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Surface Coating and functionalization of Metallic Biomaterials with Essential Oils for Antibacterial Applications
* 1 , 2 , 3 , 3 , 4 , 5 , 1 , 6 , 6 , 1
1  Politecnico di Torino
2  Politecnico Di Torino
3  Department of Public Health and Paediatrics, Microbiology Division, University of Turin
4  Plant Physiology Unit, Department Life Sciences and Systems Biology, University of Turin
6  Università del Piemonte Orientale UPO, Department of HealthSciences


Essential oils (EO) are complex mixtures of natural molecules with a great activity against bacteria, virus and fungi. Despite their wide use in folk medicine, their employment in medicine or in biomedical products is still scarce and there are only few studies in literature. Their antibacterial and anti-adhesive properties are of interest for the development of coatings or functionalization of implant surfaces, but also for non-implantable medical devices, with the advantage of a reduced bacterial contamination, without the risk of developing bacteria resistance. For a first attempt, a peppermint essential oil was used in this research. The aim of the work was to functionalize or to coat the surface of different materials (Ti6Al4V, Steel 316L) with different surface finishing (grinded, polished, and chemically-treated). The obtained samples were characterized by means of XPS, FTIR, Fluorescent microscope observations and tape test. These analyses highlighted the presence of grafted oil biomolecules, or of a coating, on all the substrates after the procedure of functionalization/coating with remarkable chemical stability (during soaking in water or washing with acid or basic solutions) and mechanical adhesion. The samples were also subjected to antibacterial tests selected in order to simulate non-implantable applications: the test showed a reduction of the adherent bacteria and their viability on coated surfaces. In conclusion, the research work shows the great potential of the use of essential oils for surface functionalization or coating of biomaterials to obtain enhanced antibacterial properties: according to the final application, different oils can be selected in order to obtain the desired effects.

Keywords: antibacterial; essential oil; coating; metal alloys
Comments on this paper
I want to ask about which kind of application we can use these antibacterial strategies?

Thank you for the question. The functionalization was designed for the surface of implantable devices in order to have anti-adhesive action against bacteria. The coating instead vas developped with the same purpose, but for different applications.
It was developped for non implantable applications such as case of biomedical devices, medical carts, internal surfaces of incubators and many f. It is suitable for all the surfaces that are critical for bacteria contamination.
MANAR Abdalrazeq
Thank you for your reply

Diaa Aref
Interesting work and looks promising. I would like to ask if you have investigated the temperatures effects on the coats stability. Thank you
This kind of functionalization/coating was delelopped to work at body/room temperature. The stability of the coating was tested in water at 37°C with good results and the stability of the functionalized samples is ongoing. For the future, stability test have been planned at higher temperature in order to check if it is possible to expand the field of use.

MariaCristina Tanzi
What kind of interaction between substrate and essential oil used?
Your work is interesting and seems to be of potential practical applicability.
Your comment to the tape test results is: "The higher adhesion of the coating to the wrinkled substrate highlights that the increased roughness of the surface positively influences the adhesion of the coating by means of mechanical interlocking"
I wonder if there could be any other kind of physical-chemical interaction, what is your opinion?
Thank you for the question.
In my opinion the adhesion is guided by an electrostatic interaction supported by mechanical interlocking on wrinkled surfaces.

MariaCristina Tanzi
Interaction between EO and substarte
Thank you for answering. In case you want to publish the work on a Journal, I would suggest to address this subject explicitly
Thank you for your kind suggestion. We are just working on this aspect.

Silvia Fare'
Congratulation for your work. Even if you plan to use this coating for not implantable device, do you think that in the future is should be possible to implement the procedure so to have a possible use in vivo?
Thank you for your answer.
The functionalization was designed for implant in vivo in bone contact applications. The coating could be applied for applications that don't need osteointegration, but further inwestigation are needed.