IMBIV   05474
INSTITUTO MULTIDISCIPLINARIO DE BIOLOGIA VEGETAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
CAN GREEN LEDs AND NANOPARTICLES SAVE US FROM SUPERBUGS?
Autor/es:
DE ALWIS H; LANTERNA AE; SCAIANO JC; SILVERO MJ; ROCCA D; BECERRA MC; ARTUR DE LA VILLARMOIS, E; PEREZ MF
Lugar:
SARASOTA FLORIDA
Reunión:
Conferencia; 26TH IAPS WINTER CONFERENCE; 2017
Resumen:
Photo Dynamic Therapy (PDT) has progressed dramatically since Raab took advantage of sunlight to fight a protozoa infection at the beginning of the past century. Currently, PDT is applied to treat cancer and various infections that are not susceptible to antimicrobial drugs. PDT needs a photosensitizer (PS) that can be activated by visible light and is not harmful to tissues. Several molecules are known to undergo photochemical reactions involving a long-lived excited triplet state, but recently PDT has focused on the potential use of metallic nanoparticles as PS. We have concentrated our studies on the photo-antibacterial capacity of gold and gold/silver bimetallic nanoparticles (NP) against antibiotic-resistant bacterial strains. These ?superbugs? are a major threat to human health and are already placing a substantial clinical and financial burden on healthcare systems. The synthesis of spherical (16.6 nm), mono-disperse aqueous NP was achieved by a photo-initiated method employing Irgacure 2959, a water soluble benzoin, to reduce the Au3+ to form the gold core, and UV light to deposit de silver shell. They were successfully stabilized in dilute PBS and culture media with small, biocompatible sweeteners and food supplements such as aspartame, glucosamine and sucralose. Microbiology essays proved that these new PS have a bactericidal effect on various ATCC and clinical strains; for instance, a 6 log-unit reduction in growth was observed in extended spectrum beta-lactamase producing Escherichia coli after few hours of low energy irradiation (520 nm LED Panel, ~26 W/m2). Reactive Oxygen Species (ROS) detection through fluorescent probes demonstrated that a large amount of oxidative stress is caused after 4 h of PDT with these core-shell nanoparticles. We believe that plasmon excitation of the gold core may produce high ROS levels through a photo-thermal process, up to 12x the non-irradiated inoculum without NP, and 5x the non-irradiated inoculum with NP. Further, macromolecular damage was found in both proteins and lipids, which irreversibly led to bacterial death. Indeed, for the same strains, advanced protein oxidation products were more than double with respect to the control at 4 h, whereas the maxima of lipid peroxidation were sensed through a fluorescent probe at 8 h (30000x to 60000x units more than the controls). The time needed to achieve complete inhibition of bacterial growth was shorter for combined gold/silver NP than for gold NP alone. These results suggest that the silver shell was contributing as an antibacterial agent, even though it was not significantly excited by the green LEDs. By contrast, green light did not affect the normal cell survival, neither the PS, when the proposed PDT treatment was essayed on human fibroblasts and keratinocytes: in fact, the percent of respiratory-active cells stayed above 95% even after 18 h exposure to green light.Thus, in our work, photoinduced processes are used both to synthesise the PS nanoparticles as well as to enhance their antibacterial activity. The promising potential of gold/silver core-shell NP encouraged us to continue the research and we are currently performing in vivo experiments to analyze their bio-distribution and test the organism-NP-light interaction. We ask ourselves if the antibacterial activity of photo-activated metal nanostructures could circumvent problems related to the development of drug resistance by bacteria, helping us in the battle against superbugs.