Surface modification of Ti6Al4V by forming hybrid self-assembled monolayers and its effect on collagen-I adsorption, osteoblast adhesion and integrin expression

Abstract

Silanization is a widely explored chemical technique to modify surfaces for tailoring physio-chemical properties like surface chemistry and wettability but its impact on bio-interfaces interaction i.e. protein adsorption and cellular responses is not well understood. This work focusses on modulating surface properties of Ti6Al4V to study their behavior towards collagen-I (Col-I) adsorption and subsequently on osteoblast adhesion and integrin expression. The moderate hydrophobic Ti6Al4V surfaces (θ = 78 ± 3°) were prepared by forming hybrid self-assembled monolayers (SAMs), which contain both hydrophobic and hydrophilic moieties on the same SAM molecule and were characterized using different techniques. The experimental adsorbed amounts of Col-1 were compared with the predicted ones using the Gibbs equation, which were overestimated but linearly related. AFM and secondary structure analyses of the adsorbed Col-I revealed globular morphology with significant change only in helical content. Cells adhered to hybrid surface pre-adsorbed with Col-1 exhibited better cell adhesion (~100%) and spreading area (1127 µm2) as compared to cells adhered to hybrid surface without (adhesion of 69% and cell area of 509 µm2) and with (adhesion of 94% and cell area of 908 µm2) FBS in cell culture media. Further, integrin expression was analyzed using ELISA based integrin assay to elucidate the cellular adhesion. We observed higher expression of α1 and α2 integrins on surfaces with pre-adsorbed Col-I and were correlated with the increase in nuclei area indicating α1 and α2 mediated cell adhesion promoted the cell proliferation. Overall, cell-surface interactions were improved on hybrid surfaces with pre-adsorbed Col-I, which designated the potential applications of the modified Ti6Al4V especially in metallic orthopedic implants.