Browsing by Author "Naumih Noah"

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    A Comparative Evaluation of Antibacterial Activity of Metallic Nanoparticle Formulations Synthesized Using a Poly(amic) Acid
    (sage journal, 2025-11-06) Obumba, Maxwell; Naumih Noah; Nawiri,Mildred
    Water is considered one of the most abundant natural resources, covering the largest proportion of the Earth’s total surface. The availability of clean and safe water for domestic use, however, remains the most important scientific and technological challenge facing humanity presently. Disposal of human organic waste containing large volumes of deadly microbes, including Streptococcus aureus and Escherichia coli, has been cited as the major cause of water pollution and contamination. The increasing prevalence of these antibiotic-resistant pathogens in major water sources presents a critical challenge to public and environmental sustainability. Addressing this challenge calls for the development of novel, effective antimicrobial agents. This study reports the effect of synthesis temperature on the particle size and dispersion, which in turn influence the antimicrobial activity of silver (Ag), gold (Au), and bimetallic silver/gold (Ag/Au) nanoparticles synthesized and stabilized with a biodegradable poly(amic) acid PAA-polymer against S. aureus and E. coli. The synthesis of the different nanoparticle formulations was carried out in two different sets of temperatures: ambient (25 °C) and elevated temperatures (70 °C). The elevated temperature was kept at 70 °C to minimize imidization of PAA to polyimides, a process which occurs at temperatures above 100 °C. This ensured that the stability and structural integrity of PAA were preserved throughout the synthesis process. Nanoparticles synthesized at both ambient and elevated temperatures were characterized by cyclic voltammetry, ultraviolet–visible spectroscopy, and transmission electron microscopy. The results revealed spherical particles sized between 25 and 58 nm, with elevated temperatures yielding smaller, more uniformly dispersed nanoparticles. Elevated temperatures exhibited enhanced antibacterial activity against E. coli and S. aureus using disk diffusion assays. A higher antimicrobial activity exhibited by the bimetallic Ag/Au nanoparticles synthesized at elevated temperatures (Ag/Au NPs-HT) showed superior inhibition zone against E. coli (27.67 ± 1.53 mm) and S. aureus (23.67 ± 0.58 mm), outperforming their counterparts synthesized at ambient temperature (p = 0.0088; for E. coli) and all monometallic nanoparticles (p < 0.0001 for both S. aureus and E. coli). Statistically, Ag/Au NPs-HT exhibited a stronger antimicrobial activity as compared to Vancomycin, a commercial clinical antibiotic against both S. aureus (p < 0.0007) and E. coli (p < 0.0007). These findings highlight a synergistic effect when combining silver and gold and underscore synthesis temperatures as a crucial factor in optimizing the antimicrobial performance of Nobel metal nanoparticles, with potential application in environmentally sustainable and cost-effective water purification systems.