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Coating of Sub-Micrometric Keratin Fibers on Titanium Substrates: A Successful Strategy for Stimulating Adhesion and Alignment of Fibroblasts and Reducing Bacterial Contamination
* 1 , 2 , 3 , 4 , 2 , 4 , 3 , 1
1  Department of Applied Science and Technology, Politecnico di Torino, TORINO, Italy
2  CNR-IPCB, Institute of Polymers, Composites and Biomaterials, NAPOLI, Italy
3  Department of Health Sciences, Università del Piemonte Orientale, NOVARA, Italy
4  CNR-ISMAC, Istitute for Macromolecular Studies, BIELLA, Italy

Published: 28 February 2019 by MDPI in 1st Coatings and Interfaces Web Conference session Biomaterial Surfaces & Interfaces

Coatings are a versatile tool for modulation of the biological response of biomaterials; in particular, the use of biopolymers as coating material may improve cell interactions and tissue adhesion. Among others, keratin is a natural protein able to stimulate fibroblast cells effectively and has the ability to bind metal ions. Coatings of keratin fibers onto titanium substrates can improve soft tissue adhesion, eventually coupling topographical (contact guidance) and chemical stimulus through the alignment of the fibers along sub-micrometric grooves of the substrate. Sub-micrometric keratin fibers were obtained by electrospinning both in random and oriented arrangements (though a rotating collector); in addition, antibacterial properties were added by enrichment of the coating with silver ions. This type of coating can be of interest in transmucosal dental implants, where perimplantitis is often due to infection (biofilm formation) and disease worsening is due to inflammation of the surrounding soft tissue, which is guided by fibroblasts. Keratin fibres coatings were prepared and characterized by means of Field Emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), cell (gingival fibroblasts) and bacteria (S. aureus) culture tests. FESEM observations demonstrated the possibility to deposit keratin fibres onto titanium substrates in random or oriented arrangements effectively. Keratin fibres were able to increase fibroblast adhesion and proliferation. On randomly deposited keratin fibres, fibroblast cells were significantly biologically stimulated and showed high adhesion and proliferation, but not orientation ability; on the other hand, aligned keratin fibres on a grooved substrate were able to stimulate cells both from the topographical (orientation) and biological standpoint. Finally, Ag-doped keratin fibres coatings were able to reduce S. aureus adhesion significantly, maintaining high biocompatibility. Considering these results, keratin sub-micrometric fibres coatings are a promising strategy for stimulating fibroblasts and reducing bacterial contamination.

Keywords: titanium; keratin; electrospinning; fibroblasts; antibacterial
Comments on this paper
MariaCristina Tanzi
Stability of the keratin coating on Ti substrate
Your work is original and interesting
However, there is no mention about the type of interaction between the electrospun keratin deposit and titanium substrate and coating stability
Have you any evidence about this? Did you perform any specific tests?

MariaCristina Tanzi
Stability of electrospun deposit on Titanium
Your work is original and interesting
However, there is no mention of the type of interaction between the electrospun deposit on titanium and its stability
Have you any idea? Did you perform any specific test?
Sara Ferraris
Thank you for your comments,
We investigated the stability of keratin coatings in water ( samples soaking in water at 37°C and subsequent testing of keratin presence by means of optical/SEM microscopy and FTIR spectroscopy) and we found that keratin coatings onto titanium substrates are stable up to one month. Moreover we investigated the adhesion of keratin coatings to titanium substrates by means of tape test and we found some differences depending on the substrate chemistry and topography.
As far as the interaction between keratin and titanium we can hypothesize an electrostatic interaction (we have some evidence of this from recent zeta potential measurements on uncoated/coated substrates). Moreover mechanical interlocking can improve the adhesion on rough substrates. We are actually studying more in depth these topics and we are testing some surface treatments intended to improve keratin adhesion to titanium with encouraging results.