title: 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.
abstract: 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.
authors.affiliation: Instituto de Estructura de la Materia, IEM-CSIC, Serrano, 121, 28006 Madrid, Spain.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Lopez-Tobar
authors.affiliation: University of Veterinary Medicine and Pharmacy, Komenskeho 73, 041 81 Kosice, Slovak Republic.
authors.forename: Valeria
authors.initials: V
authors.lastname: Verebova
authors.affiliation: Department of Biophysics, P.J. Safarik University in Kosice, Jesenna 5, 041 54 Kosice, Slovak Republic.
authors.forename: Ludmila
authors.initials: L
authors.lastname: Blascakova
authors.affiliation: Department of Biophysics, P.J. Safarik University in Kosice, Jesenna 5, 041 54 Kosice, Slovak Republic; Center for Interdisciplinary Biosciences, P.J. Safarik University in Kosice, Jesenna 5, 041 54 Kosice, Slovak Republic.
authors.forename: Daniel
authors.initials: D
authors.lastname: Jancura
authors.affiliation: Department of Biophysics, P.J. Safarik University in Kosice, Jesenna 5, 041 54 Kosice, Slovak Republic.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Fabriciova
authors.affiliation: Instituto de Estructura de la Materia, IEM-CSIC, Serrano, 121, 28006 Madrid, Spain. Electronic address: s.sanchez.cortes@csic.es.
authors.forename: Santiago
authors.initials: S
authors.lastname: Sanchez-Cortes
mesh_terms: D000327:Adsorption; D000970:Antineoplastic Agents / Q000737:chemistry*; D019281:Dimerization; D004642:Emodin / Q000031:analogs & derivatives* / Q000737:chemistry; D000431:Ethanol / Q000737:chemistry*; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles / Q000737:chemistry; D011522:Protons; D012834:Silver / Q000737:chemistry; D013059:Spectrum Analysis, Raman / Q000379:methods; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D000970:Antineoplastic Agents; D011522:Protons; D014867:Water; D000431:Ethanol; D012834:Silver; C008905:physcione; D004642:Emodin
keywords: Adsorption; Aggregation; Fluorescence; Parietin; Surface-enhanced Raman spectroscopy (SERS); Surface-enhanced fluorescence (SEF)