Dental Materials
Volume 24, Issue 9 , Pages 1212-1222, September 2008

Injectable and strong nano-apatite scaffolds for cell/growth factor delivery and bone regeneration☆☆☆

  • Hockin H.K. Xu

      Affiliations

    • Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201-1586, USA
    • Corresponding Author InformationCorresponding author at: Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, 650 West Baltimore Street, Baltimore, MD 21201, USA. Tel.: +1 410 706 7047; fax: +1 410 706 3028.
    • ,
  • Michael D. Weir

      Affiliations

    • Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201-1586, USA
    • ,
  • Carl G. Simon

      Affiliations

    • National Institute of Standards and Technology, Gaithersburg, MD 20899-8546, USA

Received 16 January 2008; accepted 2 February 2008.

Abstract 

Objectives

Seven million people suffer bone fractures each year in the U.S., and musculoskeletal conditions cost $215billion/year. The objectives of this study were to develop moldable/injectable, mechanically strong and in situ-hardening calcium phosphate cement (CPC) composite scaffolds for bone regeneration and delivery of osteogenic cells and growth factors.

Methods

Tetracalcium phosphate [TTCP: Ca4(PO4)2O] and dicalcium phosphate (DCPA: CaHPO4) were used to fabricate self-setting calcium phosphate cement. Strong and macroporous scaffolds were developed via absorbable fibers, biopolymer chitosan, and mannitol porogen. Following established protocols, MC3T3-E1 osteoblast-like cells (Riken, Hirosaka, Japan) were cultured on the specimens and inside the CPC composite paste carrier.

Results

The scaffold strength was more than doubled via reinforcement (p<0.05). Relationships and predictive models were established between matrix properties, fibers, porosity, and overall composite properties. The cement injectability was increased from about 60% to nearly 100%. Cell attachment and proliferation on the new composite matched those of biocompatible controls. Cells were able to infiltrate into the macropores and anchor to the bone mineral-like nano-apatite crystals. For cell delivery, alginate hydrogel beads protected cells during cement mixing and setting, yielding cell viability measured via the Wst-1 assay that matched the control without CPC (p>0.1). For growth factor delivery, CPC powder:liquid ratio and chitosan content provided the means to tailor the rate of protein release from CPC carrier.

Significance

New CPC scaffolds were developed that were strong, tough, macroporous and osteoconductive. They showed promise for injection in minimally invasive surgeries, and in delivering osteogenic cells and osteoinductive growth factors to promote bone regeneration. Potential applications include various dental, craniofacial, and orthopedic reconstructions.

Keywords: Calcium phosphate cement, Nano-apatite, Macroporous scaffolds, Stress-bearing, Osteoblast cell delivery, Growth factor, Bone tissue engineering

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☆ This article was presented as an invited talk at the Academy of Dental Materials Annual Meeting in Fort Lauderdale, FL, USA, October 2007.

☆☆ Certain commercial materials and equipment are identified in this paper to specify experimental procedures. In no instance does such identification imply recommendation by NIST. One standard deviation (S.D.) was used as the estimated standard uncertainty of the measurements unless otherwise specified in the Methods. These data should not be compared with those obtained in other laboratories under different conditions. Official contribution of the National Institute of Standards and Technology; not subject to copyright in the United States.

PII: S0109-5641(08)00033-X

doi:10.1016/j.dental.2008.02.001

Dental Materials
Volume 24, Issue 9 , Pages 1212-1222, September 2008

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