Rapid fabrication of keratin–hydroxyapatite hybrid sponges toward osteoblast cultivation and differentiation

Wool keratin sponges were reported to be useful scaffolds for long-term and high-density cell cultivation (J. Biotechnol. 93 (2002) 165). The hybrid of the keratin sponges with calcium phosphate materials gave the additional function. Two rapid fabrication methods for calcium phosphate hybrid biomaterials were described. Firstly, the CaP-precipitated sponges were obtained by only the immersion of the carboxyl-sponges, chemically introduced with high amount of carboxyl groups on the sponges, in calcium and phosphate ions containing buffers such as PBS(+) for only 1–3 days. Neither sponge, introduced with amino or amido groups or non-treated, gave significant calcium phosphate precipitation. The carboxyl-sponges were mimics of matrix gamma-carboxyglutamic acid protein, which is responsible for osteoblast calcification. Secondly, the hydroxyapatite particle suspension was added onto carboxyl-sponges to fabricate trapped sponge. The trapped hydroxyapatite particles might interact with keratin protein of the sponge walls. Preliminary experiments measuring the expression of alkaline phosphatase, early osteoblast differentiation marker, suggested that both hybrid sponges, CaP-precipitated and trapped sponges, alter the differentiation pattern of preosteoblasts, MC3T3-E1.