PHOTOACTIVATED NANOPARTICLES KILL PATHOGENIC BACTERIA BUT PROVED TO BE HARMLESS TO EUKARYOTIC CELLS

MARTINEZ, SOL R; SILVERO, M. JAZMÍN; ARGUELLO, GERARDO A; BECERRA, MARIA CECILIA

Meresias

Congreso; Encontro Latino Americano de Fotoquímica e Fotobiologia; 2015

When a metal nanoparticle interacts with light, having a wavelength longer than thedimensions of the particle itself, Surface Plasmon Resonance (SPR) takes place. In case ofgold, SPR absorptions occur in the visible range; this allows us to use cheap LEDs (525nm)as radiation source.The nanomaterial employed here was synthesized according to the procedure publishedpreviously (JACS REF2014). It consists of a gold core, encapsulated in a silver shell andstabilized with a dipeptide, specifically aspartame (Asp). The gold core is designed forefficient heat delivery through established plasmonic mechanisms. The silver shell retainsthe antibacterial properties that are now well characterized in the case of AgNP. Thesurface protection with aspartame (Asp) leads to excellent aqueous stabilization with longshelf life. Further, aspartame is non-toxic, remarkably inexpensive and easy to replace byanother molecule of interest.Previous results showed that bactericidal activity was achieved after only 6h of lowenergy irradiation in samples treated with Asp@Ag@AuNPs. This could be attributed tothe synergism between the silver shell and the plasmon excitation of gold core.In this work, ROS production is detected by Fluorescence Microscopy inStaphylococcus aureus ATCC 29213 and an extended-spectrum beta-lactamases-producingEscherichia coli treated with Asp@Ag@AuNPs and irradiated at 525 nm; whileeukaryotic toxicity was evaluated with the MTT essay in fibroblast Balb/3T3 clone A31(ATCC CCL-163) culture also under irradiationMaximum ROS production was detected in S. aureus and E. coli after 2 and 3 hours ofirradiation correspondingly, suggesting that oxidative stress would be the major cause ofbacteria death.Cell survival percent was up to 98% even after 18 hours of irradiation using the sameLED panel and nanoparticles concentration.The photoactivated nanoparticles have proven to be able to kill completely the bacteriapopulation and still remain harmless for eukaryotic cells under the same conditions. Furtherinvestigation will include a co-culture experiment to confirm these results.