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. 2021 Dec;28(12):1282-1289.
doi: 10.1111/iju.14675. Epub 2021 Sep 4.

Intraluminal diamond-like carbon coating with anti-adhesion and anti-biofilm effects for uropathogens: A novel technology applicable to urinary catheters

Affiliations

Intraluminal diamond-like carbon coating with anti-adhesion and anti-biofilm effects for uropathogens: A novel technology applicable to urinary catheters

Shogo Watari et al. Int J Urol. 2021 Dec.

Abstract

Objectives: To examine anti-adhesion and anti-biofilm effects of a diamond-like carbon coating deposited via a novel technique on the inner surface of a thin silicon tube.

Methods: Diamond-like carbon coatings were deposited into the lumen of a silicon tube with inner diameters of 2 mm. The surface of the diamond-like carbon was evaluated using physicochemical methods. We used three clinical isolates including green fluorescent protein-expressing Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus. We employed a continuous flow system for evaluation of both bacterial adhesion and biofilm formation. Bacterial adhesion assays consisted of counting the number of colony-forming units and visualization of adhered bacterial cells by scanning electron microscope to evaluate the diamond-like carbon-coated/uncoated samples. The biofilm structure was analyzed by confocal laser scanning microscopy on days 3, 5, 7 and 14 for green fluorescent protein-expressing Pseudomonas aeruginosa.

Results: The smooth and carbon-rich structure of the intraluminal diamond-like carbon film remained unchanged after the experiments. The numbers of colony-forming units suggested lower adherence of green fluorescent protein-expressing Pseudomonas aeruginosa and Escherichia coli in the diamond-like carbon-coated samples compared with the uncoated samples. The scanning electron microscope images showed adhered green fluorescent protein-expressing Pseudomonas aeruginosa cells without formation of microcolonies on the diamond-like carbon-coated samples. Finally, biofilm formation on the diamond-like carbon-coated samples was lower until at least day 14 compared with the uncoated samples.

Conclusions: Intraluminal diamond-like carbon coating on a silicone tube has anti-adhesion and anti-biofilm effects. This technology can be applied to urinary catheters made from various materials.

Keywords: bacterial adhesion; biofilms; plasma gases; urinary catheters; urinary tract infection.

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Conflict of interest statement

None declared.

Figures

Fig. 1
Fig. 1
Continuous flow system. This continuous flow system was constructed in the incubator to maintain 37°C.
Fig. 2
Fig. 2
The schedule of bacterial experiments.
Fig. 3
Fig. 3
DLC coating. (a) DLC deposition on the luminal surface in the vacuum chamber. The silicon tube was loaded into the sheath tube. The arrow shows the tip of the silicon tube. Plasma emission throughout the lumen was confirmed, indicating DLC deposition. (b) Pictures of silicon tubes. The DLC coating made the silicon transparent and dark‐yellow in color. A, DLC‐coated silicon tube. B, uncoated silicon tube.
Fig. 4
Fig. 4
Physicochemical analysis. (a) Roughness (Ra) results measured using a New View 5320. The DLC‐coated surface exhibited a 70% decrease in mean Ra value relative to the uncoated silicon surface. (b) Proportions of elements on the silicon surface. Proportions of surface elements as determined by the EDX method and corrected by the ZAF method using a HITACHI S‐4800. The proportion of carbon increased on the DLC‐coated surface (A) relative to the uncoated surface (B). The arrow indicates the osmium peak. C: carbon, O: oxygen, Si: silicon.
Fig. 5
Fig. 5
SEM visualization of intraluminal surface structures. All images were acquired at 1500× magnification and accelerating voltage of 5.0 kV. (a) Uncoated silicon surface, vertical direction. (b) DLC‐coated silicon surface, vertical direction. (c) DLC‐coated silicon surface, horizontal direction. Deposition of a DLC layer approximately 3 μm in thickness was confirmed. (d) Surface structure of DLC exposed to artificial urine and bacteria following the experiments, and visualized after removing the adhered cells on the surface with hydrochloric acid.
Fig. 6
Fig. 6
Analysis of CFU counts. The number of CFUs (CFUs/cm) of bacteria irreversibly adhered on the inner surface of the DLC‐coated/uncoated silicon fragments for P. aeruginosa OP14‐210 (pMF230), E. coli OE‐128 and S. aureus OS‐3 were evaluated. Fifteen fragments per strain were evaluated in three independent experiments. P values were obtained using a paired t‐test. Values represent the mean ± SD.
Fig. 7
Fig. 7
SEM visualization of adhered P. aeruginosa OP14‐210 (pMF230) cells. Visualization of adhered GFP‐expressing P. aeruginosa cells on the inner surface of the samples 2 h after inoculum injection. All images were acquired at accelerating voltage of 5.0 kV. (a) Uncoated, 400×. (b) Uncoated, 20,000×. (c) DLC‐coated, 400×. (d) DLC‐coated, 20,000×.
Fig. 8
Fig. 8
Analysis of biofilm formation by P. aeruginosa OP14‐210 (pMF230). (a, b) Images visualized with a Zeiss LSM780 and reconstructed using LSM ZEN‐software on day 3. All images were taken on a 750 μm × 750 μm square section. (a) Three‐dimensional image. (a‐1) Uncoated. (a‐2) DLC‐coated. (b) 2.5‐dimensional image. (b‐1) Uncoated. (b‐2) DLC‐coated. (c, d) Comparison of the biofilm quantified by reconstructed CLSM images using the COMSTAT software. (c) Average thickness. (d) Total biomass. Values represent the mean ± SD of nine image stacks acquired in three independent experiments. P values were obtained using a paired t‐test. *P < 0.05, **P < 0.001.

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