Silver nanoparticles are frequently used to fight infections derived from multiresistent bacteria, however the toxicity to cells and hence the limited therapeutic window still restricts their application. In addition, the mechanism of silver-derived toxic and antimicrobial is to date not fully understood and furthermore, studies on the uptake of Ag nanoparticles by bacteria are rare.In this work, we used gold-silver alloy nanoparticles as alternative antimicrobial agents. The particles were fabricated by pulsed laser ablation in liquids, a technique which does not require any artificial organic stabilizers and hence may avoid potential toxic cross-effects from ligands.  We could show that the composition of the AgAu particles could be controlled by the composition of the ablated targets and the generated particles exhibited a fully homogeneous elemental distribution (probed by EDX line scans)  and a crystal structure identical to the used targets (determined by XRD) . In biological assays with oocytes, bacteria and human fibroblasts we found a non linear decrease of the antimicrobial activity with increasing gold molar fraction, probably attributed to an inhibition of silver dissolution from the nanoparticles by the more noble metal gold. Furthermore, we found that the cellular uptake of gold and silver nanoparticles by oocytes is material dependent. Consecutively, we studied the cellular uptake of AgAu alloy nanoparticles by the model bacterium S. aureus. Interestingly, we found only small particles inside the bacteria, however, these were<br/>significantly more silver rich than those originally exposed to the cell. Based on these findings we could conclude that these intracellular silver-rich particles were probably formed by dissolution and intracellular reduction of the silver ions.

How does nano-silver get inside bacteria? Mechanistic studies using AgAu alloy nanoparticles

2019 Spring National Meeting

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