Surface Functionalization of Ti6Al4V via Self-assembled Monolayers for Improved Protein Adsorption and Fibroblast Adhesion

Abstract

Although metallic biomaterials find numerous biomedical applications, their inherent low bioactivity and poor osteointegration had been a great challenge for decades. Surface modification via silanization can serve as an attractive method for improving the aforementioned properties of such substrates. However, its effect on protein adsorption/conformation and subsequent cell adhesion and spreading has rarely been investigated. This work reports the in-depth study of the effect of Ti6Al4V surface functionalization on protein adsorption and cell behavior. We prepared self-assembled monolayers (SAMs) of five different surfaces (amine, octyl, mixed [1:1 ratio of amine:octyl], hybrid, and COOH). Synthesized surfaces were characterized by Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy, contact angle goniometry, profilometry, and field emission scanning electron microscopy (FESEM). Quantification of adsorbed mass of bovine serum albumin (BSA) and fibronectin (FN) was determined on different surfaces along with secondary structure analysis. The adsorbed amount of BSA was found to increase with an increase in surface hydrophobicity with the maximum adsorption on the octyl surface while the reverse trend was detected for FN adsorption, having the maximum adsorbed mass on the COOH surface. The α-helix content of adsorbed BSA increased on amine and COOH surfaces while it decreased for other surfaces. Whereas increasing β-turn content of the adsorbed FN with the increase in the surface hydrophobicity was observed. In FN, RGD loops are located in the β-turn and consequently the increase in Δ adhered cells (%) was predominantly increased with the increasing Δ β-turn content (%). We found hybrid surfaces to be the most promising surface modifier due to maximum cell adhesion (%) and proliferation, larger nuclei area, and the least cell circularity. Bacterial density increased with the increasing hydrophobicity and was found maximum for the amine surface (θ = 63 ± 1°) which further decreased with the increasing hydrophobicity. Overall, modified surfaces (in particular hybrid surface) showed better protein adsorption and cell adhesion properties as compared to unmodified Ti6Al4V and can be potentially used for tissue engineering applications.

Local Surface Electric Field’s Effect on Adsorbed Proteins’ Orientation

“…These results illustrate that the morphology of the adsorbed film was different in the amorphous parts and crystalline parts, suggesting that there may be two distinct adsorption mechanisms occurring on these structurally different networks. These AFM observations require a quantitative study that involves the measurement of the adsorbed protein amount, following the methodology presented in [24], in order to provide a more complete assessment of the adsorption mechanism around the NPs on one hand, and on the a-Si:H part of the surface on the other hand. This would provide an estimate of the strength of the binding forces around the nanocrystals and correlate this with the qualitative results obtained using AFM that show that the adsorbed protein amount was significantly greater on the NC substrate compared with the PM substrate.…”

“…involves the measurement of the adsorbed protein amount, following the methodology presented in [24], in order to provide a more complete assessment of the adsorption mechanism around the NPs on one hand, and on the a-Si:H part of the surface on the other hand. This would provide an estimate of the strength of the binding forces around the nanocrystals and correlate this with the qualitative results obtained using AFM that show that the adsorbed protein amount was significantly greater on the NC substrate compared with the PM substrate.…”

“…Whenever a solid surface is placed in a solution containing a given protein, the protein will generally tend to rapidly adsorb until it saturates the surface. The final organization of the adsorbed protein layer (i.e., the orientation, conformation, and packing arrangement of the adsorbed proteins) depends on the chemical and physical structure of the protein, the surface, the aqueous solution, and the thermodynamics of the interactions between these system components [24,25]. This phenomenon includes a number of interactions at the solid-liquid interfaces that involve hydrophobic, electrostatic, and van der Waals interactions, as well as hydrogen bonding [26][27][28][29].…”

Design of engineered surfaces for prospective detection of SARS-CoV-2 using quartz crystal microbalance-based techniques

“…SAMs are prepared spontaneously through the covalent attachment on a surface, without interfering with the bulk properties of the material. SAMs are formed on a wide range of substrates including glass, silica, indium tin oxide (ITO), gold, polymers, and metals using suitable surface-modifying agents [27][28][29][30].…”

Nanomaterial-based hydrogels for coronary interventions: a mini review

“…The surface-to-volume ratio, surface charge, and integration with the cells and proteins make nanomaterials highly effective in various fields of biomedical science, including CTE. The wide biomedical applications of nanotechnology include but are not limited to drug delivery [8,9] , tissue engineering [10,11] , hyperthermia [12,13] , and nanoantibiotics [14][15][16][17] .…”