title: Low temperature formation of hydroxyapatite-poly(alkyl oxybenzoate)phosphazene composites for biomedical applications.
abstract: The formation of biodegradable composites which may be suitable as bone analogs is described. Polyphosphazene-hydroxyapatite (HAp) composites were produced via an acid-base reaction of tetracalcium phosphate and anhydrous dicalcium phosphate in the presence of polyphosphazenes bearing alkyl ester containing side-groups. The polyphosphazenes used were poly(ethyl oxybenzoate)phosphazene (PN-EOB) and poly(propyl oxybenzoate) phosphazene (PN-POB). The effects of temperature and the proportions of polymers, PN-EOB and PN-POB on the kinetics, reaction chemistry and phase evolution during the formation of stoichiometric HAp were studied. Kinetics, phase evolution and microstructural development were evaluated using isothermal calorimetry, X-ray diffraction and scanning electron microscopy, respectively. Analysis of solution chemistry revealed that the increases in the pH during the formation of SHAp, resulted in partial hydrolysis of the polymer surfaces, which led in turn to the formation of a calcium cross-linked polymer surface. The calcium cross-linked polymer surface appeared to facilitate the nucleation and growth of apatite deposits on the polymer. The current study illustrates the in situ formation of HAp in the presence of polyphosphazenes, where HAp is chemically bonded to the polymer.
authors.affiliation: Intercollege Materials Research Laboratory, Materials Research Institute, The Pennsylvania State University, A5 Materials Research Laboratory Building, University Park, PA 16802, USA. yeg100@psu.edu
authors.forename: Y E
authors.initials: YE
authors.lastname: Greish
authors.forename: J D
authors.initials: JD
authors.lastname: Bender
authors.forename: S
authors.initials: S
authors.lastname: Lakshmi
authors.forename: P W
authors.initials: PW
authors.lastname: Brown
authors.forename: H R
authors.initials: HR
authors.lastname: Allcock
authors.forename: C T
authors.initials: CT
authors.lastname: Laurencin
mesh_terms: D020341:Absorbable Implants; D001698:Biomedical Engineering / Q000379:methods; D018786:Bone Substitutes / Q000138:chemical synthesis / Q000737:chemistry*; D003460:Crystallization / Q000379:methods*; D017886:Durapatite / Q000737:chemistry*; D007700:Kinetics; D008420:Manufactured Materials; D008422:Materials Testing; D008968:Molecular Conformation; D009943:Organophosphorus Compounds / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature
chemical_list: D018786:Bone Substitutes; D009943:Organophosphorus Compounds; D011108:Polymers; C108974:poly(phosphazene); D017886:Durapatite