Metallic nanoparticles: antibacterial activity and ecotoxicity

Nanotechnology has many applications in the healthcare; in particular the use of metal nanostructures in now widely exploited for the obtainment of antibacterial compounds which are not susceptible to resistance development and could represent an alternative to antibiotics. Examples of applications in this field are antibacterial paints, antibacterial patches or even antibacterial films. The possibility to synthesize metallic nanoparticles of different composition and the possibility to tune their size as well as structure to improve antibacterial activity has played an important role. Despite their numerous advantages, leakage of heavy metals represents the major problem responsible of their toxicity[1]. Thus, coating with antimicrobial peptides represents an emerging strategy to reduce toxicity and enhance antibacterial activity.[2] The presence of nanoparticles and released metal ions in the aquatic environment is considered to be amongst the greatest environmental concerns because of their potential harmful effects on both aquatic organisms and humans via direct or indirect exposure. Among freshwater aquatic organisms, the crustacean Daphnia magna is often the best choice for toxicity evaluations because of its high sensitivity, short life cycle, easiness of manipulation in laboratory. In addition, it is widely present in diverse freshwater lakes and ponds, and plays a key role in transfer of energy and nutrients to upper food webs, representing also an important ecological sentinel species. In this study we evaluated the ecotoxicity of quantum dots and Au nanoparticles coated with indolicidin, one of most common antibacterial peptide.