Coating nanothickness degradable films on nanocrystalline hydroxyapatite particles to improve the bonding strength between nanohydroxyapatite and degradable polymer matrix

  1. Heather L. Nichols1,
  2. Ning Zhang1,2,
  3. Jing Zhang2,
  4. Donglu Shi3,
  5. Sarit Bhaduri4,
  6. Xuejun Wen1,2,5,*

Article first published online: 12 FEB 2007

DOI: 10.1002/jbm.a.31066

Issue

Journal of Biomedical Materials Research Part A

Journal of Biomedical Materials Research Part A

Volume 82A, Issue 2, pages 373–382, August 2007

Additional Information

How to Cite

Nichols, H. L., Zhang, N., Zhang, J., Shi, D., Bhaduri, S. and Wen, X. (2007), Coating nanothickness degradable films on nanocrystalline hydroxyapatite particles to improve the bonding strength between nanohydroxyapatite and degradable polymer matrix. J. Biomed. Mater. Res., 82A: 373–382. doi: 10.1002/jbm.a.31066

Author Information

  1. 1

    Clemson–MUSC Bioengineering Program, Department of Bioengineering, Clemson University, Charleston, South Carolina 29425

  2. 2

    Department of Cell Biology and Anatomy, Medical University of South Carolina, Charleston, South Carolina 29425

  3. 3

    Department of Chemical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio 45221-0012

  4. 4

    Department of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634

  5. 5

    Department of Orthopedic Surgery, Medical University of South Carolina, Charleston, South Carolina 29425

*Clemson–MUSC Bioengineering Program, Department of Bioengineering, Clemson University, Charleston, South Carolina 29425

Publication History

  1. Issue published online: 14 JUN 2007
  2. Article first published online: 12 FEB 2007
  3. Manuscript Accepted: 29 AUG 2006
  4. Manuscript Revised: 15 JUN 2006
  5. Manuscript Received: 16 MAR 2006

Funded by

  • AO Research Fund, Switzerland. Grant Number: 04-W55
  • NASA South Carolina EPSCoR, USA
  • National Science Foundation, USA. Grant Number: 0522057
  • NIH, USA. Grant Number: C06 RR018823

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Keywords:

  • nanostructured materials;
  • hydroxyapatite;
  • coating;
  • degradation;
  • cytocompatibility;
  • bone tissue engineering;
  • mechanical properties

Abstract

Hydroxyapatite (HA) nanoparticles are similar to bone apatite in size, phase composition, and crystal structure. When compared with micron-size HA particles, nano-HA possesses improved mechanical properties and superior bioactivity for promoting bone growth and regeneration. However, scaffolds fabricated from nano-HA alone cannot meet the mechanical requirements for direct-loading applications. A number of studies suggest that nanostructured composites may offer surface and/or chemical properties of native bone, and therefore represent ideal substrates to support bone regeneration. However, a common problem with nanohydroxyapatite (nano-HA)–polymer composites is the weak binding strength between the nano-HA filler and the polymer matrix since they are two different categories of materials and cannot form covalent bonds between them during the mixing process. Often, the mechanical strength of the composite is compromised due to the phase separation of the HA filler from the polymer matrix during the tissue repair process. To overcome this problem, an ultrathin degradable polymer film was grafted onto the surface of nano-HA using a radio-frequency plasma polymerization technology from acrylic acid monomers. The treated nano-HA powders are expected to bind to the polymer matrix via covalent bonds, thus enhancing the mechanical properties of the resultant composites. High-resolution transmission electron microscopy (HRTEM) experiments showed that an extremely thin polymer film (2 nm) was uniformly deposited on the surfaces of the nanoparticles. The HRTEM results were confirmed by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (TOFSIMS). Tensile tests performed on the specimens revealed that the degradable coating had improved elastic and strength properties when compared with the nondegradable and uncoated controls. XPS and TOSIMS data revealed that more functional carboxyl groups were formed on degradable coatings than cross-linked nondegradable coatings. Cytocompatibility assay demonstrated that both the degradable and nondegradable coatings are cytocompatible. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007

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