The antibacterial effect of non-thermal atmospheric pressure plasma treatment of titanium surfaces according to the bacterial wall structure

Myung-Jin Lee,Kwang-Mahn Kim,Jae-Sung Kwon,Gyungsoon Park,Heng Bo Jiang,Eun Ha Choi

doi:10.1038/s41598-019-39414-9

Abstract

Titanium is commonly used as a biomaterial for dental implants. In this study, we investigated the antibacterial properties of titanium samples following treatment with a non-thermal atmospheric pressure plasma jet (NTAPPJ) on bacteria with two different cell wall structures, including gram-positive and gram-negative bacteria. The hydrophilicity and surface energy of titanium surfaces were significantly increased after NTAPPJ treatment without altering topographical features. Changes in the chemical composition and reductive potential were observed on the NTAPPJ-treated titanium surfaces. The adhesion and biofilm formation rate of bacteria were significantly reduced on the NTAPPJ-treated titanium surfaces compared with the untreated samples, which was confirmed by fluorescent imaging. Regarding the comparison between gram-positive and gram-negative bacteria, both adhesion and the biofilm formation rate were significantly lower for gram-negative bacteria than gram-positive bacteria on samples treated for longer durations with the NTAPPJ. Transmission electron microscopy imaging showed a comparably more disruptive membrane structure of gram-negative bacteria than gram-positive bacteria on the NTAPPJ-treated surfaces. Our results indicated that the NTAPPJ treatment could be useful for preventing bacterial adhesion and biofilm formation on titanium dental implant surfaces, while the reductive potential on surfaces treated by the NTAPPJ could cause oxidation of bacteria, which could be more sensitive to gram-negative bacteria due to differences in the cell wall structure.

Highlights

Dental implants are a key tool used to facilitate the prosthetic replacement of missing teeth in the field of dentistry[1]
Characteristics of non-thermal atmospheric pressure plasma jet (NTAPPJ)-treated surfaces were investigated in terms of roughness, surface energy and chemical composition, which may influence biological effects on bacterial cells[19,28]
The topographical characteristics of the NTAPPJ-treated surfaces are related to the physical form of the surface, such as roughness, and the topography of the control and test groups was examined by noncontact 3D optical microscopy

Summary

Introduction

Dental implants are a key tool used to facilitate the prosthetic replacement of missing teeth in the field of dentistry[1]. The inactivation of bacteria can be achieved by chemical and/or physical means, such as heat (steam or dry autoclaves), chemical treatment (active gases, such as chlorine or ozone), and irradiation (ultraviolet or gamma)[11] Most of these conventional techniques can cause damage to the treated substrate[11,12]. Another study has investigated the mechanism of surface changes and the effect on bacterial inhibition, for bacteria with different cell wall structures. This study aimed to investigate the effect of NTAPPJ treatment on the surface properties of titanium, which is a commonly used material for dental implants, and the consequential influence on the adhesion of bacteria with two different cell wall structures (gram-positive and gram-negative bacteria). The null hypothesis was as follows: 1) there is no difference in the chemical change of the titanium surface after NTAPPJ treatment, and 2) there is no difference in the antibacterial effects against gram-positive and gram-negative bacteria when they are cultured on NTAPPJ-treated titanium surfaces

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Conclusion