Abstract
Mesoporous silica microparticles were prepared, loaded with the dye safranin O (M-Saf) or with the drug budesonide (M-Bud) and capped by the grafting of a bulky azo derivative. Cargo release from M-Saf at different pH values (mimicking those found in the gastrointestinal tract) in the absence or presence of sodium dithionite (a reducing agent mimicking azoreductase enzyme present in the colon) was tested. Negligible safranin O release was observed at pH 6.8 and 4.5, whereas a moderate delivery at pH 1.2 was noted and attributed to the hydrolysis of the urea bond that linked the azo derivative onto the external surface of the inorganic scaffold. Moreover, a marked release was observed when sodium dithionite was present and was ascribed to the rupture of the azo bond in the molecular gate. Budesonide release from M-Bud in the presence of sodium dithionite was also assessed by ultraviolet-visible spectroscopy and high performance liquid chromatography measurements. In addition, preliminary in vivo experiments with M-Saf carried out in mice indicated that the chemical integrity of the microparticles remained unaltered in the stomach and the small intestine, and safranin O seemed to be released in the colon.
Highlights
Inflammatory bowel disease (IBD) is a group of chronic inflammatory conditions of the colon and small intestine with alternate periods of relapse and remission [1,2]
We found that the presence of the bulky azoderivative on the external surface of mesoporous support loaded with safranin O (M-Saf) and M-Bud inhibited cargo delivery, yet both solids were able to deliver their cargo in the presence of a reducing agent and to some extent at acidic pH (1.2)
Nuclear magnetic resonance (NMR), mass spectrometry, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), transmission electronic microscopy (TEM), N2 adsorption – desorption, ultraviolet-visible spectroscopy (UV-vis), fluorescence spectroscopy and high performance liquid chromatography (HPLC) techniques were employed to characterize the synthesized materials. 1H and 4 13C NMR spectra were acquired with a Bruker DRX500 spectrometer
Summary
Inflammatory bowel disease (IBD) is a group of chronic inflammatory conditions of the colon and small intestine with alternate periods of relapse and remission [1,2]. Ulcerative colitis (UC) and Crohn’s disease (CD) are the most common types of IBD [4,5]. UC affects only the colon and the rectum, whereas Crohn’s can affect any part of the digestive tract. UC is a disease that causes inflammation and sores (ulcers) in the lining of the large intestine. It usually affects the lower section (sigmoid colon) and the rectum, but it can affect the entire colon
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