Study of hydrocortisone stabilization within the network of nanostructured Silica and titania biomaterials
E. Ortiz, T. Lopez, R. Gonzalez
Instituto Nacional de Neurología y Neurocirugía, MX
Keywords: hydrocortisone, silica, titania, biomaterials
Abstract:The biological and physico chemical attractive properties of many inorganic oxides materials such as good biocompatibility, large surface area and mesoporous structures are crucial in many medical applications. Specifically, for controlled release applications, they are able to store and gradually release neurological drugs [1, 2]. The sol-gel process is a convenient and versatile method to prepare oxide materials under ambient temperature conditions and also to enable entrapment of numerous organic, organometallic, and biological molecules in the mesoporous network of the oxides. With this in mind, we have occluded hydrocortisone (HC) within the nanostructured silica and titania materials for use as HC delivery systems. The sol-gel process was used to obtained TiO2-HC and SiO2-HC materials. For this purpose HC´s were added to silica and titania during the alkoxide hydrolysis step. The materials obtained were characterized by FTIR and UV-VIS spectroscopy and by “in vitro” profiles for HC delivery. Figure 1 shows the FTIR spectra of different samples. The most important bands of HC are those observed at 3435 cm-1, 2923 cm-1, 1710 cm-1 and 1637 cm-1. These are assigned to the stretching vibrations of OH, CH, C=O and C-(C=O)-COH functional groups. These bands are observed in both the TiO2-HC and SiO2-HC samples, with exception of the band corresponding to C=O groups. These results suggest the presence of an interaction between these groups and OH of silica and titania biomaterials. In order to quantify the HC delivered, a calibration curve (Figure1B) was obtained. Figure 3C shows the general trend of the kinetics of the hydrocortisone release from the. SiO2-HC samples used in this study. As one can see from this figure, the drug delivery follows two steps. Initially a rapid release is observed which is then followed by a second stage in which a slower rate of delivery is observed. These results suggest that titania and silica are good candidates for hosting HC that can subsequently be released.