Drug loading and release from core-shell silicate particles: a case study for thiamine drug

Spherical mesoporous silica and core-shell silicate particles loaded with thiamine hydrochloride water-soluble drug were investigated as new drug delivery platforms. The particles were synthesized by Stober method using dodecylamine as organic template, which was removed through a suitable heat treatment and left behind mesopores. A shell of aluminum oxide or a mixture of aluminum and iron oxides was developed on silica cores to extend the application fields of these particles. Both silica and core–shell particles were characterized as matrices for drug loading and release using various experimental techniques as scanning electron microscopy (SEM), specific surface area and porosity, particle size distributions and Zeta potential, X-ray diffraction (XRD), differential thermal analysis (DTA/TGA), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, as well as dissolution tests evaluated by UV-VIS spectrophotometry. Thiamine hydrochloride loaded onto these particles by solvent evaporation method was used as a model drug. The XRD results showed that the crystalline state of the loaded drug is thiamine hydrochloride monohydrate. According to DTA/TGA data, after the loading process the samples contain almost equal amounts of mesoporous particles and thiamine. The XPS analysis indicated the presence of thiamine on the surface of the spheres, but the low concentration of the elements entering the thiamine and the high concentration of the elements occurring from particles composition reveal that thiamine is mainly entrapped inside the pores of the particles. On the other hand, FTIR spectroscopy additionally indicated that thiamine is attached to the inner and/or outer surface of the particles via hydrogen bonds. A drug release delay was noticed for the investigated particles loaded with thiamine.