2014-Sustainable Industrial Processing Summit
SIPS 2014 Volume 5: Composite, Ceramic, Quasi-crystals, Nanomaterials & Coatings
| Editors: | Kongoli F |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2014 |
| Pages: | 578 pages |
| ISBN: | 978-1-987820-07-2 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Biomimetic Bone Graft Substitutes using a Polymer-Induced Liquid-Precursor (PILP) Mineralization Process
Laurie Gower1;1UNIVERSITY OF FLORIDA, Gainesville, United States;
Type of Paper: Regular
Id Paper: 135
Topic: 16
Abstract:
Bone is a hierarchical composite which, at the nanostructural level, consists of an assembly of collagen fibrils that are embedded with uniaxially-aligned nanocrystals of hydroxyapatite. Our studies have revealed that this nanostructure can be reproduced in vitro using a polymer-induced liquid-precursor (PILP) mineralization process. The polymeric additive consists of acidic polypeptides (e.g. polyaspartic acidic) or proteins (e.g. osteopontin) that can mimic the action of non-collagenous proteins found in bone. The high charge density of the polyanionic additive sequesters ions so that liquid-liquid phase separation occurs, forming nanodroplets of a hydrated amorphous mineral precursor. The infiltration of nanodroplets into the collagen fibrils leads to intrafibrillar mineral, which is the foundation of bone nanostructure. We have put forth a (controversial) hypothesis regarding the mechanism of intrafibrillar mineralization, which proposes that a liquid-phase amorphous precursor induced by the polypeptide can be drawn into the gaps and grooves of collagen fibrils by capillary action, which upon solidification and crystallization, leads to an interpenetrating organic-inorganic composite with bone-like nanostructure. Through reaction parameters optimization, bone compositions matching (60-70wt% mineral) have been achieved in various types of collagen scaffolds. Biogenic collagen matrices can also be mineralized by this process, such as rat tail tendon and demineralized bone; however, there are currently limitations in the depth of penetration that can be attained in these dense scaffolds. Therefore, our current studies are directed at assembling parallel-fibered collagen which can be mineralized in the form of laminated composites, mimicking the lamellar microstructure of bone. Through cell signaling mechanisms provided by the osteopontin additive, the potential for modulating osteoclast resorption of these bone-like composites might be achieved. The long range goal of these studies is using this model system to understand bone formation and pathologies, and from applications perspective, preparing bioresorbable load-bearing bone substitutes.