Ionic Content Reduction and Aspect Ratio Control in Nanoconfined Silver Citrate Nanoparticles through Redox Decomposition

Safety applications of silver-based biomaterials remain a challenge due to chemical instability and uncontrolled ion release. In this study, silver citrate nanorods (Ag-Cit) have been synthesized as a synergistic formulation from citrate and silver, reducing agglomeration. However, reaction time and chemical decomposition influence the final product, making it essential to examine how the composite evolves at each synthesis time. To address this, Ag-Cit through different time reaction was synthetised to determine the best ionic reduction and antibacterial effectiveness stage. Sodium citrate method reaction at a constant low temperature (60 °C) was used to prepare 5 samples with reaction times ranging from 1 to 5 h. The resulting colloidal solutions transitioned from yellowish to brownish in color. Each sample was characterized using XRD/DSC/TEM, DLS/SEM/UV-vis, FTIR, and XPS/EPM to assess physical and chemical changes. Antimicrobial activity was evaluated using the method of antibiotic assay disk and time-kill curve assays. Results showed that the 5 h sample exhibited enhanced crystallinity and aspect ratio, despite reduced particle size, achieving over 50% silver ion reduction, and electrical neutrality. Both, bacteriostatic (ZOI) and bactericidal (time-kill curve) activities against E. coli and S. aureus were strongest in the 1 h (larger size) and 5 h (higher aspect ratio) samples. Brown coloration indicated optimal stability of the Ag-Cit compound. This study provides valuable insights for developing low ionic content antimicrobial materials based on Ag-Cit compounds.