Antioxidant and Antibacterial Potential of Silver and Cerium Oxide Nanoparticles Biosynthesized Utilizing Chitosan Derived From Crab ( <i>Portunus sanguinolentus</i> ) Shell Waste

ABSTRACT This study focused to compare the synthesis, characterization and antibacterial, and antioxidant efficacy of chitosan‐mediated silver (Ag) and cerium oxide (CeO 2 ) nanoparticles (NPs) from marine biowaste of Portunus sanguinolentus . The Ag and CeO 2 NPs were synthesized and preliminarily characterized by microscopic and spectroscopic techniques, which revealed chitosan‐assisted Ag and CeO 2 NPs were mostly spherical and irregular in form, respectively. Findings of the NPs for their effectiveness in combating bacteria: chitosan‐assisted Ag and CeO 2 NPs exhibited excellent activity against Bacillus subtilis (23.3 ± 0.28 and 15.2 ± 0.19 mm) followed by Klebsiella pneumoniae (20.3 ± 0.11 and 18.5 ± 0.28 mm), respectively. The findings of in vitro antioxidant activity revealed that chitosan‐mediated NPs possess significant reducing power and hydroxyl radical scavenging properties; the concentration was raised to 125 µg/mL, and the scavenging capacity of Ag NPs improved drastically to 63.8% and 58.7%, for CeO 2 NPs. The findings of chitosan‐mediated Ag and CeO 2 NPs derived using crab's shell waste reveal that they possess a potential effect on bacterial infections and free radicals.