Background:The initial osteoblastic adhesion to materials characterize the first phase of cell material interactions, and the quality of this stage influences all the events leading to the formation of new bone. In the previous work, we developed a novel amorphous calcium phosphate (ACP)/poly(L-lactic acid) (PLLA) material, which could experience morphological variations in the microstructure. The aim of this study was to investigate initial response between this material and osteoblastic cells. The cellular attachment and corresponding signal transduction pathway were investigated.

Methods:The porous ACP/PLLA composite and PLLA scaffold (as control) were incubated in fetal bovine serum (FBS) containing phosphate buffered saline (PBS) medium and the protein adsorption was detected. The osteoblastic MG63 cells were seeded on the materials and cultured for 1, 4, 8 and 24 hours. the cell attachment was evaluated by MTS method. The cell morphology was observed by Scanning Electron Microscopy (SEM). The gene expressions of intergin subunits α1, α5, αv, β1, FAK and GAPDH were determined using real-time RT-PCR.

Results:The ACP/PLLA material significantly increased the protein adsorption with 6.4-fold at 1 hour and 2.4-fold at 24 hours compared to the pure PLLA scaffold. The attachment of osteoblastic cells on ACP/PLLA was significantly higher than that on PLLA scaffold. SEM observation revealed that cells on ACP/PLLA exhibited polygonal spread shape with filopodia adhering intimately to the scaffold surface, whereas cells on the PLLA scaffold exhibited a spherical or polygonal morphology. In addition, real-time RT-PCR revealed that higher levels of gene expressions of integrin subunits α1, αv, β1 and FAK were detected on ACP/PLLA composite.

Conclusions:The ACP/PLLA composite could promote protein adsorption and osteoblastic adhesion. The enhanced cell adhesion might be mediated by the binding of integrin subunits α1, αv and β1, and subsequently regulated through FAK signal transduction pathway.