Diamond-like carbon coating to inner surface of polyurethane tube reduces Staphylococcus aureus bacterial adhesion and biofilm formation

Abstract

Staphylococcus aureus is one of the main causative bacteria for polyurethane catheter and artificial graft infection. Recently, we developed a unique technique for coating diamond-like carbon (DLC) inside the luminal resin structure of polyurethane tubes. This study aimed to elucidate the infection-preventing effects of diamond-like carbon (DLC) coating on a polyurethane surface against S. aureus. We applied DLC to polyurethane tubes and rolled polyurethane sheets with our newly developed DLC coating technique for resin tubes. The DLC-coated and uncoated polyurethane surfaces were tested in smoothness, hydrophilicity, zeta-potential, and anti-bacterial properties against S. aureus (biofilm formation and bacterial attachment) by contact with bacterial fluids under static and flow conditions. The DLC-coated polyurethane surface was significantly smoother, more hydrophilic, and had a more negative zeta-potential than did the uncoated polyurethane surface. Upon exposure to bacterial fluid under both static and flow conditions, DLC-coated polyurethane exhibited significantly less biofilm formation than uncoated polyurethane, based on absorbance measurements. In addition, the adherence of S. aureus was significantly lower for DLC-coated polyurethane than for uncoated polyurethane under both conditions, based on scanning electron microscopy. These results show that applying DLC coating to the luminal resin of polyurethane tubes may impart antimicrobial effects against S. aureus to implantable medical polyurethane devices, such as vascular grafts and central venous catheters.

Keywords: Diamond-like carbon; Luminal coating; Polyurethanes; Prevention of infection; Staphylococcus aureus.

Fig. 1

Circuit for perfusion condition. A pair of DLC-coated and uncoated polyurethane tubes were placed in the chambers of the silicone tube circuit. The bacterial fluid was perfused in the circuit to expose the surface of the polyurethane tube to the bacteria. The bacterial fluid was supplied at a flow rate of 60 mL/min using a roller pump. The silicone chambers were immersed in a constant-temperature bath at 37 °C

Fig. 2

Comparison of surface properties between DLC-coated and uncoated polyurethane surface: a results of Raman spectroscopy, b results of surface roughness measurements; PU, polyurethane, c results of water contact angle, and d results of zeta-potential measurements

Fig. 3

Results of the static condition: a results of absorbance measurement for biofilm, b results of attached bacteria counts, c scanning electron microscope analysis of DLC-coated and uncoated polyurethane surfaces

Fig. 4

Results of perfusion condition: a results of absorbance measurement for biofilm, b results of attached bacteria counts, c scanning electron microscope analysis of DLC-coated and uncoated polyurethane surfaces