MACROMOLECULAR OXIDATION IN PHOTODYNAMIC ANTIBACTERIAL CHEMOTHERAPY WITH NANOPARTICLES

SCAIANO JC; SILVERO J; BECERRA M C; HASITHA DE ALWIS WEERASEKERA

Santiago de Chile

Congreso; 25th IAPS Meeting; 2016

MACROMOLECULAR OXIDATION IN PHOTODYNAMIC ANTIBACTERIAL CHEMOTHERAPY WITH NANOPARTICLES M. Jazmín Silvero,1,2 Hasitha de Alwis Weerasekera,2 J. C. Scaiano2, M. Cecilia Becerra 1 IMBIV, CONICET and Dpto. de Farmacia, FCQ, UNC. X5000HUA Córdoba, Argentina.2 Department of Chemistry and Biomolecular Sciences and Centre for Catalysis Research and Innovation, UO, Ottawa, Ontario K1N 6N5, CanadaPhotodynamic Antibacterial Chemotherapy (PACT) has emerged as an interesting alternative to treat antibiotic resistant infections. In this case, metallic nanoparticles were used as photosensitizers: gold nanoparticles (AuNP) and coreshell nanoparticles with gold core and silver shell, stabilized with aspartame, (Asp@Ag@AuNP). According to our previous studies, just a few hours of plasmon excitation at 525 nm (9 h for AuNP 2 mM and 6 h for Asp@Ag@AuNP 6.25 µM) are enough to completely inhibit the bacterial growth of Staphylococcus aureus ATCC 29213 and extended spectrum beta-lactamase (ESBL) producing Escherichia coli. In the present work, reactive oxygen species (ROS) and reactive nitrogen species (RNS) production during PACT treatment was detected through Fluorescent Microscopy with the fluorescent probe 2′,7′-dichlorodihydrofluorescein (DCFH) and quantitatively measured using 1,2,3- dihydrorhodamine. Macromolecular damage was evaluated by spectrophotometric quantification of Advanced Oxidation Protein Products (AOPP) in presence of KI at 340 nm.Maximum ROS and RNS generation for both bacterial strains were observed after 4 h of PACT with AuNP and Asp@Ag@AuNP, but levels produced by coreshell nanoparticles were significantly greater. As expected, this major oxidative stress caused important damage in biomolecules. AOPP quantities were 30 times higher in treated samples respect to the control.The bactericidal effect achieved in PACT would be the result of irreversible structural and functional damage caused by large ROS and RNE production. The coreshell nanoparticles accomplished this propose in a shorter time due to the bactericidal properties of the silver shell, which contributes to the already described photothermic effect of gold core excitation with visible light.