Juha Tuukkanen
Preparation and bioactive properties of nanocrystalline HA thin films and electrospun fibers
Juha Tuukkanen1,3, Jani Holopainen2, Kyösti Kauppinen1, Jenni Pasuri1, Eero Santala2, Petri Lehenkari1, and Mikko Ritala2
1University of Oulu, Finland
2Universityof Helsinki, Finland
3 JSPS Fellowship
Calcium phosphate (CaP) ceramics are biocompatible and widely used to treat bone defects such as orthopedic and maxillofacial augmentation. However,
CaPs like hydroxyapatite (HAp) or βTCP are fairly insoluble and lack osteogenicity. It has been shown, that proper CaP can modulate mesenchymal stem cell (MSC) function to induce regenerative inflammation and osteoclastogenesis,
which induces subsequent bone formation. We have further investigated possibilities to develop novel biocompatible CaP coatings for metallic implants and bioactive CaPs for tissue engineering applications.
Nanocrystalline hydroxyapatite thin films were fabricated on titanium by atomic layer deposition (ALD) of CaCO3 and its subsequent conversion to HAp by diammonium hydrogen phosphate (DAP) solution. The coating converted with 0.2 M DAP at 95 °C was calcium deficient with a Ca/P ratio of 1.39. The coatings were non-dissolvable in the cell culture medium and the Scotch Tape test revealed good attachment on titanium. The biocompatibility was confirmed by human bone marrow derived cells in vitro
Electrospun HAp was fabricated by electrospinning a solution of Ca(NO3)2•4H2O, triethyl phosphate and polyvinylpyrrolidone in 2-methoxyethanol followed by annealing at 800 °C in air. The resulting HAp fibers were around 500 nm in diameter. RAW 264.7 macrophages and human bone marrow derived primary osteoclasts (hOC) were cultured with electrospun HAp. For control activation of macrophages bacterial lipopolysaccharide (LPS) was used. LPS, but not HAp fibers, stimulated TNF-α and IL-6 secretion by macrophages. The mineral scaffold supported osteoclastogenesis and osteoclasts were able to resorb the HAp nanofibers.
In the future, more extended in vitro and in vivo studies will find out the feasibility of these applications in orthopedics, prosthetic dentistry and bone tissue engineering.