Addition of Wollastonite Fibers to Calcium Phosphate Cement Increases Cell Viability and Stimulates Differentiation of Osteoblast-Like Cells

Abstract

Calcium phosphate cement (CPC) that is based on α-tricalcium phosphate (α-TCP) is considered desirable for bone tissue engineering because of its relatively rapid degradation properties. However, such cement is relatively weak, restricting its use to areas of low mechanical stress. Wollastonite fibers (WF) have been used to improve the mechanical strength of biomaterials. However, the biological properties of WF remain poorly understood. Here, we tested the response of osteoblast-like cells to being cultured on CPC reinforced with 5% of WF (CPC-WF). We found that both types of cement studied achieved an ion balance for calcium and phosphate after 3 days of immersion in culture medium and this allowed subsequent long-term cell culture. CPC-WF increased cell viability and stimulated cell differentiation, compared to nonreinforced CPC. We hypothesize that late silicon release by CPC-WF induces increased cell proliferation and differentiation. Based on our findings, we propose that CPC-WF is a promising material for bone tissue engineering applications.

Figure 1

MTT assays after 1, 7, and 14 days of cell culture on CPC disks. Data are expressed as means and standard deviation. p values of <0.01 are indicated by an asterisk.

Figure 2

Scanning electron micrographs of CPC and CPC-WF disks after 1, 7, and 14 days of culture. Osteoblast-like cells were well adhered, and the topography of the material did not interfere with cell adhesion.

Figure 3

Alkaline phosphatase activity after 7, 10, and 14 days of culture. Negative control represents cells induced to differentiate and cultured in the well plate. p values of <0.01 are indicated by an asterisk.

Figure 4

Ca²⁺, Si, and P ion concentrations in culture medium during the 3-day ionic balance period (quantifications at days 1 and 3) and under cell culture (days 1 and 7). DMEM alone was used as a control.