Nanoparticle reinforced bioactive polysaccharide hybrid composites for medical applications (Nanobiocomp)
Final Report Abstract
Cellulose-apatite composite fibres with a diameter of 22 µm were prepared by coextrusion of a cellulose slurry loaded with 10, 30 and 50 vol.-% (with respect to dry cellulose, (C6H10O5)n with n = 400) hydroxyapatite (HA, Ca10(PO4)6(OH)2) powder with an average particle size of 4.1 µm. In the dry state, the tensile strength st and the ultimate strain eu of cellulose fibres decrease with increasing HA filler loading. In the wet state, however, intermolecular incorporation of water in the cellulose matrix results in an increase of the ultimate strain of the composite fibre containing 10 vol.-% HA from 5.6 % (dry) to 9.9 % (wet). Hybride fibres of cellulose and biphasic calcium phosphate (produced by wet chemical precipitation reaction, d50 of 1.4 µm) were prepared by coextrusion via the ALCERU®- process. Tensile strengths of 448 MPa and 246 MPa were achieved for fibres with a filler content of 16 vol.-% and 37 vol.-%, respectively. The in vitro bioactivity of the hybrid fibres was proven by the formation of carbonated hydroxyapatite during exposure to simulated body fluid. The evenly distributed fine grained filler in combination with the swelling behaviour of the cellulose matrix showed a bioactive surface for filler contents much lower than for typical commercial composites of calcium phosphate and polyethylene. Nonwoven structures of cellulose acetate fibres of 90 nm – 5 µm in diameter were produced by electrospinning. Based on Hansens solubility theory composition of binary solvent mixtures (ketones - acetone, methyl ethyl ketone (MEK), and alcohols - benzyl alcohol, propylene glycol and dimethyl sulfoxide) was optimised with respect to control of fibre felt morphology. Highly crosslinked fibre networks of high packing density were obtained with binary low volatile alcohols/MEK solvent mixtures, a decreased spinning distance and an increased feed rate. Substituting MEK by acetone in the solvent mixture resulted in the formation of nanofibre felt with a low degree of fibre cross-links. Thus, solvent control is a key aspect for control of electrospun fibre felt structures which may serve as scaffolds for tissue engineering.
Publications
- Mechanical Properties of Cellulose-Apatite Composite Fibers, lecture at the EUROMAT, X41 417, September 13th, 2007
D. Haas, I. Hofmann, A. Eckert, H. Rüf, H. Firgo, D. J. Kim, F. A. Müller and P. Greil
- Mechanical Properties of Cellulose-Apatite Composite Fibers for Biomedical Applications, Advances in Applied Ceramics 107 (2008) 293-297
I. Hofmann, D. Haas, A. Eckert, H. Rüf, H. Firgo, F. A. Müller and P. Greil
- Solvent control of cellulose acetate nanofibre felt structure produced by electrospinning, Journal of Materials Science 45 (2010) 1299-1306
D. Haas, S. Heinrich and P. Greil
