NANOSILICEOUS MATRIX FOR DRUG INCAPSULATION L. G. HANU 1, A. M. HANU 1, E. POPOVICI 1, G. BURTICĂ 2, D. TIMPU 3 1 Faculty of Chemistry, Univ. Al. I. Cuza, Iaºi 2 University Politehnica, Timiºoara 3 P. Poni Institute of Macromolecular Chemistry, Iaşi evelinepopovici@yahoo.com Received May 28, 2004 The aim of this study was testing the possibility of employing a nanocomposite system: mesoporous matrix-methotrexate as drug delivery system. All the data suggest that the studied matrix impregnated with anti-cancer drug represents a good choice for the controlled drugs release. Key words: MCM-41, adsorption, methotrexate. INTRODUCTION Cancer is a major cause for morbidity and mortality in industrialized countries. For patients with advanced disease, chemotherapy based on methotrexate is currently the mainstay of treatment. In the recent years, a new field in research advanced materials is the use of siliceous matrix, such as siliceous zeolite, smectite clays, as a matrix for adsorption and release of suitable drug molecules. The MCM-41 mesoporous material possesses a regular honeycomb-like array of cylindrical mesopores with a narrow pore size distribution varying from 15 to 100 Å, specific surface area, and well-defined morphology. The important characteristics of this novel materials are its large BET surface area are high porosity. The MCM-41 exhibits novel physical and chemical proprieties. The pore walls have free silanol groups that could be reactive toward appropriate guest molecules. The diameter of the channels can be tailored during synthesis by using of a different kind of surfactant template. The MCM-41 materials are the bioinert silicates, having a superior capability to intercalate large molecules. These main properties allow MCM-41 materials to work as siliceous matrix for adsorption and release of drug molecules. In this study, we try to incorporated methotrexate into the MCM-41 channels and to find out an optimum condition for drug release under different experimental conditions mimicking some biological compartments. Rom. Journ. Phys., Vol. 49, Nos. 9 10, P. 817 822, Bucharest, 2004
818 L. G. Hanu et al. 2 EXPERIMENTAL 1. THE SILICEOUS MATRIX PREPARATION The siliceous matrix was prepared following two steps: the former was the LCT synthesis MCM-41 loaded with template and the second was the template removal. The first step was the gel preparation having the following composition: SiO 2 0.06 R 2 O 0.25Na 2 O 134H 2 O. For this purpose the silicate source aqueous tetraethyl orthosilicate, TEOS 98% (Janssen Chemica), the template hexadecyltrimethylammonium chloride n C 16 H 33 N + (CH 3 ) 3 Cl solution (Fluka) and mineralization agent tetrapropylammonium hydroxide (Fluka) were mixed to obtain the above molar composition. The ph value was adjusted to 12. The resulting mixture was stirred for an additional hour and then heated at 413K in autoclave, for 72 hours. After separation by filtration, the solid was washed and dried at room temperature for 12 hours and then calcinated at 540 C. 2. THE MATRIX DRUG COMPOSITE PREPARATION The methotrexate, with chemical structure presented below, loading into mesoporous matrix was achieved by impregnation, soaking for one day at room temperature, under continuous stirring. In this purpose, 1 g of the matrix was treated at 25 C with 50 ml solution containing 125 mg bioactive in water. Finally, the solvent was removed by filtration and samples dried under vacuum. 3. THE SIMULATED BIOLOGICAL FLUID The gastric juice was simulated using 0.1 N HCl solution, ph = 1.0.
