Aims: Different polyurethane foam matrices (PUF) loaded with hydroxyapatite (HA) or α-tricalcium phosphate were proposed as scaffold for bone regeneration [1,2]. In this work new PUFs were developed and loaded with HA or α-TCP.

Methods: PUFs were synthesized by a one-step polymerisation from a hydrophilic polyol mixture (LF 2946, Elastogran, Italy) and polymeric MDI (B141, BASF), using Fe acetyl-acetonate as catalyst and 2% water as expanding agent. The composites were prepared in the same way, by adding HA or α-TCP to the reacting mixture.

In vitro cell interactions were evaluated with human osteoblasts (HOB, 2nd passage) isolated from the trabecular bone of the femoral head of patients undergoing total hip replacement and cultured following the usual procedure. HOB cells (1x105 cells/sample) were kept in contact with the scaffolds for 7 and 14 days. At each time endpoint HOB metabolic activity, intracellular and released ALP were evaluated.

Results: By water adsorption test, newly synthesized PUFs showed a higher hydrophilicity compared to that of the previous matrices (600% vs 110% water uptake after 100h). Due to the presence of inorganic salts, composite scaffolds showed density values higher (0.131B80.200g/cm3) than those of unloaded PUFs (0.071B80.093g/cm3). Yet, open cell percentage (57–75%) and average pore size (350B8520mm) resulted similar to those of the PUFs.

HOB cells grown on scaffold samples showed an increase of metabolic activity from 7 to 14 days. The amount of intracellular ALP increased too, whereas the amount of ALP in the medium was quite low. HOB cells, after 14 days, appeared closely adherent to the scaffolds, with an elongated and flattened shape.

Conclusions: These preliminary results showed that, even if slow, the growth of HOB onto PUF scaffolds was quite good. After 14 days, PUF composites showed higher cells growth than PUF-matrices, confirming the role of the bone-like inorganic particles in improving osteoblasts functions. Long-term in vitro tests are now in progress.