Design, synthesis, and evaluation of polydopamine-laced gelatinous hydroxyapatite nanocomposites for orthopedic applications
An ideal bone graft for restoring critical size defects (CSDs) should be sturdy enough to tolerate physiological loads, be malleable enough to fit into defects in the patient's bone, and stimulate bone regeneration. Here, we report a new nanocomposite material called Gemussel, made of gelatinous hydroxyapatite (HAP-GEL) with polydopamine crosslinking. We found that the mechanical performance of Gemussel is superior to calcium phosphate cement, can harden within aqueous environment, and is suitable for chair side applications. Gemussel is injectable and suitable for scaffolding. The combined physical properties of Gemussel were equivalent to that of cortical bone. Our result also showed that Gemussel had a compressive strength (120MPa), a biaxial flexure strength (110Mpa), and a compressive modulus (2.2GPa) that are approximating 80%, 50%, and 60% of cortical bone, respectively. We also found experimental evidence indicating that the polydopamine material in Gemussel may be bioactive and might play a role in stimulating bone formation. In support of this hypothesis, we found that osteoblasts express specific dopamine receptor subunits and adding polydopamine increased in vitro osteoblastic cell proliferation and differentiation. Mineralization and osteocalcin expression were increased by dopamine, suggesting an osteoconductive effect. To our knowledge, this is the first report which shows that osteoblasts express dopamine receptors and respond to dopamine. Taken together, our data demonstrate that polydopamine crosslinking significantly reduces brittleness of the previous HPA-GEL system and improves osteoconductivity possibly by stimulating bone formation through bioactive dopamine. Therefore, our new Gemussel bioceramics is an ideal material for restoring CSDs and bone regeneration.
Ko, CC; Guez, C; Lee, DJ; Wang, Z; Tseng, H
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International Standard Book Number 13 (ISBN-13)