title: The interaction of encapsulated pharmaceutical drugs with a silica matrix.
abstract: A series of seven drugs, namely, fluoxetine, gentamicin, lidocaine, morphine, nifedipine, paracetamol and tetracycline, were encapsulated. The encapsulated systems were characterized using a series of complementary techniques: Fourier-transform infrared spectroscopy (FT-IR), diffusive reflectance spectroscopy in the UV-vis region (DRS) and X-ray photoelectron spectroscopy (XPS). According to the DRS spectra, most of the encapsulated systems showed a band shift of the maximum absorption when compared with the corresponding bare pharmaceutical. Additionally, after encapsulation, the drugs exhibited infrared band shifts toward higher wavenumbers, which in turn provided insight into potential sites for interaction with the silica framework. The amine group showed a band shift in the spectra of almost all the drugs (except nifedipine and tetracycline). This finding indicates the possibility of a hydrogen bonding interaction between the drug and the silica via electron donation from the amine group to the silica framework. XPS confirmed this interaction between the pharmaceuticals and the silica through the amine group. A correlation was observed between the textural characteristics of the solids and the spectroscopic data, suggesting that the amine groups from the pharmaceuticals were more perturbed upon encapsulation.
authors.affiliation: Instituto de Química, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, Porto Alegre 91501-970, Brazil.
authors.forename: Everton C
authors.initials: EC
authors.lastname: Morais
authors.forename: Gabriel G
authors.initials: GG
authors.lastname: Correa
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Brambilla
authors.forename: Claudio
authors.initials: C
authors.lastname: Radtke
authors.forename: Ione Maluf
authors.initials: IM
authors.lastname: Baibich
authors.forename: João Henrique Z
authors.initials: JH
authors.lastname: dos Santos
mesh_terms: D000042:Absorption; D002626:Chemistry, Pharmaceutical; D004583:Electrons; D004364:Pharmaceutical Preparations / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics
chemical_list: D004364:Pharmaceutical Preparations; D012822:Silicon Dioxide