Grafted Adenosine Diphosphate and Fibrinogen on Titanium Affect Platelet Function

Objectives: Titanium (Ti) dental implant osseointegration needs to be continuously improved to meet the requirements of a wide range of clinical applications. Platelets are important player in healing process. This study was aimed to modify Ti surface by grafted functional molecules (Adenosine Diphosphate, ADP and Fibrinogen, FIB) to promote platelet adhesion, aggregation and activation.
Methods: Ti substrates were first modified through the poly-dopamine anchorage. Then, ADP and FIB were immobilized on the Ti substrates via electrostatic interactions. This experiment was divided into four groups: pure titanium control group, ADP grafted group, FIB grafted group and ADP+FIB group. X-ray photoelectron spectroscopy (XPS) was performed to detect whether functional molecules were successfully grafted to Ti surface. The adhesion of platelets was detected by scanning electron microscopy (SEM), and lactate dehydrogenase (LDH) quantitative assays. After culturing human mesenchymal stromal cells (MSCs) on the grafted substrates, cytotoxicity was tested using a cell counting kit. The results were analyzed by one-way analysis of variance (ANOVA, p<0.05).
Results: XPS showed that the coated surface possessed P peaks indicating the abundance of ADP, and S peaks indicating the abundance of FIB. Under SEM, there were large numbers of platelets-like cells gathered in clusters on coated surfaces compared with the controls. LDH results of four groups were Ti-ADP-FIB (2042±36.81 IU), Ti-FIB (1812±18.03 IU), Ti-ADP (1727±16.40 IU) and Ti (1028±26.88 IU) respectively, with the Ti-ADP-FIB significantly higher than other groups (P<0.05). MSCs proliferation results showed cell number of all four groups rose at different time points, however with no significant differences in 1, 3 and 5 days (P>0.05).
Conclusions: ADP and FIB can be successfully grafted onto titanium surface. And the functionalized surface can promote adhesion, aggregation of platelets and the release of bioactive molecules from platelets. Therefore the modified Ti surface has good biocompatibility and potential for improved osseointegration.