No abstract

The rapid emergence of drug-resistant bacteria and fungi poses a threat for healthcare worldwide. The development of novel effective small molecule therapeutic strategies in this space has remained challenging. Therefore, one orthogonal approach is to explore biomaterials with physical modes of action that have the potential to generate antimicrobial activity and, in some cases, even prevent antimicrobial resistance. Here, to this effect, we describe an approach for forming silk-based films that contain embedded selenium nanoparticles. We show that these materials exhibit both antibacterial and antifungal properties while crucially also remaining highly biocompatible and noncytotoxic toward mammalian cells. By incorporating the nanoparticles into silk films, the protein scaffold acts in a 2-fold manner; it protects the mammalian cells from the cytotoxic effects of the bare nanoparticles, while also providing a template for bacterial and fungal eradication. A range of hybrid inorganic/organic films were produced and an optimum concentration was found, which allowed for both high bacterial and fungal death while also exhibiting low mammalian cell cytotoxicity. Such films can thus pave the way for next-generation antimicrobial materials for applications such as wound healing and as agents against topical infections, with the added benefit that bacteria and fungi are unlikely to develop antimicrobial resistance to these hybrid materials.

The reduction of seleno-L-cystine is examined on gold and platinum electrodes in aqueous solution. The voltammetric behavior is indicative of a two-step process, in which the metallic substrate is modified by the diselenide analyte prior to observation of diffusionally controlled, proton-coupled electron transfer. X-ray photoelectron spectroscopy confirms the presence of selenium on gold foil samples that have been reductively cycled in selenocystine solution. The selenium-based surface modification, which is accessible through multiple preparation routes, can be removed by anodic stripping and fully restored through subsequent cycling. The described electrochemical approach allows for the analysis of redox-active chalcogen-containing species under physiologically relevant conditions. Results and Discussion Voltammetric Behavior of Seleno-L-cystine on GoldThe voltammetric response of selenocystine on gold features a quasi-reversible redox couple centered at À486 mV vs. Ag/ AgCl. [10] Figure 1 shows a comparison of cyclic voltammograms recorded for increasing selenocystine concentrations (0.2-2 mM) in phosphate buffered saline (PBS, pH 7). For each concentration, the electrode has been reductively cycled (À0.2 to À0.7 V vs. Ag/AgCl) for 100 consecutive scans in the selenium-containing solution to reach a steady signal. [10] The dependence of peak current on concentration is linear (Figure S1), consistent with the measured redox process corre- [a]