Synthesis, Characterisation, and Antibacterial Evaluation of Silver Nanoparticles Stabilised by Cassava Starch Matrix

The combination of silver nanoparticles with biopolymer matrices offers a dual advantage of antimicrobial activity and controlled stabilisation, and the use of cassava starch as a locally available, inexpensive, and biodegradable matrix material is particularly relevant to the Nigerian context where cassava is the dominant starchy staple crop. This study synthesised silver nanoparticles within a cassava starch matrix using silver nitrate as the metal precursor and cassava starch extract as both reducing and capping agent, eliminating the need for external chemical reducing agents. The effect of synthesis parameters including starch concentration, silver nitrate concentration, temperature, and pH on nanoparticle formation and properties was investigated. Characterisation was performed by ultraviolet-visible spectroscopy, X-ray diffraction, transmission electron microscopy, selected area electron diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, and dynamic light scattering. Antibacterial activity was evaluated against Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, and methicillin-resistant Staphylococcus aureus. The surface plasmon resonance peak at 415 nm confirmed nanoparticle formation. Transmission electron microscopy revealed spherical particles with an average diameter of 12 nm and narrow size distribution. Minimum inhibitory concentrations ranged from 3.1 to 25 micrograms per millilitre, with methicillin-resistant Staphylococcus aureus showing the greatest susceptibility at 3.1 micrograms per millilitre. The starch-nanocomposite film demonstrated sustained antibacterial activity over 72 hours in disk diffusion assays. These results establish a low-cost, green synthesis route for antimicrobial silver nanocomposites with practical applications in food packaging, wound dressing, and surface coating materials relevant to the Nigerian manufacturing context.

Keywords: silver nanoparticles, cassava starch, green synthesis, antibacterial activity, nanocomposite