Osteoblast growth on titanium coated with electrically conductive polypyrrole

Purpose:Electrically conductive polypyrrole(PPy)has demonstrated substantial potential for biomedical application because it may be used in contact with biological components to apply an electrical stimulation and electrochemically grown directly onto metallic substrates of any shape and dimension. The objectives of this study were to evaluate osteoblast responses to this PPy modified Ti surfaces with current electrical stimulation in vitro.Materials and Methods: Ti disks(15 x 10x1mm)were ground to 1200 grit, ultrasonically cleaned with acetone and ethanol for 10 minutes, followed by rinsing with deionized water. PPy coatings were electrochemically grown on titanium disks in 0.1M KCl and 0.3M PPy aqueous solution at current densities of 0.25mA/cm2. Cells culture tests on the PPy coating surface using primary adult rat bone marrow cell cultures(BMC)were performed to determine the cells behavior under the 10µA anodic current stimulus. Controls used were non-coated Ti disks. Cell attachment was evaluated by counting the number of cells in 24h. Cytoskeletal actin organization was examined using confocal laser scanning microscopy. Cell proliferation and differentiation activities were tested by total intracellular protein content, ALP activity and osteocalcin secretion. Calcium-containing in the extracellular matrix and mineralization experiment were completed to examine the cell's mineralization ability. One-way ANOVA and t-test were used for statistical analysis.Results: Osteoblasts cultured on the PPy-coated titanium substrates and subjected to an anodic current stimulus through the PPy coating showed a significant increasing number attachment and well-formed actin filaments localization. It could also enhance the cytoskeleton protein distribution, total protein synthesis, ALPase activity, osteocalcin expression and calcium-containing in the extracellular matrix. Under the induction of mineralizing medium, the osteoblasts could form mineralized nodules on PPy coating in vitro.Conclusion: Electrically conductive polypyrrole-coated titanium enhanced osteoblast functions in vitro significantly. This novel surface modification has potential applications to improve performance of titanium implants in vivo.