3 Nanosiliceous matrix for drug incapsulation 819 4. DETERMINATION OF BIOACTIVE AGENTS ENTRAPPED IN THE MATRICES For determination of the amounts of loaded drug into matrix, has been used the following method: samples impregnated with the agents were extracted with water at 50 60 C for 3 4 hours. The solvent after extraction was collected by filtration under vacuum and analyzed. The water solution was analyzed a HPLC system, an Agilent 1100 Series instrument, with an injector fitted with a 20 µl loop, an isocratic pump, a thermostat for the column and a UV detector, on line with a HP workstation. The column was a Zorbax Eclipse XDB C 18 (5 µm of 150 mm 4.6 mm obtained from Agilent). The mobile phase was solution of anhydrous disodium hydrogen phosphate with sodium dihydrogen phosphate monohydrate adjusts to ph 6.9 with dilute sodium hydroxide solution. To this mixture was added propanol. The detection was made at 264 nm. 5. IN VITRO DRUG RELEASE STUDIES The release study of drug from mesoporous silicate matrices were carried out by keeping 25 mg of each composite, prepared according by with 2.2., with 25 ml of a 0.1 N HCl solution, at 37 C, under stirring, for 2 hours. After filtration, the aqueous solution was analyzed by HPLC according to the conditions previously reported. 6. METHODS The as-synthesized samples were characterized by X-ray diffraction, thermogravimetric analysis, FTIR, UV-Vis, SEM microscopy. The X-ray diffraction pattern of the siliceous matrix was recorded on a Difractometer TUR M-62, using the Ni-filtered Cu-Kα radiation (λ = 0.1518 nm). The working conditions were 36 kv and 20 ma, the goniometer speed of 0.5 /min. All the difractograms were investigated in the range of 1 40, 2θ degrees, at room temperature. FTIR spectra were registered on a BOMEM model MB 104 spectrometer in the 500 4000 cm 1 range. The thermal stability studies were performed on MOM Budapest derivatograph of the Paulik Paulik Erdey type. RESULTS AND DISCUSSION SEM investigation of the siliceous matrix was performed in order to investigate the size, surface morphology and homogeneity of the samples. We observe the samples contain spherical shaped particles with size < 1 µm.
820 L. G. Hanu et al. 4 Fig. 1. SEM image of siliceous matrix. XRD patterns of calcinated siliceous matrix exhibit four reflection peaks: d 100 = 3.84, d 110 = 2.32; d 200 = 1.92, d 210 = 1.41, which is consistent with the supposition that the pore channel form a regular hexagonal array. This allowed us to calculate the hexagonal unit cell parameter: 2d100 a 0 = = 4.45 nm (1) 3 For the matrix-methotrexate nanocomposite, the d 100 peak and unit cell parameter of 3.90 and 4.52 nm were respectively. The data demonstrate that siliceous matrix and the composite (matrix-methotrexate) have a hexagonal pore array, type MCM-41. Fig. 2. The RDX pattern of siliceous matrix. From the FTIR spectra (Fig. 3) we observed that the characteristic bands of methotrexate (Fig. 3c) are present nemodified in nanocomposite spectrum (Fig. 3b), that confirm its nondestroyed incorporation in matrix channels. Thermogravimetric analysis of the mesoporous matrix was performed in the temperature range 20 600 C. The data show, the first, a weight loss around 300 C, assigned to the condensation of two vicinal silanol groups with loss of
5 Nanosiliceous matrix for drug incapsulation 821 a b c Fig. 3. FTIR spectra: a matrix; b nanocomposite; c - methotrexate. water molecule and the second, the thermal stability of the matrix in the studied temperature range. Thermal behavior of methotrexate-nanocomposite points out the presence of two effects: the condensation of vicinal silanols and the methotrexate degradation around 380 C. The thermogravimetric data show that all quantity of methotrexate was incorporated. The RDX, FTIR spectra and thermal behavior demonstrated the methotrexate retention in matrix channel. The retention is based on the one hand on the compatibility between the molecular size of methotrexate molecules and matrix diameter, and on the other hand on both the high surface area and the pore volumes characteristic for MCM-41 structure. The water adsorption on matrix, about 500 mg/g, was stressed a good hydrophilic character and this makes it potentially biocompatible. For the
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