Bone-implant interface. Evaluation of osteoblastic cells behavior on nanopatterned titanium surfaces: an in vitro analysis

Protein-adsorption occurs immediately following implantation of biomaterials. It is unknown at which extent protein-adsorption impacts the cellular events at bone-implant interface. To investigate this question, we compared the in-vitro outcome of osteoblastic cells grown onto titanium substrates and glass as control, by modulating the exposure to serum-derived proteins. Substrates consisted of 1) polished titanium disks; 2) polished disks nanotextured with H2SO4/H2O2; 3) glass. In the pre-adsorption phase, substrates were treated for 1h with ?MEM alone (M-noFBS) or supplemented with 10%-foetal-bovine-serum (M-FBS). MC3T3-osteoblastic-cells were cultured on the pre-treated substrates for 3h and 24h, in M-noFBS and M-FBS. Subsequently, the culture medium was replaced with M-FBS and cultures maintained for 3 and 7days. Cell-number was evaluated by: Alamar-Blue and MTT assay. Mitotic- and osteogenic-activities were evaluated through fluorescence-optical-microscope by immunolabeling for Ki-67 nuclear-protein and Osteopontin. Cellular morphology was evaluated by SEM-imaging. Data were statistically analyzed using ANOVA-test, (p<0.05). At day3 and day7, the presence or absence of serum-derived proteins during the pre-adsorption phase had not significant effect on cell-number. Only the absence of FBS during 24h of culture significantly affected cell-number (p<0.0001). Titanium surfaces performed better than glass, (p<0.01). The growth rate of cells between day3 and 7 was not affected by the initial absence of FBS. Immunolabeling for Ki-67 and Osteopontin showed that the mitotic- and osteogenic- activity were ongoing at 72h. SEM-analysis revealed that the absence of FBS had no major influence on cell-shape. †¢ Physico-chemical interactions without mediation by proteins are sufficient to sustain the initial phase of culture and guide osteogenic-cells toward differentiation. †¢ The challenge is avoiding adsorption of †˜undesirables' molecules that negatively impact on the cueing cells receive from surface. This may not be a problem in healthy patients, but may have an important role in medically-compromised-individuals in whom the composition of tissue-fluids is altered.