title: Dual-setting brushite-silica gel cements.
abstract: The current study describes a dual-mechanism-setting cement that combines a brushite-forming cement paste with a second inorganic silica-based precursor. Materials were obtained by pre-hydrolyzing tetraethyl orthosilicate (TEOS) under acidic conditions following the addition of a calcium phosphate cement (CPC) powder mixed of β-tricalcium phosphate and monocalcium phosphate. Cement setting occurred by a dissolution-precipitation process, while changes in pH during setting simultaneously initiated the condensation reaction of the hydrolyzed TEOS. This resulted in an interpenetrating phase composite material in which the macropores of the CPC were infiltrated by the microporous silica gel, leading to a higher density and a compressive strength ∼5-10 times higher than the CPC reference. This also altered the release of vancomycin as a model drug, whereby in contrast to the quantitative release from the CPC reference, 25% of the immobilized drug remained in the composite matrix. By varying the TEOS content in the composite, the cement phase composition could be controlled to form either brushite, anhydrous monetite or a biphasic mixture of both. The composites with the highest silicate content showed a cell proliferation similar to a hydroxyapatite reference with a significantly higher activity per cell. Surprisingly, the biological response did not seem to be attributed to the released silicate ions, but to the release of phosphate and the adsorption of magnesium ions from the cell culture medium.
authors.affiliation: Department of Functional Materials in Medicine and Dentistry, University of Würzburg, 97070 Würzburg, Germany.
authors.forename: Martha
authors.initials: M
authors.lastname: Geffers
authors.affiliation: Department of Surgery, Faculty of Medicine, Faculty of Dentistry, McGill University, Montreal, Quebec H3A 2B2, Canada.
authors.forename: Jake E
authors.initials: JE
authors.lastname: Barralet
authors.affiliation: Department of Functional Materials in Medicine and Dentistry, University of Würzburg, 97070 Würzburg, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Groll
authors.affiliation: Department of Functional Materials in Medicine and Dentistry, University of Würzburg, 97070 Würzburg, Germany. Electronic address: uwe.gbureck@fmz.uni-wuerzburg.de.
authors.forename: Uwe
authors.initials: U
authors.lastname: Gbureck
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001843:Bone Cements / Q000138:chemical synthesis* / Q000494:pharmacology; D002130:Calcium Phosphates / Q000737:chemistry* / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D055119:Elastic Modulus; D006244:Hardness; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D044367:Phase Transition; D058428:Silica Gel / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: D001843:Bone Cements; D002130:Calcium Phosphates; D058428:Silica Gel; C494366:calcium phosphate, dibasic, dihydrate
keywords: Brushite; Calcium phosphate cement; Composite; Monetite; Silica gel