title: Diffusion-Controlled Drug Release From the Mesoporous Magnesium Carbonate Upsalite(®).
abstract: In vitro drug release from well-defined particle-size fractions of the mesoporous magnesium carbonate material Upsalite(®) was investigated in detail using ibuprofen, a biopharmaceutics classification system class II drug, as the model compound. The weight of loaded drug corresponded to 30% of the weight of the carrier and the pores were filled to approximately 80%. The incorporated ibuprofen was found to be in an amorphous state and was physisorbed, rather than chemisorbed, to the surfaces of the pore walls. In contrast to ibuprofen in mesoporous silica, there was no detectable drug on the outer surface of the carrier particles. Two ibuprofen doses were loaded into Upsalite(®) particles with size fractions ranging from 25 μm to more than 200 μm. The initial release rate was controlled by the particle size; the dissolution rate of the loaded ibuprofen during this period was more than four times faster than that of the crystalline drug. An extended-release period of about 24 h followed the initial rapid-release period. The features of this extended-release period were dependent on the total drug concentration in the release medium. Detailed analysis of the diffusion of ibuprofen in Upsalite(®) provided the ibuprofen diffusion coefficient (9.8 × 10(-8) cm(2)/s), the constrictivity of the diffusion process (0.47) and the tortuosity of the carrier (15). This relatively high tortuosity value indicates that Upsalite(®) can be used not only to enhance the dissolution rate of poorly soluble drugs but also as a carrier in sustained-release applications by using larger particle sizes or even pellets of the material.
authors.affiliation: Division of Nanotechnology and Functional Materials, Department of Engineering Sciences, Uppsala University, Uppsala SE-751 21, Sweden.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.affiliation: Division of Nanotechnology and Functional Materials, Department of Engineering Sciences, Uppsala University, Uppsala SE-751 21, Sweden.
authors.forename: Teresa
authors.initials: T
authors.lastname: Zardán Gómez de la Torre
authors.affiliation: Division of Nanotechnology and Functional Materials, Department of Engineering Sciences, Uppsala University, Uppsala SE-751 21, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Forsgren
authors.affiliation: Department of Pharmacy, Uppsala Biomedical Centre, Uppsala University, Uppsala SE-751 23, Sweden.
authors.forename: Christel A S
authors.initials: CAS
authors.lastname: Bergström
authors.affiliation: Division of Nanotechnology and Functional Materials, Department of Engineering Sciences, Uppsala University, Uppsala SE-751 21, Sweden. Electronic address: maria.stromme@angstrom.uu.se.
authors.forename: Maria
authors.initials: M
authors.lastname: Strømme
mesh_terms: D004058:Diffusion; D065546:Drug Liberation; D007052:Ibuprofen / Q000737:chemistry* / Q000378:metabolism*; D008274:Magnesium / Q000737:chemistry* / Q000378:metabolism*; D016062:Porosity; D012995:Solubility; D014961:X-Ray Diffraction
chemical_list: C005479:magnesium carbonate; D008274:Magnesium; D007052:Ibuprofen
keywords: Upsalite(®); constrictivity; controlled release; diffusion; ibuprofen; magnesium carbonate; mesoporous material; poorly soluble drugs; tortuosity