title: High-strength resorbable brushite bone cement with controlled drug-releasing capabilities.
abstract: Brushite cements differ from apatite-forming compositions by consuming a lot of water in their setting reaction whereas apatite-forming cements consume little or no water at all. Only such cement systems that consume water during setting can theoretically produce near-zero porosity ceramics. This study aimed to produce such a brushite ceramic and investigated whether near elimination of porosity would prevent a burst release profile of incorporated antibiotics that is common to prior calcium phosphate cement delivery matrices. Through adjustment of the powder technological properties of the powder reactants, that is particle size and particle size distribution, and by adjusting citric acid concentration of the liquid phase to 800mM, a relative porosity of as low as 11% of the brushite cement matrix could be achieved (a 60% reduction compared to previous studies), resulting in a wet unprecompacted compressive strength of 52MPa (representing a more than 100% increase to previously reported results) with a workable setting time of 4.5min of the cement paste. Up to 2wt.% of vancomycin and ciprofloxacin could be incorporated into the cement system without loss of wet compressive strength. It was found that drug release rates could be controlled by the adjustable relative porosity of the cement system and burst release could be minimized and an almost linear release achieved, but the solubility of the antibiotic (vancomycin>ciprofloxacin) appeared also to be a crucial factor.
authors.affiliation: Biomaterials Unit, School of Dentistry, University of Birmingham, St. Chad's Queensway, Birmingham B4 6NN, UK. m.p.hofmann@bham.ac.uk
authors.forename: M P
authors.initials: MP
authors.lastname: Hofmann
authors.forename: A R
authors.initials: AR
authors.lastname: Mohammed
authors.forename: Y
authors.initials: Y
authors.lastname: Perrie
authors.forename: U
authors.initials: U
authors.lastname: Gbureck
authors.forename: J E
authors.initials: JE
authors.lastname: Barralet
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry; D001672:Biocompatible Materials / Q000737:chemistry*; D001843:Bone Cements / Q000737:chemistry*; D002130:Calcium Phosphates / Q000008:administration & dosage* / Q000737:chemistry; D002939:Ciprofloxacin / Q000008:administration & dosage; D019343:Citric Acid / Q000737:chemistry; D016503:Drug Delivery Systems; D008855:Microscopy, Electron, Scanning; D008956:Models, Chemical; D010316:Particle Size; D011208:Powders; D011312:Pressure; D013314:Stress, Mechanical; D014640:Vancomycin / Q000008:administration & dosage
chemical_list: D000900:Anti-Bacterial Agents; D001672:Biocompatible Materials; D001843:Bone Cements; D002130:Calcium Phosphates; D011208:Powders; C485817:beta-tricalcium phosphate; D019343:Citric Acid; D002939:Ciprofloxacin; D014640:Vancomycin; C494366:calcium phosphate, dibasic, dihydrate