Surface enhanced fluorescence of anti-tumoral drug emodin adsorbed on silver nanoparticles and loaded on porous silicon
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NANO EXPRESS
Open Access
Surface enhanced fluorescence of anti-tumoral drug emodin adsorbed on silver nanoparticles and loaded on porous silicon Margarita Hernandez1, Gonzalo Recio2, Raul J Martin-Palma2, Jose V Garcia-Ramos1, Concepcion Domingo1 and Paz Sevilla3,1*
Abstract Fluorescence spectra of anti-tumoral drug emodin loaded on nanostructured porous silicon have been recorded. The use of colloidal nanoparticles allowed embedding of the drug without previous porous silicon functionalization and leads to the observation of an enhancement of fluorescence of the drug. Mean pore size of porous silicon matrices was 60 nm, while silver nanoparticles mean diameter was 50 nm. Atmospheric and vacuum conditions at room temperature were used to infiltrate emodin-silver nanoparticles complexes into porous silicon matrices. The drug was loaded after adsorption on metal surface, alone, and bound to bovine serum albumin. Methanol and water were used as solvents. Spectra with 1 μm spatial resolution of cross-section of porous silicon layers were recorded to observe the penetration of the drug. A maximum fluorescence enhancement factor of 24 was obtained when protein was loaded bound to albumin, and atmospheric conditions of inclusion were used. A better penetration was obtained using methanol as solvent when comparing with water. Complexes of emodin remain loaded for 30 days after preparation without an apparent degradation of the drug, although a decrease in the enhancement factor is observed. The study reported here constitutes the basis for designing a new drug delivery system with future applications in medicine and pharmacy. Keywords: Surface-enhanced fluorescence, Porous Silicon, Emodin, Drug delivery
Background Porous silicon (PSi) is a mesoporous material which has been proposed for an increased number of drug delivery applications in the last few years [1,2]. PSi, as well as mesoporous silica materials [3,4], shows biodegradability and biocompatibility; both of them being fundamental requirements for the development of controlled-release drug delivery system. PSi materials are termed “topdown” materials as opposed to the synthesized mesoporous molecular sieves, which are so called “bottom-up” silica materials that refer to the self-assembly of silicon oxide by means of polymeric templates determining the structure obtained. Besides, the efficient visible * Correspondence: [email protected] 1 Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, Madrid 28006, Spain 3 Departamento de Quimica Fisica II, Facultad de Farmacia, UCM, Madrid 28040, Spain Full list of author information is available at the end of the article
photoluminescence of PSi, as first reported by Canham [5] in 1990, can be used as a sensing signal of the carried drug, once it has been duly immobilized onto the PSi surface which sometimes requires its adequate functionalization [6-8]. PSi can also incorporate metal nanoparticles (NPs) which are furthermore useful as nanocarriers and imaging agents [9,10]. In particular, noble metal NPs, due t
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