Experimental study evaluating stem cells by biofunctionalization of titanium surface

To accelerate the activation and differentiation of mesenchymal cells to the titanium surface acting on the physical properties (surface wettability), and chemical properties (by adhering to the titanium surface immobilized substances that generate an accelerated response of living tissue).

Method:

The samples were 20 rectangular test tubes (4mm-length screws with a 3mm head-diameter) of Ti6Al4V, which underwent a process of immersion for 24 hours at 76ºC in 50ml of tetrahydrofuran and 55mg of carboxietilphosphonic acid. Using wet tests we will check the wettability.

Afterwards,  phosphonic acid is activated with EDC and NHS, so they are able to react with amino groups of proteins. The preparation of 5ml of water is mixed with 175ml of EDC plus 54 mg of NH. pH is reduced with hydrochloric acid to pH = 7.

To check the efficiency of the reaction, it has been measured the presence of the protein on the surface of titanium by using a fluorescein labeling “NHS-Fluorescein”.

For cell culture, a 96-wells-chamber was used. 72 samples  were deposited. After different incubation times, cell migration, cell proliferation and cell differentiation were evaluated by using scanning electronic microscopy, histological techniques and immunohistochemistry towards osteogenic differentiation.

Result:

The initial cell-adhesion processes are determined by the wettability, surface charge and chemical properties. 

Carboxietilphosphonic acid could improve wettability while the addition of EDC and NHS would allow to immobilize proteins through covalent bonds.

Conclusion:

The surface modification of titanium has been based on controlling the surface topography, and more recently, in an approach from the standpoint of physical-chemical, leading to the formation of biocompatible layers. 

Changing the hydrophilic environment and immobilizing BMP-2, we will succeed in promoting mesenchymal cell migration to the surface of titanium, improving cell adhesion and cell proliferation and stimulating osteoblastic differentiation.