Detection and aggregation of the antitumoral drug parietin in ethanol/water mixture and on plasmonic metal nanoparticles studied by surface-enhanced optical spectroscopy: Effect of pH and ethanol concentration

7 págs.; 7 figs.In the present paper, we have investigated the effect of ethanol in aqueous media, the pH and the presence of Ag nanoparticles (NPs) on the aggregation processes of the antitumoral anthraquinone parietin in aqueous media and on the metal surface. UV-visible absorption, fluorescence and Raman spectra of parietin were used for such purpose. The present study provides information about the deprotonation and molecular aggregation processes occurring in parietin under different environments: ethanol/water mixture and when adsorbed onto Ag nanoparticles. The effect of ethanol on the optical properties of parietin in alcohol-water mixtures was also investigated at different ethanol concentrations with the time. For the case of the adsorption and organization of parietin molecules on the surface of Ag NPs, special attention was paid to the use of surface-enhanced optical techniques, SEF (surface-enhanced fluorescence) and SERS (surface-enhanced Raman scattering), for the characterization of the parietin aggregates and the ionization of the molecule on the surface. In particular, we have studied the variation of the SEF signal with the pH, which depends on the molecular organization of the molecule on the surface. Furthermore, a detailed analysis of the SERS spectra at different pH was accomplished and the main Raman bands of the protonated, mono-deprotonated and di-deprotonated parietin were identified. Finally, the second ionization pK of parietin on metal NPs was deduced from the SERS spectra. © 2016 Elsevier B.V. All rights reservedThis work has been supported by the Spanish Ministerio de Economía y Competitividad (FIS2014-52212-R), by Structural funds of the EU (contracts: NanoBioSens (ITMS code: 26220220107, 50%), SEPO II (ITMS code: 26220120039), and CEVA II (ITMS code: 26220120040), by the contract APVV-0242-11, and the 7FP EU project CELIM(316310).Peer Reviewe

Estudio Raman de la adsorción de fármacos antraquinónicos sobre nanopartículas de Ag y de sus complejos con albúminas de diferente origen

II CIE – XVIII RNE, Coimbra, Portugal, 16-21 Septiembre 2002Proyecto BFM2001-2265N

Interaction of photodynamic antitumoral drugs with bovine and human albumins studied by surface-enhanced Raman scattering (SERS) spectroscopy

Las Palmas de Gran Canaria, 4-9 Julio, 2004Project BFM2001-2265N

Formation of ABTS radical cation in the presence of silver nanoparticles as revealed by surface-enhanced Raman scattering

Espectroscoía, Universidad de la Rioja, Logroño, La Rioja, 9-11 de julio de 2014. PO83; http://www.unirioja.es/espectroscopia2014/ABTS [2,2¿-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] has been extensively employed to evaluate the free radical trapping capacity of pure compounds and complex mixtures such as biological fluids or foods [1], when it is incubated in presence of a free radical source in the so-called Trolox equivalent antioxidant capacity (TEAC) assay. The latter assay is performed by using a colorimetric experiment, where ABTS is previously oxidized by persulfate to get the radical cation ABTS*+ [2], giving rise to an intense absorbance at 734 nm. In this work we report the formation of the radical cation in the presence of star-shaped silver nanoparticles (AgNS) [3]. ABTS*+ was characterized by surface-enhanced Raman scattering (SERS) and detected at trace concentrations (2 µM). The ABTS*+/AgNS system is proposed here as a reliable substrate to test the antioxidant activity of foods based on the high sensitivity of plasmonic nanostars as an alternative method to the TEAC testPeer Reviewe