous leaf extract of Carica papaya and evaluates their antibacterial properties against common nosocomial pathogens. Papaya leaves were collected from home gardens in Abeokuta, Ogun State, South West Nigeria. The extract was prepared by aqueous maceration and mixed with silver nitrate solution at room temperature. Formation of silver nanoparticles was confirmed by the development of a brownish-yellow colouration and characterised using UV-visible spectrophotometry, X-ray diffraction, Fourier-transform infrared spectroscopy, and transmission electron microscopy. Antibacterial activity was assessed against Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae using the agar disc diffusion method, with ampicillin as a positive control. UV-vis spectra revealed a characteristic surface plasmon resonance peak at approximately 430 nanometres, and TEM imaging confirmed particle sizes in the range of 15 to 45 nanometres with predominantly spherical morphology. Significant antibacterial activity was observed against all tested organisms, with Staphylococcus aureus showing the highest susceptibility. The results demonstrate the feasibility of using Carica papaya extract as a bioreductant for nanoparticle synthesis with potential biomedical applications. Keywords: silver nanoparticles, green synthesis, Carica papaya, antibacterial activity, Ogun State