Department for Advanced Materials and Structures, Centre de Recherche Public Henri Tudor, 66 rue de Luxembourg, L-4002 Esch-sur-Alzette, Luxembourg.
J Colloid Interface Sci. 2011 Dec 15;364(2):359-65. doi: 10.1016/j.jcis.2011.08.038. Epub 2011 Sep 6.
Dopamine-melanin films produced through the oxidation of dopamine in the presence of oxygen as an oxidant allow to reduce silver ions onto silver particles as already described in the paper by Lee et al. (H. Lee, S.M. Dellatore, W.M. Miller, P.B. Messersmith, Science 318 (2007) 426.). This reduction process has to occur through the oxidation of moieties present in the melanin film. This investigation shows that the free radicals present in the pseudomelanin film, quantified by means of electron spin resonance spectroscopy (ESR) for the first time, are not used in the transformation of Ag(+) cations to deposit silver. The ESR signal is hardly affected by the deposition of silver particles. On the other hand, X-ray photoelectron spectroscopy shows a small increase in the density of quinone groups and a small decrease of catechol groups on the surface of the film during the deposition of silver. This suggests that the deposited pseudomelanin films contain a significant fraction of catechol groups able to trigger reduction processes of metallic cations. These silver nanoparticles remain adherent to the melanin films and allow for a quantitative killing of Escherichia coli over a broad range of bacterial dilutions. However, the presence of the bacteria induces a release of the nanoparticles. The pseudomelanin films cannot be reused again for a silver ion reduction step. Nevertheless, the easy preparation of the pseudomelanin-silver composite and its effective one shot bacterial killing activity renders the strategy presented in this paper attractive. Some fundamental questions about redox process allowed by the pseudomelanin films will also be asked.
通过多巴胺在氧气存在下的氧化产生的多巴胺-黑色素膜允许将银离子还原到银颗粒上，正如 Lee 等人在论文中已经描述的那样。（H. Lee、S.M. Dellatore、W.M. Miller、P.B. Messersmith，Science 318（2007）426.）。这个还原过程必须通过黑色素膜中存在的部分的氧化来发生。这项研究表明，通过电子自旋共振光谱（ESR）首次定量的假黑色素膜中的自由基，不会用于将 Ag（+）阳离子转化为银的沉积。ESR 信号几乎不受银颗粒沉积的影响。另一方面，X 射线光电子能谱显示，在银沉积过程中，膜表面的醌基团密度略有增加，儿茶酚基团略有减少。这表明沉积的假黑色素膜含有能够引发金属阳离子还原过程的大量儿茶酚基团。这些银纳米颗粒仍然附着在黑色素膜上，并允许在广泛的细菌稀释范围内定量杀死大肠杆菌。然而，细菌的存在会诱导纳米颗粒的释放。黑色素膜不能再次重复用于银离子还原步骤。尽管如此，由于假黑色素-银复合材料的制备简单且具有有效的一次性杀菌活性，使得本文提出的策略具有吸引力。还将提出一些关于假黑色素膜允许的氧化还原过程的基本问题。
