Effect of Capping Agent and Diffusivity of Different Silver Nanoparticles on Their Antibacterial Properties

The effect of stabilizing agent on antimicrobial properties and diffusivity of silver nanoparticles (AgNPs) are not well-known. The objective of this work was to study the effect of diffusivity of AgNPs synthesized with different capping agents, on their antimicrobial properties, in order to advance in the modeling, mechanistic description and development of nanostructured antimicrobial agents. For that, AgNPs were synthesized and characterized using different stabilizing agents (citrate, N-methyl-D-glucamine, cysteine, cysteamine). Later, AgNPs synthesized with cysteine and cysteamine were functionalized with poly(allyl chloride) and added to PVC as model of biomedical material. Antibacterial tests were performed using Tryptic Soy Broth as liquid phase. Simulation was based in the determination of diffusion coefficients, the progressive viscosity changes using poly(ethylene glycol) solutions as model and average viscosity data of growth medium, artificial phospholipid bilayer and cytoplasm reported in the literature. Nature of capping agent affects the antimicrobial activity of AgNPs. For stabilizing substances and AgNPs the antimicrobial activity decreases in the following order: cysa > PClA > AgNPs-cit = AgNPs-cysa > nmdg > PVC > AgNPs-cys > AgNPs-nmdg > cys. Changes in the antimicrobial properties were associated mainly to size and size distribution depending of stabilizing capacity, interparticle interaction as a result of functional groups on structure of capping agent, as well as, changes in the diffusion coefficient (AgNPs size is directly related with the nature of capping agent, affecting of this way their mobility).