Structural, Spectroscopic (NMR, IR, and Raman), and DFT Investigation of the Self-Assembled Nanostructure of Pravastatin-LDH (Layered Double Hydroxides) Systems

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• 作者：Vanessa R. R. Cunha ; Philippe A. D. Petersen ; Marcos B. Gon莽alves ; Helena M. Petrilli ; Christine Taviot-Gueho ; Fabrice Leroux ; Marcia L. A. Temperini ; Vera R. L. Constantino
• 刊名：Chemistry of Materials
• 出版年：2012
• 出版时间：April 24, 2012
• 年：2012
• 卷：24
• 期：8
• 页码：1415-1425
• 全文大小：587K
• 年卷期：v.24,no.8(April 24, 2012)
• ISSN：1520-5002

文摘

Layered double hydroxide (LDH) nanocontainers, suitable as carriers for anionic drugs, were intercalated with Pravastatin drug using magnesium鈥揳luminum and zinc鈥揳luminum in a M^II/Al molar ratio equal 2 and different Al³⁺/Pravastatin molar ratios. Postsynthesis treatments were used in order to increase the materials crystallinity. Hybrid materials were characterized by a set of physical chemical techniques: chemical elemental analysis, X-ray diffraction (XRD), mass coupled thermal analyses, vibrational infrared and Raman spectroscopies, and solid-state ¹³C nuclear magnetic resonance (NMR). Results were interpreted in light of computational density functional theory (DFT) calculations performed for Sodium Pravastatin in order to assign the data obtained for the LDH intercalated materials. XRD peaks of LDH-Pravastatin material and the one-dimensional (1D) electron density map pointed out to a bilayer arrangement of Pravastatin in the interlayer region, where its associated carboxylate and vicinal hydroxyl groups are close to the positive LDH. The structural organization observed for the stacked assembly containing the unsymmetrical and bulky monoanion Pravastatin and LDH seems to be promoted by a self-assembling process, in which local interactions are maximized and chloride ion cointercalation is required. It is observed a high similarity among vibrational and ¹³C NMR spectra of Na-Pravastatin and LDH-Pravastatin materials. Those features indicate that the intercalation preserves the drug structural integrity. Spectroscopic techniques corroborate the nature of the guest species and their arrangement between the inorganic layers. Changes related to carboxylate, alcohol, and olefinic moieties are observed in both vibrational Raman and ¹³C NMR spectra after the drug intercalation. Thus, Pravastatin ions are forced to be arranged as head to tail through intermolecular hydrogen bonding between adjacent organic species. The thermal decomposition profile of the hybrid samples is distinct of that one observed for Na-Pravastatin salt, however, with no visible increase in the thermal behavior when the organic anion is sequestrated within LDH gap.

Keywords:

sodium Pravastatin; X-ray diffractometry; FTIR spectroscopy; Raman spectroscopy; thermal analysis; ¹³C NMR spectroscopy; DFT calculation