Fibrinogen Adsorption and Sponge-like Aggregate Formation on Titanium Modified by Electrochemically Deposited CaCO₃

Fibrinogen adsorption governs biological responses to implantable medical devices; however, surface properties influence the overall functionality of the biomaterial, and guided fibrinogen adsorption remains limited. In the present work, CaCO₃ was electrochemically deposited on commercial Ti at -1.6 V for 1 h, 2 h, and 3 h. Furthermore, the effects on fibrinogen adsorption were detailed by using dye-assisted scanning electron microscopy (d-SEM), X-ray photoelectron spectroscopy (XPS), and Fourier Transform Infrared Spectroscopy (ATR-FTIR). Longer deposition times produced thicker calcite layers with maximum surface coverage of 99.80 ± 0.40%, accompanied by progressively greater calcium-ion release, ranging from 3.5 mg·L^-1·cm^-2 (1 h) to 12.2 mg·L^-1·cm^-2 (3 h) over 240 min. The results show that electrochemically deposited calcite crystals for 3 h lead to the formation of sponge-like fibrinogen aggregates via calcium ion-mediated conformational activation, particularly by chelating with the histidine and carboxylate residues of the Bβ chain segment Gly-His-Arg-Pro (β15-β18). This structural reorganization was supported by XPS N 1s binding energy at 398.80 eV and a red shift in Amide I and Amide II bands in FTIR spectra. Overall, this study reveals that careful modification of surface chemistry can guide fibrinogen adsorption, which can be beneficial for advanced biomaterials to orchestrate tissue integration at the protein and cellular levels.