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Mineralization of Biocompatible Scaffolds

IB-1857

APPLICATIONS OF TECHNOLOGY:

  • Artificial bone implants
  • Dental implants
  • Spinal cord injury repairs
  • Soft-tissue engineering
  • Bioceramics
  • Structural materials

ADVANTAGES:

  • Rapid mineralization
  • Tunable mineralization and crystallinity
  • Improved fracture resistance
  • Higher mineral-hydrogel adhesion strength
  • Better bone-tissue attachment and in-growth

DESCRIPTION:

Carolyn Bertozzi and colleagues at Berkeley Lab have developed a technique to produce bone-like composite materials by promoting high-affinity integration of hydroxyapatite (HA), the main mineral component of natural bone, with poly (2-hydroxethyl methacrylate) or pHEMA hydrogel polymers.

Unlike the bioinert materials currently used in the fabrication of orthopedic implants (metals, ceramics, polymers or a coarse combination of these components), the Berkeley Lab composite displays robust incorporation of osteophilic HA with the hydrogel polymer, hence encouraging tissue attachment and ingrowth. In addition, the polymer-mineral adhesion strength of the new composite is significantly greater than that of existing polymer-HA materials. This improved adhesion strength prevents rapid disintegration of the two components both during surgical handling and upon implantation. The Berkeley Lab technology encourages these functional improvements through controlled integration of the two materials.

High-affinity integration of HA with hydrogel scaffolds can be achieved using urea-mediated mineralization. (A) Vickers indentation test with a 15 N load performed over the surface of the composite did not lead to delamination of the mineral layer, suggesting excellent mineral-gel interfacial adhesion strength. Both the extent (B) and the crystallinity (C) of the HA mineralization can be fine-tuned.

pHEMA and its functionalized copolymers are the most widely used synthetic hydrogel polymers in tissue engineering. The Bertozzi group adapted to pHEMA a urea-mediated solution precipitation technique that has been used previously to prepare composite ceramic powders. The protocol induces hydrolysis at the surface and interior of the hydrogel, causing negatively charged carboxylate groups to be exposed. The negative charges serve as binding sites for calcium ions and orient them to promote nucleation and mineralization of hydroxyapatite in a manner that mimics the biosynthesis of natural bone.

In addition to mimicking the natural bone formation process, the Berkeley Lab technique also allows control of the degree of mineralization, strength of mineral adhesion at the hydrogel-mineral interface, and mineral crystallinity, factors that affect the final properties and hence applications of the composite. The composites prepared by this technique can also be used as structural materials for non-biological purposes.

STATUS:

  • Published patent application 2004-0161444 A1 available at www.uspto.gov. Available for licensing or collaborative research.

FOR MORE INFORMATION:

Song, J., Malathong, V., Bertozzi, C. R., "Mineralization of Synthetic Polymer Scaffolds: A Bottom-Up Approach for the Development of Artificial Bone", J. Am. Chem. Soc., 2005, 127, 3366.

Song, J., Saiz, E., Bertozzi, C. R., "A New Approach to Mineralization of Biocompatible Hydrogel Scaffolds: An Efficient Process toward 3-Dimensional Bonelike Composites", J. Am. Chem. Soc., 2003, 125, 1236.

Song, J., Saiz, E., Bertozzi, C. R., "Preparation of pHEMA-CP Composites with High Interfacial Adhesion via Template-driven Mineralization", J. Eu. Cer. Soc., 2003, 23, 2905.

REFERENCE NUMBER: IB-1857

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