Iodine-doped TiO2 nanotube coatings: a technique for enhancing the antimicrobial properties of titanium surfaces against Staphylococcus aureus

Abstract

Background: Implant-related infections are a challenging complication of orthopedic surgery, primarily due to the formation of bacterial biofilms on the implant surface. An antibacterial coating for titanium implants was developed to provide novel insights into the prevention and treatment of implant-related infections.

Methods: Titanium plates were coated with TiO₂ nanotubes by anodization, and iodine was doped onto the coating via electrophoretic deposition. The obtained plates were characterized using a range of analytical techniques. Subsequently, Staphylococcus aureus was inoculated onto the surfaces of untreated titanium plates (control group), TiO₂-nanocoated titanium plates (TiO₂ group), and iodine-doped TiO₂-nanocoated titanium plates (I-TiO₂ group) to compare their antibacterial properties.

Results: Twenty-four hour in vitro antimicrobial activity test of the I-TiO₂ group against Staphylococcus aureus was superior to those of the other groups, and this difference was statistically significant (P < 0.05).

Conclusions: This coating technology provides a new theoretical basis for the development of anti-infective implants against Staphylococcus aureus in orthopedics.

Keywords: Antibacterial coating; Iodine; TiO2 nanotubes; Titanium plate.

Fig. 1

Technological pathway. Preparation of the iodine-doped TiO₂ nanotube-coated titanium plates

Fig. 2

Visual characteristics of the titanium plate. The titanium plate after grinding and pretreatment (left) and the titanium plate bearing TiO₂ nanotubes after anodization (right)

Fig. 3

SEM images of TiO₂ nanotube arrays. SEM observations of the growth of TiO₂ nanotube arrays on the titanium plate surface after anodization for 10 h. Left: SEM surface view structure of titanium plate surface without anodization (×5000 magnification). Middle: SEM surface view structure of the TiO₂ nanotube array on the titanium plate surface (×5000 magnification). Right: SEM image showing the longitudinal structure of the TiO₂ nanotube array on the titanium plate surface (×5000 magnification)

Fig. 4

Visual characteristics of iodine-doped TiO₂ nanotube-coated titanium plate. Appearance of the iodine-doped TiO₂ nanotube-coated titanium plate. After the electrophoretic deposition of iodine onto the TiO₂ nanotube arrays, a light-yellow granular coating was observed on the surface of the titanium plate

Fig. 5

SEM images of the iodine-doped TiO₂ nanotube structure. Microscopic representation of the iodine-doped TiO₂ nanotube structure. At 10,000-fold (left), 20,000-fold (middle), and 50,000-fold (right) magnifications, the microscopic representation of the iodine-doped TiO₂ nanotube structure as observed by SEM imaging. Some crystal structures were deposited on the surfaces of the nanotubes, which were tightly bound and distributed along the orifices and circumferences of the tubes

Fig. 6

Element content analysis. Elemental content map of the titanium plate surface as determined using XRF spectrometry. The elements on the surface of the titanium plate include titanium, oxygen, fluorine, iodine, carbon, aluminum, and vanadium

Fig. 7

Element distribution analysis. Elemental electronic image of the titanium plate surface as determined using EDS. The elemental composition of the titanium plate surface follows a descending order: titanium, oxygen, fluorine, iodine, carbon, aluminum, and vanadium. Iodine exhibits a uniform distribution across the surface

Fig. 8

Statistical analysis. Comparison of the bacterial counts in the three experimental groups. Upon carrying out statistical ANOVA, the F value was determined to be 50.8139, and the difference was statistically significant (P = 7.037 × 10⁻¹⁰, < 0.05). Compared with the Ti group, the bacterial counts of the TiO₂ and I-TiO₂ groups decreased to varying degrees, and the differences were statistically significant (P < 0.05). Moreover, compared with the TiO₂ group, the bacterial count of the I-TiO₂ group was significantly lower (P < 0.05)