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The bioactivity of biomaterials is closely related to cell response in contact with them. However, shortly after their insertion, materials are soon covered with proteins that constitute the biological fluids, and which render the direct surface recognition by cells almost impossible. The control of protein adsorption at the interface is therefore desirable. Extracellular matrix proteins are of particular interest in this sense, due to their well-known ability to modulate cell behavior. Particularly, fibronectin plays a leading role, being present in both healthy and injured tissues undergoing healing and regeneration. The aim of the present work is to give an overview on fibronectin and on its involvement in the control of cell behavior providing evidence of its pivotal role in the control of cell adhesion, spreading, migration, proliferation and differentiation. A deep insight into methods to enrich biomaterials surface with fibronectin will be then discussed, as well as new cues on the possibility to design tailored platforms able to specifically retain fibronectin from the surrounding extracellular milieu., (© 2019 The Authors.)

In vitro studies have consistently shown that titanium surface wettability affects the response of osteoprogenitors, leading to important advances in the clinical osseointegration of dental implants. However, the underlying molecular mechanisms remain unknown. Since surface conditioning by blood components initiates within milliseconds after insertion, it is reasonable to hypothesize that the amount and the type of blood proteins adsorbed influences the interaction between the implant surface and osteoprogenitors. To test this hypothesis, titanium implant surfaces with different characteristics, in terms of topography and wettability, have been conditioned with selected plasma proteins. Pure fibronectin (HFN) and albumin (HSA) solutions, or their mixture at the relative plasma concentrations were allowed to adsorb on titanium surfaces for 60 min. Protein adsorption was monitored by Bradford assay, while the contribution of HSA and HFN in forming the microfilm layer at the interface was studied by Western Blot. Subsequently, the same protein-conditioned surfaces were used to culture C2C12 cells, thus studying their capacity to adhere and to spread after 3 h. Cell viability was evaluated up to 7 days, while the expression of osteogenic genes was assessed after 3 days. Under competitive adsorption conditions, hydrophilicity promotes the selectivity of titanium for HFN regardless of the surface microtopography. As a consequence of selective HFN adsorption, cells on hydrophilic surfaces displayed enhanced adhesion and spreading, as well as increased proliferation. On the other hand, selective HFN adsorption did not appreciably affect cell differentiation. These data suggest that implant surface hydrophilicity plays a key role in guiding the selective adsorption of specific proteins from blood plasma. Moreover, the selective adsorption of HFN, as a consequence of surface hydrophilicity, was found to account for early cell responses amelioration. Thus, titanium surface hydrophilicity contributes to the clinical success of dental implant by selectively controlling protein adsorption at the interface., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Objectives: To investigate how a thermal treatment to increase titanium wettability influences proteins adsorption from blood serum and osteoblasts responses., Methods: Titanium discs with machined or micro-rough profiles were thermally treated to obtain hydrophilic surfaces. The adsorption kinetics of two representative serum proteins were determined by Bradford assay, while the stable protein adsorption pattern from blood serum was investigated by SDS-PAGE and Western Blot analysis. Subsequently, MC3T3-E1 cells were cultured on titanium for 24h and assayed for adhesion and morphology., Results: Thermally-induced hydrophilicity dramatically improved the capacity of titanium to selectively adsorb fibronectin and fibrinogen from blood serum, without evident influence on other representative serum proteins. The selective adsorption of fibronectin was linked to the improved capacity of MC3T3-E1 cells to adhere and spread on hydrophilic surfaces., Significance: We identified a potential method to improve selective protein adsorption on titanium by enhancing implant surface wettability through a thermal treatment. Selective fibronectin adsorption was further indicated as the responsible for improved osteoblasts adhesion. Targeting specific cell response by selective protein adsorption appears to be crucial to conceive even more performant therapies., (Copyright © 2019 Elsevier B.V. All rights reserved.)