Examinando por Autor "Martín, A."

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Effect of the dual incorporation of fullerene and polyethyleneimine moieties into SBA-15 materials as platforms for drug delivery
(Springer Nature, 2019-05-28) Martín, A.; Morales, V.; Ortiz-Bustos, J.; Sanz, R.; García-Muñoz, R.A.
Mesostructured SBA-15 silica materials have been successfully dual functionalized with polyethyleneimine (PEI) groups and C60 fullerene moieties to allow an evaluation of their properties as nanovehicles for controlled drug delivery. Methylprednisolone sodium succinate was selected as a model drug for adsorption on the surface of functionalized SBA-15 silica materials. The resulting dual-functionalized SBA-15 silica materials exhibit mesoscopic arrangements, although with a remarkable reduction in their textural properties as compared to pure silica SBA-15. The adsorption capacity of methylprednisolone on functionalized SBA-15-PEI improved remarkably compared with that of raw SBA-15, while the drug release rate slowed, as the amount of PEI anchored in the SBA-15 increased. The strong attractive electrostatic interactions between methylprednisolone and the silica surfaces of SBA-15-PEI materials, measured by zeta potential, account for these results. In a second step, wherein C60 fullerene species in combination with PEI were grafted to the silica, the results establish that the steric effects and hydrophobicity of the C60 moieties hinder methylprednisolone transport within the silica pores. The kinetic parameters obtained from the drug release profiles, fitted to four kinetic models, show that the incorporation of C60 species yields lower methylprednisolone release rates from SBA-15-PEI-C60 materials than from SBA-15-PEI materials. Additionally, the incorporation of fullerene groups into PEI-modified materials provides an increment in cell viability. Confocal microscopy evidences the cellular internalization of the dual-functionalized mesoporous SBA-15 materials inside the plasmatic membrane.
Modelling the adsorption and controlled release of drugs from the pure and amino surface-functionalized mesoporous silica hosts
(Elsevier, 2018-05-15) Martín, A.; Morales, V.; Ortiz-Bustos, J.; Pérez-Garnés, M.; Bautista, L.F.; García-Muñoz, R.A.
Several mesoporous silica materials with different structures were investigated as matrices for controlled drug delivery. The aim of this study is correlating the textural and surface chemical properties of these materials with the adsorption and delivery of the drug model methylprednisolone sodium succinate. The materials were synthesized according to different protocols, and employing both cationic and non-ionic surfactants. Additionally, the functionalization of the materials' surface with 1-[3-(trimethoxysilyl)propyl]diethylenetriamine (DT) was accomplished to study the synergistic effect of the incorporation of amine groups and textural properties on the loading and delivery of drug. The thermodynamics and dynamic adsorption behavior of these materials were determined and fitted to several isotherms models to provide information about the drug adsorption processes. The maximum adsorption capacities of the raw silica supports were correlated with the pore size and the results indicated that the drug adsorption ability improved as the material pore size increases. Moreover, it is observed that the drug adsorption on materials with mesoporous size higher than 10 nm are very close to the theoretical saturation capacity. Regarding amino-modified materials, isotherms models confirmed that the factor governing the adsorption process were mainly the electrostatic interactions, hydrogen bonding and/or hydrophobic-hydrophilic interactions between the drug moieties and amino-functionalized silica surfaces, and in a lesser degree the textural properties of the support. Furthermore, the kinetics of the drug release from these materials functionalized with amino groups were also modelled to finally obtain a correlation between the adsorption and release drug cargo from the host pure and surface-functionalized materials.
Perfluorinated nafion-modified SBA-15 materials for catalytic acylation of anisole
(ELSEVIER, 2008) Martínez, F.; Morales, G.; Martín, A.; van Grieken, R.
Mesoporous SBA-15 silica materials have been functionalized with perfluorosulfonic acidic Nafion resin using a post-synthetic impregnation method. The remarkable physicochemical properties of hexagonally ordered SBA-15 silicas (high surface area, large and narrow pore size distribution and thermal stability) make them particularly attractive for the immobilization of strongly acidic perfluorosulfonic sites. The loading of Nafion resin was varied between 10 and 20 wt%. The synthesized Nafion/SBA-15 hybrid materials were evaluated in the Friedel Crafts acylation of anisole. The optimum catalytic performance of Nafion/SBA-15 hybrid material with a resin loading around 13 wt% was compared with other perfluorosulfonic acid-based catalysts either commercially available or prepared following recipes reported in the literature. The influence of several variables on the acylation of anisole, such as the reaction temperature and the anisole/acylating agent ratio, has also been assessed by means of a factorial design of experiments. The catalytic activity of Nafion-modified SBA-15 materials is strongly affected by the reaction temperature, whereas a lesser effect was evidenced for the reaction mixture composition in the range under study. The optimal operation conditions in terms of anisole conversion were achieved at 150ºC and equimolar anisole/acetic anhydride mixture. The deposition of poly-acetylated by-products on the catalytic acid sites is mainly responsible for the catalyst deactivation, whereas the leaching of sulfonic groups and their contribution in the anisole acylation via homogeneous catalysis has been ruled out. Finally, the recovery of the catalytic activity by regeneration of the spent catalyst by refluxing in nitric acid solution was demonstrated. The characterization of the regenerated catalyst indicates that the regained activity is likely related to the displacement of the deactivating by-products out of the perflurorosulfonic acid sites during the nitric acid regeneration.