Singlet oxygen generation enhanced by silver nanoparticles. Biological applications

M.B. RIVAS AIELLO; D.O. MARTIRE

Encuentro; XII ELAFOT; 2015

The cytotoxic effect of singlet oxygen (O2(1g)) is currently used in photodynamic therapy (PDT), where the controlled production of O2(1g) leads to the eradication of undesired tissue[1]. The inefficient production of O2(1g) can limit the use of PDT photosensitizers, sometal-enhanced O2(1g) generation is a desired effect.Recently, using Riboflavin (Rf) as the sensitizer, the enhancement of O2(1g) generation by pectin-coated silver nanoparticles (Pec.AgNPs) was demonstrated by indirect methods [2]. In this work, we investigate the effect of Pec.AgNPs on the O2(1g) generation by Rf by time-resolved phosphorescence (TRP) of O2(1g) at 1270 nm. Thecell damage caused by the sensitizer with and without de Pec.AgNPs, when the cells were exposed to light was also evaluaed.The Pec.AgNPs were prepared byamodification of the procedure reported in reference [3].The method is based on the reduction of AgNO3 with pectin in basic medium The average diameter of the particles (13±6 nm) was measured by atomic force microscopie. The UV-Vis spectroscopy showed that the maximum of the plasmon absorbance of the Pec.AgNPs is located at 410 nm.Negative Zeta potential values in the pH range 4-10 confirm the effective coating of the particles.The TRP data confirm the metal enhanced production of O2(1g) by Rf in the presence of Pec-AgNPs and show the O2(1g) generation upon excitation of the particles in the plasmon band (420nm).Hela cells were incubated with the Rf with and without the Pec.AgNPs and irradiated at 420 nm. Irradiated cells treated with Rf and Pec.AgNPs showed necrosis 15 min earlier than thsose treated under similar conditions but without the particles. These resuts are in agreement with the TRP data.[1] R. Bonnett, Chemical Aspects of Photodynamic Therapy; Gordon and Breach Science Publishers: Amsterdam, 2000.[2] L.S.A. de Melo, A.S.L. Gomes, S. Saska, K. Nigoghossian, Y. Messaddeq, S.J.L. Ribeiro, R.E. de Araujo, J. Fluoresc., 2012, 22, 1633.[3] Y.L. Balachandran, S. Girija, R. Selvakumar, S. Tongpim, A.C. Gutleb and S. Suriyanarayanan, Plos One, 2013, 8, e77043.