Dopant-driven fibrinogen self-assembly on titanium surfaces: Contrasting effects of calcium doping and calcium/silver...

Fibrinogen adsorption conditions the biological responds to implantable medical devices; however, this effect is surface chemistry dependent and associated mechanism is unclear. Here, it is shown that fibrinogen self-assembly distinctively on doped titanium because of its different binding sites to calcium ions and immobilized silver nanoparticles. Calcium doping and silver-calcium co-doping are applied on pure titanium by plasma technology, and their effects on fibrinogen adsorption are detailed by using X-ray photoelectron spectroscopy (XPS), dye-assisted scanning electron microscopy (d-SEM), and scanning electrochemical microscopy (SECM). It demonstrates that calcium-doping induces mesh-like fibrinogen assembly via calcium ion mediated conformational activation, particularly chelating with the histidine and carboxylate residues of the Bβ chain segment Gly-His-Arg-Pro (β15-β18). Conversely, silver addition disrupts calcium chelation by preferentially coordinating with cysteine thiol groups in Aα chain (Aα 161-165), and produces a dense fibrinogen layer on titanium. Since fibrinogen adsorption is a native action during medical device placement, the present study provides new insights into advancing surface modification of implantable biomaterials to orchestrate tissue integration at the protein and cellular levels.