title: Electrospinning of calcium carbonate fibers and their conversion to nanocrystalline hydroxyapatite.
abstract: Calcium carbonate (CaCO3) fibers were prepared by electrospinning followed by annealing. Solutions consisting of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) and polyvinylpyrrolidone (PVP) dissolved in ethanol or 2-methoxyethanol were used for the fiber preparation. By varying the precursor concentrations in the electrospinning solutions CaCO3 fibers with average diameters from 140 to 290 nm were obtained. After calcination the fibers were identified as calcite by X-ray diffraction (XRD). The calcination process was studied in detail with high temperature X-ray diffraction (HTXRD) and thermogravimetric analysis (TGA). The initially weak fiber-to-substrate adhesion was improved by adding a strengthening CaCO3 layer by spin or dip coating Ca(NO3)2/PVP precursor solution on the CaCO3 fibers followed by annealing of the gel formed inside the fiber layer. The CaCO3 fibers were converted to nanocrystalline hydroxyapatite (HA) fibers by treatment in a dilute phosphate solution. The resulting hydroxyapatite had a plate-like crystal structure with resemblance to bone mineral. The calcium carbonate and hydroxyapatite fibers are interesting materials for bone scaffolds and bioactive coatings.
authors.affiliation: Laboratory of Inorganic Chemistry, Department of Chemistry, P.O. Box 55, FI-00014, University of Helsinki, Finland. Electronic address: jani.holopainen@helsinki.fi.
authors.forename: Jani
authors.initials: J
authors.lastname: Holopainen
authors.affiliation: Laboratory of Inorganic Chemistry, Department of Chemistry, P.O. Box 55, FI-00014, University of Helsinki, Finland.
authors.forename: Eero
authors.initials: E
authors.lastname: Santala
authors.affiliation: Laboratory of Inorganic Chemistry, Department of Chemistry, P.O. Box 55, FI-00014, University of Helsinki, Finland.
authors.forename: Mikko
authors.initials: M
authors.lastname: Heikkilä
authors.affiliation: Laboratory of Inorganic Chemistry, Department of Chemistry, P.O. Box 55, FI-00014, University of Helsinki, Finland.
authors.forename: Mikko
authors.initials: M
authors.lastname: Ritala
mesh_terms: D002119:Calcium Carbonate / Q000737:chemistry*; D017610:Calcium Compounds / Q000737:chemistry; D020099:Coated Materials, Biocompatible / Q000737:chemistry; D003460:Crystallization; D017886:Durapatite / Q000737:chemistry*; D005026:Ethylene Glycols; D053758:Nanoparticles / Q000737:chemistry*; D009566:Nitrates / Q000737:chemistry; D013818:Thermogravimetry; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D017610:Calcium Compounds; D020099:Coated Materials, Biocompatible; D005026:Ethylene Glycols; D009566:Nitrates; D017886:Durapatite; C005219:methyl cellosolve; D002119:Calcium Carbonate; C059948:calcium nitrate
keywords: Calcium carbonate; Dip coating; Electrospinning; Hydroxyapatite; Nanofiber; Spin coating