title: The effect of amorphous pyrophosphate on calcium phosphate cement resorption and bone generation.
abstract: Pyrophosphate ions are both inhibitors of HA formation and substrates for phosphatase enzymes. Unlike polyphosphates their hydrolysis results simultaneously in the complete loss of mineral formation inhibition and a localised elevation in orthophosphate ion concentration. Despite recent advances in our knowledge of the role of the pyrophosphate ion, very little is known about the effects of pyrophosphate on bone formation and even less is known about its local delivery. In this work we first developed a self setting pyrophosphate based calcium cement system with appropriate handling properties and then compared its in vivo degradation properties with those of a non-pyrophosphate containing control. Contrary to expectation, the presence of the pyrophosphate phase in the cement matrix did not inhibit mineralisation of the healing bone around the implant, but actually appeared to stimulate it. In vitro evidence suggested that enzymatic action accelerated dissolution of the inorganic pyrophosphate ions, causing a simultaneous loss of their mineralisation inhibition and a localised rise in supersaturation with respect to HA. This is thought to be a rare example of a biologically responsive inorganic material and these materials seem to be worthy of further investigation. Bioceramics to date have mainly been limited to orthophosphate, silicate and carbonate salts of calcium, here we report the successful application of a pyrophosphate material as a degradable osteoconductive bone repair cement.
authors.affiliation: School of Chemical Engineering, University of Birmingham, Edgbaston, B15 2TT, UK. l.m.grover@bham.ac.uk
authors.forename: Liam M
authors.initials: LM
authors.lastname: Grover
authors.forename: Adrian J
authors.initials: AJ
authors.lastname: Wright
authors.forename: Uwe
authors.initials: U
authors.lastname: Gbureck
authors.forename: Aminat
authors.initials: A
authors.lastname: Bolarinwa
authors.forename: Jiangfeng
authors.initials: J
authors.lastname: Song
authors.forename: Yong
authors.initials: Y
authors.lastname: Liu
authors.forename: David F
authors.initials: DF
authors.lastname: Farrar
authors.forename: Graeme
authors.initials: G
authors.lastname: Howling
authors.forename: John
authors.initials: J
authors.lastname: Rose
authors.forename: Jake E
authors.initials: JE
authors.lastname: Barralet
mesh_terms: D000818:Animals; D001843:Bone Cements / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry*; D011756:Diphosphates / Q000737:chemistry; D011122:Polyphosphates / Q000737:chemistry; D012756:Sheep; D014961:X-Ray Diffraction
chemical_list: D001843:Bone Cements; D002130:Calcium Phosphates; D011756:Diphosphates; D011122:Polyphosphates; C107241:diphosphoric acid; C020243:calcium phosphate