Differences between top-down and bottom-up approaches in mineralizing thick, partially demineralized collagen scaffolds

Yan Liu, Sui Mai, Nan Li, Cynthia K.Y. Yiu, Jing Mao, David Henry Pashley, Franklin Chi Meng Tay

Research output: Contribution to journalArticlepeer-review

103 Scopus citations


Biominerals exhibit complex hierarchical structures derived from bottom-up self-assembly mechanisms. Type I collagen serves as the building block for mineralized tissues such as bone and dentin. In the present study, 250-300 μm thick, partially demineralized collagen scaffolds exhibiting a gradient of demineralization from the base to surface were mineralized using a classical top-down approach and a non-classical bottom-up approach. The top-down approach involved epitaxial growth over seed crystallites. The bottom-up approach utilized biomimetic analogs of matrix proteins to stabilize amorphous calcium phosphate nanoprecursors and template apatite nucleation and growth within the collagen matrix. Micro-computed tomography and transmission electron microscopy were employed to examine mineral uptake and apatite arrangement within the mineralized collagen matrix. The top-down approach could mineralize only the base of the partially demineralized scaffold, where remnant seed crystallites were abundant. Minimal mineralization was observed along the surface of the scaffold; extrafibrillar mineralization was predominantly observed. Conversely, the entire partially demineralized scaffold, including apatite-depleted collagen fibrils, was mineralized by the bottom-up approach, with evidence of both intrafibrillar and extrafibrillar mineralization. Understanding the different mechanisms involved in these two mineralization approaches is pivotal in adopting the optimum strategy for fabricating novel nanostructured materials in bioengineering research.

Original languageEnglish (US)
Pages (from-to)1742-1751
Number of pages10
JournalActa biomaterialia
Issue number4
StatePublished - Apr 2011


  • Biomimetics
  • Bottom-up
  • Collagen
  • Mineralization
  • Particle-mediated
  • Top-down

ASJC Scopus subject areas

  • Biotechnology
  • Biomaterials
  • Biochemistry
  • Biomedical Engineering
  • Molecular Biology


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