Biomimetic Self-Assembling Copolymer-Hydroxyapatite Nanocomposites with the Nanocrystal Size Controlled by Citrate

TitleBiomimetic Self-Assembling Copolymer-Hydroxyapatite Nanocomposites with the Nanocrystal Size Controlled by Citrate
Publication TypeJournal Article
Year of Publication2011
AuthorsHu YY, Liu XP, Ma X, Rawal A, Prozorov T, Akinc M, Mallapragada SK, Schmidt-Rohr K
Journal TitleChemistry of Materials
Volume23
Pages2481-2490
Date Published05/10
Type of ArticleArticle
ISBN Number0897-4756
Accession NumberISI:000290063600025
Keywordsbiocompatibility, bioinspired materials, bone, calcium-phosphate nanocomposites, citric-acid, COLLAGEN, composites, crystal control, HYBRID, materials, microscopy, MINERALIZATION, nmr-spectroscopy, nuclear magnetic resonance, nucleation, POLYMER
Abstract

Citrate binds strongly to the surface of calcium phosphate (apatite) nanocrystals in bone and is thought to prevent crystal thickening. In this work, citrate added as a regulatory element enabled molecular control of the size and stability of hydroxyapatite (HAp) nanocrystals in synthetic nanocomposites, fabricated with self-assembling block copolymer templates. The decrease of the HAp crystal size within the polymer matrix with increasing citrate concentration was documented by solid-state nuclear magnetic resonance (NMR) techniques and wide-angle X-ray diffraction (XRD), while the shapes of HAp nanocrystals were determined by transmission electron microscopy (TEM). Advanced NMR techniques were used to characterize the interfacial species and reveal enhanced interactions between mineral and organic matrix, concomitant with the size effects. The surface-to-volume ratios determined by NMR spectroscopy and long-range P-31{H-1} dipolar dephasing show that 2, 10, and 40 mM citrate changes the thicknesses of the HAp crystals from 4 nm without citrate to 2.9, 2.8, and 2.3 nm, respectively. With citrate concentrations comparable to those in body fluids, HAp nanocrystals of sizes and morphologies similar to those in avian and bovine bones have been produced.

URL<Go to ISI>://000290063600025
DOI10.1021/cm200355n
Alternate JournalChem. Mat.